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Office: EKA

FXUS66 KEKA 112206
AFDEKA

AREA FORECAST DISCUSSION
National Weather Service Eureka CA
206 PM PST Mon Dec 11 2017

.SYNOPSIS...Mainly dry conditions, accompanied by mild afternoons
and cool nights, will persist during the next 7 days.

&&

.DISCUSSION...A compact upper low positioned offshore from WA was
in the process of moving north along the west side of a WRN CONUS
ridge Monday afternoon. An increase in midlevel southerlies
associated with the wave was aiding in transporting smoke produced
by wildfires in SRN CA northward across the Redwood Coast.
However, model guidance during the next 24 hours shows midlevel
flow becoming northerly over the CNTRL/SRN CA coast, which will
allow smoke to clear the region during Tuesday into Wednesday.
Otherwise, high level cirrus is forecast to increase during
midweek, resulting in a decrease in nocturnal surface radiational
cooling and cold air drainage into area valleys. Thus, overnight
lows are expected to gradually moderate. By Friday, model guidance
shows the ridge over the west coast breaking down as a weak upper
impulse moves west across the region. This process will allow an
increase in westerly moisture flux to develop over the OR/WA
coast during the weekend into early next week, the brunt of which
is forecast to be too far north to yield significant rain
probabilities over NWRN CA.

&&

.AVIATION...A persistent strong ridge will continue to result in
VFR conditions at all terminals. Some smoke aloft and high clouds
have been noted at both ACV and UKI today due to the fires down
south. Some interior river valleys will also see patchy fog again
tomorrow morning however it will clear by late morning. /WCI

&&

.MARINE...Quiet marine weather pattern will continue through
Tuesday. A strong high pressure remains over western North
America, while the main storm track remains offshore. By middle of
the week, a thermal trough is forecasted to develop along the CA
coast, and this will enhance the northerly pressure gradient over
NW CA waters at that time. A strong high will build north of NW CA
water by the end of the work week, and this will further tighten
the northerly pressure gradient in the area.

Light and variable winds in NW CA coastal waters through Tuesday.
North winds will start to increase on Tuesday night to around 10
to 20 kt. North winds will further increase on Friday to 15 to 25
kt, before diminishing through the weekend.

Through Tuesday, we will just be seeing decaying west swell,
giving us a combined seas of around 5 to 7 feet. On Tuesday night,
looks like we will have a fresh NW swell coming in, with a
developing short period wind wave. Combined seas will be around 7
to 9 feet. The short period wind wave will increase later this
week as the northerly winds strengthen.

There is a slight potential for sneaker wave late Tuesday
afternoon through Tuesday evening. However, there is some forecast
uncertainty with this. The long period swell is marginal in terms
of its energy. The wave period will be decreasing, from 18 to 15
seconds. Meanwhile, the wave magnitude will increase from 1 to 5
feet. In addition, the short period wind wave may erode the energy
provided by the long period swell. The short period wave is
forecasted to be around 3 to 6 feet. The higher the magnitude of
the wind wave, the less likely the threat for sneaker wave. Due to
these conflicting indicators, confidence is low in determining
the potential for sneaker wave, but the threat does exist at this
time.

