714
FXUS66 KPDT 251018
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
318 AM PDT FRI APR 25 2025
SHORT TERM...TODAY THROUGH SUNDAY
1. ISOLATED THUNDERSTORMS BOTH TODAY AND SATURDAY AFTERNOON
2. INCREASED WINDS SATURDAY AFTERNOON
3. RETURN TO DRY CONDITIONS SUNDAY WITH LINGERING ISOLATED MOUNTAIN
SHOWERS
CURRENT NIGHT TIME SATELLITE SHOWS CLOUDS SLOWLY MAKING THEIR WAY
INTO THE REGION FROM THE SOUTH. WATER VAPOR IMAGERY SHOWS THERE TO
BE SOME MOISTURE COMING IN ALONG WITH IT. HOWEVER, GROUND
OBSERVATIONS REMAIN DEVOID OF PRECIPITATION AT THIS TIME.
MODELS SHOW THE UPPER LEVEL LOW TO BE OFF THE COAST NEAR THE OR/CA
BORDER. IT HAS BEGUN TO INFLUENCE THE REGION WITH SOUTHERLY FLOW
ALOFT USHERING BOTH WARM AIR ADVECTION AS WELL AS MOISTURE. THIS IS
A PATTERN WELL KNOWN TO THE PACNW FOR BRINGING IN AN UNSTABLE
ATMOSPHERE AND BRINGING THE AREA CHANCES FOR THUNDERSTORMS ALONG THE
EASTERN MOUNTAINS. WITH THE WARM TEMPERATURES, MID LEVEL LAPSE RATES
7.5-8.5 C/KM, MUCAPE 300-500 J/KG AND LIS OF -2 TO -4, ONE CAN NOT
RULE OUT SOME ISOLATED THUNDERSTORMS. LOOKING AT THE NBM RAW
ENSEMBLES, THEY SHOW 10-20% PROBABILITIES OF THUNDERSTORMS FRIDAY
AFTERNOON. SATURDAY, CAMS SOUNDINGS SHOW A STRONGER INVERTED V
PROFILE WITH HIGHER MUCAPE VALUES (400-600J/KG), LAPSE RATES OF 8-9
C/KM AND LIS OF -3 TO -4. PROBABILITIES INCREASE TO 25-35% FOR
THUNDERSTORMS ALONG THE EASTERN MOUNTAINS SATURDAY.
MODELS SHOW AS THE UPPER LEVEL LOW BEGINS TO SWING CLOSER TO THE
COAST, SURFACE GRADIENTS WILL TIGHTEN ALONG THE CASCADES CAUSING
BREEZY CONDITIONS THROUGH THE CASCADE GAPS. 70-80% OF THE RAW
ENSEMBLES SHOW KITTITAS AND THE UPPER YAKIMA VALLEY WILL SEE GUSTS
BETWEEN 35-40 MPH ON SATURDAY. AS FOR THE GORGE, SIMCOES AND A
PORTION THE FOOTHILLS OF THE SOUTHERN BLUES, 60-80% OF THE RAW
ENSEMBLES SHOW THESE AREAS ALSO SEEING WIND GUSTS OF 35-40 MPH.
LASTLY, MODELS SHOW THAT BY SUNDAY, MUCH OF THE AFFECTS OF THE UPPER
LEVEL LOW WILL HAVE DIMINISHED LEAVING THE REGION UNDER DRY
CONDITIONS. THERE WILL HOWEVER BE SOME LINGERING SHOWERS ALONG THE
FAR EASTERN MOUNTAINS OF GRANT AND WALLOWA COUNTIES LEAVING THE
REMAINDER OF THE REGION PRECIPITATION FREE. BENNESE/90
LONG TERM...MONDAY THROUGH FRIDAY
SENSIBLE WEATHER CONCERNS
THROUGH THE EXTENDED FORECAST WILL CENTER ON THE PASSAGE OF AN
UPPER LEVEL SHORTWAVE TROUGH TUESDAY, FOLLOWED BY UPPER LEVEL
RIDGING BUILDING OVER THE PACNW INTO THE END OF NEXT WEEK.
PERSISTENT BREEZY TO LOCALLY GUSTY CONDITIONS WILL IMPACT THE
CASCADE GAP AREAS EARLY IN THE WORK WEEK, WHILE MAINLY MOUNTAIN
AREAS AND ADJACENT FOOTHILLS WILL SEE IMPACTS FROM LIGHT SHOWERS
LATE MONDAY THROUGH TUESDAY (CONFIDENCE 60-85%). OTHERWISE,
MOSTLY DRY CONDITIONS WITH LIGHT WINDS AND A WARMING TREND WILL
DEVELOP OVER THE FORECAST AREA THROUGH LATE NEXT WEEK (CONFIDENCE
45-70%).
MONDAY WILL START WITH UPPER LEVEL RIDGING SWINGING OVER THE
REGION, WITH MOSTLY DRY CONDITIONS ACROSS THE FORECAST AREA.
