Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 032201 CCA

Area Forecast Discussion
National Weather Service Seattle WA
250 PM PDT Fri Apr 3 2020

.SYNOPSIS...Lowland rain and mountain snow showers will continue
today as another low pressure system affects the region. Drier
conditions are expected on Saturday before a chance of showers
returns for Sunday as a trough of low pressure moves onshore
south of the area. A building ridge of high pressure is expected
to lead to dry and warmer conditions from Monday into the middle
part of the coming week.


.SHORT TERM /TODAY THROUGH SUNDAY/...Convergence zone from this
morning shifting southward to cover mainly Snohomish county this
afternoon. Some showers within this area have produced brief periods
of small hail. Near term models suggest that this feature may drift
south into King County during the late afternoon/early evening
before dissipating. Remainder of the CWA still seeing some scattered
activity that...much like the past few days...will linger into the
early evening before also tapering off.

Near term models remain consistent with earlier solutions regarding
weak upper level ridge for Saturday with a brief spat of dry
conditions as well as bringing up moisture from an upper low passing
to the south into the southern portions of the CWA Saturday night
into Sunday. Sunday sees this consensus break down as the GFS is
still trying to link the aforementioned southern low with an upper
level trough well to the north deep in Canada while the ECMWF
continues to look like the more reasonable solution...keeping
moisture generally to the south...possibly spilling over into the
farthest southern portions of the CWA Sunday...keeping at least the
area from Seattle north dry. Temps will once again be below normal
today before starting to warm Saturday and Sunday with afternoon
highs Saturday generally in the lower 50s then getting near normal
with mid 50s expected Sunday.  18

.LONG TERM /MONDAY THROUGH THURSDAY/...Models agree on a Pacific
upper level ridge nudging into the region starting Monday bringing
what looks to be the first extended period of dry weather the area
has seen in a this system will be the primary weather
factor at least into the middle of next week. In a slight change
from inherited forecast...this dry period even seems to stretch into
Thursday...drying out the remainder of the forecast period. Have
trended the forecast more in that direction...but left slight chance
PoPs in as this is still a bit of a new solution. Should models
remain consistent...could end up seeing future forecast zeroing out
said PoPs. Temps during this period look to get the area back on
track when it comes to seasonal normals...with highs in the upper
50s for Monday and Tuesday and lower to mid 60s possible by mid-
week. Spring may have taken the long way around...but it might
finally be making its way to the Pac NW after all.  18


.AVIATION...A broad upper level trough is over the Pac NW with
isolated to scattered showers across western WA. The flow aloft is
northerly. The air mass is moist with pockets of MVFR cigs in
showers. Showers will be focused over Snohomish and King counties
tonight with a convergence zone. Showers will gradually taper off
after midnight. Patchy low clouds and MVFR cigs are possible
Saturday morning. Weak high pressure will bring drier weather toward
the afternoon. 33

KSEA...Showers with a convergence zone in the vicinity this evening,
then tapering off after midnight. Wind shift possible out of the N
between 00-06z. Drier weather on Saturday with N winds.


.MARINE...Onshore flow will continue across western WA this
afternoon and evening. Strongest wind/waves will be through the
Strait of Juan de Fuca and a Small Craft Advisory remains in effect.
Winds will ease tonight. Low pressure will shift toward OR/CA over
the weekend with generally light N/NE flow over western WA. The flow
will turn onshore again by Monday as high pressure builds over the
NE Pacific. 33


.HYDROLOGY...No river flooding is expected over the next 7 days.


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


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