FXUS66 KEKA 182247
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
247 PM PST Sun Feb 18 2018
.SYNOPSIS...A cold storm system will bring rain and snow showers to
northwest California through early Monday morning. Some showers may
contain small hail. Behind this system a cold air mass settles
over the area. The coldest temperatures will be Tuesday morning.
.DISCUSSION...The upper level trough moving over the area is
bringing widespread showers to Humboldt and Del Norte counties.
Snow levels have dropped to around 2,000 feet as of noon. Snow
levels will continue to fall tonight to around 1,000 feet.
Additional snow accumulations of up to 3 inches are possible
tonight in Humboldt and Del Norte counties. Locally lower snow
levels are possible in the heavier showers. A few flakes are
possible at the coast towards morning, but nothing is expected to
stick. Along the coast below the snow level numerous showers are
producing small hail. This has been accumulating on roadways. One
of these storms produced a couple lightning strikes. So have added
a slight chance for thunder and small hail this evening. These
showers are expected to continue tonight and start to diminish
Monday isolated showers will diminish through the day.
Temperatures are expected to only warm into the 40s and snow
levels will be around 1,000 to 1,500 feet, but no significant
accumulation is expected. Monday night into Tuesday morning looks
like the coldest morning. Temperatures at the coast look to drop
to around 30 at the immediate coast with 20s just a mile two
inland. The hard freeze watch for the coastal areas looks to be on
track and confidence is growing that we will see these
temperatures. Farther inland temperatures will drop into the low
20s and teens. Single digit temperatures are possible in the
northern mountains. There will likely be some clouds around from
a system off the coast, but models have slowed down this system
and come into better agreement that these clouds will not impact
temperatures too much. Tuesday afternoon temperatures will warm
slightly, but most areas will remain in the 40s. Tuesday evening
and overnight a few showers and some clouds likely as the weak
system moves by just off the coast. Snow levels will be fairly
low, but only a dusting of snow is expected.
Wednesday the airmass starts to warm slightly with temperatures
warming back into to low 50s. Northwest flow persists and a few
sprinkles are possible with some clouds around. Thursday into the
Weekend the models are showing additional systems moving over the
area from the northwest. There is not very good agreement in the
models on these systems yet. However, there is reasonable
confidence that temperatures will be fairly cool and there will be
periods of light rain and snow. MKK
.AVIATION...An active day of showers at the coastal terminals
today will continue trough the evening before diminishing in
intensity and coverage later tonight. The showers have and will
bring brief periods of mvfr conditions otherwise sites will mainly
observe VFR conditions through the next taf cycle. Some interior
valley locations sheltered from the north winds could see some ground
fog develop very early tomorrow morning.
.MARINE...Gusty Northwest to north winds will continue through
tomorrow across all waters. Some of these winds are also enhanced
from passing showers...although the shower activity should diminish
over night. Meanwhile, a large swell from the northwest will move
through the waters this evening through Monday morning. The
combination of steep wind-driven seas and the arriving swell will
result in very large and hazardous seas with combined wave heights
reaching 20 to 25 feet throughout much of the waters. As a result, a
Gale Warning remains in effect for the outer waters from late this
morning through Monday afternoon. Hazardous Seas Warning has been
issued for the nearshore waters of Humboldt, Del Norte, and
Mendocino counties. Winds will steadily decrease through the day
Tuesday, allowing seas to slowly subside. Tuesday and Wednesday,
north winds of 15 to 20 kt will maintain somewhat elevated seas,
likely with wave heights between 7 and 9 feet. However, north winds
will increase again Thursday through the end of the week, resulting
in the buildup of steeper seas that will last through at least the
end of Friday. /KAR/JT
CA...Hard Freeze Watch from late Monday night through Tuesday morning
High Surf Advisory from 1 AM to noon PST Monday for CAZ109.
Winter Weather Advisory until 4 AM PST Monday for CAZ102-104>108.
High Surf Advisory from 7 PM this evening to 4 AM PST Monday for
NORTHWEST CALIFORNIA COASTAL WATERS...Gale Warning until 3 PM PST Monday for PZZ470-475.
Small Craft Advisory for winds until 3 PM PST Monday for PZZ450-
Hazardous Seas Warning until 3 PM PST Monday for PZZ450-455.
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FXUS66 KHNX 182335
Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
335 PM PST Sun Feb 18 2018
A southward moving cold front will bring an unseasonably cold air
mass into the central California interior by this evening.
Blustery winds will accompany the change to colder weather this
afternoon through Monday and snow showers are possible in the
mountains and foothills by this evening. Below freezing
temperatures are likely in the San Joaquin Valley Tuesday morning
and Wednesday morning. Colder than normal weather will continue
for the remainder of the week.
