Area Forecast Discussion

from: NWS Pendleton, OR

FXUS66 KPDT 231049

Area Forecast Discussion
National Weather Service Pendleton OR
249 AM PST Sun Jan 23 2022

.SHORT TERM...Sunday through Tuesday...Much of the Columbia Basin
currently experiencing low stratus and dense freezing fog as high
pressure remains centered just off the Pacific coast. Currently
experiencing the worst of the fog in Pendleton and Walla Walla, as
well as the lower Yakima valley. Yakima itself is clear as of 2AM,
but expecting fog to work its way up valley through the early
morning. Drier air over the Kittitas Valley should keep them clear
for this morning. Current freezing fog advisory remains up through
1PM this afternoon.

Satellite imagery depicting some overhead cirrus as the ridge
overhead begins to break down and the upper-level winds usher some
N. Pacific moisture overhead. This has made fog difficult to
track overnight, however expecting much of the fog extent to lie
in similar areas impacted early yesterday morning, with an
increase in severity. While the ridge overhead will wane in
influence, light winds and low dew point depressions will allow
low stratus and fog to persist well into the day Sunday,
especially for the lower Basin and Walla Walla. A shortwave
passing to our east will allow for breezy conditions in the Grande
Ronde Valley, however conditions elsewhere will remain stagnant
through Monday.

Transitory ridge then builds in behind the shortwave beginning
late Monday night into Tuesday. Models suggesting widespread low
winds and dew point depressions, meaning fog could become more
widespread despite dry northerly flow aloft. Should the low
stratus deck persist, could see some of it start to creep towards
central OR Monday night into Tuesday as well. Will need to see how
much dry air entrains into the area in light of the upper-level
wind shift before increasing confidence in fog forecast.
Otherwise, still expecting cool 30s to prevail for highs in the
Basin and adjacent valleys, while central OR sees 50s and our
mountains see upper 30s to low 40s. Overnight lows will primarily
be in the 20s. 74

.LONG TERM...Wednesday through Sunday...Weather pattern will
continue to be dominated by a ridge of high pressure through
Thursday. This will result in a continued inversion trapping stratus
and fog across the Columbia Basin. Models continue to show a
weakening of the ridge Friday through Sunday with a transition to a
more westerly flow. However, models are not in good agreement with
timing and strength of systems that would be clipping the region
during that stretch. NBM captures this with low POPs and low QPF
starting late Friday and through the weekend. This is likely to
start weakening the inversion and provide some partial mixing of the
fog and stratus through the weekend.


.AVIATION...12Z TAFs...RDM and BDN will remain VFR over the
next 24 hours. The other terminal sites will be under the influence
of low clouds and fog with some fluctuating conditions at times
ranging from VLIFR to IFR. YKM is currently VFR but expect fog
and/or stratus to increase there in the next 4-6 hours.


PDT  35  28  35  25 /   0   0   0   0
ALW  36  27  35  26 /   0   0   0   0
PSC  35  27  36  25 /   0   0   0   0
YKM  37  23  39  23 /   0   0   0   0
HRI  36  27  38  25 /   0   0   0   0
ELN  35  20  39  18 /   0   0   0   0
RDM  55  29  56  26 /   0   0   0   0
LGD  40  25  41  22 /   0   0   0   0
GCD  48  29  48  24 /   0   0   0   0
DLS  41  31  43  29 /   0   0   0   0


OR...Freezing Fog Advisory until 1 PM PST this afternoon for ORZ044-

WA...Freezing Fog Advisory until 1 PM PST this afternoon for WAZ028-




NWS PDT Office Area Forecast Discussion