There is no marine hazards in effect at this time. /RCL

&&

.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...None.
&&

$$

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Office: HNX FXUS66 KHNX 120926 AFDHNX Area Forecast Discussion National Weather Service San Joaquin Valley - Hanford CA 126 AM PST Tue Dec 12 2017 .SYNOPSIS...High pressure will remain over the region for the next several days with continued dry weather. && .DISCUSSION...Very dry easterly flow aloft continues this morning as the rex block pattern of high pressure to the north and low pressure to the south of the Central California Interior continues. Many many consecutive hours of single digit relative humidity values in the Sierra and foothills where the dry air can move in from the east. Other locations facing the San Joaquin Valley are being influenced by air that is not as dry. With the calender saying mid December, the long nights. dry air and clear skies are allowing for a continuation of cold overnight temperatures at most lower elevation locations and this trend will continue for the next several days. High pressure aloft has really locked in an inversion at elevations ranging from 4500 to around 7500 feet over the entire area and below this inversion there is very little mixing of air. Over the San Joaquin Valley, terrain is trapping the airmass and daily increases in particulate matter will cause increasingly dirtier air which may allow for additional fog formation. Over the past few nights, fog has been very isolated with most locations seeing visibility reduced to about one mile at the worst. This situation is not causing much concern from a traffic perspective and even though airport sensors may show a downward trend in visibility, values have not reached critical levels for impacts on transportation. Will continue to monitor overnight in case things change. Forecast models keep the ridge in place over the region for the next several days, and shunt any incoming Pacific weather systems well to the north. One is progged to move across Oregon and into the Great Basin on Friday night however the only affect over the forecast area may be some high clouds. Through Tuesday of next week, forecast models continue to hold the ridge in place for dry weather. After Tuesday, the latest ECMWF model develops and drives into the area a deep, closed low. It must be noted that this solution was NOT present on the previous run of this model. Additionally the GFS is hinting at a deepening trough and a fundamental shift in the longwave pattern way out Wednesday of next week. Model accuracy gets RATHER LIMITED this far into the future, therefore as of today this forecaster is not putting too much confidence in this change in the pattern. The pattern will undoubtedly change sometime and maybe for only for a short time. As of this morning a wait and see approach seems to be the most reasonable way to proceed. && .AVIATION... Widespread MVFR visibility in haze and mist will persist in the San Joaquin Valley, with areas of IFR and local LIFR/VLIFR in fog developing until 18Z Tuesday. Otherwise, VFR conditions will prevail over the central CA interior during the next 24 hours. && .AIR QUALITY ISSUES... On Tuesday December 12 2017... Unhealthy in Kern County. Unhealthy for sensitive groups in Fresno... Kings and Tulare Counties. Fireplace/Wood Stove Burning Status is: No Burning Unless Registered in Fresno... Kings... Madera... Merced and Tulare Counties. No Burning For All in Kern County. Further information is available at Valleyair.org && .CERTAINTY... The level of certainty for days 1 and 2 is high. The level of certainty for days 3 through 7 is high. Certainty levels include low...medium...and high. Please visit www.weather.gov/hnx/certainty.php for additional information an/or to provide feedback. && .HNX Watches/Warnings/Advisories... NONE. && $$ public...Dudley avn/fw...BSO synopsis...Dudley weather.gov/hanford
Office: LOX FXUS66 KLOX 120631 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 1031 PM PST Mon Dec 11 2017 .SYNOPSIS... Gusty offshore winds, warm afternoon temperatures, and dry conditions will persist through the week. Smoke from the fires will impact regional air quality through the week as well. && .SHORT TERM...(MON-THU) High pressure aloft with offshore flow closer to the surface continues to cling to the area this evening. A trough of low pressure over northern Mexico continues to undercut the ridge and reinforce offshore flow. Offshore gradients will tighten Tuesday morning as vorticity maximum moving east to west moves over the area. Surface pressure gradients should turn more offshore behind the vorticity maximum and reinforce the overall offshore flow. Winds should remain below advisory levels into Tuesday as upper- level wind and low-level thermal support looks marginal. Model solutions do indicate some breezy to locally windy conditions developing supporting the current Red Flag Warning, but remaining just below advisory criteria. Weaker offshore flow this evening is allowing for a cooler start to the night and temperatures have been cooled for the forecast for tonight. Patchy to areas of frost have been added to the forecast for some of the interior valleys and wind-sheltered locations. Temperature were dropped substantially along the Central Coast and in the Cuyama and Ojai Valley. No frost advisories were added as air mass may be