Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 312128

Area Forecast Discussion
National Weather Service Seattle WA
228 PM PDT Tue Mar 31 2020

.SYNOPSIS...Lowland rain showers and mountain snow showers will
continue off and on for the next several days along with below
normal temperatures.


.SHORT TERM /TONIGHT THROUGH FRIDAY/...Scattered rain and mountain
snow showers continue to push east across the region this
afternoon. There remains a chance of isolated thunderstorms this
afternoon and early evening, with instability peaking in the next
couple of hours. The main threats with any convective cells will
be small hail and lightning. In the mountains, brief heavy snow
would be possible with any stronger cells.

The threat of storms will decrease overnight, except along the
coast where instability will remain as an upper level low drifts
south just offshore. Wrap around moisture may combine with outflow
through the Fraser River Valley to bring enhanced upslope flow
along the northern Olympic Peninsula Wednesday morning. The low
will continue to push south through the day Wednesday, dragging
its forcing along with it and allowing conditions to dry out from
north to south through the day.

Thursday will remain cool and somewhat drier, though isolated
showers cannot be ruled out. Another wave rotating through a high
amplitude trough centered over the Rockies looks to side swipe
the region Friday. There is still some uncertainty with how far
west the impacts from this system will be experienced. The odds
are higher for areas along and east of the Cascade crest.

continues through the long term period and may continue for the
next couple of weeks. This would result in continued below normal
temperatures and occasional periods of wet/showery weather.


.AVIATION...Mostly VFR to higher MVFR ceilings across Western
Washington this afternoon. Plenty of breaks in the clouds but
showers are still scattered around the region, with localized lower
ceilings. Little change into the afternoon, though still cannot rule
out a few isolated thunderstorm into the evening. Predominantly VFR
conditions into the evening with localized or brief lower conditions
in the heavier showers. Air mass stabilizes a bit this evening with
predominantly MVFR conditions with local IFR possible. Winds
generally southerly or southwesterly across the area, but expect a
shift to northeasterly winds across the northern parts of the area
late tonight, impacting KBLI and KCLM, and northerly winds
developing through the Puget Sound terminals into Wednesday

KSEA...Generally broken VFR ceilings this afternoon, though a short
reduction to MVFR possible if any heavier showers make it into the
terminal area. Otherwise, the air mass stabilizes a bit into this
evening and expect a trend toward MVFR after 10z. Generally
southerly winds continue this evening and much of overnight, but
expect a switch to northerly winds at the terminal around 18z
Wednesday.                     Cullen


.MARINE...Onshore flow continues across the waters today with
relatively light surface gradients. A small craft advisory will
remain in place for the coastal waters, with seas holding around 10
ft through tonight, before easing closer to 7 to 8 feet Wednesday.

A surface low with move south through the coastal waters tonight.
This will bring increasing winds on the NE side of the low across
the northern inland waters and down the Strait of Juan de Fuca very
early Wednesday to high-end small craft advisory level winds. Cannot
rule out a localized gale force gusts, but don`t expect widespread
gales to develop. These northerly winds also look to eventually make
it into Admiralty Inlet, Puget Sound, and the portions of the
northern Coastal Waters a little bit later in the day on Wednesday.
Winds may then remain elevated into Thursday across the interior
waters before finally relaxing through the remainder of the week.
Seas may steepen a bit in response to stronger northerly winds
behind the low on Wednesday, but at this point are expected to
remain below advisory thresholds. Thereafter, seas look to remain
benign through the remainder of the week.       Cullen


.HYDROLOGY...An unsettled pattern will continue through the week
ahead, but the progressive nature of the pattern and precipitation
amounts are not expected to lead to flooding concerns.


WA...Winter Weather Advisory until 5 AM PDT Wednesday for Cascades of
     Pierce and Lewis Counties-Cascades of Snohomish and King

PZ...Small Craft Advisory until 5 AM 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-Grays Harbor Bar.

     Small Craft Advisory from 5 AM to 3 PM PDT Wednesday for
     Northern Inland Waters Including The San Juan Islands.

     Small Craft Advisory until 2 PM PDT this afternoon for West
     Entrance U.S. Waters Strait Of Juan De Fuca.

     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.


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