Change is finally in store for Central California as a cold front
from the Gulf of Alaska continues to descend toward the district.
While the sun continued to shine this Sunday, clouds and showers
have spread into Northern California behind the cold front.
Surface Frontal analysis has the cold front over Northern
California and quickly approaching the Central California
Interior. Many surface observations are already showing a more
northwesterly wind component which places the cold front nearby.
Satellite IR imagery is showing the cold air cellular cloud
formations pushing past the Bay area and moving further southward.
Therefore, the cold air-mass will descend down into the region
tonight with elevated wind speed being the saving grace from a
very cold night. Clouds development from marginal instability will
be the other saving grace, but will also produce spotty showers
tonight as snow level could reach down into the foothills.
However, moisture continues to lack which will keep precipitation
on the lower accumulation-side with a few inches possible over the
higher terrain of the Sierra Nevada.
Current model prog timing still has the disturbance and associated
cold front crossing into Central California today as surface winds
have already started to increase. The cold front is entering the
region and should reach the southern portion of the district just
after sunset. At which time, the disturbance aloft will drop into
the region and place a good portion of its energy offshore along
the Central Coast. Model prog is still showing the flow pattern in
a more channel flow pattern characteristic. This channel flow
pattern is more indicative of strong winds than precipitation.
Satellite imagery and surface observations are already showing
this trend. Therefore, the higher confidence levels are with the
strong winds then the lower confidence of possible precipitation.
Yet, a portion of the wind component could become perpendicular to
the Sierra Nevada Range and Tehachapi Mountains. Therefore, can
not rule out precipitation over the higher terrain. However,
forecast precipitation accumulation is small for this event as
Central California is not favored in this flow pattern. Yet, the
lack of precipitation and the fact that lower elevations may see
snow will warrant the winter weather advisories for tonight.
Behind Today's cold front, models have been very consistent in
prog sub-freezing temperatures across the San Joaquin Valley from
around Tuesday through Thursday morning. While during the early
onset of the cold frontal passage, the coldest air will reside
over the area with possible moderation in conditions going into
Thursday morning. Therefore, the best chances of a hard freeze
[min's < 28F] will exist on Tuesday morning (once the winds settle
down and the skies clear out from Monday's event) with a good
chance of freezing [min's < 32F but > 28F] Wednesday morning.
While not as widespread as Wednesday morning, freezing will still
be possible on Thursday morning. By Friday, Modification of the
air-mass will make the potential for freezing less likely.
Furthermore, another disturbance will enter the region on Thursday
afternoon, which will increase winds and clouds along with mixing
of the atmosphere to prevent the freeze potential. While the
potential for precipitation is very low, will at least mention a
potential as very low accumulation will be likely. By next
weekend, an inside slider will maintain clouds, winds and possible
mixing of the atmosphere to moderate temperatures.
Strong surface winds with gusts to 45 knots developing this
evening across the Kern County Mountains and Deserts. IFR
conditions in Blowing Dust will be also be possible across the
Mojave Desert overnight. Increasing clouds this afternoon with
clouds and showers obscuring the mountains after 00Z Monday.
Otherwise, VFR conditions will prevail across the Central CA
Interior during the next 24 hours.
.AIR QUALITY ISSUES...
The level of certainty for days 1 and 2 is high.
The level of certainty for days 3 through 7 is medium.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.php for additional information
an/or to provide feedback.
Winter Weather Advisory from 9 PM this evening to 3 AM PST
Wind Advisory until 9 PM PST this evening CAZ095.
Winter Weather Advisory from 6 PM this evening to 4 PM PST
Hard Freeze Warning from midnight Monday night to 8 AM PST
Freeze Watch from late Tuesday night through Thursday morning
Wind Advisory until 4 PM PST Monday CAZ098-099.
FXUS66 KLOX 190411
Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
811 PM PST Sun Feb 18 2018
Light rain and mountain snow will fall across much of the region
tonight and Monday with snow falling as low as 1500 feet Monday
morning. Gusty winds and a blast of cold air will create very cold
wind chill temperatures through Monday with frost or freezing
conditions Tuesday and Wednesday mornings. Conditions will be dry
but cool for the remainder of the week.
Very difficult forecast this evening as a weak and fairly dry
but very cold system moves in from the north. There are a fair
amount of showers over MRY county and these will move over SLO and
western SBA counties in a few hours. The forecasted eddy and
convergent flow for SE LA county really did not materilize so the
odd of that area seeing a shower tonight are much reduced.
