-- Discussion containing changed information from previous version are highlighted. --
000
FXUS66 KPQR 270225 AAA
AFDPQR

Area Forecast Discussion...UPDATE
National Weather Service Portland OR
724 PM PDT Mon Oct 26 2020

Updated the marine and aviation discussions

.SYNOPSIS..High pressure will build in over the Pacific Northwest
through the middle of this week. This will bring dry weather along
with temperatures slowly warming. A weak front towards the end of
this week brings the next chance for rain.

&&

.SHORT TERM...Tonight through Thursday...Sky cover and temperatures
are the main forecast challenge in the short term as dry weather
persists under high pressure and light winds. Temperatures will
gradually moderate closer to what is normal for this time of the
year.

Satellite imagery shows marine stratus over the NE Pacific banking up
to the Washington coast late this afternoon. These low clouds are
ahead of a east-west oriented front well north of Washington. The
forecast models show that the marine stratus will move southward
tonight and Tuesday as the front shifts further south. The front will
remain north of the Portland forecast area as high pressure holds
over the Pacific NW and NE Pacific, but the low clouds ahead of it
will likely move into SW Washington and extreme Northwest Oregon
tonight, and possibly further south into western Oregon on Tuesday.

A thermal trough along the SW Oregon coast tonight with higher
pressure to the NE, may maintain enough of an offshore component to
the winds to prevent the stratus from moving onto the central Oregon
coast tonight. Light north winds moving through the interior valleys
though, will likely move any stratus that may make it to the north
Willamette Valley tonight further south into the Willamette Valley
Tuesday morning. The forecast confidence of the stratus making it to
Salem is low, and really do not think the clouds will make it to
Eugene. Regardless, the interior valleys will likely clear in the
afternoon and daytime highs will likely warm into the mid to upper
50s. There will be little change Tuesday night and Wednesday, with
some stratus moving inland Tuesday night into Wednesday.

High pressure weakens Wednesday night and Thursday allowing another
warm front well north of the area to move southward and likely
bringing stratus into SW Washington and NW Oregon. Have updated the
sky cover and temperature forecasts this evening to account for the
increasing chance of diurnal marine stratus. ~TJ

.LONG TERM...No Changes. Previous discussion follows...Thursday night
through Monday...Models are continuing to agree that Friday is the
next chance for precipitation, as a cold front looks to impact the
area, temporarily breaking the hold of the high pressure which has
been the dominate synoptic feature. The models are in general
agreement as to the timing and location. However, there remains
enough differences in precipitation between operational model
families as they continue to show this cold front weakening each
successive run. Next weekend operational models are supported by
ensembles, as they show the ridge of high pressure rebuilding. This
will likely lead to dry weather returning for most of the area. /42

&&

.AVIATION...Satellite imagery Tuesday evening shows an area of
MVFR marine stratus with cigs generally between 2000 and 3500 ft
quickly moving southward down the Washington coast and through
the Puget Sound. Expect this area of stratus to continue pushing
southward tonight, moving into the south Washington and north
Oregon coast between 02-06Z Tuesday and then the central Oregon
coast between 06-12Z. It appears stratus will also move down the
Cowlitz Valley and into the northern Willamette Valley late
tonight, and possibly into the central valley as well. The
biggest forecast challenge for the 06Z TAF cycle is expected cigs
at KSLE and KEUG tonight into Tuesday morning, as there is some
uncertainty in regards to how far south the stratus will make it
tonight. The latest trends suggest stratus may be able to push to
the south of KSLE, possibly approaching KEUG. Stratus should
scatter out some Tuesday afternoon, before redeveloping and
expanding across the entire Willamette Valley Tuesday night.

For detailed regional Pac NW weather information, go online to:
http://weather.gov/zse

KPDX AND APPROACHES...Scattered to broken MVFR stratus will most
likely move into the KPDX terminal early Tuesday morning, by 15Z
at the latest. At least some scattered clouds with cigs around
3000 ft may linger through Tuesday afternoon before skies become
overcast later Tuesday night with cigs around 2000 ft. -TK

&&

.MARINE...High pressure offshore will maintain northerly winds
across the waters over the next several days, with the strongest
winds expected over the coastal waters south of Cascade Head.
Seas will stay in the 3 to 6 ft range, with the highest seas
well offshore. Do not expect much change in this pattern through
early Thursday.

A front will approach the region later Thursday and shift across
the coastal waters Thursday night. This will bring the return of
light to moderate southerly winds to the waters on Friday,
sustained around 15 to 20 kt. Seas will see a bump upward, but
will most likely peak between 6 and 9 ft Friday night. Seas and
winds should east this weekend. -TK/Rockey


&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.
&&

$$

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