wa discuss
Office: SEW
FXUS66 KSEW 182102
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
202 PM PDT Thu Apr 18 2024
.SYNOPSIS...Pleasant conditions tonight and Friday as an upper
level ridge offshore moves across the area Friday. Slow moving
frontal system brings the next chance for showers Saturday night
into Sunday. Weak upper level ridge over Western Washington
Monday into Tuesday replaced by a weak upper level trough Tuesday
night and Wednesday.
&&
.SHORT TERM /TONIGHT THROUGH SUNDAY/...A very pleasant day across
western Washington today with temps in the upper 50s to low 60s
and clear skies. Dewpoints are a bit higher and with a little bit
more wind overnight expected across the area, currently not
expecting widespread frost, with low temperatures a touch warmer,
in the upper 30s to low 40s, except in the low to mid 30s through
the Southwest Interior.
Clear skies expected again tomorrow as a weak upper-level ridge
moves into the region. With a thermal surface trough, winds will
be primarily easterly, and may be a bit breezy through the gaps in
the terrain. These conditions set up for a warmer day on Friday,
with highs reaching into the upper 60s to lower 70s, especially
through the Southwest interior up into the Cascade foothills south
and west of Seattle (50-70% probabilities). Low temperatures will
also be warmer, into the low to mid 40s.
An upper level trough will swing into the area Saturday into
Sunday, bringing with it a surface low pressure system. With
trough strongly negatively tilted, rain will work its way slowly
from southwest to northeast. Rain will begin on the southwest
coast Saturday morning with areas Seattle and north staying mostly
dry until Saturday evening. Temperatures still above average, in
the mid 60s, with offshore flow becoming southerly and breezy
ahead of the front Saturday night into Sunday. Lows in the low to
mid 40s.
Scattered showers continue across the region into Sunday. A few
lightning strikes are possible late Saturday night into Sunday
behind the frontal passage, but instability should be fairly
limited and restricted to the Pacific coast. Sunday will be much
closer to normal with high temperatures in the mid to low 50s.
With snow levels ranging from 5000 ft on Saturday down
to around 3500 ft on Saturday, not expecting significant
accumulations on the passes, with an inch or two possible on
Stevens Pass and along the soon- to-be-open Route 20. Three-
quarters to an inch of rain is possible along southwest facing
portions of the Olympics and the North Cascades, with a tenth of
an inch possible in the lowlands and up to a quarter of an inch
along the coast.
.LONG TERM /MONDAY THROUGH THURSDAY/...Deterministic and ensemble
guidance both indicate an upper level ridge developing over the
area on Monday for another warmer and drier period with highs back
in the 60s. Tuesday should also be on the warm side mostly dry
across the area. There is also good consensus on an upper level
trough developing and moving into the area Tuesday night into
Wednesday. Moisture looks to be be very limited, with only a
handful of ensemble members showing the potential for rain making
it into the interior Wednesday and beyond. Temperatures
accordingly cool back closer to normal.
LH
&&
.AVIATION...Flow aloft will remain out of the northwest through the
TAF forecast as an upper level ridge continues to build offshore. A
thermal trough also remains positioned off the coast. Weather
remains dry as well with VFR conditions/clear skies expected. A
couple pockets of frost are possible overnight (although overnight
temperatures are slightly warmer than the previous night) - but no
fog is expected for Friday morning with dry grounds/upper level
ridging. Gusty north winds up to 20 kt remain possible through
Thursday afternoon - which will decrease to under 5 kt and become
northeasterly for Friday - picking up again in the afternoon to 20
kt.
KSEA...VFR/clear skies through the TAF period. Gusty winds out of
the north Thursday afternoon at 20 kt will diminish overnight to
around 5 to 8 kt northeasterlies, and pick up out of the north again
Friday.
HPR
&&
.MARINE...An upper level ridge will begin to move inland
tonight/Friday. A thermal trough remains positioned off the coast of
Washington. Northerly winds (with easterlies in the Strait of Juan
de Fuca) will continue through Friday. Gusty winds to 20 kt have
been observed in Puget Sound and central Strait of Juan de Fuca
waters this afternoon, but are expected to remain largely under
criteria needed for a small craft advisory. However, the next
approaching system for this weekend will increase gradients in the
central Strait of Juan de Fuca Friday (with stronger easterly winds
to 25 kt). A small craft advisory was issued Friday morning through
the evening. Additional gusty winds are possible Saturday and Sunday
with the next system.
