Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 261542
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
900 AM PDT Sun Mar 26 2017

.SYNOPSIS...A front will move over Western Washington today.
Showers will follow the front tonight--tapering off on Monday.
A warm front will reach the area on Tuesday for more rain. A
rather wet frontal system will move slowly through the region
Tuesday night and Wednesday. A cool upper trough will keep showers
in the forecast Thursday. Dry weather is expected on Friday.

&&

.SHORT TERM...Rain will continue to spread into Western Washington
today. The rain will break up to showers tonight and the showers
will become more scattered on Monday. Tuesday will see a warm front
arrive. Looking at the NAM, 850mb temps will only come up to around
0C with the front early this evening, and then the temp aloft cools
back to around -2c Monday and Tuesday--and the 0c isotherm does not
start pushing back into the area later Tuesday as a warm front nears.
The forecast snow level tonight through Tuesday is 3500 feet.

.LONG TERM...A rather wet and frontal system will move through
the region Tuesday night and Wednesday. The snow level will rise to
around 5500 feet but then fall back to the passes Wednesday night
and Thursday as a cool upper trough moves into the region. Friday
should be dry as high pressure builds.

&&

.AVIATION...An upper level trough off the coast is forecast to
move onshore into Western Washington Monday. SW flow aloft over
Washington through tonight. At the surface, a frontal system just
off the coast this morning should reach the coastline around 21z and
thru the interior around 23z-01z. Low level offshore flow to turn
onshore with the front. Air mass stable ahead of and with the front
becoming more unstable in the wake of the front.

VFR ceilings with rain moving onshore this morning spreading inland
before 19z. Ceilings likely to drop to MVFR in the vicinity of the
front. Mountains to become obscured.

KSEA...VFR conditions into early this afternoon with rain. MVFR
ceilings likely to develop in the vicinity of the front beginning
around 22 OR 23z. SE winds near 10 kt to become southerly when the
front arrives. Buehner

&&

.MARINE...An occluded front within 100 nm of the coast at 15Z today
should move ashore around 21z and through the western interior
around 00z late this afternoon. Low level offshore flow to turn
onshore with the front. Gale warnings in place ahead of the front
most coastal waters and north interior - though marginal.

A surface trough is expected to move onshore Monday with a showery
weather regime with higher pres building behind it. The next Pacific
frontal system is expected to arrive Tuesday and Wednesday. Buehner

&&

.HYDROLOGY...River flooding is not expected for the next 7 days
with the exception of possibly the flood prone Skokomish river in
Mason County, where heavier rain in the Olympics Tuesday night
and Wednesday could be enough to get the river above flood stage
Wednesday.

&&

.CLIMATE...It has been a wet March with all of the climate sites
in the forecast area headed for at minimum a top 10 wettest March
finish. There is a good chance all of the stations will end up
in the top 5 wettest for March. Below is a table with the
precipitation values through the 25th with the current rank, the
5th wettest value and the record for the month.

                   Current       5th wettest      Record

Seattle-Tacoma      6.12" (10th)    7.12"          9.44" (2014)
Olympia             9.37" (4th)                   11.79" (1997)
Bellingham          4.44" (12th)    5.07"          7.02" (1950)
Hoquiam            12.83" (8th)    13.25"         15.13" (1997)
Quillayute         15.76  (10th)   17.95"         23.23" (2007)

In Seattle since October 1st there has been measurable
precipitation on 121 days ( 69 percent ) out of the 176 days.
This is 2 more than the total from October 1st through March 31st
last year during the record setting rainfall. In over 120 years
of weather records the most days with measurable precipitation in
Seattle from October 1st through March 31st is 125 days set in
1950-51.

There was only 11 days with measurable precipitation in January in
Seattle. Taking that month out that makes 110 days out of 145 ( 76
percent ) for the other 5 months. Felton

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather advisory for the Cascades of Lewis and Pierce
     counties from noon today through early Monday morning.

     Winter weather advisory for the Cascades of Whatcom and Skagit
     county tonight

PZ...Gale Warnings are in effect for much of the coastal waters,
 east entrance to the Strait of Juan de Fuca, and the Northern
  Inland Waters.

 Small Craft Advisories are in effect for the remaining waters
 except the Puget Sound/Hood Canal.

&&

$$

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You can see an illustrated version of this discussion at
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