202
FXUS66 KPDT 272153
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
253 PM PDT Thu Mar 27 2025

.SHORT TERM...Tonight through Saturday night...Key Messages...
 - Showers with embedded isolated thunderstorms this afternoon
   and evening.

 - Unsettled weather continues through Saturday.

 - Near average high temperatures.

Marginally unstable conditions have supported 20-45 CG strikes per
ground-based networks across the southern Blues into the foothills
the last two hours. KPDT radar depicts scattered-numerous showers
with a few stronger embedded cores across eastern OR north into
the eastern Lower Basin and southeast WA. Latest water vapor
imagery shows a closed low offshore the PacNW with a shortwave
trough starting to move into southwest OR. The coming shortwave
trough will help steepen lapse rates a tad more the next 2-4 hours
that combined with modest instability seen via 500-750 J/kg
MUCAPEs will promote continued thunder chances into 8-9 PM with
the threat then shifting northeast out of the area. Thinking
lightning will be infrequent and should lessen with loss of
daytime heating with chances 20-30% through the evening. While
severe storms are not expected, the combination of a modest mixed
BL with moderate winds in this synoptically-forced environment
could promote some stronger gusts from downdrafts in excess of 35
mph. Seeing winds 20-30 kts and 30-40 kts at 850 and 700 mb,
respectively, across OR that support this limited risk with HREF
also showing probs for 30 kts of more with a weak reflectivity
core reaching 50% across parts of eastern OR.

This closed low over the next 24-hrs will weaken into an open wave
by early Friday offshore the Pacific NW with additional shortwave
troughs expected to cross the area during this time frame. A new
closed low will deepen upstream in the eastern North Pacific by
Saturday as the winds aloft slacken with a weak ridge building in
late Saturday. Looking ahead, a modest IVT surge is currently
directed into the Cascades with values in excess of 200 Kg/ms that
will persist overnight before tapering off tomorrow. This should
set up the wettest period across the crest of the Cascades
tonight-tomorrow. However, high snow levels, Santiam pass current
in the lower 40s, will attribute to a large portion being seen as
rain to mix before snow levels drop late tonight. This should
limit impacts via wet snow and minor snow accumulations.
Otherwise, unsettled weather continue tomorrow as we remain under
cyclonic flow with the highest chances tied to the eastern
mountains and Cascades.

.LONG TERM...Sunday through Thursday...Sunday will likely be a
transition day, with dry weather during the day in most areas.
However, southwesterly flow will increase later in the day and
moisture will increase by later afternoon/early evening in advance
of the next low approaching the coast.

A piece of this low will move onshore on Monday, then depart the
area on Tuesday. By Wednesday, considerable uncertainty enters
the forecast as the GFS has a very large low approaching the coast
and the ECMWF does not. Obviously, whether this low exists and
its strength and position will have a big effect on the forecast
from Wednesday onward.

QPF amounts on Sunday will generally be on the lighter side, with
amounts mainly 0.50 inch or less in the crest of the Cascades
and much less elsewhere with most locations having 0.10 inches.
Snow levels will rise from 2500-3500 feet on Sunday morning to
4000 to 5000 feet Sunday afternoon. Snow levels will decrease by
MOnday morning to between 3500-4500 feet. With that said, most
precipitation will fall as rain, but there could be a couple of
inches at the highest elevations.

On Monday, with the low moving onshore, QPF will be higher. There
could be upwards of 0.50 t0. 0.75 inches and possibly local
amounts up to 1 inch in the Cascades and around 0.75 inches along
the crest of the Blue Mountains. and again, much less elsewhere
generally 0.15 inches or less. Snow levels will decrease to below
3000 feet by Tuesday morning everywhere. There could be 4 inches
plus along the crests, but much less elsewhere.

On Tuesday, QPF will be less once again and mainly focused in the
mountains. The Oregon Cascade crest looks to get the brunt of the
precipitation, upwards of 0.50 inches, with around 0.25 inches in
the Washington Cascade crest and Blues. Snow levels will still be
fairly low between 2500-3500 feet, but the lower QPF will keep
snow amounts limited, perhaps a few inches along the crests.

Beyond Tuesday, there is considerable uncertainty as to how the
pattern evolves. However it looks like there could be a more
widespread precip event everywhere.

The GFS stronger solution is not favored in the ensembles (37& to
27%) on day 6 and 38% to 26 % on Day 7, plus coupled with the
natural variability of that time scale, allows for a lot of
uncertainty beyond Tuesday.

There will be diurnal breezes Monday and Tuesday, especially across
the Blue Mountain Foothills, Simcoe Highlands and Columbia Basin.
Monday`s winds should be a bit stronger but wind gusts should
generally be in the 25 to 30 mph range.


&&

.AVIATION...18Z TAFS...VFR conditions are expected through the TAF
period. Periods of rain will impact all TAF sites, but should
not be hard enough to bring lowered CIGS or VSBYS. Gusty winds are
expected to develop at BDN and RDM later this afternoon and
continue through the night at BDN and RDM. Winds at these
locations should gust in the 25 to 20 kt range. Elsewhere, winds
will mainly be 10 kts or less, though there could be some winds
around 10 to 15 kts.

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  47  59  39  57 /  60  70  40  20
ALW  48  59  40  56 /  60  80  40  30
PSC  46  63  40  62 /  50  20  10  10
YKM  42  57  34  58 /  70  20   0  10
HRI  45  63  38  61 /  50  40  20  10
ELN  42  56  33  56 /  70  30   0  10
RDM  40  55  29  53 /  50  30  10   0
LGD  43  52  35  49 /  30  90  80  40
GCD  41  54  33  49 /  30  90  70  40
DLS  45  60  39  59 /  60  60  10  20

&&

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

$$

SHORT TERM...80
LONG TERM....77
AVIATION...77