Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
FXUS66 KSEW 221100
Area Forecast Discussion
National Weather Service Seattle WA
300 AM PST Sun Jan 22 2017
.SYNOPSIS...An upper trough will bring showers at times through
tonight. High pressure aloft will result in mainly dry conditions
Monday through Wednesday and possibly through the remainder of
next week as well.
.SHORT TERM...An upper short wave and an associated weak frontal
system will move from south to north through the area today,
bringing some showers. This feature will be falling apart as it
moves north and shower activity looks pretty disorganized.
An upper low well offshore will sag south tonight and Monday,
with shower chances ending for Western Washington. An upper ridge
will build over the area on Tuesday for a dry and partly sunny
day. The GFS shows spotty showers bubbling up across the area but
that looks overdone given the northerly flow aloft. The dry ECMWF
is preferred for now. Schneider
.LONG TERM...A weak weather system could bring spotty light rain
later Wednesday into Thursday. It`s hard to believe this will
amount to much as it will be moving into a sharp upper ridge but
a small chance of showers cannot be ruled out. High pressure aloft
will remain in control Friday and Saturday with dry weather
.AVIATION...A W-E oriented occluded front over the central
Oregon coast at 10Z will move northward across W WA 15Z through 21Z.
An upper level low will remain about 350 NM offshore through
09Z tonight maintaining somewhat moist S flow aloft over W WA.
The air mass is already somewhat moist from a couple of passing
shower bands overnight. Conditions are mainly VFR with a mix of
stratus BKN-OVC030-050, higher VFR CIGS and some patchy low stratus
and fog. The occluded front should bring more uniform CIGS BKN-
OVC035-050 with some light rain. CIGS are expected to rise behind
the front this afternoon to VFR CIGS 5000 feet or higher.
KSEA...CIGS BKN-OVC035-050 will lift to SCT-BKN050-100 by 12Z. The
occluded front lower CIGS back down to BKN-OVC035-050 around 16Z
with some light rain. CIGS should lift to BKN080-100 sometime 21Z-
23Z. Surface winds will be E-SE 6-14 KT up through 20Z then shift S
5-10 KT. Kam
.MARINE...A deep 964 MB surface low will remain about 350 NM W of
Grays Harbor or near 45N/131W through this evening. The associated
occluded front will move northward across W WA and the coastal
waters this morning. Gale force winds are expected over the coastal
waters and SCA winds over the Strait of Juan de Fuca and over the N
Inland waters today as the front crosses the area. The low will
begin filling and moving back S late tonight, allowing a weak
surface ridge to build over W WA. Winds over the coastal waters will
finally ease below SCA levels Monday afternoon. Weak winds will
persist over the area through Wednesday. A weak front will approach
the coast Wednesday but should eventually dissipate just offshore
on Thursday. Kam
.HYDROLOGY...River flooding is not expected for the next 7 days.
PZ...Gale Warning until 6 PM PST this evening 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 for rough bar until 6 PM PST Monday for
Grays Harbor Bar.
Small Craft Advisory until 6 PM PST this evening for Central
U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
Waters Strait Of Juan De Fuca-Northern Inland Waters
Including The San Juan Islands-West Entrance U.S. Waters
Strait Of Juan De Fuca.
You can see an illustrated version of this discussion at