363
FXUS66 KPDT 092217
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
217 PM PST Sat Nov 9 2024

.SHORT TERM...Tonight through Monday...The remnants of a weakening
upper level trough is passing over the region late today and
overnight. This will produce some light precipitation across the
forecast area overnight through Sunday morning before it exits to
the east leaving just some lingering mountain showers. Precipitation
amounts will range from a couple hundreths in the lower elevations
to .10-.20 inches in the mountains. There is not much cold air with
this so snow levels remain high at around 6000 to 7000 feet with
very little accumulations.

A deeper and stronger upper level trough over the Gulf of Alaska
will be approaching the Pacific Northwest late Sunday. This will
clip the forecast area with a warm front Sunday night followed by a
cold frontal passage on Monday. The brunt of the warm frontal
precipitation will be along the Cascades and the east slopes of the
Washington Cascades Sunday night with snow levels remaining around
6000 feet. The warm front will bring increasing warm southerly winds
across eastern Oregon overnight but not have much impact in the
lower elevations around the Columbia Basin. The cold front then
passes over the forecast area on Monday shifting the winds to
westerly and begins to ushers in cooler air and lowering snow levels
through the day and overnight. The combination of a warm front
followed by cold frontal precipitation will bring a high probability
(60-90%) of around 1 inch to the Cascade crest but without cold air
support there will not be much snow accumulation through Monday
afternoon. Lowering snow levels Monday night into Tuesday to 3500 to
4500 feet will produce some snow along the crest at the magnitude of
3 to 6 inches above 4000 feet.

Snow levels will lower over the eastern mountains Monday night
resulting in 1 to 3 inches above 4000 feet.



.LONG TERM...Tuesday through Saturday...


Key Messages:

1. Progressive rounds of precip and gusty winds through Thursday
morning.

2. Snow levels drop Thursday onwards.

3. Cooler temps occur Friday into Saturday.


This long term period is characterized by progressive frontal
systems sweeping across the PacNW, bringing rounds of precip and
gusty winds. Potential mix of mountain rain and snow might also be
produced due to excessive moisture from these systems. Over 50% of
the raw ensembles favor QPF amounts exceeding between 0.50-1" along
the WA/OR Cascades through Thursday before steadily decreasing
Friday until the next system occurs Saturday night. The northern
Blues has a 40-80% probability of QPF amounts at 0.25-0.50". The
remaining mountain areas (rest of the Blues and high terrains of
central OR) will have a bit lighter QPF at around 0.10-0.15" (>50%
prob) through Friday as the trough begins moving out of the area.
Things should gradually simmer down a bit Friday as the shortwave
trough moves eastward before we enter in between systems Saturday.
However, lingering mountain showers will be left behind from
Tuesday`s and Wednesday`s frontal systems. And given the increased
west to southwesterly flow from this weather pattern, there is a
moderate to high chance (50-90%) of gusty winds (25-35 mph) over the
Foothills, Grande Ronde valley, the Simcoe Highlands, the Gorge and
Santiam Pass Tuesday into Thursday morning. Though, breezy winds (up
to 25 mph) returns across the forecast area Thursday afternoon
onwards as the frontal system weakens.

Snow levels for Tuesday will be 4-4.5 kft with the cold front moving
across our area, then increases above 5kft Wednesday into Thursday
morning as the warm front passes. Snowfall may accumulate up to 4-8"
at the crest of the Cascades including Santiam Pass through
Wednesday (>60% prob). Snow levels will then steadily drop with
another frontal system arriving Thursday night into Friday from 4-
4.5 kft to 3-4 kft with >40% prob for snowfall developing up to 6"
over those areas. Snow levels for Saturday drops further to 2-3 kft
as the trough exits the PacNW with lingering showers for snowfall to
exceed up to 3-4" over the Cascades including Santiam Pass (30-60%
prob).

Temperatures will be seasonably warm for Tuesday through Thursday
due to the warm front. However, temps will then start steadily
becoming cooler Friday onwards with the trough sweeping across the
PacNW. Feaster/97


&&

.AVIATION...00Z TAFs...VFR conditions continues prevailing for rest
of the TAF period with KDLS currently having light showers. Light
rain develops tonight with the frontal system passing through. MVFR
conditions may occur at KPDT and KALW tomorrow morning due to CIGs
and VSBYs dropping from the fog/mist and low clouds. However, VSBY
for KPDT will improve tomorrow afternoon. No IFR concerns for now
but will monitor and make adjustments when necessary. Winds remains
less than 10 kts. Feaster/97


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  40  55  46  56 /  60  30  30  90
ALW  41  56  47  57 /  70  40  40  90
PSC  42  55  47  59 /  60  10  50  80
YKM  36  53  41  56 /  60  10  80  80
HRI  41  56  45  58 /  60  20  40  80
ELN  35  51  40  52 /  60  10  90  90
RDM  39  58  43  50 /  60  10  30  90
LGD  39  50  43  49 /  70  60  20 100
GCD  39  53  42  49 /  50  60  20 100
DLS  42  58  47  58 /  60  10  80 100

&&

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

$$

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