This system will very likely produce highly changable skies but
not much rain. There is a pretty good chc that SLO and most of SBA
county (but not the SBA south coast) will see some light showers.
The best chc of showers will occur after midnight with the cold
north flow impinges on the north faceing slopes near the Kern
Current suite of winter...wind and freeze products looks good.
Updated the forecast to raise pops in the advisory areas as well
as SLO and western SBA counties. Al;so play with the cloud wording
a little to reflect current conditions.
.SHORT TERM (SUN-WED)...
Skies were mostly clear early this afternoon with some partly
cloudy skies across portions of the Central Coast down to Ventura
County coastal areas. Surface gradients between LAX and DAG have
trended over +8 mb in the last 24 hours. A wind advisory is now in
effect for the Antelope Valley due to the strong onshore
gradients causing SW winds to increase to around 30 to 35 mph with
gusts expected to be around 45 to 50- mph through this evening.
There will be locally gusty winds across the Highway 14 corridor
as well, including the Soledad Pass through this evening as well.
Motorists driving high profile vehicles should slow down if
encountering gusty cross winds. There will be gusty NW winds
developing this afternoon across the Central Coast this afternoon
but remain below advisory thresholds. Temps were trending down
6-10 degrees in most areas today compared to yesterday at this
time. Highs today are expected to be around normal for this time
For this evening, NW winds will expand across the Santa Barabara
County Mtns and adjacent wind prone south coast as well as the
Los Angeles and Ventura County Mountains. Wind advisories will be
in effect by 8 pm this evening in these locations.
Synoptically, an upper level low located in the PAC NW will begin
to dive south into the Great Basin tonight while the base of the
low continues to dig into southern California. The trajectory of
the trough will remain mainly over land, therefore not expecting
much precip with this system. However, the combination of strong
height falls and cold temperatures expected with this system will
help squeeze out what little moisture there is to tap into to
tonight through Monday evening. The best chance for light showers
will be across L.A. County, especially the southern and eastern
areas where the cyclonic flow aloft will be most most favorable.
Otherwise, broad NW to N flow will bring a chance of rain and snow
to the north facing slopes of SBA/Ventura and the NW portion of
the LA County Mtns near the Grapevine and I-5 Corridor. The NW
portion of the Antelope Valley could see a few showers as well
through Monday eve.
Snow levels will plummet tonight, dropping from between 5000 and
5500 feet this evening, to between 2500 and 3000 feet late
tonight, and to 1500 to 2000 feet Monday morning. This could
bring snow showers into foothills areas Monday morning. Little or no
snow accumulation is expected in the foothills, but in the mountains
above 2500 feet, snow accumulations of 2 to 4 inches are possible.
1-2 inches possible for the Santa Barbara County Mountains, and
around an inch of snow for portions of the Cuyama Valley including
highway 166. A winter weather advisory is in effect for the mtns
of L.A. and VTU Counties as well as the Santa Barbara mountains
and the Cuyam Valley this evening through Monday night for the
snow and advisory level northwest winds. There could be a dusting
of snow across the Antelope Valley foothills as well. Especially
across the western portion, but not expecting valley floor
Gusty northwest winds will begin to shift out of the north and
filter into the Santa Clarita and San Fernando Valleys and likely
into West L.A. monday night into Tuesday morning. Additional wind
advisories might be needed during that time. It will be very cool
on Monday, with highs only in the 50s in most coastal and lower
valley areas, in the mid to upper 40s in the interior valleys, in
the upper 30s to mid 40s in the lower mountains and the Antelope
Valley and in the mid 20s to mid 30s at higher mountain locations.
With the cold conditions and added wind, it will feel much
colder. In fact, wind chill values could drop to between 10
degrees and -10 degrees in the higher elevation of the mountains
late tonight and Monday. This is unusually cold for Southern
California. People planning to hike, camp, ski or snowboard in the
mountains on the holiday are urged to plan for the unusual cold
and low wind chill values.
Winds are expected to decrease rather suddenly Monday night in
most areas. With light winds and clear skies expected Monday night
into Tuesday morning, radiational cooling will help temps drop
significantly. The Hard Freeze Watches have been converted to Hard
Freeze Warnings for both Monday night into Tue and Tuesday night
into Wednesday morning for the Central Coast, the Santa Ynez and
Cuyama Valleys, and the interior valleys of Ventura County,
especially for the Ojai Valley. In these areas, temperatures will
drop to 28 degrees or lower for at least two hours Monday night.
