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000
FXUS66 KPDT 211621
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
921 AM PDT Mon Sep 21 2020

.UPDATE...Satellite this morning showing upper level shortwave
moving onshore and producing some cumulus over the WA Cascades
with cirrus over portions of the Columbia Basin. Shortwave will
clip the WA Cascades later today possibly producing some light
rain showers over the crests, with partly to mostly cloudy
conditions for the rest of the forecast area. Tomorrow, surface
front and upper level shortwave trough will begin to approach the
PNW, with mid to high level clouds increasing later in the
afternoon. Temperatures will be above normal today, generally mid
70s to lower 80s, with overnight lows in the upper 40s to mid 50s
in the Columbia Basin and adjacent valleys while mid 30s to mid
40s in central OR and the mountains. Minor changes made to sky
cover and chance precip in morning forecast package with rest of
forecast on track. Lawhorn/82

&&

.PREV DISCUSSION... /issued 403 AM PDT Mon Sep 21 2020/

SHORT TERM...Today through Wednesday...A flat west to southwest
flow will continue through Tuesday before the next major weather
system arrives on Wednesday. A weak shortwave passing to the north
late Monday could produce a few showers along the crest of the
Washington Cascades otherwise the pattern will keep conditions dry
with no precipitation until Wednesday. The Wednesday system will
consist of a slow moving cold front moving across the forecast area
as a broad upper level trough begins to push into the region.
This will be a good scenario for some significant rainfall to occur
across some portions of the forecast area.

LONG TERM...Thursday through Monday...A broad upper trough will
continue to settle over the Pacific Northwest. There will be
shortwaves of energy rotating around the parent upper trough. Each
of these shortwaves will bring a chance of rain, along with periodic
breezy conditions. The longer range models are in good agreement
through about Saturday with this unsettled pattern. After that the
longer range models are hinting that another upper ridge will build
over the region and suppress the moisture northward. Shortwaves may
skirt the northern fringe of the CWA, but most of the forecast area
will be dry during the latter part of the extended period (Saturday
night through Monday. The atmosphere looks to be too cool and not
unstable enough to support any thunderstorm activity during the
first few days of the extended period, before drying takes place
with the building ridge on Saturday. Temperatures will be cooler
than normal through Saturday, and then a warming trend will begin as
the upper ridge builds at the end of the extended period. 88

AVIATION...12Z TAFS...VFR conditions will prevail through the next
24 hours. There will be mainly just high thin clouds above250. Winds
may increase locally to 5-10 kts today, but most areas will just
have light winds. 88

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  78  52  76  51 /   0  10   0   0
ALW  79  53  78  53 /   0  10   0   0
PSC  81  54  79  54 /   0   0   0   0
YKM  79  51  78  52 /   0   0   0  10
HRI  81  52  79  51 /   0  10   0   0
ELN  74  50  75  50 /   0   0   0  10
RDM  78  41  76  43 /   0   0   0   0
LGD  78  49  77  47 /   0  10  10   0
GCD  82  49  79  50 /   0  10   0   0
DLS  83  56  81  56 /   0   0   0   0

&&

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

$$

UPDATE...82