Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 111100

Area Forecast Discussion
National Weather Service Seattle WA
400 AM PDT Sun Mar 11 2018

.SYNOPSIS...A weak upper level disturbance will spread clouds over
parts of the area this morning. An upper level ridge will rebuild
over Western Washington this afternoon and tonight. The ridge will
shift east on Monday. In the lower levels offshore flow will
continue through Monday. High temperatures today will be well
above normal with possible record breaking highs Monday. Rain
will return Tuesday as a front moves through the area. A cool
upper level low will move by to the west of the area Wednesday
then stall south of the area through the end of the week giving
partly to mostly cloudy skies and a chance of showers at times.


.SHORT TERM...Satellite imagery shows cloudy skies associated with
a weak shortwave embedded in the southwesterly flow aloft over
the southern portion of the area early this morning. Mostly clear
skies over the remainder of the area. Wide range of temperatures
with the colder locations near 30 degrees and the warmer locations
with a little exposure to an easterly wind in the mid 40s.

Shortwave will dissipate over the central portion of the area this
morning. Doppler radar shows isolated showers in Cowlitz county
are already falling apart. Surface observations put the ceilings
in the 7000-10000 foot range. Can`t rule out a brief shower over
the Southwest Interior early this morning. For the most part the
shortwave will bring some cloud cover to the central and southern
portions of the area this morning. Upper level ridge rebuilding
this afternoon for more sunshine. Low level flow is offshore with
the cross cascades gradient in the -2 to -3 mb range. This will
increase a little later today into tonight. With the offshore
flow and plenty of afternoon sunshine highs will be in the mid 50s
to mid 60s.

Upper level ridge over the area tonight with the low level
offshore flow remaining intact. Lows will be in the mid 30s to
lower 40s.

Upper level ridge shifting east on Monday. Low level offshore
flow increasing as the next frontal system to move into the area
stalls offshore. Model cross Cascade gradient by 00z Tuesday in
the -6 to -8 mb range. In addition model 850 mb temperatures
warming into the plus 7 to 9C range. This is a perfect set up for
a very warm day in March for Western Washington. Most of the
guidance has highs in the 60s. The warmest guidance is off the
MM5 which is 3 to 5 degrees warmer than the rest of the model
suite. With the strong downslope warming from the easterly winds
on Monday will lean the forecast towards the MM5 and stay with
highs near 70 from about Seattle southward and 60s for the
remainder of the area. There is a good chance we will see some
record highs set Monday afternoon.

Upper level ridge over Montana by early Tuesday morning with the
front offshore becoming a little negatively tilted as the strong
jet drives the southern portion of the front inland over Northern
California and Southern Oregon. Models a little slower wit the
onset of the precipitation over western Washington early Tuesday
morning. With the front becoming negatively tilted have cut back
on the pops a little for the interior in the 06z-12z Tuesday

Front weakening/splitting as it moves inland on Tuesday spreading
rain over the area. With the increasing cloud cover overnight
temperatures will only drop into the 40s and lower 50s. It is
possible a few record high minimum could be set on Tuesday.
Temperatures will only warm 5 degrees or so from the min
temperatures with highs in the upper 40s to mid 50s.

.LONG TERM...Extended models in pretty good agreement the 00z
Sunday run with a cool upper level low to the west Wednesday
dropping southeast to Northern California Thursday and Friday. The
low will weaken and continue to move south on Saturday with the
flow aloft over Western Washington becoming northerly. Low close
enough to keep a chance of showers in the forecast at least
through Friday. If the model trends continue with the idea of the
low tracking further south on Saturday will be taking the chance
of showers out of the forecast for next weekend. Highs through the
period will be near normal, lower to mid 50s. Felton


.AVIATION...Southerly flow aloft will continue today and into
Sunday. This has resulted in some high clouds spilling into southern
portions of the CWA from a weak disturbance making its way through
OR. How far these clouds push north will in particular have an
impact on the OLM if these clouds make it to that
particular terminal...fog may not be an issue here in the early
morning hours. Current satellite trends indicate that they should
reach...but current obs at the time of this writing are starting to
hint at fog that might be a forecast that will
likely see a few updates during these early morning hours.

Remainder of area under generally clear skies...but may see some SCT
high clouds from previously discussed combo of southerly flow and
clouds seeping in from OR. Nothing expected to bring conditions down
out of VFR for the next 24 hours.  SMR

KSEA...VFR with some mid and high clouds this morning, then skies
will clear. NE wind 4-8 kt. SMR


.MARINE...Offshore flow will continue through Monday, with small
craft advisory strength east winds near the west entrance to the
strait at times. A front will turn winds southerly on Tuesday, and
small craft advisories are likely on the coast and possible over
some inland waters then. Low end gales are possible over some
coastal zones on Tuesday. Winds will become northerly on Wednesday
and Thursday as a series of weather systems moves by to the south. CHB


.HYDROLOGY...River flooding is not expected the next 7 days.


.CLIMATE...How rare in a 70 degree plus day in Seattle in march.
Since records started in the 1890`s it has only occurred 30 times.
Out of the 30 only 8 have happened in the first half of the month.
In the last 20 years there have been two occurrences, 71 degrees
on March 31, 2016 and the all-time record warm day for march of
78 degrees on March 29, 2004. Felton


PZ...Small Craft Advisory until 5 PM PDT Monday for Coastal Waters
     From Cape Flattery To James Island Out 10 Nm-West Entrance
     U.S. Waters Strait Of Juan De Fuca.


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