Some areas within the Hard Freeze Warning will experience lows in
the lower 20s. A Freeze Watch has also been converted to a Freeze
Warning for the same time periods across South Coast of SBA
County, coastal sections of VTU County, and the VTU County coastal
valleys. Temperatures in these areas could bottom out between 29
and 32 degrees for at least two hours Monday night. It will also
be very cold in the interior valleys of SLO County and the
Antelope Valley, with temps between 17 and 27 degrees there, but
those locations have already experienced two hard freezes this
season. Frost is likely in the colder locations in the valleys of
L.A. County Monday night, and a Frost Advisory will likely be
needed for those areas. Tuesday will be mostly sunny but it will
continue to be very cool across the region.
.LONG TERM (THU-SUN)...
The EC and GFS are coming into better agreement with large scale
features from Wednesday through Saturday. Temperatures will remain
quite cool through the extended period as a broad upper trough
across the west will persist. Skies should be mostly sunny Tuesday
through Thursday before clouds increase Thursday night.
Another trough will drop southward through the Pac NW Thursday.
The GFS shows this trough moving eastward into Arizona Thu night
and Fri, while the EC is farther west and slower with it, tracking
just to the northeast of the area Fri morning. Slight chance POPs
have been added across most of the forecast area except the
Antelope Valley for Thursday night into Fri at this time. High
temps will remain quite cool and there could be more issues for
anyone going across the I-5 Corridor Thurday night and Friday.
Again, this looks like a light precip maker at this point, but
will have to continue to monitor.
Models were hinting at a more significant and another cold system
the following Monday and Tuesday. So expect the cooler than normal
pattern to continue for a while.
At 23Z over KLAX, a weak inversion bottom was at 2000 ft and 9
degrees Celsius, and a top at 2600 ft and 11 degrees Celsius.
Challenging next 24 hour forecast. Low confidence on timing and
heights of ceilings. 30 percent chance of occasional -SHRA and
BKN015-025 through 16Z KPRB KSBP KSMX KSMO KLAX KLGB KBUR KVNY.
Moderate confidence on timing and strength of winds, with fairly
widespread gusty westerly winds. Occasional LLWS and turbulence
anywhere, especially over KSBA tonight.
KLAX...Low confidence on ceilings, moderate confidence in winds.
Periods of BKN015-025 with -SHRA possible through around 12Z.
North winds likely over airport 12-16Z Monday, either surfacing
or creating LLWS issues.
KBUR...Low confidence on ceilings, moderate confidence in winds.
Periods of BKN015-025 with -SHRA possible through around 12Z.
10KT LLWS possible from North winds over airport 12-16Z Monday.
Updated marine forecast, with significant larger sea heights for
the next 48 hours, and expanded Gale Warnings to the Santa Barbara
Channel and western Santa Monica Basin.
High confidence in Gale Force winds (around 35 KT) everywhere by
3 AM tonight, except for the eastern Santa Barbara Channel and the
nearshore waters of Los Angeles and Ventura Counties. With the
strong winds however, all areas will see dangerous and large short
period seas developing tonight. High confidence in the winds
expanding and peaking Monday afternoon, with gusts of 30 to 40 KT
over all waters. The winds will continue through Monday evening,
then weaken through Tuesday, but Small Craft Advisory (SCA) are
likely from the Central Coast to San Nicolas Island. Improved
conditions are likely on Wednesday.
CA...High Surf Advisory in effect from 6 AM Monday to 2 PM PST
Tuesday for zones 34-35. (See LAXCFWLOX).
Hard Freeze Warning in effect from 1 AM to 9 AM PST Tuesday
for zones 34>36-38-44. (See LAXNPWLOX).
Hard Freeze Warning in effect from 1 AM to 9 AM PST Wednesday
for zones 34>36-38-44. (See LAXNPWLOX).
Winter Weather Advisory in effect until 3 AM PST Tuesday for
zones 38-52>54. (See LAXWSWLOX).
Wind Advisory in effect until 10 PM PST Monday for zones
39-52-59. (See LAXNPWLOX).
Freeze Warning in effect from 1 AM to 9 AM PST Tuesday for
zones 39-40-45. (See LAXNPWLOX).
Freeze Warning in effect from 1 AM to 9 AM PST Wednesday for
zones 39-40-45. (See LAXNPWLOX).
PZ...Small Craft Advisory in effect until 9 AM PST Monday for zone
645. (See LAXMWWLOX).
Gale Warning in effect from 9 AM to 9 PM PST Monday for zone
645. (See LAXMWWLOX).
Gale Warning in effect until 9 PM PST Monday for zone 650. (See LAXMWWLOX).
Small Craft Advisory in effect until 1 AM PST Monday for zone
655. (See LAXMWWLOX).
