095
FXUS66 KPDT 152336
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
436 PM PDT THU MAY 15 2025
.UPDATED AVIATION DISCUSSION.
AVIATION...00Z TAFS
VFR CONDITIONS CURRENTLY ACROSS ALL SITES,
WHICH IS EXPECTED TO STAY THE COURSE THROUGH THE PERIOD. THE ONLY
EXCEPTIONS WILL BE BRIEF MVFR CONDITIONS FOR KALW/KPDT EARLY TO
MID-MORNING ON FRIDAY DUE TO REDUCED CEILINGS OF 2500 FEET. LIGHT
RAIN IS ALSO ANTICIPATED AT KRDM/KBDN THIS EVENING AND KALW/KPDT
LATER TONIGHT. BREEZY WINDS WITH GUSTS BETWEEN 20-30KTS WILL
PERSIST FOR KDLS/KPDT/KRDM/KBDN, BUT WILL TAPER OFF THROUGH THE
EVENING. 75
PREV DISCUSSION
/ISSUED 256 PM PDT THU MAY 15 2025/
SHORT TERM...THIS AFTERNOON THROUGH SATURDAY NIGHT...A WEAK
SHORTWAVE WILL ARRIVE FROM THE PACIFIC LATE THIS AFTERNOON,
TRAVERSING THE REGION THROUGH FRIDAY MORNING. THE SYSTEM WILL
FACILITATE LOW CHANCES (10-30%) OF WETTING RAINS FOR THE
MOUNTAINS, HIGHEST FOR THE NORTHERN BLUES, AND LOCALLY BREEZY
WESTERLY TO NORTHWESTERLY WINDS. CONFIDENCE IN WINDS REACHING
ADVISORY LEVELS IS LOW (<30%), HIGHEST FOR THE KITTITAS VALLEY.
A BRIEF BREAK IN ACTIVE WEATHER IS FORECAST FRIDAY AS THE REGION
IS BETWEEN WEATHER SYSTEMS.
LATE FRIDAY, THE FIRST OF BACK-TO-BACK WAVES IS EXPECTED TO ARRIVE
(>90% CONFIDENCE). SHOWER CHANCES WILL INCREASE BY FRIDAY NIGHT,
WITH SOME WEAK ELEVATED INSTABILITY PERHAPS FACILITATING ISOLATED
EMBEDDED THUNDERSTORMS FOR PORTIONS OF THE EASTERN MOUNTAINS
(HIGHEST CHANCE OF 10-15% IN GRANT COUNTY FRIDAY NIGHT).
THE BEST AREA-WIDE SHOWER CHANCES WILL BE SATURDAY AS THE SECOND
WAVE DIGS SOUTHEAST INTO THE PACNW AND THE FIRST WAVE TRACKS EAST
OVER THE GREAT BASIN. DELVING INTO CLUSTERS OF ENSEMBLE SOLUTIONS
DOES REVEAL SOME UNCERTAINTY IN THE EVOLUTION OF THE SYSTEM AS THE
TWO WAVES INTERACT; ENSEMBLE MEMBERS ARE SPLIT ON WHETHER THE
SYSTEM WILL MORPH INTO A CLOSED LOW OVERHEAD LATE SATURDAY THROUGH
SATURDAY NIGHT OR IF IT WILL REMAIN A WEAKER OPEN WAVE TROUGH.
REGARDLESS, HAVE INCLUDED AN AREA-WIDE SLIGHT CHANCE (15-24%
PROBABILITY) TO CHANCE (25-35% PROBABILITY) MENTION OF THUNDER IN
THE FORECAST THROUGH THE DAY SATURDAY AS THE LOW/TROUGH MOVES
OVERHEAD. BEST CHANCES OF THUNDERSTORMS WILL BE OVER THE BLUE
MOUNTAINS DURING THE AFTERNOON (25-35% PROBABILITY).
WESTERLY WINDS WILL INCREASE IN MAGNITUDE SATURDAY THROUGH THE
CASCADE GAPS AS CROSS-CASCADE PRESSURE DIFFERENCES RAMP UP.