too dry to support frost or not enough coverage exists to support an issuance. In addition, most other locations that will solid at or below freezing have experienced two prior frost or freeze events already. *** FROM PREVIOUS DISCUSSION *** Very similar weather conditions expected across the 4 county area through mid week. Light offshore flow generating 15-25 mph Santa Anas across Ventura and LA Counties (some isolated gusts to 35 mph in the mountains) but no Sundowners expected in SB County which is good news for people in the vicinity of the Thomas fire. There have been some ridge winds along the Santa Ynez range generally in the 10-15 mph range but that's about it and even lighter down at lower elevations. The pattern changes very little through mid week so what you see today is what you'll likely get through Thu. Temperatures will remain 10-15 degrees above normal in most areas except where thick smoke is obscuring the sun. .LONG TERM...(FRI-MON) An upper low will move into the Pac NW Friday and into the Rockies Saturday. Onshore trends ahead of it will cool temps a few degrees Fri/Sat but still well above normal. Models going back and forth on how much offshore flow will develop behind it Sunday and Monday but the 12z runs were pretty light with the gradients. So a slight warm up expected Sun/Mon with the weak offshore push but at this time it doesn't look like we'll see any significant Santa Anas or Sundowners from it. && .AVIATION...12/0630Z. At 06Z, there was no marine inversion at KLAX. VFR conditions are expected throughout the period, except for a chance of MVFR conditions in smoke at coastal and valley terminals across SBA, SLO and VTU counties. Periods of moderate low-level wind shear and turbulence are possible Ventura County terminals through 20z. KLAX...VFR conditions are expected throughout the period. There is a 30 percent chance of MVFR conditions in smoke through 010Z. Any east winds should remain less than 7 knots. KBUR...VFR conditions are expected throughout the period. No wind issues are expected at this time. && .MARINE...11/900 PM. For the Inner Waters south of Point Conception, winds will remain below SCA strength tonight through Wednesday. The near shore waters north of Point Sal will remain below SCA level through at least early Friday. Elsewhere, winds and seas are expected to remain below Small Craft Advisory levels through Thursday, and then rise to SCA level from the northwest on Friday. There is a 30 percent chance of Gale level winds for the Outer Waters North of Point Conception sometime Friday or Saturday. There will be areas of smoke from the Thomas fire over portions of the Coastal Waters, mainly from the waters west of Ventura County through the Santa Barbara Channel and over the outer waters. Local visibilities could possibly drop to near one nautical mile or lower at times. && .FIRE WEATHER...11/100 PM. The Red Flag Warnings have changed. It has been EXTENDED to 8 PM Wednesday for the Los Angeles and Ventura Interior Mountains. It has been EXTENDED to 8 PM Tuesday for the Ventura Coasts, Ventura Valleys, the Santa Clarita Valley, and the Santa Monica Mountains. It is NO LONGER in effect for the Los Angeles Coasts, the San Gabriel Valley, and the San Fernando Valley due to the winds aloft being more easterly than before, which has weakened the winds significantly in those areas. Little change is expected through Thursday. The extended period of offshore flow will continue, but will be half as strong as what occurred last week. Expect daily peak gusts in the 20 to 40 mph range...but some weakening is expected Wednesday into Thursday. The humidities will remain incredibly dry with extremely poor overnight recoveries nearly everywhere. San Luis Obispo and Santa Barbara Counties will continue to see periods of north to east winds (gusts of 15 to 25 mph) through Thursday morning, including areas near the Thomas Fire. While these winds are NOT Sundowner winds in terms of strength and source, they will combine with the continued warm and very dry conditions to result in elevated to near critical fire weather conditions. In addition, the air mass is fairly unstable above the Thomas Fire through Wednesday, resulting in a greater risk for large fire plumes which will locally enhance winds near the fire. Some improvement is expected for Friday into Saturday as the winds shift to more westerly, but more offshore flow is possible beginning Saturday night or Sunday. If fire ignition occurs, very rapid spread and extreme fire behavior is likely. Those near current wildfires need to stay aware of and follow official evacuation orders. Everyone needs to exercise extreme caution when handling any potential fire ignition sources...such as campfires, cigarettes, welding and brush clearing equipment. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Red Flag Warning in effect until 8 PM PST Tuesday for zones 240-244>246-288. (See LAXRFWLOX). Red Flag Warning in effect until 8 PM PST Wednesday for zones 253-254. (See LAXRFWLOX). PZ...NONE. && .HAZARD POTENTIAL OUTLOOK...(THU-MON) Critical fire weather conditions possible Thursday with light offshore winds and single digit humidities. && $$ PUBLIC...Hall/MW AVIATION...Kaplan MARINE...Kaplan FIRE...Kittell SYNOPSIS...Kj weather.gov/losangeles