Gale Warning in effect from 1 AM to 9 PM PST Monday for zone
655. (See LAXMWWLOX).
Gale Warning in effect until 3 AM PST Tuesday for zones
670-673-676. (See LAXMWWLOX).
.HAZARD POTENTIAL OUTLOOK (WED-SUN).
Widespread temperatures around or below freezing is expected
early Wednesday morning away from the beaches, posing a risk for
hypothermia and plant damage.
FXUS66 KSTO 182303
Area Forecast Discussion
National Weather Service Sacramento CA
303 PM PST Sun Feb 18 2018
A COLD WEATHER SYSTEM BRINGS BREEZY WINDS AND SNOW OVER THE
MOUNTAINS AND FOOTHILLS INTO MONDAY, IMPACTING TRAVEL. THIS WILL
BE FOLLOWED BY NEAR RECORD COLD TEMPERATURES WITH A POSSIBLE
SCATTERED SHOWERS ARE SPREADING ACROSS THE MOUNTAINS, WITH THE
HEAVIEST SHOWERS CURRENTLY OVER THE NORTHERN SIERRA NORTH OF
HIGHWAY 50. WEBCAMS ON I80 SHOW MODERATE TO HEAVY SNOW SHOWERS.
SNOW SHOWERS OVER THE SIERRA ARE EXPECTED TO BRING SLIPPERY ROADS
AND TRAVEL DELAYS. A WINTER WEATHER ADVISORY CONTINUES TO BE IN
EFFECT UNTIL 4 PM MONDAY. USE CAUTION IF TRAVELING IN THE
MOUNTAINS AND UPPER FOOTHILLS. A DUSTING OF SNOW WILL BE POSSIBLE
ACROSS THE FOOTHILLS OVERNIGHT INTO MONDAY. SNOW ACCUMULATIONS ARE
NOT EXPECTED TO BE IMPRESSIVE, BUT THIS HOLIDAY WEEKEND
TRADITIONALLY SEES A HIGH VOLUME OF TRAFFIC OVER THE MOUNTAINS AND
SNOW COULD CAUSE EXACERBATED IMPACTS.
WHAT WILL LIKELY BE THE COLDEST AIR OF THE WINTER SEASON WILL
BEGIN TO IMPACT PORTIONS OF THE REGION TONIGHT. FOR LOWER
ELEVATIONS, THE COLDEST TEMPERATURES TONIGHT WILL LIKELY BE ACROSS
THE NORTHERN VALLEY, WHERE SKIES CLEAR AND WINDS SLACKEN. SKIES
SHOULD CLEAR FURTHER MONDAY NIGHT INTO TUESDAY MORNING, AND
CURRENTLY APPEARS TO BE THE COLDEST NIGHT OF THIS EVENT.
WIDESPREAD FREEZE CONDITIONS MAY CONTINUE TUESDAY NIGHT. WIDESPREAD
FROST IS EXPECTED. AGRICULTURAL IMPACTS COULD BE SIGNIFICANT, DUE
TO AN EARLY BLOOM FROM UNUSUALLY MILD WEATHER IN RECENT WEEKS.
PEOPLE SHOULD BEGIN PLANNING NOW ON WAYS TO PROTECT SENSITIVE
PLANTS, OUTDOOR PETS, AND OUTDOOR PIPES.
ANOTHER SYSTEM WILL BRING LIGHT SNOW SHOWERS TO THE MOUNTAINS ON
WEDNESDAY. SNOW LEVELS WILL BE AROUND 1000 FEET, POSSIBLY LOWER,
BUT JUST A DUSTING OF SNOW IS EXPECTED.
.EXTENDED DISCUSSION (Thursday THROUGH Sunday)
A series of cold shortwave troughs will pass through NorCal for
the extended period. Models are more aligned today with timing and
placement. The first system arrives Wednesday night into Thursday
and will bring precip chances for both the Valley and higher
elevations. The best chances for Valley showers will be Thursday
afternoon when some weak instability builds in and the trough axis
swings through. With not a ton of moisture to work with, precip
totals should remain rather low. Low snow levels will be a
concern though as they will be 1000 to 2500 feet. Hazardous
Mountain travel will be possible Thursday lasting into Friday
A weak ridge builds in Friday into early Saturday with another
short wave trough passing just to our east on Saturday. This will
bring the chances for light showers mainly to the northern
Mountains. Another system arrives Sunday into Monday. The EC is
just a bit further to the west with it and is able to pull in
higher moisture levels but the GFS is drier. Cool temperatures
will remain in place for the period running 5-10 below normal to
start but will gradually warm a few degrees each day.
