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fxus66 kpqr 131029 

Area forecast discussion
National Weather Service Portland or
230 am PST Wed Nov 13 2019

Synopsis...dry weather returns today and continues through
Thursday as an a ridge of high pressure redevelops over the Pacific
northwest. A cold front will move across the region Thursday night
and Friday for the next chance of rain.


Short through Friday...the upper level ridge of high
pressure can be seen in water vapor pictures rebuilding offshore
between 130w and 140w early this morning as the front trough that
pushed the cold front through yesterday was already crossing The
Rockies. Satellite and surface observations showed widespread low
clouds and fog over much of the forecast area. Models have remained
consistent in depicting the ridge moving east across the area later
today and tonight, setting up an offshore flow pattern in the low
levels with high pressure east of the Cascades. This will bring
drier air back into the region today and tonight, with the net
result of less low clouds and fog tonight and Thursday morning, and
mainly limited to the wind protected valleys away from The Gorge.

Late tonight and Thursday the upper level flow turns to the
southwest on the backside of the upper ridge. A weak shortwave in
the southwest flow is expected to bring an increase in high level
moisture and clouds. Models remain consistent showing a stronger
shortwave approaching the region late Thursday night and moving
across Friday, pushing the next in the series of weak cold fronts
across the area early Friday. As with the previous couple of weak
fronts, some tropical moisture will pulled up with the front, with
GFS indicating precipitable water values peaking a little higher
than 1.0" as the front moves across early Friday. Moisture again
will be concentrated in the low to mid levels, which coupled with
sufficient dynamics should be good for likely to categorical pops
for most of the forecast area for at least a few hours as the front
moves through. As the pattern remains progressive, expect the
chances for rain to diminish quickly behind the front Friday

Long term...Friday night through changes. Previous
discussion follows. Low amplitude ridging moves back over the area
behind friday's system. Models try to bring another system into the
Pacific northwest Saturday, but operational runs are showing most of the
moisture staying north of the local forecast area. Some ensemble
members must have a weaker ridge, though, because the nbm paints
slight chance to chance pops across most of the forecast area by
Saturday evening. Left in these low end pops, but not confident in
saturday's forecast at this point. Models continue to show a cold
front pushing inland Sunday, but moisture looks less impressive than
with past runs and again the best rain chances stay north. Models
remain in general agreement that a progressive pattern persists for
the Pacific northwest into early next week, but there are significant
differences in timing of systems, so confidence remains low. There
is a chance that snow levels could drop to Cascade Pass level next
week. Bowen


Aviation...moist and stable at the lower levels with widespread
stratus across the interior lowland and north coast. Mainly low MVFR
for the interior airports with cigs around 1000-1500 ft. But there
are pockets of IFR/IFR in the keug and kkls area. Coastal areas are
LIFR at Pacific City northward, but VFR south. However stratus
filling in coastal valleys may drain low stratus to the coast so may
see a few hours IFR through 15z or so. Overall trend is for offshore
flow to increase which will eat away at the stratus today. Coastal
areas should break out to VFR 15-18z. For interior locations, 16-19z
around kpdx and 20-22z otherwise. Fog and low stratus should return
for the interior tonight except for the areas near The Gorge where
east winds will keep the lower air mass mixed.

Kpdx and approaches...cigs around 1500 ft have been slowly lowering
overnight. A persistent 600 ft cig at kttd should spread to kpdx for
a few hours this morning, but no definite indications as of 10z.
Kttd-kdls gradient just turned -0.5 mb which the NAM model handled
best. Kpdx-kttd gradient is +0.2 mb and models bring it to 0 mb
around 19z, so expect around that time cigs should dissipate. By 17z
Wed, easterly winds will begin to pick up causing the inversion to
break up slightly and mixing to occur dissipating the stratus. /Mh


Marine...high pressure builds inland today for increasing offshore
flow. The next front arrives later Thursday bringing the potential
wind gusts to 25 kt. Model solutions have stabilized and have higher
confidence for Small Craft Advisory winds Thursday night. Expect a
fresh westerly swell behind the Thursday night front to bring seas
up to 10 to 12 ft late Thursday and through early Saturday. Another
front will arrive next Sat into sun,and could also bring Small Craft
Advisory winds into our waters through the weekend. /Mh /42


Pqr watches/warnings/advisories...



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