838 
FXUS66 KPQR 262248
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR 
248 PM PST Sat Jan 26 2019

.SYNOPSIS...High pressure will support a dry weather pattern through 
at least Tuesday, with areas of valley fog and clouds. Offshore 
winds through the Gorge will pick up on Mon. The latter part of the 
next week looks more active as a trough of low pressure moves over 
the region.

&&

.SHORT TERM...Tonight through Tuesday...Models keep a strong upper 
ridge just off the coast through Tue. Through Sun the surface 
pressure pattern remains weak, which will tend to favor the 
continuation of fog and low stratus in the inland valleys. The fog 
and stratus as normal will be most widespread in the late night and 
morning hours, but with little drying of the air mass and the 
strength of the inversion, areas of clouds and fog are likely to 
persist through the afternoon. Fog and low clouds are likely to 
continue into Mon and Tue, but a shot of cooler air with a shortwave 
coming down Mon over the Rocklies and Columbia Basin will strengthen 
an inland high, resulting in a strengthened offshore flow through 
the Gorge. Drier air with the east winds will tend to minimize the 
clouds and fog in the north Willamette Valley and west end of the 
Gorge. Along the coast, and in the Coast Range and Foothills above 
the inversion skies will remain mostly clear, continuing the trend 
of mild temps during the dayimes through Tue. Temps in the 
Willamette and Lower Columbia valleys will tend to remain a bit 
cooler under the clouds. In the central Gorge and Hood River Valley 
expect an expansion of Columbia Basin stratus over the next few 
days. 

.LONG TERM...Tuesday night through Saturday...The start of the 
extended forecast has the models in some disagreement. The GFS has a 
developed ridge, which will keep the area mild and dry. The ECWMF on 
the other hand has a small compact low which will bring slightly 
cooler temperatures as well as precipitation to the area through 
Wednesday evening. The differences between the models continue 
through the end of next week. The GFS has the ridge as the 
dominating feature through Thursday afternoon. The ECWMF has a 
shortwave ridge pushing through around the same time. Behind these 
ridge seen in the GFS and the shortwave ridge in the ECWMF, the 
models start to slowly come into agreement. The operational models 
both show a trough, which looks to bring in some cooler air along 
with moisture. 850mb temperatures starting on Friday morning look to 
be around 4 to 5 degrees Celsius (39 to 41 degrees Fahrenheit), and 
looks to drop to around -4 to -3 degrees Celsius (25 to 27 degrees 
Fahrenheit) through the early next weekend. What these 850mb temps 
mean is that if the models verify, we could see a lowering of 
surface temperatures, snow levels falling and the possibility of 
winter precipitation coming to areas that have seen little to no 
winter precipitation given elevation. It should be noted that the 
area will typically see winter precipitation on the valley floor 
with 850mb temperatures between -8 to -6 degrees Celsius (18 to 21 
degrees Fahrenheit).

With the noted disagreement in the models at the start of the 
extended period, I have leaned into more of a blend between multiple 
models. Especially, when looking at precipitation chances as the 
models tend to have a dry bias. To summarize, the mild and somewhat 
dry pattern will continue though next week, with an increase in 
precipitation chances steadily increasing through the middle of the 
week, and into next weekend. /42

&&

.AVIATION...Conditions along the coast will generally remain VFR
the next 24 hours under offshore flow. The exception may be a few
hours of fog/low stratus near KAST during the low tide Sunday
morning.

Conditions in the interior valley are slowly starting to improve
this afternoon, but there is still some stubborn LIFR stratus
sticking around south of KUAO. The latest guidance has backed off
on the strength of the easterly flow developing near the Columbia
River Gorge this afternoon. As such, not expecting a whole lot of
improvement in conditions this afternoon. Expect conditions in
the interior valley to lower after sunset, with widespread fog
likely this evening. There is still a chance that dry easterly 
winds will develop near the Gorge which may help to delay fog 
development near KTTD until later tonight. There is an increasing
chance for the development of freezing fog and/or frost later 
tonight/early Sunday morning. Expect LIFR conditions that develop
tonight to linger through at least Sunday morning.

KPDX AND APPROACHES...IFR stratus looks to briefly scatter out
for a few hours this afternoon, but will likely redevelop shortly
after sunset. Expect foggy conditions to return this evening and
persist through at least Sunday morning. There is a chance that
we could see some LLWS concerns this evening as flow aloft
increases. /64

&&

.MARINE...High pressure will remain over the NE Pac through early
next week, with varying degrees of thermal low pressure along the
northern California and Oregon coast. This will maintain a N-NE
wind pattern over the waters, though the winds will likely ease
as high pressure briefly weakens from a trough dropping south
across the Northern Rockies. Winds look to then strengthen and
become more easterly on Monday as high pressure builds in the 
Columbia Basin. This could bring some SCA gusts to 25 kt over the
northern outer waters. Seas are expected to remain around 6 to 8
feet during this time and may become choppy on Monday as the 
winds pick up. 

Based on the latest guidance winds look to then become southerly on
Wednesday as a series of frontal systems moves across the waters
late next week. This could bring another round of SCA gusts
around 25 to 30 kt with seas possibly building into at least the
lower teens. However, confidence in the forecast is low late 
next week due to model variability. /64

&&

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