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000
FXUS66 KPDT 110521
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1021 PM PDT Wed Apr 10 2024

UPDATED AVIATION...06Z TAFS...VFR conditions thrives on for all
sites during the rest of this period, with prevailing high clouds
(FEW to OVC, 100-250 kft) and light winds. KRDM/KBDN will remain
breezy Thursday afternoon up to 18 kts until becoming light
overnight into Friday morning. Feaster/97


&&

.PREV DISCUSSION... /issued 426 PM PDT Wed Apr 10 2024/

AVIATION...00Z TAFS...High clouds (FEW to OVC, 100-250 kft) will
arrive tonight and continue through Thursday morning, with all sites
at VFR. Winds remain light for all sites except KRDM/KBDN being
breezy Thursday afternoon up to 18 kts. Feaster/97

SHORT TERM...Tonight through Friday night...Satellite imagery
reveals an upper-level ridge overhead this afternoon with some
thin cirrus streaking across the PacNW. Otherwise, clouds are
currently limited to some isolated stratocumulus primarily over
the Blue Mountains. Quiet weather is forecast tonight with the
ridge in place.

Thursday, ensemble guidance is in excellent agreement (99-100%
chance) that the broad closed low currently located in the Gulf of
Alaska will drop southeast towards the PacNW. The frontal
boundary in the Pacific is anticipated to weaken as it approaches
the coastline Thursday afternoon and eventually make landfall
through Thursday night before stalling across the region Friday.
Given the position of the offshore closed low, deep southwesterly
flow aloft should facilitate a slight chance to chance (15-55%) of
shower development for the mountains foothills as moisture
increases.

Friday presents the biggest forecast challenge of the period.
While confidence is high (95-100% chance) in the closed upper-
level low continuing to track southeast offshore of northern
California, uncertainty in cloud cover and boundary-layer moisture
leads to low confidence in a low-end severe thunderstorm threat
for eastern Oregon on Friday afternoon and evening. More
aggressive forecast soundings in CAMs are presenting MUCAPE of up
to 750-1500 J/kg supported by surface dew points of 45-50 F and
mid-level lapse rates of 7-8 C/km, EBWD of 35-60 kts, and
effective SRH of 50-200 m2/s2 so potential is there for isolated
rotating updrafts, but confidence is low in any organized severe
threat at this time. Plunkett/86

LONG TERM...Saturday through Wednesday...Saturday will see a deep
closed upper level low along the California coast with some
moisture and instability wrapping back around into eastern Oregon.
Meanwhile, the polar jet will be north of the region cutting
across southern Canada. The moisture wrapping around the low will
lead to some showers and possible thunderstorms Saturday afternoon
and evening mainly across eastern Oregon. On Sunday the low
pressure begins moving into California with a shortwave breaking
free and moving towards SW Idaho while a shortwave trough begins
dropping south along the Canadian border. Under this situation
there will continue to be some showers and thunderstorm potential
over the eastern mountains of Oregon. Then on Monday the Canadian
trough begins dropping into the Pacific Northwest ushering in
cooler showery conditions to most of the forecast area through
Tuesday. The trough then exits to the east on Wednesday leaving
the forecast area under cool northerly flow and some lingering
showers.

Snow levels remain high through the weekend but then begin to
lower Monday and drop to around 3000 feet Tuesday and Wednesday.
Likewise, temperatures will be in the 60s and low 70s over the
weekend then lowering into the 50s to low 60s through first of the
week. Windy conditions will accompany the arrival of the Canadian
trough on Monday then breezy and cool Tuesday and Wednesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  39  63  43  62 /   0   0  10  30
ALW  42  67  46  66 /   0   0  20  40
PSC  42  69  48  68 /   0   0   0  10
YKM  38  66  42  66 /   0  10   0  10
HRI  41  67  46  66 /   0   0   0  20
ELN  38  63  40  64 /   0  10   0   0
RDM  35  65  38  58 /   0   0  10  30
LGD  37  67  41  65 /   0  10  20  50
GCD  37  70  41  68 /   0   0  20  50
DLS  44  65  47  65 /   0   0  10  10

&&

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

$$

SHORT TERM...86
LONG TERM....91
AVIATION...97