Generally VFR conditions are expected at the TAF sites the next 24
hours. SCT to BKN clouds between 5000 and 10000 feet can be
expected this afternoon rising to around 10000 feet overnight.
Scattered snow showers continue in the higher elevations through
15z Monday and MVFR/IFR conditions can be expected in any
showers. Breezy northerly winds 15-30 knots diminish to 5-11 knots
Winter Weather Advisory until 4 PM PST Monday for West Slope
Northern Sierra Nevada.
Freeze Warning from 2 AM Monday to 8 AM PST Wednesday for
Carquinez Strait and Delta-Central Sacramento Valley-Clear
Lake/Southern Lake County-Motherlode-Northeast
Foothills/Sacramento Valley-Northern Sacramento Valley-Northern
San Joaquin Valley-Shasta Lake Area / Northern Shasta County-
Southern Sacramento Valley.
FXUS66 KSGX 190548 AAA
Area Forecast Discussion
National Weather Service San Diego CA
945 PM PST Sun Feb 18 2018
Onshore flow will be increasing tonight, becoming strong and gusty
over the mountains and deserts as a cold low pressure trough drops
south into the Great Basin. Scattered, light rain and snow showers
will pop over and west of the mountains late tonight into Monday as
the marine layer builds. Expect the coldest days of the winter so
far on Monday and Tuesday. Dry and a little warmer for Wednesday and
Thursday. Then cooler again into Friday, with a chance for some more
scattered showers as another cold low pressure system drops into the
Great Basin from the north. Dry and a little warmer into next
weekend as temperatures edge back toward average.
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
Rain showers are developing offshore, likely to
move onshore after 10 pm. Most of this activity will be quite light
as it moves inland through the night. Snow showers will be likely in
the mountains late tonight but again on the light side. With
temperatures already down into the mid 40s in the high desert, there
is a slight chance of seeing some snow flurries by Monday morning
there as well once the cooler air is ushered in by the vigorous
trough which will be dropping through California overnight. No
significant changes were needed to the forecast this evening.
...Remainder of previous discussion...
A longwave trough will dive into the Great Basin on Monday, grazing
SoCal with strong onshore winds and scattered light precipitation.
It will also bring the coldest air of the season, plunging maximum
temps on Monday into the 15 to 20 degrees below normal range. given
the extended period of well above normal temps this winter, it will
be a profound change.
This wave is actually the beginning of a more sustained cooler
weather pattern for the SoCal as the longwave is maintained for
sometime in the model runs. Various shorter wavelength disturbances
will periodically drop into the longwave, creating gusty onshore
flow over the coastal waters, mts and deserts, and chances for light
precip. So for the foreseeable future, daytime temperatures will
be mostly below average.
A variety of Warnings and Advisories are in effect from frost/freeze
to wind and winter conditions. Please visit our webpage for more
detail on all of these. Of most significance will be the strong
westerly winds late tonight into Monday. Gusts over 70 MPH are
expected on the upper desert slopes and ridge tops, while on the
desert floor, it will be breezy, but potentially damaging gusts look
to be more isolated and near the foothills late tonight into Monday
morning. windy conditions are also expected for coastal San Diego
County on Monday. Precipitation will be light and scattered, but it
will be cold enough so that some light snow accumulations are
forecast above 4000 FT. Freezing conditions on the passes, could
create a hazard to travelers.
As this system moves east, another, weaker trough slips south across
the area midweek with little weather. Temps will moderate some, then
a stronger disturbance drops south for Friday. this one could
generate more light showers, and gusty winds over the mts/deserts/
coastal waters. Slightly warmer and dry into the weekend, then both
the 12Z GFS/ECMWF runs are advertising a stronger system early next
week. Who knows, we may be able to salvage some precip before the
end of the month.
190515Z...Mostly BKN-OVC clouds with bases 2000-4000 ft MSL will
prevail through Monday afternoon from the mountains to the coast,
with scattered -SHRA, most frequent 07Z-13Z, plus scattered -SHSN in
the mountains. Higher terrain will be obscured, with tops to 8000 ft
MSL possible, but at TAF sites, most vis will remain above 5 miles.
By Monday evening, most areas will have SCT clouds, generally above
3000 ft MSL.
Southwest to west winds 25-35 kt with gusts to 55 kt will continue
to spread over the mountain crests and desert mountain slopes
tonight with these strong winds continuing through Monday afternoon.
Areas of west winds 20-30 kt will occur near the coast Monday and
will likely bring gusts around 30 kt at KSAN at times.
