<pre>538
FXUS66 KPDT 181811
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1011 AM PST Thu Dec 18 2025

.DISCUSSION...


&&

.AVIATION...18Z TAFs...MVFR or lower conditions expected in the
period at most sites. A frontal system moving across the region
will continue to bring precip impacts to all sites through the
tonight. This frontal system is also producing CIGs that are at
IFR conditions for sites DLS/YKM with MVFR vsby at sites DLS/BDN
at this time. Low CIGs will persist into this evening at site DLS
while site YKM will continue to remain at MVFR or lower through
tomorrow morning. Sites RDM/BDN will also see MVFR CIGs (1.5kft to
2.5kft) develop overnight as winds decrease. Winds will be
increasing to 12-17kts with gusts 25kts at sites
DLS/PDT/RDM/BDN/ALW/PSC into this afternoon, with winds increase
to 20-30kts and gusts 30-40kts later this evening and overnight
at sites PDT/RDM/BDN/ALW/PSC. Low level wind shear 40-60kts from
the southwest and within 2kft ground level will also impact all
sites, except YKM, through around 09Z tonight. Lawhorn/82


&&

.PREV DISCUSSION... /issued 443 AM PST Thu Dec 18 2025/

DISCUSSION...Current satellite and radar imagery show light showers
developing across the forecast area with this frontal system approaching
our forecast area.

The shortwave along with the atmospheric river (IVT of 500-700 kg
m/s) will bring windy conditions starting this late morning across
most of the forecast area. These winds will continue to be driven by
the strong low-level jet streak above 70 kts along with a surface
pressure difference of 3-7 mb over the Grande Ronde Valley (BKE and
MEH) through most of today and 9-11 mb between (PDX (Portland) and
GEG (Spokane) overnight. Wind Advisories will be in effect from 10
AM today to 1 AM PST tomorrow for the following areas: from central
OR to Simcoe Highlands (Klickitat County) and portions of the
Foothills-Northern and Southern Blue Mountains. Strongest wind gusts
of 45-55 mph are expected along east slopes of OR Cascades, central
OR, portions or north central OR, and Northwest Blues. Overnight
into late tomorrow morning, winds will then slowly decrease with
lingering winds at 30-40 mph over Simcoe Highlands and portions of
the Northwest Blues including high terrains of central OR. However,
confidence is about 30-40% for the east slopes of OR Cascades to
gust up to 60 mph or higher during evening hours.

Mountain snow for WA/OR Cascades will continue with widespread
precipitation taking over through tomorrow. Winter Weather
Advisories will remain in effect through this afternoon for the WA
Cascades and Northern Blues of OR, given with snow levels at 2.5-3.5
kft with additional snowfall up to 1 foot. This also to take in
account of potential blowing snow in those areas with gusts of 20-30
mph or higher (>60% confidence). The east slopes of OR Cascades has
a Winter Weather Advisory as well, but through later this morning
when snow levels start to increase above 5 kft with snow transitioning
to mostly rain. Freezing rain may develop over the WA Cascades
and portions of the Northern Blues, but confidence is low (15-30%)
considering that those mountain areas has a better chance at
receiving mainly snow.

River Flood Watches and Flood Watches remain in effect due to
anticipated rising river levels through the rest of this week.
Feaster/97


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  56  37  47  33 / 100  90  60  10
ALW  54  39  47  36 / 100 100  70  30
PSC  54  37  49  35 / 100  80  20  10
YKM  46  29  46  28 / 100  90  10  20
HRI  55  38  49  33 / 100  90  40  10
ELN  41  26  39  23 / 100  90  30  40
RDM  56  34  46  23 / 100 100  90  10
LGD  46  34  44  27 / 100 100  90  30
GCD  50  39  46  24 / 100  90 100  20
DLS  48  38  46  36 / 100 100  70  70

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory until 1 AM PST Friday for ORZ041-507-508-510-511.

     Winter Weather Advisory until 4 PM PST this afternoon for ORZ502.

     Flood Watch through late Friday night for ORZ509>511.

WA...Wind Advisory until 1 AM PST Friday for WAZ024-521.

     Winter Weather Advisory until 4 PM PST this afternoon for WAZ030-
     522-523.

     Flood Watch through Friday afternoon for WAZ522-523.

&&

$$

DISCUSSION...97AVIATION...82</pre>