Weather Service Report


119 
FXUS66 KPQR 231734 AAB
AFDPQR

Area Forecast Discussion...UPDATED
National Weather Service Portland OR 
933 AM PST Sun Feb 23 2020


Updates to the short term, aviation and marine discussions. 


.SYNOPSIS...A pacific front will bring breezy conditions, valley rain
and mountain snow to the region today. Large waves will bring 
increasingly hazardous surf conditions to the beaches this afternoon 
and tonight. High pressure will then return to the West Coast of 
the US and result in cool nights, mild days, and mainly dry weather 
this upcoming work week.


&&


.SHORT TERM...Today through Wednesday...Satellite imagery early this
morning shows a rather impressive ~990mb low pressure moving
eastward between Vancouver Island and Haida Gwaii. This front brought
considerable rainfall to much of the forecast area with accumulations
upwards of a quarter of an inch. With significant lift and convection
along the leading edge of the front, conditions quite gusty,
especially along higher terrain like Mt. Hood. 

Behind the cold front there will be a brief lull in the wet weather 
and even an hour or two of sunshine is likely. With clearing skies
and daytime heating, instability will increase so cannot rule out a
thunderstorm or two across the northern zones and northern waters.
This instability will gradually deepen through the day so expect
showers to spread eastward across the area this afternoon. Brief
heavy rain and small hail will likely accompany the most intense
showers. With the coldest temperatures aloft remaining over
Washington today, expect showers this afternoon to be more
numerous and more intense across our northern zones when compared to
our southern zones. 

Snow levels around 4000-5000 ft range will begin to drop into the
2000-3000 ft range later this afternoon and evening behind the cold
front. Thus, the main winter weather impacts at the Cascade passes
will likely hold off until late this morning/midday. Snowfall amounts
in the Cascades do not appear overly impressive with this storm
system and will likely be marginal for an advisory at pass level.
Nonetheless, the rapidly falling snow levels this afternoon and
evening will likely enable to snow to stick rapidly under any heavier
or more persistent showers.

Models remain in good agreement that a shortwave ridge will build
over the eastern Pacific and Pacific Northwest tonight and Mon. This
will result in decreasing showers with most of the area  drying out
entirely by Mon afternoon or evening. As is common with a ridge
building in behind a front, there is a chance of late night and
morning valley fog on Tue giving way to mostly sunny skies. Models
suggest that this ridge will flatten Tue afternoon as a shortwave
trough advances towards the area. While weak, it could bring
precipitation to the area but in a high PoP, low QPF format.
NBM guidance has struggled to capture these type of events on several
occasions over the past year so opted to trend PoPs a bit higher than
NBM guidance across our northwestern zones Tue evening into Tue
night. Ridging will again build over the area Wed. -Neuman/Muessle


.LONG TERM...Wednesday night through Sunday...Models and their 
ensembles are in good agreement shortwave ridging will be the 
dominant feature over the Pacific Northwest Wednesday night through
Friday. This will bring predominantly dry conditions, morning valley
fog in spots and mild temperatures. In fact, temperatures appear
likely to top out in the upper 50s to low 60s next Thursday and
Friday. Models and their ensembles suggest a more active weather
pattern will try to take hold next weekend as a shortwave trough
slides into the ridge. However, there are still substantial
differences in how this will play out among the models with some
scenarios keeping us dry through the weekend while many others result
in valley rain and high mountain snow next weekend. NBM PoPs were
maintained as it seems to capture the uncertainty well. /Neuman

&&

.AVIATION...Radar is showing the front has crossed the middle of
the CWA and is continuing to move southeast at a good pace. MVFR
conditions ahead of the front is still being observed in central
and southern valley sites. The front is expected to be fully out
of the area by 19Z. VFR conditions in the post-frontal air mass 
is already being met in KAST with inland sites not too far 
behind. An MVFR-VFR mix should be expected for a couple of hours
between 18-20Z. Pockets of rain showers will continue through 
the morning as the unstable air mass moves across the area. LLWS
has been reported across the area as well as moderate to severe 
turbulence. There is an increased chance of thunderstorm 
activity mainly to the north coast and southwest WA near the 
Columbia River. Gusty westerly winds along the coast and
gusty southwesterly winds inland will continue until around 02Z
Mon. VFR conditions will continue through the afternoon and into
this evening. 


KPDX AND APPROACHES...VFR conditions prevailing through the day.  
South to southwest winds will continue to produce gusts around 
30 kt through 00Z Mon. LLWS as well as moderate to severe 
turbulence has been reported over KPDX as the front moves 
through. These conditions should diminish through the afternoon.
-BPhillips


&&

.MARINE...Gale force winds looking likely today for the waters
north of Cascade Head. Coastal and buoy obs at 3 am showing south
wind gusts to 33 kt. Wind should switch to west then northwest
this morning after the cold front moves through but winds will
continue to gust to 35 kt into the early evening. This a all
brought about by a deep low heading to Vancouver Island with the
associated front trailing into the WA & OR waters. 

Swell generation occurring not too far offshore is producing a 
fresh swell that will move into the waters this afternoon. 
Expect seas to peak around 18 to 23 ft late this afternoon. The 
higher waves will be over the northern zones. Spectral wave 
guides for buoy-29 are indicating seas will reach 22 ft at 14 sec
around 4 pm and fall below 20 ft around 10 pm tonight. Winds and
seas will drop through Monday reaching sub-SCA criteria by 
Monday night. /mh -BPhillips

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...High Surf Advisory from 1 PM this afternoon to midnight PST 
     tonight for North Oregon Coast.

     Winter Weather Advisory until 10 PM PST this evening for 
     Northern Oregon Cascades.

WA...High Surf Advisory from 1 PM this afternoon to midnight PST 
     tonight for South Washington Coast.

     Winter Weather Advisory until 10 PM PST this evening for South 
     Washington Cascades.

PZ...Gale Warning until 6 PM PST this evening for coastal waters 
     from Cape Shoalwater WA to Cascade Head OR out 60 NM.

     Small Craft Advisory until 10 AM PST Monday for coastal waters 
     from Cascade Head OR to Florence OR out 60 NM.

     Small Craft Advisory until 6 AM PST Monday for Columbia River 
     Bar.

&&

$$

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This discussion is for Northwest oregon and Southwest Washington 
from the Cascade crest to 60 nm offshore. This area is commonly 
referred to as the forecast area.

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Western Regional Climate Center, wrcc@dri.edu