407
FXUS66 KPDT 142335
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
435 PM PDT TUE APR 14 2026
KEY MESSAGES
- MOUNTAIN SNOW TODAY INTO THURSDAY
- BREEZY TO WINDY THROUGH THURSDAY
- NEAR- TO SUB-FREEZING MORNING LOWS THURSDAY AND FRIDAY FOR THE
LOWLANDS
DISCUSSION
ENSEMBLE AND DETERMINISTIC NWP GUIDANCE ARE IN EXCELLENT
AGREEMENT THAT THE NEXT WEATHER SYSTEM TO AFFECT THE REGION, AN
UPPER-LEVEL CLOSED LOW CURRENTLY CENTERED OVER SOUTHEAST ALASKA,
WILL CONTINUE TO TRACK ALONG THE COAST OF BRITISH COLUMBIA AND
EVENTUALLY INTO THE PACIFIC NORTHWEST THROUGH THURSDAY. ITS
ATTENDANT COLD FRONT IS EXPECTED (99 PERCENT CONFIDENCE) TO
SLOWLY TRAVERSE THE FORECAST AREA OVERNIGHT (WASHINGTON
CASCADES) THROUGH WEDNESDAY AFTERNOON (FAR NORTHEAST OREGON),
LOWERING SNOW LEVELS BELOW MOUNTAIN PASS ELEVATIONS.
WINTER WEATHER HEADLINES REMAIN IN EFFECT, AND CONFIDENCE IS
HIGH (80 PERCENT) IN 4-8 INCHES OF SNOWFALL FOR THE WASHINGTON
CASCADES, 6-12 INCHES FOR THE OREGON CASCADES, AND 5-10 INCHES
FOR THE NORTHERN BLUE MOUNTAINS WITH LOCALLY HIGHER TOTALS ALONG
THE CRESTS. THE BULK OF THE SNOWFALL WILL LIKELY (80 PERCENT
CONFIDENCE) END BY WEDNESDAY MORNING (WASHINGTON CASCADES) TO
WEDNESDAY AFTERNOON (OREGON CASCADES AND BLUES) AS THE FRONT
SAGS SOUTHEAST, BUT SNOW SHOWERS WILL PERSIST THROUGH WEDNESDAY
NIGHT OR THURSDAY MORNING AS THE AFOREMENTIONED UPPER LOW MOVES
OVERHEAD.
PRECIPITATION ASSOCIATED WITH THE COLD FRONT IN NON-MOUNTAIN
AREAS WILL BE MOSTLY RAIN BELOW 1500-2000 FEET, THOUGH
UNCERTAINTY STILL EXISTS IN SNOWFALL BETWEEN 2000 AND 4000 FEET.
MUCH OF THIS UNCERTAINTY IS DRIVEN BY HOW LONG THE FRONTAL BAND
LINGERS OVER THE LOWLANDS (I.E. HOW MUCH PRECIPITATION FALLS
AND HOW MUCH RATE-DRIVEN COOLING WILL OCCUR WITHIN THE BAND),
AND ALSO IN THE LOCATION/MAGNITUDE OF POST-FRONTAL SNOW SHOWERS.
WIDESPREAD BREEZY TO WINDY SOUTHWESTERLY TO WESTERLY WINDS ARE
EXPECTED THIS AFTERNOON AND TONIGHT IN ADVANCE OF THE COLD
FRONTAL PASSAGE. CONFIDENCE WAS TOO LOW (50 PERCENT) IN
WIDESPREAD ADVISORY-LEVEL SUSTAINED WINDS OR WIND GUSTS TO ISSUE
ANY WIND HEADLINES. BY WEDNESDAY AFTERNOON, WINDS WILL BECOME
WESTERLY TO NORTHWESTERLY IN THE WAKE OF THE FRONT AND REMAIN
DIURNALLY BREEZY TO WINDY THROUGH THURSDAY. NBM PROBABILITIES OF
EXCEEDING ADVISORY LEVELS VARY WIDELY (30-80 PERCENT) ACROSS
THE LOWER ELEVATIONS EACH DAY, HIGHEST FOR WIND-PRONE LOCATIONS
OF THE FOOTHILLS OF THE BLUE MOUNTAINS AND NORTH-CENTRAL OREGON
AS WELL AS THE KITTITAS VALLEY.
