Weather Service Report


236 
FXUS66 KSEW 251637
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
937 AM PDT Thu May 25 2017

.SYNOPSIS...Temperatures will slowly rebound today with enough 
moisture and instability for a few afternoon showers and 
thunderstorms over the Cascades. A warm and dry upper ridge axis 
off the coast on Friday will pass directly over Western Washington
on Saturday. Its warm and dry influence will continue from Sunday
through Tuesday, including Memorial Day.

&&

.SHORT TERM...Slightly cyclonic northerly flow aloft will prevail
today with an upper ridge offshore and an upper trough over the
Intermountain West. This is not a classic thunderstorm pattern 
but there is enough lingering instability and moisture for a 
slight chance of thunderstorms near the Cascade crest from about 
mid afternoon to early evening today. Otherwise, it looks like a 
mostly sunny day with highs warming to a few degrees above normal.

The offshore upper ridge will move closer to the region on Friday
and then overhead this weekend. At the same time, low level 
onshore flow will weaken slightly and turn a bit more northerly. 
All of this means there will be an extended warm and dry period. 
Highs should climb into the 70s most areas on Friday. Highs in 
the lower to mid 80s will be common this weekend with mid 60s and 
70s near the coast and water. Schneider

.LONG TERM...Previous discussion...Beyond the holiday...the first
half of next week seems to want to transition a bit. Starting 
with late Monday night...models remain consistent on some degree 
of instability and scattered precip signatures possibly signaling 
a bit of a marine push...though not nearly as intense as the 
previous one. Still looks to be enough to start cooling temps with
afternoon highs Tue falling back into the upper 70s for the 
interior. This downward trend will continue as an upper level 
trough starts to approach the area by midweek...where we finally 
start to see the prospect of showers re-enter the forecast. SMR

&&

.AVIATION...Light northerly flow over Western Washington through 
Friday with a trough over the Rockies and high pressure aloft over 
the northeast Pacific. Light low level onshore flow. The air mass is 
somewhat moist in the lower and mid levels and dry above 10k ft. 
Generally stable conditions except weakly unstable over the Cascades 
this afternoon and early evening leading to a chance of isolated 
thunderstorms. These are not expected to reach the lowlands or 
affect any terminals. Any thunderstorms will dissipate after sunset.

Patchy low clouds and fog around the southwest interior will scatter 
out by 17-18z. MVFR stratus near the coast and affecting HQM 
may briefly scatter after 22z.

KSEA...VFR. Light and variable winds will become NW near 10 knots 
this afternoon. dtm

&&

.MARINE...High pressure centered over the northeast Pacific along 
with lower pressure east of the Cascades will result in light 
onshore flow through Friday. The offshore high will weaken and 
redevelop farther west on Saturday, causing the flow to become light 
northerly. Diurnally driven small craft winds are expected in the 
central/eastern Strait late this afternoon and evening. Hazardous 
seas around 10 feet over the coastal waters will subside to 7 to 8 
ft during the afternoon. dtm

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory for hazardous seas until 3 PM PDT this 
     afternoon 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.

     Small Craft Advisory from 3 PM this afternoon to midnight PDT 
     tonight for Central U.S. Waters Strait Of Juan De Fuca-East 
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$

www.weather.gov/seattle

You can see an illustrated version of this discussion at
www.wrh.noaa.gov/sew/gafd/latest_webafd.html

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Western Regional Climate Center, wrcc@dri.edu