895
FXUS66 KPDT 180534
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
934 PM PST MON FEB 17 2025
UPDATED FOR AVIATION
AVIATION
06Z TAFS...CONDITIONS RANGED FROM VFR TO IFR ACROSS THE AREA, WITH
PDT AND ALW FLUCTUATING IN AND OUT OF LIFR. EXPECT BDN AND RDM TO
REMAIN VFR THROUGH THE PERIOD (THOUGH SOME LOCAL MVFR AROUND
DAYBREAK CAN NOT BE RULED OUT). EVERYONE ELSE SHOULD SEE SOME
DETERIORATION OVERNIGHT OR TOWARD MORNING, WITH MOST SITES ENDING
UP IFR BY MORNING. ALL GUIDANCE SUGGESTS PDT WILL BE BACK WITH 1/4
TO 1/2 SM VSBYS OVERNIGHT AND THROUGH MUCH OF TUESDAY, SO IT SEEMS
THAT THE CURRENT IMPROVEMENT IN VSBY WILL BE SHORT-LIVED. WINDS
ARE EXPECTED TO BE LIGHT, LESS THAN 10 KTS THROUGH THE PERIOD.
PREV DISCUSSION
/ISSUED 753 PM PST MON FEB 17 2025/
EVENING UPDATE...RADAR SHOWS PRECIP WINDING DOWN ACROSS MOST OF
THE FORECAST AREA, WITH THE EXCEPTION BEING THE NORTHERN BLUES
WHICH IS EXPECTED TO RECEIVE SNOW THROUGH TOMORROW MORNING AS AN
UPPER-LEVEL WAVE PASSES THROUGH AND CONTINUES TO PROVIDE THE AREA
WITH FAVORABLE UPSLOPE FLOW. A WINTER STORM WARNING REMAINS IN
EFFECT FOR THE NORTHERN BLUES ZONES, WHILE ALL OTHER WINTER
HEADLINES HAVE EXPIRED.
NOT MUCH CHANGE IN THE CURRENT FORECAST. DID ADD MENTION OF FOG
ACROSS THE FOOTHILLS OF THE BLUES AND THE JOHN DAY BASIN, WHERE
DENSE FOG HAS BEEN REPORTED. WITH TRANSITORY RIDGING NOSING ITS
WAY IN HEADING INTO TOMORROW, MUCH OF THIS FOG AND LOW CLOUDS
COULD STICK AROUND THROUGH TOMORROW EVENING, BUT LEFT MENTION OF
FOG ONLY THROUGH TOMORROW MORNING, AS CONFIDENCE IS ON THE LOWER
END (30-40%) ON JUST HOW LONG FOG WILL PERSIST. EVANS/74
PREV DISCUSSION... /ISSUED 312 PM PST MON FEB 17 2025/
SHORT TERM...TONIGHT THROUGH WEDNESDAY NIGHT...SNOW WILL
GRADUALLY TAPER OFF THIS AFTERNOON THROUGH TONIGHT FOR THE
CASCADES AND MUCH OF THE BLUE MOUNTAINS AS A BRIEF SHORTWAVE
RIDGE BUILDS INTO THE PACIFIC NORTHWEST THROUGH TUESDAY. HOWEVER,
A DEEP, MOIST UPSLOPE FLOW REMAINS IN PLACE OVER THE NORTHERN
BLUE MOUNTAINS THROUGH TUESDAY MORNING, WHICH SHOULD FACILITATE
CONTINUED SNOWFALL, SO OPTED TO EXTEND THE WINTER STORM WARNING
FOR THE NORTHERN BLUE MOUNTAINS THROUGH 4 AM PST TUESDAY.
CONFIDENCE IS HIGH (70-90%) IN AN ADDITIONAL 4-8 INCHES OF
SNOWFALL ABOVE 4000 FEET AND 2-4 INCHES BETWEEN 3500 AND 4000 FEET
THROUGH TUESDAY MORNING.
TUESDAY EVENING THROUGH TUESDAY NIGHT, A RETURN TO ACTIVE WINTER
WEATHER IS EXPECTED (90-100% CHANCE) AS AN UPPER-LEVEL TROUGH AND
ATTENDANT SURFACE LOW AND FRONTAL SYSTEM ARRIVE FROM THE PACIFIC.
OF NOTE, SIGNIFICANT SPREAD STILL EXISTS IN ENSEMBLE SOLUTIONS
REGARDING PATTERN DETAILS SUCH AS THE MAGNITUDE/TRACK OF THE
SURFACE LOW, REMNANT COLD AIR TRAPPED TO THE LEE OF THE CASCADES,
AND THERMAL PROFILES. AS SUCH, CONFIDENCE IN FORECAST DETAILS
INCLUDING PRECIPITATION TYPE AS WELL AS SNOW AND ICE ACCUMULATIONS
FOR THE LOWER ELEVATIONS IS ONLY MEDIUM (50%).
TUESDAY NIGHT THROUGH WEDNESDAY MORNING, CALIBRATED PROBABILITIES
FROM THE NBM SUGGEST A 40-90% CHANCE OF MEASURABLE LOWLAND SNOW
FOR WASHINGTON, WITH LOW-MEDIUM (20-50%) CHANCES FOR THE LOWLANDS
OF OREGON. THE YAKIMA AND KITTITAS VALLEYS HAVE THE BEST CHANCE
OF REACHING ADVISORY-LEVEL SNOW (2" OR GREATER) OR WARNING-LEVEL
SNOW (4" OR GREATER) AT 10-35% AND 5-10% FOR ADVISORY AND
WARNING, RESPECTIVELY.
THE MAIN TROUGH IS FORECAST TO SWING THROUGH WEDNESDAY AFTERNOON
THROUGH WEDNESDAY NIGHT WITH PRECIPITATION LIKELY (75% CHANCE OR
HIGHER) FOR THE MOUNTAINS AND FOOTHILLS WITH A CHANCE (25-54%) OF
PRECIPITATION FOR MUCH OF THE LOWER ELEVATIONS. PLUNKETT/86
LONG TERM...THURSDAY THROUGH MONDAY...WITH THE SYSTEM WEAKENING
THROUGH FRIDAY, WINTERY MIX WILL FINALLY TAPER OFF AS THE UPPER
RIDGE BUILDS OVER THE PACNW. SNOW MAY ACCUMULATE UP TO 6" AT THE
WA/OR CASCADES (30-60% CHANCE) WITH THE BLUES HAVING 2" OR LESS
(>50% CHANCE). OTHERWISE, LOWLANDS WILL GET ABOUT LIGHT QPF
AMOUNTS EXCEEDING TO 0.25 OR LESS BEFORE DECREASING FRIDAY. WE
WILL THEN HAVE PROGRESSIVE SYSTEMS ACROSS THE FORECAST AREA
SATURDAY ONWARDS STARTING AT THE WA/OR CASCADES FIRST BEFORE
BECOMING WIDESPREAD. OVER THE WEEKENDS, THE QPF AMOUNTS OVER THE
WA CASCADES MAY REACH UP TO 1" ALONG WITH THE OR CASCADES AND THE
NORTHERN BLUES UP TO 0.75" (>50% CONFIDENCE). MOUNTAIN SHOWERS
WILL CONTINUE TO LINGER MONDAY UP TO 0.25-0.50" AT THE CASCADES
AND BLUES. THE LOWLANDS WILL REMAIN HAVING LIGHT RAIN (0.10" OR
LESS).
BREEZY WINDS (15-25 MPH) MAY DEVELOP THROUGH FRIDAY AT THE WA
CASCADES AND THE FOOTHILLS OF THE BLUES OF OR. WINDS WILL BECOME
GUSTY (25-35 MPH) OVER THE FOOTHILLS OF THE BLUES, YAKIMA VALLEY,
THE CASCADES, AND CENTRAL OR SATURDAY ONWARDS. THESES SYSTEMS WILL
ARRIVE TO THE PACNW DURING THOSE AFOREMENTIONED DAYS AS THE WESTERLY
FLOW INCREASES. TEMPERATURES WILL GRADUALLY BECOME ABOVE NORMAL
THROUGH FRIDAY AND ABOVE NORMAL BY THE WEEKEND. FEASTER/97
AVIATION...00Z TAFS...MIX OF FLIGHT CATEGORIES WILL CONTINUE FOR
MOST SITES (KDLS/KPDT/KYKM/KALW/KPSC) THROUGH THE REMAINING TAF
PERIOD. KRDM/KBDN REMAINS IN VFR FOR THE REST OF THE DAY. THE
REMAINING SITES (KDLS/KPDT/KYKM/KALW/KPSC) WILL REMAIN
DETERIORATING TO MVFR OR LESS DUE TO RAIN, MIST AND LOW CLOUDS,
WHICH COULD LOWER CIGS AND VSBYS. FREEZING RAIN AND FOG MAY
DEVELOP OVERNIGHT AND/OR MORNING HOURS (<40% CONFIDENCE).
FEASTER/97
PRELIMINARY POINT TEMPS/POPS
PDT 33 41 31 42 / 40 10 10 100
ALW 33 39 31 39 / 60 30 10 100
PSC 29 41 31 39 / 20 0 20 90
YKM 29 41 31 39 / 0 0 50 90
HRI 30 42 32 42 / 20 10 20 90
ELN 29 41 31 39 / 10 10 50 90
RDM 25 46 32 49 / 10 10 40 70
LGD 33 41 29 39 / 70 20 10 100
GCD 30 42 31 44 / 40 0 30 100
DLS 35 47 36 45 / 20 10 70 100
PDT WATCHES/WARNINGS/ADVISORIES
OR...WINTER STORM WARNING UNTIL 4 AM PST TUESDAY FOR ORZ502.
WA...WINTER STORM WARNING UNTIL 4 AM PST TUESDAY FOR WAZ030.
SHORT TERM...74
LONG TERM....97
AVIATION...77
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