THE COLD AIR MASS ASSOCIATED WITH THE UPPER LOW THURSDAY
MORNING HAS PROMPTED CONCERNS FOR NEAR- TO BELOW-FREEZING
MORNING TEMPERATURES. NBM CALIBRATED PROBABILITIES SUGGEST
MEDIUM-HIGH CHANCES (60-90 PERCENT) OF FREEZING TEMPERATURES
FOR THE YAKIMA AND KITTITAS VALLEYS, MEDIUM PROBABILITIES (30-70
PERCENT) ALONG THE FOOTHILLS OF THE BLUE MOUNTAINS, AND LOW-
MEDIUM-MEDIUM (20-50 PERCENT) FOR THE LOWEST ELEVATIONS
INCLUDING THE EASTERN COLUMBIA RIVER GORGE AND LOWER COLUMBIA
BASIN. HAVE OPTED TO ISSUE A FREEZE WATCH WHERE CHANCES OF
FREEZING ARE HIGHEST (KITTITAS AND YAKIMA VALLEYS AND THE
FOOTHILLS OF THE NORTHERN BLUE MOUNTAINS OF OREGON), BUT WILL
NOTE THERE ARE STILL A LOT OF MOVING PARTS TO THE FORECAST WITH
UNCERTAINTY IN HOW MUCH CLOUD COVER WILL PERSIST AND HOW WINDY
CONDITIONS WILL REMAIN OVERNIGHT INTO THE MORNING HOURS. ALSO
WORTHY MENTIONING, WITH THE NOTABLE EXCEPTION OF SEVERAL CAMS
(AND PERHAPS A FEW OTHER INPUTS NOT EXAMINED), RAW INPUTS TO
THE NBM ARE LARGELY NOT SUPPORTIVE OF SUB-FREEZING TEMPERATURES
WHILE BIAS-CORRECTED INPUTS ARE. THIS IS NOT UNCOMMON, BUT WHEN
CONDITIONS ARE NOT CALM, RAW INPUTS ARE MORE LIKELY TO HAVE
THEIR WARMER TEMPERATURES VERIFY THAN WHEN RADIATIONAL COOLING
IS EFFICIENT AND GUIDANCE STRUGGLES TO RESOLVE COLD POOLS.
AN UPPER-LEVEL RIDGE WILL LIKELY (80 PERCENT CONFIDENCE) BUILD
INTO THE PACIFIC NORTHWEST FRIDAY INTO THE WEEKEND, YIELDING
LIGHTER WINDS AND MOSTLY DRY CONDITIONS. THE MAIN HEADLINE-
WORTHY CONSIDERATION FOR FRIDAY WILL BE NEAR- TO SUB-FREEZING
TEMPERATURES FOR THE LOWLANDS. THIS SET-UP LOOKS MORE FAVORABLE
FOR MOSTLY CLEAR TO CLEAR SKIES AND LIGHTER WINDS RELATIVE TO
THURSDAY MORNING, SO WHILE THE COLDEST AIR MASS WILL HAVE EXITED
THE REGION TO THE EAST, RADIATIONAL COOLING SHOULD BE MORE
EFFICIENT.
BY SUNDAY THROUGH MONDAY, UNCERTAINTY IN THE 500-HPA PATTERN
GROWS, BUT SOME FLAVOR OF A 500-HPA CLOSED LOW (~85 PERCENT OF
MEMBERS) OR TROUGH (~15 PERCENT OF MEMBERS) IS ADVERTISED BY
ALL ENSEMBLE CLUSTERS TO BE IN THE VICINITY OF, OR OVER, THE
PACIFIC NORTHWEST. WILL NOTE THE TREND IN 12Z ENSEMBLES HAS BEEN
TOWARDS THE OFFSHORE CUT-OFF LOW, A SOLUTION THAT ANECDOTALLY
MATERIALIZES MORE OFTEN RELATIVE TO THE MORE PROGRESSIVE
SOLUTIONS.
AVIATION /00Z TAFS THROUGH 00Z THURSDAY/
VFR CONDITIONS CURRENTLY PREVAIL WITH THE MAIN CONCERNS OVER THE
TAF PERIOD WILL BE PERIODS OF LIGHT TO MODERATE RAIN SHOWERS
WITH BREEZY TO LOCALLY WINDY CONDITIONS. RAIN SHOWERS WILL
DEVELOP FOR THE MAJORITY OF SITES OVER THE EVENING TO MORNING
HOURS TOMORROW, WITH 20-30 MPH GUSTS EMBEDDED. A SMALL CHANCE
REMAINS WITH THE MORE MODERATELY DEVELOPED SHOWERS, THAT MVFR
CONDITIONS OR LOWER WILL TEMPORARY DEVELOP (5-15% CHANCE) WITH
LOW CIGS AND/OR VIS.
PRELIMINARY POINT TEMPS/POPS
PDT 41 52 31 53 / 50 90 40 20
ALW 42 52 34 53 / 80 90 60 30
PSC 44 58 34 61 / 30 70 30 0
YKM 38 55 30 59 / 60 40 10 0
HRI 42 56 32 59 / 30 80 20 0
ELN 32 48 29 52 / 60 30 10 0
RDM 34 48 23 49 / 40 80 30 0
LGD 39 48 29 46 / 90 100 80 60
GCD 38 49 26 45 / 70 100 70 60
DLS 41 53 35 57 / 80 80 20 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...WINTER WEATHER ADVISORY UNTIL 11 PM PDT WEDNESDAY FOR WAZ030.
FREEZE WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY MORNING
FOR WAZ026-027.
WINTER WEATHER ADVISORY UNTIL 11 PM PDT WEDNESDAY FOR WAZ522.
OR...WINTER WEATHER ADVISORY UNTIL 11 PM PDT WEDNESDAY FOR ORZ502.
FREEZE WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY MORNING
FOR ORZ507.
WINTER STORM WARNING UNTIL 5 AM PDT THURSDAY FOR ORZ509.
DISCUSSION...86
AVIATION...95
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