Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 141604
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
900 AM PDT Thu Jun 14 2018

.SYNOPSIS...An upper level trough will remain over the area today
keeping at least a slight chance of showers in the forecast. A weak
upper level low will move south through the area Friday night. The
low will stall over southeastern Oregon/northern Nevada over the
weekend into next week. Temperatures will warm beginning Sunday with
the warming trend continuing into the middle of next week.

&&

.SHORT TERM...The convergence zone has faded and most areas are dry,
though there are still a few showers on the coast and other places.
Showers will continue to diminish today and there will be sunny
places or at least sun breaks. Highs today will be in the 60s.

An upper level low will move south through British Columbia on
Friday ending just north of the border by late afternoon. Most of
the shower activity with the low will develop in the afternoon with
some daytime heating and remain fairly confined to around the low
center. This will keep showers north of the area Friday afternoon.
The air mass will become slightly unstable over the mountains for a
slight chance of showers with the best chances near Mount Baker.
Isolated thunderstorms in the Cascades are a possibility. Weak low
level onshore flow will keep some low level moisture in the area at
least in the morning hours. There should be some sun, especially in
the lowlands. Highs Friday will be 65-70.

The upper low will move south through western Washington on Friday
night. The low is weak and without any daytime heating to add a
little extra pop will keep the chance of showers confined to the
mountains Friday night. A drying and warming trend will commence on
Saturday with the flow aloft becoming northeasterly after the low
passes through and the surface gradients turn northerly. Highs will
be well into the 70s with perhaps a few spots near 80. Showers and
thunderstorms will again be possible in the Cascades in a return
flow around the upper low to the south. Burke

.LONG TERM...Previous discussion...Big question in the extended is
where will the upper level low end up. The 00z model runs are a
little further south with the low keeping the wrap around moisture
south and east of the area through the period. Temperatures aloft
warming with model 850 mb temperatures rising to plus 20C or higher
by Tuesday and Wednesday. Northwesterly surface gradients continuing
on Sunday with a thermally induced surface trough trying to develop
along the coast Monday into Tuesday with the trough shifting inland
on Wednesday. Have gone ahead and warmed the high temperatures up a
few degrees in the extended with 70s to mid 80s on Sunday rising to
the mid 70s to near 90 on Tuesday and possibly into Wednesday. Felton

&&

.AVIATION...A broad upper trough will be over the area today and
tonight with northwest flow aloft. At the surface, onshore flow
will continue. The air mass is moist and slightly unstable.

There is a mix of VFR and MVFR low clouds across the area this
morning with some patches of IFR ceilings over Central Puget
Sound. The general trend today will be for ceilings to lift to
VFR. Some locations will scatter but others will maintain a ceiling
in the 4000-7000 foot range. Clouds should increase and ceilings
should lower again tonight under continued onshore flow.

KSEA...MVFR ceilings should lift to VFR around midday today.
Clouds could scatter at times later today but a 5000-7000 foot
ceiling is expected to be prevalent this afternoon and evening.
Ceilings should lower to MVFR again Friday morning. Southerly wind
4-8 knots will become westerly this afternoon and northerly this
evening. Schneider

&&

.MARINE...Onshore flow will will continue for the next several
days with high pressure offshore and lower pressure east of the
Cascades. The onshore flow is expected to weaken slightly and
turn a bit more northwesterly this weekend.

Small craft advisory strength west winds are likely in the
Central and Eastern Strait of Juan de Fuca the next couple of
evenings. Small craft advisory strength northwest winds are
expected at times for the Coastal Waters Friday through Sunday.
Schneider

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 6 PM this evening to midnight PDT
     tonight for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$

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