West-northwest winds will increase to 20-30 kt tonight and continue
through Monday night, with gusts 35 to 40 kt possible in the outer
waters Monday morning. Combined seas of 9-13 ft with steep waves are
likely Monday through Monday evening in the outer waters with 7-11
ft in the inner waters. Conditions will improve Tuesday.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
CA...Winter Weather Advisory from 6 PM this evening to 10 PM PST
Monday for Riverside County Mountains-San Bernardino County
Mountains-San Diego County Mountains.
Wind Advisory from 2 PM this afternoon to 6 PM PST Monday
for Coachella Valley-San Diego County Deserts-San Gorgonio
Pass Near Banning.
High Wind Warning from 2 PM this afternoon to 6 PM PST Monday
for Apple and Lucerne Valleys.
Frost Advisory from 10 PM Monday to 9 AM PST Tuesday for San
Diego County Valleys-San Gorgonio Pass Near Banning.
Wind Advisory from 8 AM to 6 PM PST Monday for San Diego County
Coastal Areas-San Diego County Valleys.
Frost Advisory from 10 PM Tuesday to 8 AM PST Wednesday for San
Bernardino and Riverside County Valleys-The Inland Empire.
Freeze Warning from 10 PM Monday to 9 AM PST Tuesday for San
Bernardino and Riverside County Valleys-The Inland Empire.
PZ...Gale Warning from 10 PM this evening to 6 AM PST Tuesday for
Waters from San Mateo point to the Mexican Border Extending
30 to 60 nm out including San Clemente Island.
Small Craft Advisory from 10 PM this evening to 6 AM PST Tuesday
for Coastal Waters from San Mateo Point to the Mexican
Border and out to 30 nm.
FXUS66 KMTR 190512
Area Forecast Discussion
National Weather Service San Francisco Bay Area
912 PM PST Sun Feb 18 2018
.SYNOPSIS...Blustery and much colder weather conditions
developed across the region today in wake of a strong frontal
passage. Scattered post frontal showers will occur tonight into
Monday morning, mainly near the coast and in Santa Cruz and Santa
Lucia Mountains. Snow levels are forecast to drop to or below
1,000 feet by Monday morning. Widespread freezing temperatures are
then expected for inland areas once winds subside Monday night
into Tuesday morning. Cool and unsettled weather is expected to
persist through the end of the week and into early next week.
.DISCUSSION...As of 9:10 PM PST Sunday...A strong, but mostly
dry, cold front swept across our region earlier today. As
expected, blustery and much cooler conditions developed behind the
front. Local wind gust of up to 45 mph were observed along the
coast and in the hills today. Today's high temperatures were
generally 10 to 20 degrees cooler compared to Saturday.
Scattered showers developed late this afternoon in the cold and
unstable post frontal environment. Most of these showers were
confined to the coastal waters, as well as coastal San Mateo and
Santa Cruz Counties, and northwest Monterey County. These showers
have been brief and rain totals thus far have been just a few
Models have been consistent in developing more widespread shower
activity overnight as the upper trough continues to dig south and
drags an even colder and more unstable airmass across our region.
Precipitation overnight is expected to be concentrated in coastal
areas and especially in the Santa Cruz Mountains and northern
Santa Lucia mountain range of Monterey County. Very little, if
any, precipitation is expected in the North and East Bay (except
northwest Sonoma County). In general, the bulk of tonight and
tomorrow morning's rain and snow is expected to fall west of
Snow levels are currently at about 2000-2500 feet but are expected
to drop to 1500 feet overnight and 1000 feet on Monday morning.
Snow could even fall briefly as low as 500 feet in heavier
showers. Latest HRRR and WRF models agree on where the greatest
precipitation totals will occur through midday Monday. Both models
forecast liquid precipitation of about a quarter to a third of an
inch in the Santa Cruz Mountains and maximum amounts of a half
inch (HRRR) and 1 inch (WRF) in the Santa Lucias. Given the
anticipated low snow levels these QPF values would translate into
between 2 and 4 inches of snow at the higher elevations of the
Santa Cruz Mountains and from 5 to 10 inches in the Santa Lucia
Mountains. The primary impact from a travel standpoint will be
near the summit of highway 17 in Santa Cruz County and along
Skyline Boulevard (highway 35) in the Santa Cruz Mountains. A
Winter Weather Advisory is in effect from midnight tonight until
10 am Monday for the Santa Cruz Mountains and Santa Lucia
Mountains. The models agree that precipitation will taper off by
mid morning on Monday and mostly end by midday.
Blustery conditions continue near the coast and locally in the
hills this evening with northwest winds gusting between 30 and 40
mph. Expect gusty winds to persist overnight and then increase
slightly again by Monday afternoon, especially along the coast.