Office: STO FXUS66 KSTO 120527 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 925 PM PST Mon Dec 11 2017 .Synopsis... Dry weather into early next week with mild days and chilly nights. && .Discussion... High cloudiness mostly over the Srn portion of the CWA eroding this evening paving the way for clear skies and good radiational cooling again tonite. RHs generally lower in our CWA than last nite, so fog should remain local, patchy, or ground fog. The exceptions would be VCB, SUU, EDU (Davis) where the dewpoints are a little higher. Winds should go L/V overnite, more conducive for fog than the light NWly. JHM Strong blocking pattern continues along the West Coast. As a result, dry conditions will persist across interior NorCal with mild days and chilly nights. Afternoon temperatures are running a few degrees lower compared to 24 hours ago, with Valley locations generally in the 60s. Atmospheric pattern remains relatively unchanged as the ridge remains anchored overhead and dry weather persists. Some patchy morning frost or fog will be possible in the Central Valley. Daytime highs are forecast to be several degrees above normal, with an area of 30 yr return intervals at 850 mb that supports possible record highs across portions of the northern Sacramento Valley. && .EXTENDED DISCUSSION (Friday THROUGH Monday) A trough will be pushing into the PacNW to start the extended period. This will push a cold front through NorCal with no precip expected. The ridge will build back in for the weekend continuing our streak of dry weather. High temperatures will remain mild throughout the extended period running 6-12 degrees above normal with near normal overnight lows. -CJM && .AVIATION... VFR conditions expected over the next 24 hours at TAF sites. Areas of HZ increase after sunset and local areas of MVFR/IFR at the southern terminals between 12 and 16z Tuesday due to patchy fog. Winds remain light under 10 knots. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$
Office: SGX FXUS66 KSGX 121008 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 208 AM PST Tue Dec 12 2017 .SYNOPSIS... High pressure aloft and weak offshore flow at the surface will continue warm dry weather into next week. Brisk offshore winds will occur mainly in the foothills during most nights and mornings. Skies will be mostly clear. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... We're forecasting very persistent weather from day to day this coming week. Barely perceptible is a subtle drop this morning in humidity across most areas. Winds are about the same as on Monday morning, with a few foothill areas gusting over 30 mph. This picture will appear much the same on Wednesday. On Thursday a coastal eddy will increase the humidity near the coast, but low clouds and fog are not likely. In fact, we only expect a few high clouds from time to time. Tis the season for dry offshore flow, interspersed with winter storms. We're just not getting the winter storm part. High pressure aloft will persist over Alta California along with a stationary upper low over Baja California. The resulting easterly flow over Southern California will provide most nights and mornings with areas of brisk offshore winds in the foothills. High temperatures will be 5 to 15 degrees higher than average, meaning a lot of 70s and 80s at lower elevations. A shortwave trough scoots through the interior West Friday night and Saturday, forcing a touch of onshore flow that will bring us our coolest day in the coming week with upper 60s and 70s. That will be immediately followed by a boost in offshore flow and warmer weather Sunday into Monday. The storm door has been closed and locked, thanks to a persistent high amplitude ridge of high pressure along the West Coast. There are some signs that maybe enough lows or troughs will knock or even bang on the western ridge enough to finally break through the door and allow storms to come in. Both the GFS and Euro models show a general long wave switch: the western ridge for the eastern trough. That is indicated ten days out around 21 or 22 December, which is in weather fantasy land. && .AVIATION... 120955Z...Mostly clear with unrestricted vis through Wednesday morning. && .MARINE... No hazardous marine weather is expected through Saturday. && .FIRE WEATHER... Very dry weather will continue this coming week, with brisk offshore winds mainly in the foothills through Wednesday. Slightly higher humidity is expected Thursday through Saturday and winds will be light. Offshore flow redevelops Sunday into Monday for dry weather again along with brisk offshore winds mainly in the foothills. A higher than average fire danger will persist as fuels and air remain very dry, but critical fire weather conditions are not expected. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC/FIRE WEATHER...MM AVIATION/MARINE...SS
