404
FXUS66 KSEW 010944
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
244 AM PDT Mon Jul 1 2024

.SYNOPSIS...Strong upper level ridge building offshore today will
slowly move east during the week. The ridge will move over Western
Washington Friday and remain over the area through the weekend.
This will produce the warmest weather of the year so far in
Western Washington after the 4th.

&&

.SHORT TERM /TODAY THROUGH WEDNESDAY/...Satellite imagery shows
upper level ridge starting to build offshore between 140-150W.
Cloudy skies over Western Washington early this morning with light
precipitation echoes over the Central Cascades. With the cloud
cover temperatures on the mild side at 2 am/09z, in the mid 50s to
lower 60s.

Upper level ridge building well offshore today with northwesterly
flow aloft over the area. Weak shortwave moving down the backside
of the ridge this morning will clip the Northern and Central
Cascades. This feature could produce a light shower or even some
drizzle in the this area but more than likely will just keep the
skies cloudy. For the lowlands, stratus along the coast spreading
inland this morning with the light low level onshore flow. By 12z
the stratus in some locations will be east of the Puget Sound.
The marine layer is not very thick but with middle level moisture
associated with the weak shortwave over the area expect the
stratus to last into the late morning hours before dissipating
over the interior. Skies clearing a couple of hours later along
the coast. Highs today near normal, mid 60s coast and upper 60s to
mid 70s inland.

Not much change in the pattern tonight and Tuesday. Upper level
ridge offshore will slowly start to move east. Some of the models
have the center of the ridge at 600 dms. Increasing onshore flow
behind the weak shortwave will bring the stratus deck back inland
overnight with the stratus hanging around a couple hours longer
Tuesday morning into early Tuesday afternoon. With the morning
clouds lasting a little longer high temperatures will be a couple
of degrees cooler inland, mid 60s to lower 70s. Highs will remain
in the mid 60s along the coast. Lows tonight in the 50s.

Upper level ridge continuing to move east Tuesday night and
Wednesday. 500 mb heights building to the lower to mid 580 dms
over Western Washington by Wednesday afternoon. Low level flow
remaining onshore with the marine layer along the coast moving
inland Wednesday morning. Stratus will not be as thick Wednesday
morning over the interior leading to an earlier break out and
warmer high temperatures, in the 70s. Highs along the coast mid to
upper 60s. Lows Tuesday night in the 50s.

.LONG TERM /THURSDAY THROUGH SUNDAY/...There is good agreement in
the extended models that Western Washington will be getting into a
prolonged spell of warm/hot weather extending well beyond Sunday.
There is better agreement on the 00z model runs on the placement
of the upper level ridge with both the GFS and the ECMWF having
the ridge axis close to Western Washington through the weekend.
500 mb heights rising into the mid 580 dms to lower 590 dms by the
Saturday. Surface thermally induced trough moving up the Oregon
coast over the weekend but models have been reluctant to move the
trough all the way up the Washington coast leaving the low level
flow flat over the weekend. 850 mb winds never turn easterly as
well through the period. On the flip side the temperatures aloft
will be warm with 850 mb temperatures rising from plus 14C to 18C
Thursday to plus 22C to 24C Sunday. If we had some offshore flow
with temperatures that warm aloft we would be talking 90s and
close to 100 for the interior. Without the offshore flow in the
lower levels will keep highs over the weekend in the 80s and lower
90s over the interior and mid 70s to lower 80s on the coast.
Highs Thursday and Friday in the mid 70s to mid 80s for the
interior with Friday a couple of degrees warmer than Thursday.
Highs both days on the coast in the lower to mid 70s.

Beyond the extended period models showing no signs of this pattern
breaking down. The ridge weakens a little with time but stays
over the west coast. Hello summer 2024. Both the ECMWF and GFS
ensemble means have the high temperature in Seattle 80 degrees or
warmer beginning on the 5th continuing all the way into the
middle of the month. Felton

&&

.AVIATION...Upper level ridge offshore will begin to build into
the region today with northwesterly flow aloft. The low level flow
is onshore. The air mass remains moist in the low levels.
Widespread low MVFR ceilings are expected across the interior
lowlands this morning with LIFR/IFR along the coast. Ceilings will
lift to VFR across the interior 18Z-20Z, but are likely remain
MVFR near the immediate coast. MVFR ceilings will redevelop across
much of the interior late tonight into Tuesday morning.

KSEA...MVFR ceilings improving to VFR 18Z-20Z. MVFR ceilings are
expected again 12Z-18Z Tuesday. Surface winds light and variable
becoming southwesterly under 7 knots for a period this morning
before veering light west to northwesterly late this afternoon.  27

&&

.MARINE...Strong surface ridging will remain centered well
offshore through much of the week ahead with lower pressure across
the interior for varying degrees of onshore flow. Winds are expected
to reach small craft advisory strength in the central and east
strait later today and perhaps again on Tuesday. Thermally induced
low pressure expanding northward across the interior later this week
will likely tighten the gradient enough to produce small craft
advisory strength northwesterlies across portions of the coastal
waters at times.   27

&&

.CLIMATE...The average temperature in Seattle for the month of
June was 61.0 degrees ( normal is 62.0 degrees ). This is the
coldest June in Seattle since 58.3 degrees in 2012. 2012 was also the
last year Seattle had a below normal July but given the way the
month is starting this year not looking for a repeat of 2012.

It`s way early at this point but a stat to keep in mind,
the Seattle record for consecutive days with highs 80 degrees plus
is 15 days ( June 25th thru July 9th 2015 and July 30th thru
August 13th 1977 ). There have only been 5 streaks of 12 days or
more in the 79 years of records at Seattle-Tacoma airport. Felton

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 3 AM PDT early this morning for
     Central U.S. Waters Strait Of Juan De Fuca-East Entrance
     U.S. Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 2 PM this afternoon to 5 AM PDT
     Tuesday for Central U.S. Waters Strait Of Juan De Fuca-East
     Entrance U.S. Waters Strait Of Juan De Fuca.

&&

$$