551 
FXUS66 KPQR 111706 CCA
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
902 AM PST Mon Nov 11 2019

.SYNOPSIS...Drier weather is expected today with high pressure 
back over the Pac NW. Offshore flow will lead to above normal 
temperatures and less cloud cover. Another weak cold front is likely 
to clip the region Tuesday with some rain, mostly north. The latter 
half of the week may see additional frontal systems moving through 
for a return to more seasonable wet weather.

&&

.SHORT TERM...Today through Wednesday...High pressure over eastern
Washington/Oregon will maintain increasing offshore flow today. Area
of fog and low stratus still to the north of Portland/Vancouver, and
to south of Portland. But, offshore winds have brought somewhat drier
air to the low levels into the Willamette Valley. This drier air
leading to clearing skies to in the Portland/Vancouver metro, and to
the south to the west of I5 as far south as Albany. Low clouds and
fog still hugging areas east of I5 to south of Aurora, with most
widespread fog/stratus covering the south Willamette Valley southward
through Cottage Grove into the Umpqua Valley. Coast has best
conditions, under mostly clear skies, with just variable high clouds.

Offshore pressure gradient across the Columbia Gorge, from The 
Dalles to Troutdale, near 7.0 mb offshore at 9 am. This will 
maintain breezy east winds in the western Columbia Gorge, with gusts 
35 to 45 mph but locally to 55 mph such as at Crown Point. Closer to 
the metro, gusts generally 20 to 35 mph, with strongest at 
Troutdale. Winds will gradually east tonight into Tue. 

Models have been fairly consistent in showing a short wave topping 
the upper ridge late tonight and Tuesday, allowing a cold front to 
push east across the forecast area Tuesday. Not unlike the previous 
front from late last week, some tropical moisture has been entrained 
into this system as seen in satellite imagery, and GFS continues to 
suggest precipitable water values on the order of 1.0" to 1.2" as 
the front moves through Tuesday. Best dynamics will be across the 
north part of the forecast area, with chances for rain ranging from 
categorical in the north to slight chances in the south. After 
slightly above normal temperatures for many areas today, clouds and 
precipitation will bring temperatures back to near or even a little 
below normal during the daytime Tuesday. The clouds will also tend 
to limit diurnal temperature swings Tuesday night, keeping the low 
temperatures above normal. 

By Wednesday models are quick to restrengthen the upper ridge over 
the region, allowing an offshore flow to redevelop. Strong 
subsidence along with initially moist low levels suggest plenty of 
fog or low clouds are likely to develop Tuesday night and persist 
into Wednesday morning. 			    /Rockellson

.LONG TERM...No Changes. Previous discussion follows...Wednesday
night through Sunday...Upper level ridging builds back across the
forecast area Wednesday night and Thursday, though not quite as
strong as the ridge building in tonight/Monday. Forecast models also
suggest some baggy troughing somewhere in the vicinity of the
California coast Thursday, which appears likely to encourage split
flow with the next front expected for Friday. This seems to suggest
Friday's front will be fairly weak for this time of year. Longer
range guidance suggests the pattern should become more active either
during the weekend or the following week, which makes sense
considering the active phase of the MJO is currently entering the
West Pacific. This can often be a sign of a pattern change toward
more active weather 7 to 10 days out as the north Pacific jet
strengthens and becomes more zonal.  Weagle

&&

.AVIATION...Westerly flow aloft will maintain variable high clouds
across the region today into tonight. Areas of IFR stratus remain in
the lower Columbia River between Clatskanie and Vancouver, with IFR
stratus/fog also along to east of I5 from Aurora southward to Albany,
then more extensive stratus on to south through Eugene and Cottage
Grove. Tops generally 1000 to 1500 feet, so think should burn out for
most areas between 19Z and 21Z. Then, VFR through tonight. Moderate 
offshore pressure gradient of 7.0 mb across the Columbia Gorge, with 
east winds 25 to 40 kt in that area. East winds less degree continue 
along the coast, inland areas and over the higher terrain. Gradients 
weaken somewhat tonight, and likely to get areas of fog/stratus 
reforming to south of Salem as well as the Cowlitz Valley after 05Z 
tonight. 

KPDX AND APPROACHES...Cross-Gorge pres gradient now near 7.0 mb 
offshore, which keeps easterly winds 15 to 25 kt at KTTD, and 10 to 
15 kt across rest of PDX ops area today. But, still have lee side 
trough along I205, which is keeping winds at KPDX and downstream to 
KVUO and KSPB as light westerly. East winds staying just above KPDX.
This pattern will hold til 18Z, then will see east wind surface at 
KPDX as trough shifts to west a bit more. /Rockey

&&

.MARINE...Surface high will gradually build over the inland Pac NW, 
with increasing east to northeast winds across the coastal waters 
into Mon. Think most gusts stay in the 5 to 15 kt range at most, but 
could see a few gusts 20 to 25 kt in gaps of the coastal terrain and 
near larger bays later today. 

Winds relax on Tue and gradient weakens thanks to the warm front 
slowly approaching and lifting to the north of the region. Southerly 
winds stay in the 10 to 15 kt, with 4 to 6 ft seas.

Models continue to show another front arriving late Thu. But, models 
have had inconsistency in strength and timing of the front. Will see 
a boost in westerly swell behind the front, with swell getting up to 
10 to 13 ft. Another front will arrive later next Sat into Sun, with 
stronger potential for 25 to 35 kt winds and building seas. /mh -
Rockey/Muessle

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Air Stagnation Advisory until noon PST Tuesday for Cascade 
     Foothills in Lane County-Central Columbia River Gorge-
     Central Willamette Valley-Greater Portland Metro Area-
     Lower Columbia-Northern Oregon Cascade Foothills-South 
     Willamette Valley-Upper Hood River Valley-Western Columbia 
     River Gorge.

WA...Air Stagnation Advisory until noon PST Tuesday for Central 
     Columbia River Gorge-Greater Vancouver Area-I-5 Corridor 
     in Cowlitz County-South Washington Cascade Foothills-
     Western Columbia River Gorge.

PZ...None.
&&
$$


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