Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
FXUS66 KSEW 251614
Area Forecast Discussion
National Weather Service Seattle WA
914 AM PDT MON JUL 25 2016
Surface high pressure remains off the coast with mid level ridging
present across Western Washington. This will allow for mild and
dry weather this week. A slight cooling will occur Tuesday, but
then be followed by a steady warming trend for the remainder of
this week. By Thursday and Friday the warmest temperatures this
week are expected with highs a few degrees above normal.
Morning satellite shows lingering low clouds on the coast and
portions of southwest forecast area. Otherwise, abundant sun with
just mid-high level clouds present. Temperatures are responding
well with lots of 60s to low 70s already. Highs today will top out
a few degrees above normal in most spots with the sunshine and
850mb readings around +15C. This will be followed by a subtle
cooling trend tomorrow as mid level heights fall slightly and a
bit more low level marine intrusion is present. Generally 3-5
cooler than todays highs for Tuesday with near normal
temperatures. Then a warming trend commences on Wednesday with
rising heights, plenty of sun and dry conditions.
.LONG TERM... Previous discussion follows.
Small small differences in the extended models this morning. No
changes for Thursday with the 500 mb heights near 590 dms with
northwesterly surface gradients. Look for highs in the mid 70s on
the Coast and mid 70s to near 90 for the interior. The 00z run of
the gfs is a little faster with the approaching weak trough on
Friday. 500 mb heights falling a bit and the model temperatures
aloft cooler than previous runs...850 mb temps plus 17-18c versus
plus 20c. The ECMWF is staying with the idea of a slower approach
of the trough leaving Friday as the warmest day of the week. Since
the gfs solution is a new one will stay with the slower trough
idea and keep Friday as the warmest day with warmer locations in
the lower 90s. Models are slowly trending stronger with the trough
over the weekend. Not strong enough to produce any precipitation
but if the trends continue the stronger onshore flow will result
in more morning cloudiness and cooler forecast highs. Current
forecast has temperatures near normal over the weekend with highs
in the mid 60s on the coast and 70s for the interior. Will stay
with this idea for now. Felton
Expect light westerly winds aloft to persist through
Tuesday. Low level flow is light onshore; the onshore flow will
strengthen this evening as a weak upper level disturbance moves
across the region. The air mass will be stable with areas of low
level moisture mainly near the coast. Marine moisture will spread
inland and deepen late tonight as the upper level disturbance
passes across the area.
Visible satellite imagery shows an area of stratus giving low IFR
ceilings along the coast and through the Chehalis Gap to around
KSHN. This stratus will burn back to the coastal waters by 21Z.
Expect the stratus to push inland reaching the interior terminals
08Z-10Z tonight and many areas by 12Z will see ceilings between
700 and 1000 feet. IFR conditions will persist until about 20Z
Tuesday in the interior. Albrecht
KSEA...Expect scattered cirrus through much of tonight. Stratus
with bases 700-1000 feet will arrive at the terminal about 10Z
late tonight. Light southwest winds will turn more westerly 18Z-
20Z then will shift to NW 7-9 kt about 21Z. Winds will veer to
more north/northeast this evening then will shift to southerly 5-7
kt by 10Z as the marine stratus moves in. Albrecht
.MARINE...High pressure offshore combined with lower pressure
east of the Cascades will give onshore flow for the upcoming
week. The onshore flow will become strong late this afternoon as
an upper level disturbance moves through the area, tightening
pressure gradients. Westerly gales are expected in the central and
eastern Strait of Juan de Fuca tonight, while small craft advisory
conditions are expected over southern portions of the Northern
Inland Waters and in Admiralty Inlet.
Moderate onshore flow will resume from Tuesday through Thursday.
Onshore pressure gradients will tighten again on Friday. Small
Craft Advisory northwest winds are expected over the coastal
waters for most of the upcoming week. Albrecht
PZ...Small Craft Advisory from 2 PM this afternoon to 2 AM PDT
Tuesday for Coastal Waters From Point Grenville To Cape
Shoalwater Out 10 Nm.
Small Craft Advisory until 9 AM PDT Tuesday for Coastal Waters
From Cape Flattery To James Island 10 To 60 Nm-Coastal
Waters From James Island To Point Grenville 10 To 60 Nm-
Coastal Waters From Point Grenville To Cape Shoalwater 10
To 60 Nm.
Gale Warning from 6 PM this evening to 3 AM PDT Tuesday for
Central U.S. Waters Strait Of Juan De Fuca-East Entrance
U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory from 6 PM this evening to 3 AM PDT Tuesday
for Admiralty Inlet-Northern Inland Waters Including The
San Juan Islands.
You can see an illustrated version of this discussion at