000
FXUS66 KPDT 271800 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
1000 AM PST Thu Jan 27 2022

Updated aviation discussion

.UPDATE...Most of the lower elevations are under a thick stratus
layer, but fog is not widespread. Visible satellite clearly shows
the expansive stratus east of the Cascades. A Freezing Fog
Advisory remains in effect for central and north central Oregon
where web cameras shows continued dense fog along Highways 97 and
197. The advisory was cancelled in Wallowa County as fog has lift
in the Wallowa Valley but there remains some fog along State Route
82 along Minam Summit. WSR-88D barely picked up the  freezing
drizzle that was observed along the Blue Mtn Foothills this
morning, but roads do not appear to be icy. Weather graphics and
social media posts should cover the spots of ice due to freezing
drizzle.

A tight pressure gradient is present from the Lower Treasure
Valley across the Grande Ronde Valley and will continue to tighten
the next 24 hours. However, the thermal gradient from BKE to LGD
will be around 5-7 degrees which will likely keep winds below
advisory criteria. Wister/85

&&

.AVIATION... 18Z TAFs...High pressure remains in place over the
Pacific Northwest this morning and will continue for a couple more
days. A low stratus layer remains over the lower elevations
affecting all TAF sites to varying degrees. Currently MVFR/IFR cigs
with VFR visibilities are present at all TAF sites except RDM and
BDN where the low stratus has created LIFR cigs and MVFR vsby at RDM
and LIFR vsby at BDN. Expect that conditions there will improve to
VFR as the stratus/fog burns away in the next few hours. Models want
to at least partially clear out the stratus in general this
afternoon/evening but do not see a reason for this happening, so
have discounted this. Have lifted ceilings somewhat this afternoon
in response to the models then had them lowering again tonight. Have
mostly limited vsbys to 6SM tonight as low vsbys didn`t happen last
night and this seems like a persistence situation. Do foresee a
return of the stratus to RDM and BDN after 06Z but have limited vsby
to 3SM due to model guidance not going any lower than that. Winds
will remain below 10 kts for the next 24 hours. Perry/83

&&


.PREV DISCUSSION... /issued 347 AM PST Thu Jan 27 2022/

Updated for Aviation...

SHORT TERM...TODAY THROUGH SATURDAY...Current infrared satellite
imagery shows a persistent layer of low stratus extending through
much of the area including the Lower Columbia Basin, Kittitas
Valley, Yakima Valley, Wallowa County, and across Central Oregon.
Madras, Redmond, and Bend are currently experiencing visibilities
at or below a quarter mile, thus a Freezing Fog Advisory is in
effect until 10AM Thursday morning for these areas. The presence
of dense fog and freezing fog will continue to be the main weather
concern through the remainder of the workweek as high pressure
stays in control. Roadways and walkways may be slick as a result,
especially during the morning and evening hours - so make sure to
exercise caution. There may also be the potential for areas of
drizzle or freezing drizzle along the foothills of the Blue
Mountains this morning. Accumulations will be lacking and minimal,
but any added frozen precipitation will increase the potential
for slick conditions. The other concern will be windy conditions
in the Grande Ronde Valley beginning this evening and extending
through Friday night, peaking Friday morning into the early
afternoon hours. Wind gusts of 30-40 mph will be possible out of
the south. These heightening winds are in response to the
departing upper level ridge losing its influence to an approaching
upper level trough, which will lead to tightening isobars along
the Northeast Mountains.

The upper level ridge that is currently located just off the
Oregon coast will slowly track east and push into the Pacific
Northwest through the day today, allowing the ridge`s axis to be
over our area during the early morning hours on Friday. This will
allow for another night of developing fog and freezing fog as
valley inversions strengthen to keep the stratus deck present. The
ridge then begins to depart our area to the southeast through the
day on Friday as a closed low off the coast of California pushes
inland and erodes the ridge as it nears the Four Corners region
early Saturday. This will allow an upper level trough to drop down
the British Columbia coast late Saturday into Sunday morning,
providing widespread showers and an end to the persistent foggy
and low stratus conditions that have plagued our region over the
last several days.

Temperatures will slowly increase through the rest of the
workweek, finally breaking into the low 40s through the Basin by
Saturday as the ridge`s influence begins to wane. 75

LONG TERM...SUNDAY THROUGH WEDNESDAY...A pattern change will be
underway on Sunday as weak ridging gives way to more zonal flow
and eventually troughing for the early portion of the week. This
change will also help clear out the low clouds and fog. As the
upper trough moves onshore, a surface cold front will accompany it
and bring mainly mountain snow, with some chance of lower
elevation rain/mixed precip. High temperatures will be above
freezing at the lower elevations, though lows will still be below
freezing, so anything that falls at night could be of the wintry
variety. However, QPF amounts in the lower elevations are expected
to be light. This system moves out of the region by later Tuesday
and the rest of the extended period is dry.

There is still uncertainty as to how the pattern develops from
midweek and beyond.  The guidance has come into better agreement as
to the evolution of an upper trough over the Great Basin around
Wednesday.  The GFS has trended toward the more amplified ECMWF
solution.  However, it is faster in its timing.  The timing
differences also impact the upstream flow over the Pacific Northwest
later in the week.  The ensemble clusters show quite a bit of spread
by Tuesday, but favor the less more progressive solution around the
midweek period.

High temperatures will mainly be in the 40s, except around 50 in
Central Oregon on Sunday. Overnight lows will be in the 20s.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  33  24  34  23 /  10   0   0   0
ALW  33  25  32  26 /  10   0   0   0
PSC  34  26  33  24 /   0   0   0   0
YKM  31  22  30  19 /   0   0   0   0
HRI  35  25  36  25 /  10   0   0   0
ELN  28  18  26  19 /   0   0   0   0
RDM  46  26  46  25 /   0   0   0   0
LGD  33  21  33  21 /   0   0   0   0
GCD  43  22  42  22 /   0   0   0   0
DLS  36  29  36  28 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Freezing Fog Advisory until 10 AM PST this morning for ORZ510-
     511.

WA...None.
&&

$$

SHORT TERM...75
LONG TERM....77
AVIATION...83

NWS PDT Office Area Forecast Discussion