Office: MTR FXUS66 KMTR 120514 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 914 PM PST Mon Dec 11 2017 .SYNOPSIS...Strong high pressure will remain in place through much of the week and result in dry weather conditions along with above average daytime temperatures. Clear skies and weak offshore flow will allow for cool overnights which will warm slightly late in the forecast period as onshore winds return. && .DISCUSSION...as of 9:00 PM PST Monday...High pressure at the surface and aloft over the Great Basin continues to bring offshore flow to the area with well-above normal temperatures. The airmass continues to be extremely dry with the 00Z OAK sounding showing pw value of 0.13 inches. The ridge will start to retrograde on Tuesday and will move off the California coast on Wednesday. This will still have an influence on the area and temperatures will continue to run 5 to 10 degrees above normal. 850 mb temperatures actually rise slightly on Wednesday so have adjusted forecast highs higher. Should see highs in the mid to upper 60s across the SFO Bay Area with 70s from the Santa Clara Valley south. Surface high weakens over the next couple of days but pressure gradients are still higher inland through Wednesday so weak offshore flow will continue. By Thursday pressures equalize between the coast and the interior so a seabreeze should finally bring some humidity into the area. The ridge flattens out Friday as an upper level shortwave moves through the Pacific Northwest. A weak front associated with this system fizzles out before reaching any part of the district. The only impact from this system will be slightly cooler temperatures. The ridge rebuilds Saturday but a little farther off the west coast so temperatures will not get as warm as they have been this week. Longer range guidance suggest a potential change in the weather pattern sometime next week that might bring light precipitation to portions of the state. However confidence is low at this time and will need to be monitored in the coming days. Until then look for ongoing dry weather conditions and above average daytime temperatures to persist. && .AVIATION...As of 5:40 PM PST Monday...for 00Z TAFs. VFR except patchy fog is possible tonight over KSTS. Vicinity of KSFO...VFR. Light to calm wind through the forecast period. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...VFR. Generally light offshore winds. && .MARINE...as of 2:10 PM PST Monday...Light to moderate winds will continue along the Central Coast as high pressure remains over the region. Winds will gradually increase out of the north midweek. A longer period swell arrived today and will impact the coast thru midweek. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...NONE. && $$ PUBLIC FORECAST: W Pi/RGass AVIATION: Canepa MARINE: CW Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea FXUS66 KMTR 120543 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 943 PM PST Mon Dec 11 2017 .SYNOPSIS...Strong high pressure will remain in place through much of the week and result in dry weather conditions along with above average daytime temperatures. Clear skies and weak offshore flow will allow for cool overnights which will warm slightly late in the forecast period as onshore winds return. && .DISCUSSION...as of 9:00 PM PST Monday...High pressure at the surface and aloft over the Great Basin continues to bring offshore flow to the area with well-above normal temperatures. The airmass continues to be extremely dry with the 00Z OAK sounding showing pw value of 0.13 inches. The ridge will start to retrograde on Tuesday and will move off the California coast on Wednesday. This will still have an influence on the area and temperatures will continue to run 5 to 10 degrees above normal. 850 mb temperatures actually rise slightly on Wednesday so have adjusted forecast highs higher. Should see highs in the mid to upper 60s across the SFO Bay Area with 70s from the Santa Clara Valley south. Surface high weakens over the next couple of days but pressure gradients are still higher inland through Wednesday so weak offshore flow will continue. By Thursday pressures equalize between the coast and the interior so a seabreeze should finally bring some humidity into the area. The ridge flattens out Friday as an upper level shortwave moves through the Pacific Northwest. A weak front associated with this system fizzles out before reaching any part of the district. The only impact from this system will be slightly cooler temperatures. The ridge rebuilds Saturday but a little farther off the west coast so temperatures will not get as warm as they have been this week. Longer range guidance suggest a potential change in the weather pattern sometime next week that might bring light precipitation to portions of the state. However confidence is low at this time and will need to be monitored in the coming days. Until then look for ongoing dry weather conditions and above average daytime temperatures to persist. && .AVIATION...As of 9:43 PM PST Monday...for 06Z TAFs. VFR except patchy fog is possible tonight over KSTS. Vicinity of KSFO...VFR. Light to calm wind through the forecast period. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...VFR. Generally light winds except E-SE wind near 10 knots late tonight into early Tuesday afternoon at KSNS. && .MARINE...as of 9:35 PM PST Monday...A high pressure ridge covers the offshore waters and far northern California and connects to a strong high center over the interior west. High pressure over the interior west will weaken by late this week and the offshore ridge will remain nearly stationary. A nearly dry cold front located within a very weak, barely discernible trough over the eastern Pacific will sweep at a moderate speed to the south across the coastal waters Friday night into early Saturday morning. Steadily larger, longer period swell will impact the coast mid to late week. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...NONE. && $$ PUBLIC FORECAST: W Pi/RGass AVIATION/MARINE: Canepa Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea