FXUS66 KPDT 241758
AFDPDT
Area Forecast Discussion
National Weather Service Pendleton OR
958 AM PST Mon Feb 24 2025
.UPDATED AVIATION DISCUSSION...
.AVIATION...18Z TAFs...All sites will be VFR for this morning. As
the system passes through, widespread rain along with gusty winds
(25-35 kts) will affect all sites this morning through later
tonight. However, there is a low to moderate chance (30-50%) of
gusts exceeding above 35 kts. The rain could also bring flight
conditions down to MVFR, but confidence was low (15-30%) on
mentioning in the TAFs at this time. LLWS continues for KRDM/KBDN
later tonight due to the strong winds aloft. Isolated thunderstorms
may impact KPDT/KALW/KPSC, but confidence is low (<30%) at this
time. Feaster/97
&&
.PREV DISCUSSION... /issued 300 AM PST Mon Feb 24 2025/
SHORT TERM...Today through Wednesday...Current satellite imagery
shows a transient upper ridge moving across the PacNW tonight,
withe partly cloudy conditions across the forecast area at this
time. Meanwhile, water vapor imagery shows an upper trough
offshore starting to develop into a closed low.
Early today, a stacked low pressure system offshore will begin to
lift a warm front north across the PacNW, beginning another round
of widespread precipitation across the forecast area. Snow levels
will start above 6kft across much of the forecast area, and above
4kft along the WA Cascade east slopes, limiting snow potential to
higher ridges and peaks during the warm front passage. As the warm
front lifts into eastern WA, the offshore low will push a cold
front across the PacNW, with the cold front boundary expected to
briefly hang on the Cascades, then push across eastern OR and
southeastern WA in the late afternoon into tomorrow night. Cooler
air behind the cold front boundary will result in snow levels
dropping to between 3kft and 4kft in the evening and overnight
period. This will result in moderate to locally heavy snow
accumulations along the Cascade east slopes generally above 4kft
tonight through Wednesday morning. Otherwise, behind the warm
front passage, a strong low level jet and increasing lapse rates
will develop across portions of the Columbia Basin. The cold front
boundary will interact with this area of increased instability in
the late afternoon and early evening, and result in convective
type showers developing in these areas and into the northern Blue
mountains. Light to moderate rain/snow showers will continue
through Tuesday afternoon as the upper low moves inland and
develops into an open wave. In the lower elevations, however,
precipitation chances will taper off by late Tuesday morning.
Strong winds will be a concern across the forecast area beginning
this afternoon, with the concerns continuing into late tomorrow
afternoon. As mentioned earlier, a strong low level jet will
develop across north central OR and the Columbia Basin, with 850mb
winds between 50-60kts, with 700mb winds peaking around 70kts.
With increased lapse rates from central OR to the Columbia Basin,
CAMs favor these winds periodically mixing down across elevated
areas including central/north central OR, the Simcoe Highlands,
and the southern Blue mountain foothills late this afternoon
through Tuesday afternoon. Winds will also mix down into the
Columbia Basin/Gorge and along the northern Blue mountain
foothills, albeit not as strong as the aforementioned elevated
areas. That said, the Horse Heaven Hills and the Rattlesnake
mountains could see the stronger winds mix down periodically,
though confidence was not high enough (confidence 50-70%) to
issue a High Wind Warning for these areas. Otherwise, confidence
is high (80-95%) in widespread gusts between 45-55mph across
central OR, Columbia Basin/Gorge, and the Blue Mountain foothills
with high confidence (75-85%) in periodic gusts to around 60mph
across central/north central OR, southern Blue mountain foothills,
and the Simcoe Highlands through tomorrow afternoon.
Tuesday evening through Wednesday night, upper level ridging will
build into the PacNW, bringing an end to precipitation chances
and strong winds across the area.
Lastly, area rivers and streams are rising in response to the
increased snowmelt and runoff from yesterday's atmospheric river
event. Portions of the Umatilla and the John Day rivers have just
reached or are forecast to reach minor flood stage today before
decreasing again later this afternoon. Flood warnings for these
rivers will remain in effect through late this afternoon.
Otherwise, many of other rivers and streams (Klickitat, Walla
Walla, Grande Ronde) will crest today at or near bankfull and
level off into the evening hours before decreasing tomorrow.
Lawhorn/82
LONG TERM...Thursday through Monday...
Bottom Line Up Front
1) Mostly dry conditions through the end of the week
2) Precipitation returns over the weekend with widespread rain
chances and high mountain snow
3) Temperatures will remain above seasonal average through Saturday
The long term will remain relatively quite to start with an upper
level ridge overhead and some lingering rain/snow along the Cascade
crests. Models show the upper level ridge to linger over the region
through Friday night before an upper level low moves onshore
bringing increased chances of rain beginning along the Cascades
before pushing across and becoming widespread. Looking at the
statistics for 24 rain fall totals as well as ensembles
probabilities, there is only 10-20% probabilities for 0.02 inches of
rain across the Cascade crests Thursday.
Models show the next round arriving Friday night with 20-30% of the
raw ensemble probabilities of 0.02 inches of rain across the lower
elevations while a 25-45% probability of 0.02 inches along the east
slopes and crests of the OR Cascades while the crests of the WA
Cascades have 45-65% probabilities of the same amount. Sunday will
be the wettest day of the period, however the clusters begin to
falter with the timing and amplitude of the upper level low. Raw
ensembles shows 20% probabilities the Columbia Basin will see 0.05
inches, roughly 40% show the lower Columbia Basin, 50% for the
Blues, eastern mountains, central & north central OR, and 50-70% for
the Gorge and east slopes to the crests of the Cascades. Confidence
in the forecast is moderate at best at this point with regards to
rain amounts as clusters are showing only 1 cluster with rain. As
for the snow, snow levels will decrease as the low moves overhead
bringing levels to near 4500 to 5000 feet Saturday allowing for
anything above that to fall as snow. As of right now, the only
noticeable snowfall accumulation will be at the crests with NBM
showing highest amounts of near 1-2 inches.
EFI shows temperatures to be above seasonal average through Saturday
across the entire region before decreasing to at or near normal
with some isolated locations remaining at or just above normal by
Sunday. Looking at the guidance on past climate data for this time
of year, guidance shows the majority of the region to be 5 to 10
degrees above normal through Saturday before becoming at or near
normal Sunday with some locations remaining 1 to 5 degrees above
normal (Basin, Yakima/Kittitas Valley and portions of north central
OR), others areas are 1 to 5 degrees below normal (mainly along the
higher slopes and crests) some areas at normal for this time of
year. Bennese/90
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 61 42 54 32 / 50 90 10 0
ALW 56 42 52 33 / 60 90 30 0
PSC 56 43 58 32 / 60 70 10 0
YKM 45 36 54 29 / 80 60 30 0
HRI 60 42 57 31 / 50 80 10 0
ELN 43 33 50 29 / 90 60 50 0
RDM 59 36 52 26 / 60 50 10 0
LGD 48 35 45 26 / 50 80 30 10
GCD 54 34 46 26 / 60 60 10 0
DLS 52 42 55 33 / 90 70 50 0
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Wind Advisory from 4 PM this afternoon to 4 PM PST Tuesday for
ORZ041.
Wind Advisory from 7 PM this evening to 7 PM PST Tuesday for
ORZ044-507.
High Wind Warning from 1 PM this afternoon to 4 PM PST Tuesday
for ORZ508-510.
Winter Weather Advisory from 4 PM this afternoon to 4 PM PST
Tuesday for ORZ509.
High Wind Warning until 4 PM PST Tuesday for ORZ511.
WA...Wind Advisory from 4 PM this afternoon to 4 PM PST Tuesday for
WAZ024.
Wind Advisory from 7 PM this evening to 7 PM PST Tuesday for
WAZ028-029.
High Wind Warning from 1 PM this afternoon to 4 PM PST Tuesday
for WAZ521.
Winter Weather Advisory until 4 PM PST Tuesday for WAZ522.
&&
$$
SHORT TERM...82
LONG TERM....90
AVIATION...97