Heavy Snow in Washington, April 1 to 3, 2023

Area Forecast Discussion
National Weather Service Seattle WA
940 PM PDT Fri Mar 31 2023

.SYNOPSIS...A frontal system over the interior will reach the
Cascades by midnight. Lowland rain, breezy winds, and increasing
mountain snow with the front. Upper troughing will be across the
Pacific Northwest through the weekend for unsettled weather,
including isolated thunderstorms. Another subtle upper low will
bring showers Monday into Tuesday. Drier weather mid-week with
ridging offshore.

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.SHORT TERM /TONIGHT THROUGH MONDAY/...Satellite imagery shows
frontal system over the interior of Western Washington this
evening. Surface observations put the front through Forks at 02z
and Hoquiam at 03z. Doppler radar shows a steady rain coming to an
end quickly behind the front. Both Forks and Hoquiam not reporting
rain at 04z. Temperatures at 9 pm/04z were in the upper 30s to
mid 40s.

Front moving through Seattle in the next hour reaching the
Cascades around midnight. Satellite imagery has a large field of
cold cu behind the front offshore. This air mass will be moving
over the area early Saturday morning. No real changes in the
first look at the 00z models with cold upper level trough over the
area for the weekend. Showers with the chance of afternoon and
early evening thunderstorms or small hail showers will be the
forecast both days. Temperatures will remain well below normal
with highs both days having a hard time getting much warmer than
50 degrees. Trough moves east Sunday night into Monday only to be
replaced by another cold upper level low later Monday keeping
showers in the forecast. Highs on Monday near 50. Since records
started at Seattle-Tacoma airport in 1945 there has only been two
years where the first 3 days of April had highs less than 50
degrees, 2011 when the first 7 days of April had a high below 50
and 1948 when the first 4 days had a high below 50.

Current forecast in good shape tonight. No update. Felton

.LONG TERM /TUESDAY THROUGH FRIDAY/...Previous discussion follows.
Troughing will slide eastward on Tuesday with lingering showers
dissipating later Tuesday into Tuesday night. Generally decent
agreement in guidance and ensembles for mid-week with ridging
building offshore for a likely brief period of drier weather. NBM
continues to keep slight chance of POPs on Wednesday given some
uncertainty of lingering showers, so kept in the forecast.
Uncertainty increases Thursday into late week in regards to the
extent ridging influences the Pacific Northwest, or perhaps more
southwest flow bringing increasing precipitation potential, with a
chance of precipitation both Thursday and Friday. Temperatures
will warm through the week with the ridging influence, with highs
warming into the mid to upper 50s by late week across the area. JD

&&

.AVIATION...Frontal passage tonight with cool upper level trough
moving into Western Washington Saturday. Southwesterly flow aloft
becoming westerly Saturday. Post frontal low level onshore flow
will continue through Saturday.

Ceilings 1500-2500 feet with the front will isolated ceilings
below 1000 feet and visibility 3-5sm in moderate rain. Ceilings
lifting to VFR after midnight then lowering back down to MVFR
Saturday morning. Ceilings improving again Saturday afternoon back
up to VFR. Isolated thunderstorms possible 20z-03z.

KSEA...Ceilings near 2000 feet improving to near 3500 feet after
midnight. Ceilings lowering back down to mvfr 11z-15z Saturday
morning. Ceilings improving again back up to VFR after 20z
Saturday. South wind 6 to 10 knots increasing to 10 to 15 knots
with gusts to 25 knots around 18z. Felton

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.MARINE...Small craft advisory winds over most of the waters with
the frontal passage this evening. In the wake of the front, a
westerly push down Strait of Juan de Fuca is in the offing
maintaining, SCA winds for this area through the day on Saturday.

We'll see conditions remain active over the weekend as moisture
continues to stream off the Pacific. Must message the chance for a
few thunderstorms over the weekend. Additional disturbances look to
continue into the beginning of next week as well. Combined seas 8
to 9 ft tonight subsiding a little over the weekend.
McMillian/Felton

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.HYDROLOGY...No river flooding in the next 7 days.

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.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory until 5 PM PDT Saturday for Olympics.

     Winter Storm Warning until 5 AM PDT Sunday for West Slopes North
     Cascades and Passes-West Slopes North Central Cascades and
     Passes-West Slopes South Central Cascades and Passes.

PZ...Small Craft Advisory until 4 AM PDT Saturday for Grays Harbor
     Bar.

     Small Craft Advisory until 11 PM PDT Saturday for Central U.S.
     Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
     Strait Of Juan De Fuca.

     Small Craft Advisory until 11 PM PDT this evening 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-Northern Inland Waters
     Including The San Juan Islands.

     Small Craft Advisory until midnight PDT tonight for Admiralty
     Inlet.

     Small Craft Advisory until 5 AM PDT Sunday for Puget Sound and
     Hood Canal.

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