Based on the 12Z WRF wind output, a wind advisory may be needed
for coastal areas on Monday afternoon, but it looks like a
marginal event. Therefore, will wait for all the 00Z model data
before making a determination on any possible wind advisories.
Winds will subside in all areas on Monday evening.
Once precipitation and clouds depart on Monday, and winds subside
on Monday evening, the stage will be set for very cold
temperatures late Monday night into Tuesday morning. Latest model
guidance is consistent with previous guidance in indicating
widespread overnight lows ranging from the mid 20s to lower 30s
across inland areas early Tuesday morning and mostly in the 30s
near the coast. A Freeze Warning is in effect for all of our
inland areas late Monday night into Tuesday morning. In addition,
a Frost Advisory has been issued for all of our coastal and
bayside zones (except the city of San Francisco) for the same time
A shortwave trough is forecast to drop south just offshore on
Tuesday night. The models agree that nearly all precipitation
with this disturbance will remain offshore. However, enough clouds
are expected to spread across our area on Tuesday night to keep
temperatures from dropping below freezing at most locations.
Therefore, it appears unlikely that freeze warnings/frost
advisories will need to be reissued for Tuesday night/Wednesday
The models maintain a cool and unsettled pattern through the rest
of the week with another system forecast to drop in from the north
Wednesday night into Thursday. The 12Z ECMWF brings in yet
another system Thursday night into Friday. These systems are
forecast to be cold, but not as cold as our current system. Thus
snow levels will likely remain above 1500 feet.
Longer range models show a potentially more potent and wetter
system arriving sometime early next week.
.AVIATION...As of 5:30 PM PST Sunday...Cold northwest flow
settling over the area with scattered cumulus clouds. A few
showers are developing offshore and coming onshore around Monterey
Bay. This should continue through this evening with possibly an
increase in activity after 10Z from the MRY Bay Area south. Winds
gusting as high as 30-35 kt through at least 04Z.
Vicinity of KSFO...VFR. West winds 25 kt gusting to 35 kt through
at least 04Z.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...A few passing showers in MRY early
tonight but mainly VFR. MVFR cigs with shower activity increasing
Here are record low temperatures and the years they occurred for
Monday through Wednesday this week.
Location Monday Tuesday Wednesday
SF Bay Area
Healdsburg 28 in 1932 22 in 1922 28 in 1929
Santa Rosa 26 in 1932 26 in 1913 26 in 1913
Calistoga 25 in 1918 25 in 2006 25 in 2006
Kentfield 27 in 1932 27 in 1913 29 in 1953
San Rafael 32 in 1990 32 in 2006 33 in 1955
Napa 29 in 1990 28 in 1920 29 in 1955
San Francisco 38 in 1897 38 in 1897 36 in 1890
SFO Airport 36 in 1990 37 in 2011 34 in 1955
Half Moon Bay 34 in 1954 32 in 2013 31 in 2006
Oakland Airport 35 in 1955 34 in 2006 33 in 1955
Richmond 35 in 1990 35 in 1990 35 in 1981
Livermore 27 in 1956 28 in 1942 27 in 1955
Moffett Field 35 in 1949 34 in 2006 32 in 1955
San Jose 32 in 1990 30 in 1897 25 in 1897
Gilroy 27 in 1964 30 in 1990 31 in 1976
Monterey Bay Area
Santa Cruz 30 in 1990 29 in 1913 30 in 1955
Salinas 29 in 1990 31 in 2006 31 in 1970
Salinas Airport 29 in 1933 28 in 1953 30 in 1953
Monterey 35 in 1990 35 in 2006 36 in 1952
King City 25 in 1955 22 in 1953 23 in 1953
.MARINE...As of 9:02 PM PST Sunday...A 1039 mb high is centered
800 miles west of Cape Mendocino while a 995 mb low is over Utah.
The strong pressure gradients will bring gusty northerly winds
through Monday night. Winds will decrease Tuesday as the low moves
east but another system may affect the area later in the week.
.Tngt...Winter Weather Advisory...Santa Cruz Mountains and
Santa Lucia Mountains
SCA...Pt Arena to Pt Reyes 0-10 nm
SCA...Pt Reyes to Pigeon Pt 0-10 nm
SCA...Pigeon Pt to Pt Pinos 0-10 nm
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
GLW...Pt Arena to Pigeon Pt 10-60 nm
GLW...Pigeon Pt to Pt Piedras Blancas 10-60 nm
PUBLIC FORECAST: Dykema
AVIATION: W Pi
MARINE: W Pi
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