Area Forecast Discussion
Issued by NWS Pendleton, OR

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FXUS66 KPDT 232318 AAA
AFDPDT

Area Forecast Discussion...Updated
National Weather Service Pendleton OR
418 PM PDT Mon Oct 23 2017

Updated aviation discussion

.SHORT TERM...Tonight through Thursday...An upper level ridge of
high pressure will continue to build over the forecast area tonight
and into the day Tuesday. The ridge axis will be overhead on Tuesday
with 500mb heights pushing 594dm. This will keep conditions dry,
under mostly clear skies and generally light winds. With the
inversion strengthening there will be patchy valley fog late tonight
and Tuesday morning...any fog that does form should dissipate by
late Tuesday morning. Overnight lows will be in the 30s to near
40...except mid 20s to low 30s mountains and high valleys. The
inversion will keep temperatures slightly cooler in the Lower
Columbia Basin, where highs will be in the lower 60s. Elsewhere,
above the inversion highs will reach the mid-60s to lower 70s...with
the warmest area being in the John Day Basin. There will be a strong
inversion in place for Tuesday night as well...with 850mb temps
rising near +15C over the Columbia Basin. This should allow
additional areas of fog to develop overnight. A cold front is then
forecast to sweep across the region from north to south on Wednesday
and Wednesday night. The front will approach the WA East Slopes and
Kittitas Valley by late Wednesday morning...dropping south along the
WA/OR border during the afternoon hours. It will reach Central
Oregon Wednesday evening. Overall, this front will not have a lot of
moisture to work with...but it should produce more cloud cover and a
chance for mountain showers. Precipitation amounts will range from
zero in the valleys/basins to perhaps a tenth of an inch in the
higher mountains (especially along the Cascade crest). Along this
front winds will turn westerly on Wednesday and become slightly
breezy late in the day...10-20 mph. Late Wednesday night and
Thursday the entire area will dry out, with decreasing clouds under
a dry northerly flow. Slightly cooler air aloft will filter into the
area, with 850mb temps hovering around +10C Thursday afternoon.
Winds switch out of the north-northeast on Thursday, mainly 7 to 15
mph. High temperatures on Thursday will reach into the 60s for the
lower elevations, with 50s in the mountains. 77

.LONG TERM...Thursday Night through Monday. No major weather
concerns are anticipated for the long term period. Dry conditions
will prevail, skies will be mostly clear, and winds will generally
be less than 15 mph through the period. Afternoon temperatures will
range from the lower 50s to lower 60s--about 3 to 7 degrees above
seasonal average. Overnight lows will be in the mid 20s to mid 30s
in the mountains and and in the mid 30s to lower 40s in the lower
elevations. Patchy fog is common during late October when the
forecast area is under a high pressure ridge, so overnight fog is
possible but too early to pinpoint exact locations.  Wister

&&

.AVIATION...00Z TAFs...VFR conditions will be prevalent at all TAF
sites for the next 24 hours. Skies will be generally clear aside
from a few high cirrus clouds for the next 24 hours. However, with
clear skies and light winds tonight, fog will be favored a little
more than last night. This early in the fall expect that any fog
will still be patchy and have hinted at it with 6SM with BR and SCT
IFR clouds at KDLS, KYKM and KPSC. Any fog that develops should burn
off around 18Z. Winds will remain under 10 kts for the next 24
hours. Perry

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  38  61  38  66 /   0   0   0  10
ALW  41  61  41  64 /   0   0   0  10
PSC  36  60  37  66 /   0   0   0   0
YKM  35  62  36  65 /   0   0   0  10
HRI  35  62  35  66 /   0   0   0   0
ELN  34  61  37  63 /   0   0   0  10
RDM  31  67  31  73 /   0   0   0   0
LGD  36  64  41  66 /   0   0   0  10
GCD  32  69  34  71 /   0   0   0  10
DLS  41  63  41  68 /   0   0   0   0

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&

$$

77/85/83


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