NBM PROBABILITIES OF EXCEEDING ADVISORY-LEVEL GUSTS (45 MPH)
THROUGH THE EASTERN COLUMBIA RIVER GORGE, KITTITAS VALLEY, AND
WIND-PRONE PORTIONS OF THE COLUMBIA BASIN/BLUE MOUNTAIN FOOTHILLS
ARE ROUGHLY 20-50%. PLUNKETT/86
LONG TERM...SUNDAY THROUGH THURSDAY...THE UPPER TROUGH WITH THE
ASSOCIATED SYSTEM WILL GRADUALLY MOVE EASTWARD, LEAVING BEHIND
MOUNTAIN SHOWERS WITH LIGHT SNOW, ISOLATED THUNDERSTORMS AND GUSTY
WINDS FOR SUNDAY. QPF AMOUNTS MAY RANGE BETWEEN 0.05-0.15 INCHES
OVER THE BLUES, EASTERN MOUNTAINS AND WA/OR CASCADES (30-60%
CHANCE). THE LOWLANDS WILL BE LEFT DRY.GIVEN THE FRONTAL LIFT,
ISOLATED THUNDERSTORMS MAY DEVELOP LATE SUNDAY MORNING THROUGH
EVENING OVER PORTIONS OF THE BLUES AND ACROSS THE EASTERN
MOUNTAINS. HOWEVER, CHANCES ARE LOW DUE TO INHIBITION FROM LOW
MOISTURE LEVEL AND LACK OF INSTABILITY. WINDS OVER THE CASCADE
GAPS WILL BECOME GUSTY AT 30-40 MPH ALONG WITH BREEZY WINDS ACROSS
THE LOWLANDS FROM THE CROSS-CASCADE SURFACE PRESSURE DIFFERENCE.
WIND CONDITIONS SHOULD RETURN LIGHT AROUND LATER SUNDAY EVENING
INTO NIGHT WHEN THE SYSTEM BEGINS TO TAMPER OFF.
ANOTHER FRONTAL SYSTEM WILL ARRIVE MONDAY WITH LIGHT SHOWERS AT
FIRST THE CASCADES BEFORE SPREADING TO THE BLUES AND EASTERN
MOUNTAINS (20-40% CHANCE). AND WITH INCREASED WESTERLY FLOW, WINDS
COULD BECOME GUSTY OVER THE CASCADE GAPS MONDAY AFTERNOON INTO THE
EVENING BEFORE STEADILY DECREASING TO BREEZY. MODELS ARE ALIGNED
WITH SYSTEM'S ARRIVAL BUT DIFFERS ON THE TIMING A BIT WHERE THE
CANADIAN MODEL HAS IT SOONER THAN THE OTHERS. THIS MIGHT MAKE
FORECASTING THE TIMING OF SHOWERS DEVELOPMENT SLIGHTLY TRICKY FOR
MONDAY.
THE PACNW WILL BE MOSTLY OVER A ZONAL PATTERN TUESDAY ONWARDS WITH
A BRIEF SHORTWAVE WEDNESDAY. THE FORECAST AREA WILL BE
RELATIVELY DRY, BUT MAY HAVE SOME LINGERING MOUNTAIN SHOWERS OVER
THE CASCADES AND EASTERN MOUNTAINS (<30% CHANCE). THE WESTERLY
FLOW WILL DOMINATE THE REMAINING LONG TERM THUS INDUCING SLIGHTLY
GUSTS AT 25-35 MPH AT THE CASCADE GAPS TUESDAY MORNING THROUGH THE
EVENING. WINDS WEDNESDAY THROUGH THURSDAY MAY BE LOCALLY BREEZY
ACROSS THE CASCADE GAPS BUT LIGHT EVERYWHERE ELSE. FEASTER/97
PRELIMINARY POINT TEMPS/POPS
PDT 46 67 47 66 / 70 30 10 80
ALW 47 65 49 66 / 60 60 10 80
PSC 46 72 47 71 / 50 20 10 60
YKM 44 70 49 68 / 30 10 10 50
HRI 46 72 49 71 / 60 20 10 70
ELN 42 67 46 66 / 30 10 20 60
RDM 37 67 42 63 / 50 0 10 80
LGD 42 59 42 58 / 70 50 10 90
GCD 40 62 43 57 / 80 20 30 100
DLS 46 69 49 68 / 40 0 20 60
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...86
LONG TERM....97
AVIATION...75
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