SURFACE PRESSURE GRADIENTS, ON THE OTHER HAND, WILL REMAIN
TIGHTENED ACROSS THE CASCADES AND COLUMBIA BASIN MONDAY. THIS WILL
RESULT IN GUSTS BETWEEN 30-40MPH THROUGH THE CASCADE GAPS (40-60%
CHANCE >45MPH GUSTS IN THE KITTITAS VALLEY) AND GUSTS CLOSER TO
20-30MPH ACROSS THE COLUMBIA BASIN. BY LATE MONDAY, THE UPPER
RIDGE WILL BE FLATTENED BY AN APPROACHING SHORTWAVE TROUGH, WITH
LIGHT SHOWERS BEGINNING TO DEVELOP ACROSS THE CASCADE CREST,
SPREADING EAST MONDAY NIGHT THROUGH TUESDAY. ENSEMBLE GUIDANCE IS
IN GOOD AGREEMENT THAT THE SHORTWAVE TROUGH WILL BRING MOSTLY
LIGHT RAIN SHOWERS TO THE MOUNTAINS AS IT TRAVERSES THE REGION,
WITH A 40-50% CHANCE OF 0.05 INCHES OF RAIN ALONG THE BLUE
MOUNTAIN FOOTHILLS. THAT SAID, 41% OF THE ENSEMBLE CLUSTER MEMBERS
(WHERE ABOUT 90% OF THE GFS ENSEMBLE MEMBERS ARE INCLUDED) DELAY
FORECAST AREA-WIDE PRECIPITATION CHANCES TO THE LATE MORNING,
WHEREAS PRECIPITATION WILL HAVE SPREAD ACROSS THE EASTERN HALF THE
FORECAST AREA BEFORE SUNRISE ACCORDING TO THE REMAINING 59% OF
ENSEMBLE MEMBERS. OTHERWISE, BREEZY CONDITIONS WILL CONTINUE
THROUGH THE CASCADE GAPS AND INTO THE COLUMBIA BASIN TUESDAY.
WEDNESDAY THROUGH THURSDAY, THERE IS GOOD AGREEMENT AMONGST
ENSEMBLE MEMBERS THAT UPPER LEVEL RIDGING WILL BUILD BACK OVER THE
PACNW. DURING THIS TIME, CONDITIONS WILL REMAIN DRY, TEMPERATURES
WILL BE WARMING WELL INTO THE 70S WITH POCKETS OF LOW 80S
(CONFIDENCE 55-70%), AND WINDS WILL BE LIGHT WITH LOCALLY BREEZY
AFTERNOONS. THAT SAID, BY THURSDAY AFTERNOON, DISAGREEMENT ARISES
AMONGST MEMBERS, SPECIFICALLY GFS AND CANADIAN MEMBERS VERSUS
THOSE OF THE ECMWF. BY LATE THURSDAY AFTERNOON, MEMBERS OF THE GFS
AND CANADIAN PUSH THE UPPER RIDGE AXIS WELL INTO EASTERN ID AND
WESTERN MT, WITH AN UPPER SHORTWAVE TROUGH LIFTING SHOWERS
NORTHEAST ACROSS THE FORECAST AREA FRIDAY. AS FOR THE ECMWF
MEMBERS, THE UPPER LEVEL RIDGE IS SLOWER TO MOVE EAST, RESULTING
IN THE AFOREMENTIONED SHORTWAVE TROUGH WEAKENING AND NOT ARRIVING
UNTIL LATE FRIDAY. AT THIS TIME, CONFIDENCE IS MODERATE (50-60%)
IN THE TROUGH ARRIVING SOMETIME FRIDAY, BUT TIMING/IMPACTS ARE LOW
(15-30%). LAWHORN/82
AVIATION...12Z TAFS
VFR CONDITIONS TO PREVAIL THROUGH THE
PERIOD. A SYSTEM MOVING SOUTH OF THE AREA WILL PRODUCE RAIN
SHOWERS THAT WILL IMPACT SITES RDM/BDN AFTER 23Z, WITH SHOWERS
CONTINUING THROUGH THE OVERNIGHT HOURS. WORTH MENTIONING IS THE
POTENTIAL FOR AN ISOLATED THUNDERSTORM TO DEVELOP WITHIN THESE
SHOWERS, HOWEVER CONFIDENCE/CHANCES ARE TOO LOW (<20%) TO INCLUDE
AT THESE SITES AT THIS TIME. OTHERWISE WINDS WILL BE LIGHT, LESS
THAN 12KTS, THROUGH THE PERIOD. LAWHORN/82
PRELIMINARY POINT TEMPS/POPS
PDT 75 49 74 45 / 0 20 10 10
ALW 76 51 72 48 / 0 10 20 10
PSC 81 47 80 46 / 0 0 0 0
YKM 78 49 80 46 / 0 0 0 0
HRI 79 49 78 46 / 0 10 10 0
ELN 76 48 75 47 / 0 0 0 0
RDM 69 43 67 35 / 30 50 20 10
LGD 72 47 69 44 / 10 30 40 20
GCD 72 46 66 42 / 20 60 70 40
DLS 79 52 72 44 / 0 10 10 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...90
LONG TERM....82
AVIATION...82
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