Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 262136
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
236 PM PDT Tue Mar 26 2024

.SYNOPSIS...Another frontal system will produce lowland rain,
mountain snow, and breezy conditions on Wednesday. An area of low
pressure over the region will produce showery, unsettled
conditions into Friday before high pressure rebuilds early next
week for a warming and drying trend.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY/...Scattered showers continue
across parts of Western Washington this afternoon, but these will
diminish this evening before the next round of rain spreads
onshore overnight with another front. Breezy to windy conditions
are expected with the front, but winds should be below advisory
levels. Snow levels take a brief jump to 4000 to 4500 feet ahead
of the front. This combined with a lack of any significant onshore
punch behind the front will limit snowfall potential and keep
totals under advisory criteria at the passes. The rain will turn
to showers by Wednesday afternoon as the front shifts onshore.
The post-frontal air mass will be modestly unstable tomorrow as
500 millibar temps drop to around -30 C. That`ll be enough for the
mention of a slight chance of thunder mainly near the coast. A
vertically stacked trough will remain offshore into Friday as it
weakens. This will keep showers in the forecast into Friday along
with temperatures a little below seasonal norms.

.LONG TERM /SATURDAY THROUGH TUESDAY/...Signs of change emerge
over the weekend as the offshore trough digs southward into
central/southern California and eventually the Desert Southwest by
early next week. This translates to some upstream ridging building
into southern British Columbia and much of the Pacific Northwest.
The end result will be a warming and drying trend moving into the
early part of next week. This ridge won`t be the same magnitude
as that of mid-March, but it does appear that many areas could
see the return of high temps in the lower to mid 60s. Uncertainty
in the forecast increases by Tuesday...mainly due to model spread
regarding the staying power of the ridge. Ensembles generally
agree that unsettled conditions will return by the middle of next
week. 27

&&

.AVIATION...A weak upper level ridge will follow a weakened occluded
front that passed through earlier this morning. Post frontal showers
will continue, but convergence zone activity has weakened from
earlier. The ridge is helping to lift ceilings to VFR levels this
afternoon (with an isolated area of MVFR between KPAE/KAWO that is
improving). Ceilings will scatter out through the afternoon and
evening. Winds will remain out of the southwest/west at around 10 to
15 kt with gusts to 20 kt, but will diminish to around 5 kt and
become southeasterly overnight.

For Wednesday, a surface weather system will swing a weakening
warm/cold front into the region. Ceilings will lower to MVFR by mid
to late Wednesday morning. Winds will increase out of the southeast
to around 10 kt late tomorrow morning. Stronger winds to 20 kt and
higher are possible around the east entrance of the east Strait of
Juan de Fuca, and coastal waters. Showers/stratiform rain is
expected with this system, with a slight chance of a thunderstorm.
The thunder chances will be concentrated along the coast all of
Wednesday, with potential Wednesday afternoon further inland.
Confidence is low in potential hazards/timing, so will not include
any thunder chances in the TAFs at this time.

KSEA...CIGs have improved to VFR this afternoon - will continue to
scatter out some and lift. Surface system tomorrow returns MVFR
ceilings mid to late Wednesday morning as rain showers arrive early
in the morning. Slight chance of thunder exists in the afternoon,
but confidence is too low to put in the TAF forecast at this time.

HPR

&&

.MARINE...Post frontal showers continue across inland waters this
afternoon with southerly winds at the surface. A surface low will
bring the chance of rain with a couple possible thunderstorms early
Wednesday morning, and into the day. Winds are expected to increase
out of the south late tonight into Wednesday ahead of the first
surface front passing through. The gusty winds will start in the
coastal waters first, before spreading into the Strait of Juan de
Fuca, Northern Inland Waters, and Admiralty Inlet. Current
headlines/hazards in effect for gales/small crafts will continue.
Another period of gusty winds to 25 kt will pass through all
waterways Thursday into Friday. The weekend will see quiet winds
across the waters.

Seas 5 to 7 ft at 13 seconds will build tonight/Wednesday to around
10 to 13 ft, increasing again early Thursday to 13 to 16 ft, before
easing below 10 ft by the end of the week.

HPR

&&

.HYDROLOGY...A frontal system will cross the region Wednesday and
Wednesday night. Snow levels rise from around 3000 feet today to
near 4500 feet Wednesday morning ahead of the front. Total
rainfall amounts of 1.5-2.5 inches is expected across the southern
Olympic Mountains, which will lead to rises on areas streams and
rivers. No river flooding is forecast at this time, though the
Skokomish River is forecast to rise into Action Stage Wednesday
afternoon and into the latter portion of the week.

Davis


&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 2 AM to 2 PM PDT Wednesday for Central
     U.S. Waters Strait Of Juan De Fuca-West Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Gale Warning from 2 AM to 5 PM PDT Wednesday for East Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 5 AM to 5 PM PDT Wednesday for
     Admiralty Inlet-Northern Inland Waters Including The San
     Juan Islands.

     Gale Warning from 10 PM this evening to noon PDT Wednesday for
     Coastal Waters From Cape Flattery To James Island 10 To 60
     Nm-Coastal Waters From Cape Flattery To James Island Out 10
     Nm-Coastal Waters From James Island To Point Grenville 10
     To 60 Nm-Coastal Waters From James Island To Point
     Grenville Out 10 Nm-Coastal Waters From Point Grenville To
     Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point
     Grenville To Cape Shoalwater Out 10 Nm.

     Small Craft Advisory from noon to 11 PM PDT Wednesday for
     Coastal Waters From Cape Flattery To James Island 10 To 60
     Nm-Coastal Waters From James Island To Point Grenville 10
     To 60 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater 10 To 60 Nm.

&&

$$


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