Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 030938

Area Forecast Discussion
National Weather Service Seattle WA
238 AM PDT Mon Aug 3 2020

.SYNOPSIS...An upper level trough is making its arrival onshore
early this morning, resulting in some light rain along the coast
and in the northern CWA today. Inland locations may also see some
light rain as the trough moves across the area. Onshore flow will
keep the temperatures seasonable. Dry conditions expected from
late today through mid week before the next system arrives
Wednesday night into Thursday.


.SHORT TERM /TODAY THROUGH WEDNESDAY/...The upper level trough
will bring rain chances to the Olympic Peninsula and coastal
locations through the day today with inland locations seeing a
slight chance for rain as well. The upper level feature is not
going to stay incredibly cohesive as it treks east, with PoPs
featuring only slight chances for eastern and Cascadian locations.

Upper level ridging returns for late Monday into the mid-week
timeframe with dry and seasonable conditions expected. That being
said, the next system looks to arrive late Wednesday into Thursday
bringing more widespread rain chances to much of the CWA.

.LONG TERM /THURSDAY THROUGH SUNDAY/...Models seem to be in better
agreement regarding the next system to arrive on Thursday, with
light rain spreading inland through the day. Rain amounts are not
anticipated to be anything excessive for a summer system,
generally around a tenth to quarter of an inch at most at this
time. Some showers may linger on the back end of the system into
Friday with a very slim chance for thunder, primarily in the
Cascades at this time. Thunder chances will need to be evaluated
further later on.

Another quick hitter system looks to be on the way for Saturday
with light rain amounts possible, lingering into early Sunday.
Then it appears that there is some divergence in model solutions
as to whether a ridge rebuilds or that somewhat unsettled weather
lingers on. There is not too much confidence to be had for a time
frame so late in the period.



.AVIATION...An upper trough and an associated weak weather system
will move inland today. Weak high pressure aloft will build over
the area tonight. The flow aloft will be westerly. At the
surface, onshore flow will increase this afternoon as a weak
trough over the Offshore Waters falls apart and is replaced with
higher pressure. The air mass will be stable.

There will be IFR low clouds and areas of reduced visibilities in
mist near the coast and partially into the Southwest Interior
this morning. Otherwise, there will be areas of ceilings 5000-7000
feet today for the interior with some higher clouds above that.
Drier air will move into the area this afternoon and evening with
most of the clouds breaking up by this evening. Low clouds are
likely again later tonight under continued onshore flow.

KSEA...There might be some low clouds at times this morning but
mostly it looks like mid level clouds today. Even these should
clear by evening but then low clouds will probably redevelop
Tuesday morning. South to southwest wind 4-8 knots will become
northerly this evening. Schneider


.MARINE...A weak weather system will move inland today. Another
weak front will reach the area around Thursday. Otherwise, an
onshore flow pattern will continue this week with high pressure
offshore and lower pressure inland. Expect small craft advisory
strength west winds most evenings for the Central Strait of Juan
de Fuca and the East Entrance. Schneider


.HYDROLOGY...The daily hydrology discussion has ended until the
start of the next rainy season; it will only be updated as needed
until then.


PZ...Small Craft Advisory until 2 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.


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