Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 260358
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
900 PM PDT MON JUL 25 2016

.SYNOPSIS...
Warm and dry weather will remain over the region through the
weekend. Morning clouds and slightly cooler temperatures Tuesday
will trend warmer than normal through Friday, followed by more
moderate temperatures through the weekend.

&&

.SHORT TERM...
A few mid level clouds have worked into Western Washington this
evening, resulting in little more than an enhanced sunset and a very
fine late July evening. Marine stratus along the Washington coast
will push inland tonight, aided by increasing onshore flow ahead of
weak and dry upper level shortwave trough that will move over the
region late tonight and Tuesday. Morning clouds, dampened upper
level heights and somewhat cooler temperatures aloft will result in
several degrees of cooling for Tuesday. The forecast continues to
reflect about 4-6 degrees over the interior and little or no change
along the coast. Heights will begin to rebound Tuesday afternoon and
Wednesday. Marine stratus Wednesday morning will likely remain
limited to the coast and South Interior. Limited morning clouds and
and overall warming will allow temperatures to climb back into the
70s and lower 80s Wednesday.

.LONG TERM...from previous discussion...
The mid level ridge over the desert Southwest will build north
and produce a marked increase in 500 mb heights by Thursday, with
heights up to about 588dm that morning. 850 mb temps around +17c
so will expect temps in the mid-upper 80s for Seattle area with
around 90 or low 90s across the south interior. Have begun to
highlight this warmth for Thursday as it should be the warmest
temperatures in over a month across the area. There remains some
disagreement on Friday as to how quickly the cooling begins with
the GFS being more aggressive in dropping heights on Friday.
Should this play out, it would be slightly cooler on Friday than
Thursday. However the ECMWF keeps the heights a little higher and
would be expected to mean Friday is very similar to Thursday. For
now will just go with that idea that Friday should be similar to
Thursday for highs. The discrepancy continues into Saturday. Both
models agree on a stronger mid level trough pushing into the west
coast of Canada but the GFS has a faster drop in heights and a
sharper cooling trend. ECMWF has cooling on Saturday but not as
dramatic. The official forecast blends the two solutions to show a
cooling trend but not as quick as the GFS. Solutions come into
better alignment on Sunday on heights and surface temperatures,
which bring readings below normal with trough over the Pac NW.

&&

.AVIATION...Coastal marine stratus will spread inland overnight,
so there will be areas of morning low clouds across the interior of
Western Washington. The afternoon will be sunny across most of the
region, although areas of coastal stratus could linger.

KSEA...Morning low clouds are a good bet 12-18z.

&&

.MARINE...High pressure offshore combined with lower pressure
east of the Cascades will give a decent westerly push in the Strait
each evening this week. Race Rocks at 8pm this evening had a west
wind of 39kts and a gale warning is in effect for the central Strait
of Juan de Fuca. Buoy88 at 8pm has only had a peak wind of 23kts and
Smith Island was gusting to 28kts, so the forecast for the east
entrance of the Strait of Juan de Fuca is for 20-30kts with a small
craft advisory.

&&

.SEW Watches/Warnings/Advisories...
WA...None.
PZ...Gale warning central Strait of Juan de Fuca, small craft
advisory for the east entrance.


&&

$$

www.weather.gov/seattle

You can see an illustrated version of this discussion at
www.weather.gov/seattle/gafd/latest_webafd.html



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