Seas remain around 3 to 6 ft through Saturday, before rising to 8 to
10 feet Sunday.
HPR
&&
.HYDROLOGY...No river flooding is expected in the next seven days.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&
$$
Office: OTX
FXUS66 KOTX 182158
AFDOTX
Area Forecast Discussion
National Weather Service Spokane WA
258 PM PDT Thu Apr 18 2024
.SYNOPSIS...
Cool and showery conditions continue today, before drying out and
becoming breezy Friday. Showers return for Saturday evening
through Sunday. Mild and dry weather returns for the start of
work week while showers arrive by mid week.
&&
.DISCUSSION...
Tonight through Saturday night: Showers have popped up again this
afternoon across the Eastern WA and ID Panhandle. So far we have had
reports of light snow, rain, and graupel with these showers. Expect
daytime temperatures to cool in the showers. Temperatures at our
office dropped from 47F to 39F as the showers passed through,
warming again behind to 45F about an couple hour later. In areas
that won't see showers, daytime highs remain cool in the 50s.
Showers and winds will weaken in the early evening hours.
An upper level low will dig across the region that will tighten the
pressure gradient, creating gusty winds across the Columbia Basin.
Northeast winds will gust to 35 mph in the afternoon, decreasing
overnight. Besides the wind, conditions will warm slightly and dry
out, leaving sunny conditions for the region.
Weak ridging will build for Saturday, with another dry, sunny and
slightly warmer start to the day. Upper level clouds will move in
from the west ahead of the next system arriving Sunday. /KM
Sunday through Tuesday: A shortwave trough is on track to approach
from the west Saturday night into Sunday, increasing cloud cover and
bringing back chances for showers over the mountains. With the
arrival of this wave, winds will be breezy through the day on Sunday
gusting to 25-30 mph across the region. A cold front associated with
the shortwave will drop snow levels to 3-4 kft by Sunday morning, so
any mountain showers will likely be in the form of snow.
The breezy, showery weather will be short-lived, as weak ridging
will return to start off the workweek. Dry and mild weather looks to
prevail through at least the first half next week with temperatures
rising slightly above normal by Tuesday.
Temperatures will start off rather cold Monday morning in the low
30s, but will be quick to warm up after sunrise. Highs for Monday
will be in the low 60s for most locations, and on Tuesday they'll
reach the upper 60s to low 70s.
Beyond Tuesday, forecast confidence dwindles. Models disagree on how
long the ridging pattern will stick around before our next low
pressure system moves in. Most models are hinting at the next low
approaching the Washington coast sometime in the Tuesday
night/Wednesday timeframe, putting us in a mild southwest flow
regime with intermittent showers through the end of the week. More
info to come on how that pattern change will play out as it gets
closer. /Fewkes
&&
.AVIATION...
00z TAFS: Showers have redevelop this afternoon, but confidence
of them going over any particular TAF location is low. VFR
conditions will prevail.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is high
confidence in VFR conditions through the TAF period.
-----------------------
Confidence descriptors:
Low - Less than a 30 percent chance
Moderate - 30 to 70 percent chance
High - Greater than a 70 percent chance
For additional probabilistic information for NWS Spokane airports,
please refer to the Aviation Dashboard on our webpage:
https://www.weather.gov/otx/avndashboard
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 32 56 33 64 39 57 / 0 0 0 0 40 30
Coeur d'Alene 30 54 31 63 38 54 / 10 0 0 0 50 40
Pullman 30 56 33 64 37 52 / 0 0 0 0 60 30
Lewiston 35 64 36 71 43 61 / 0 0 0 0 50 20
Colville 27 56 26 63 35 58 / 10 0 0 0 40 50
Sandpoint 30 51 31 59 38 51 / 10 0 0 0 50 60
Kellogg 30 51 32 62 39 49 / 20 0 0 0 60 60
Moses Lake 36 63 38 69 40 63 / 0 0 0 0 20 10
Wenatchee 37 60 37 63 41 59 / 0 0 0 0 20 10
Omak 35 61 34 65 40 64 / 0 0 0 0 30 10
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&
$$
