Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 231102
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
302 AM PST Mon Jan 23 2017

.SHORT TERM...Today through Wednesday...an upper level trough will
continue to progress eastward over the region today but most of the
energy and precipitation will remain south of the forecast area with
some isolated to scattered type precipitation showers over central
Oregon. The trough will exit to the east as a ridge of high pressure
sets up off the coast. This will begin to place the forecast area
under a cooler northerly flow through the first of the week. This
pattern could produce some upslope show showers over the far eastern
mountains through Wednesday but very little if any accumulations
expected. Main concern this week will be the development of stagnant
air conditions as the ridge of high pressure intensifies and
inversions develop. This will lead to the possibility of a stratus
deck forming over the Lower Columbia Basin and the subsequent
formation of fog and or freezing fog.

.LONG TERM...Wednesday night through Sunday night...Wednesday night
through Sunday night a amplifying mid/upper level ridge of high
pressure builds just offshore thus putting the interior Pacific
Northwest on the eastern flank of the ridge for a northerly flow
aloft, in which a weak upper level disturbance moves southward
through the forecast area Tuesday night through Thursday afternoon
for a slight chance of snow in central Oregon and the Blue
Mountains. Otherwise, the northerly flow will produce dry conditions
Tuesday night through Saturday night. As the ridge builds slowly
over the region a surface-based inversion due to sinking air aloft
associated with the ridge will trap moisture in the boundary layer
thus producing patchy freezing fog and low stratus clouds across the
Lower Columbia Basin and adjacent valleys as well as along the
Foothills of the Blue Mountains of WA/OR.  Polan


&&

.AVIATION...12Z TAFs...areas of mvfr and lcl IFR conditions are
expected at all TAF sites into tomorrow. KYKM and KPSC could
experience areas of IFR conditions in FZFG after 08Z before
conditions slowly improve after 16Z. Elsewhere snow showers are
expected to affect KRDM and KBDN after 12Z and then pcpn should
decrease after 20Z with improving conditions expected.  Polan


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  35  22  32  22 /   0  10   0  10
ALW  36  24  32  24 /   0  10  10  10
PSC  35  22  33  20 /   0  10   0  10
YKM  36  15  32  17 /   0   0   0   0
HRI  35  22  33  21 /   0   0   0  10
ELN  35  15  31  16 /   0   0   0  10
RDM  33  12  33  12 /  30  10   0  10
LGD  34  18  30  15 /  10  10  10  10
GCD  34  17  29  16 /  30  10  10  10
DLS  37  24  37  24 /  10   0   0  10

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Dense Fog Advisory until noon PST today for ORZ041-044.

WA...Dense Fog Advisory until noon PST today for WAZ024-027-028.

&&

$$

91/99/99


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