Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS66 KSEW 051542

Area Forecast Discussion
National Weather Service Seattle WA
842 AM PDT Wed Aug 5 2020

.SYNOPSIS...High pressure aloft will weaken as a frontal system
approaches the region. The front will bring some light rain to the
area late tonight and Thursday morning. Weak troughing will
persist over Western Washington into Saturday for generally dry
but cooler conditions. High pressure will gradually rebuild early
next week for a trend toward somewhat warmer conditions.


.SHORT TERM /TODAY THROUGH FRIDAY/...Stratus that pushed part way
inland overnight is burning back to the coast this morning with
plenty of sunshine over the interior. A weak frontal system will
spread some high clouds into the area later this afternoon with some
rain possible on the coast after midnight. Light rain will spread
into the interior of Western Washington on Thursday morning, but
amounts will be light. High temperatures on Thursday should be a
good 8 to 12 degrees cooler than today. Weak upper troughing remains
over the region Friday into Saturday, but it should be dry with
night and morning clouds and temperatures near or a little below
seasonal normals. No forecast updates planned this morning. The
remainder of the previous discussion follows with updates to the
marine and aviation discussions.  27

The model interpretation for Friday is still to trend drier with a
return to seasonably normal temperatures, as low amplitude upper
level ridging builds back into the area. Highs will be in the low
to mid 70s with 60s along the coast.

.LONG TERM /SATURDAY THROUGH TUESDAY/...Moving into the weekend,
a clear pattern is lacking in the wake of the system that moves
through on Thursday. Arguably quasi-zonal flow with a broadly
unsettled pattern shaping up for Saturday, which is shaping up to
be benign across western Washington. Highs will be in the mid to
upper 70s, continuing into Sunday before the pattern starts
hinting at rebuilding a more well defined ridge.

A more well defined system looks to trek south from the Gulf of
Alaska, but at this point, it does not appear to dive south enough
into Washington. At this point in time, if the system just clips
the area, that could lead to light shower activity in the northern
parts of the CWA at best. Confidence in the exact extent of its
southward movement is low and bears monitoring in future forecast
iterations. For Tuesday, the pattern seems quiet again and
temperatures warm a few degrees from Monday`s temperatures,
although the models hint at yet another system in the first half
of next week. While too early to speculate, more details will come
into focus as the time frame of interest nears.



.AVIATION...Southwest flow aloft as an upper trough approaches the
area today. Onshore flow will stratus clouds and the coast and into
areas around the South Sound. VFR for most this morning with IFR
along the coast and Southwest Interior. Patchy fog across the
central Puget Sound near KPWT. VFR cigs by late this morning as
clouds clear towards the coast. A cold front will bring rain tonight
to the coast with low clouds and rain pushing into the interior
areas early Thursday morning. South to southwest winds light this
morning with 5 to 10 knot winds this afternoon into tonight. JD

KSEA...VFR cigs. South to southwest winds light this morning to 10
knots this afternoon. JD


.MARINE...Onshore flow through this week. Small Craft Advisory winds
for the Strait of Juan de Fuca through tonight. SCA winds tonight
for the northern inland waters. Onshore flow will increasing
Thursday as a cold front moves through the area. A second, weaker,
front will diminish over the Coastal Waters Friday night. Onshore
flow through the weekend

Onshore flow will continue today. Highest wind and
waves will be found through the Strait of Juan de Fuca - Small
Craft Advisory winds are likely. Onshore flow will increase on
Thursday as a cold front moves inland. A second, weaker, front will
diminish over the Coastal Waters Friday night. Onshore flow will
continue into the weekend. 33


.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 11 PM PDT this evening for Central
     U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
     Waters Strait Of Juan De Fuca.

     Small Craft Advisory from 5 AM early this morning to 11 PM PDT
     this evening for Northern Inland Waters Including The San
     Juan Islands.


$$ is the U.S. government's official web portal to all federal, state and local government web resources and services.