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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Thursday
• 
• High: 59 °
• Low: 45 °
• T-Storms

• Friday
• 
• High: 63 °
• Low: 48 °
• Chance of Rain

• Saturday
• 
• High: 64 °
• Low: 48 °
• Chance of Rain

• Sunday
• 
• High: 66 °
• Low: 48 °
• Partly Cloudy

• Monday
• 
• High: 64 °
• Low: 50 °
• Chance of Rain

Area forecast discussion 
National Weather Service Seattle Washington 
330 PM PDT Wednesday may 22 2013 


Synopsis...a cold upper level low will give showers with isolated 
afternoon and evening thunderstorms through Thursday. The upper low 
will wobble around the Pacific northwest through the Memorial Day 
weekend as it slowly fills and weakens. Cool temperatures through 
Thursday night will gradually moderate over the weekend and showers 
will gradually diminish starting Thursday night. 


&& 


Short term...persistent rain over the Seattle area has ended but 
there are still plenty of showers over western sections. The rain 
and cloudiness along with the ever present upper level low has left 
the Puget Sound sound region on the cool side. Ksea has been holding 
steady at 50 degrees for a few hours and may break the record low 
maximum of 54 degrees for this date. 


Showers will taper tonight but may get energized again Thursday 
afternoon and evening. There is some instability in the models so 
have kept the idea of isolated thunderstorms. There should at least 
be some sun breaks so temperatures will rise...at least into the low 
60s over the interior. 


The upper level low finally starts to fill Thursday night and 
Friday. The GFS moves it away from the area on Saturday though the 
Euro does not. Have kept basically chance probability of precipitation in the forecast with 
a slow warming trend. Burke 


Long term...Sunday could be kind of a nice day if you believe the 
GFS. The Euro still has the upper low over the area. Put a mention 
of sun in the Sunday forecast but kept the chance of showers. The 
GFS brings a weak system into the area Monday through Tuesday while 
the Euro still has the same or possibly a different upper low. 
Confidence is low in all details but went with the GFS solution and 
boosted probability of precipitation into the likely category Tuesday and Tuesday night. By 
Wednesday probability of precipitation drop back to chance. Burke 


&& 


Aviation...an upper low will remain over the Pacific northwest... 
centered mainly over north central Oregon or south central 
Washington tonight and shifting into the coastal waters Thursday. 
The air mass over western Washington will be moist and weakly 
unstable. Showery precipitation will continue...and isolated 
thunderstorms are possible mainly Thursday afternoon and evening. 
The Cascades will remain mostly obscured. 


There is a still a fairly wide range of conditions across the 
forecast area this afternoon. MVFR ceilings are common over much of 
the Puget Sound sound region where conditions have been slowly 
improving...with VFR conditions over most of the rest of the 
forecast area. At 2 PM showers were mainly to the south and west of 
the Puget Sound sound region...with locally MVFR visibilities and 
ceilings. Generally speaking these conditions should continue this 
evening...with some deterioration tonight and then improvement again 
Thursday afternoon. 


Ksea...southwest wind 6-12 knots...becoming south to southeast 4-10 knots 
tonight and southwest again Thursday. The threat of thunderstorms at 
ksea for this afternoon and evening looks minimal at this time...but 
there is a 15 percent chance of thunderstorms Thursday afternoon and 
evening. Mcdonnal 


&& 


Marine...a 1010 mb low near along the northwest side of Vancouver 
Island will weaken as it moves slowly south across the Washington 
offshore waters tonight and Thursday. It will likely be over the 
north Oregon offshore waters Thursday night. 


The models have been showing a wide range of solutions with regard 
to the movement of the low and especially the winds it will produce. 
That is still the case. The uw WRF-GFS still indicates spotty 
marginal Small Craft Advisory southeast winds Thursday over the 
coastal waters...and in the Strait of Juan Delaware fuca and adjacent 
inland waters. However the 12z run has backed off somewhat from 
previous runs. Our forecast will use a model blend...resulting in 
winds 20 knots or less over the coastal and inland waters. That looks 
like the best forecast at this time...but certainly Small Craft 
Advisory winds similar to the uw WRF-GFS are possible. 


In addition we have marginal Small Craft Advisory conditions over 
the coastal waters for hazardous seas through this evening...along 
with rough bar conditions at Grays Harbor through tonight. 


Onshore flow will develop Friday and continue Saturday and Sunday. 
Small Craft Advisory winds are possible in the central Strait of 
Juan Delaware fuca and East Entrance Strait Friday through Sunday during 
the late afternoon and nighttime hours. A front will approach the 
forecast area from the west Monday. Mcdonnal 


&& 


Sew watches/warnings/advisories... 
Washington...none. 
Pz...Small Craft Advisory for hazardous seas coastal waters through 
this evening. 
Small Craft Advisory for rough bar conditions Grays Harbor 
through tonight. 


&& 


$$ 


You can see an illustrated version of the forecast discussion at 
www.Weather.Gov/Seattle/gafd/latest_webafd.Html