988
FXUS66 KPDT 291101
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
401 AM PDT WED APR 29 2026
KEY MESSAGES
- TEMPERATURES WARMING TO ABOVE NORMAL THROUGH EARLY NEXT WEEK
- UNCERTAINTY LATE FRIDAY THROUGH EARLY NEXT WEEK IN POTENTIAL
FOR MOUNTAIN SHOWER AND THUNDERSTORM ACTIVITY
DISCUSSION
TODAY THROUGH FRIDAY: A WEAK SHORTWAVE EXITING
THE AREA HAS LEAD TO CLOUDY CONDITIONS ACROSS THE EASTERN HALF
OF THE FORECAST AREA TONIGHT. RADAR TONIGHT DOES SHOW VERY WEAK
ECHO RETURNS ACROSS PORTIONS OF THE BLUES, THOUGH SURFACE
OBSERVATIONS SHOW NOTHING MAKING IT TO THE GROUND AT THIS TIME.
ACROSS THE REMAINDER OF THE FORECAST AREA, WINDS HAVE BECOME
LIGHT, WITH OTHERWISE QUIET CONDITIONS AT THE SURFACE.
TODAY, AN UPPER LEVEL RIDGE WILL BUILD OVER THE PACNW AND
PERSIST OVERHEAD THROUGH EARLY FRIDAY (CONFIDENCE 80-90%). THE
BUILDING HIGH PRESSURE ALOFT WILL RESULT IN DRYING AND WARMING
CONDITIONS ACROSS MUCH OF THE FORECAST AREA. HIGH TEMPERATURES
WILL WARM WELL ABOVE NORMAL INTO THE UPPER 70S TO LOWER 80S
ACROSS THE LOWER AND MID ELEVATIONS BY FRIDAY AFTERNOON.
THE UPPER RIDGE WILL FLATTEN AND PUSH EAST AS AN UPPER TROUGH
SETS UP OFFSHORE THE PACNW THE SECOND HALF OF FRIDAY. CONDITIONS
WILL REMAIN MOSTLY DRY ACROSS THE FORECAST AREA, HOWEVER
INCREASING SOUTHERLY FLOW WITH AND EMBEDDED SHORTWAVE IMPULSE
WILL BRING ISOLATED SHOWER CHANCES TO THE CASCADE CREST LATE IN
THE AFTERNOON AND OVERNIGHT (CONFIDENCE 55-65%)
SATURDAY THROUGH TUESDAY: ENSEMBLE CLUSTER GUIDANCE BEGINS IN
GOOD AGREEMENT OF THE AFOREMENTIONED UPPER TROUGH DIGGING SOUTH
AND TRANSITIONING INTO A CLOSED LOW OFF THE NORTHERN CA COAST
LATE SATURDAY. DURING THIS TIME, THE TROUGH/LOW WILL PLACE A
SOUTHERLY FLOW INTO OR, ALLOWING WEAK INSTABILITY TO DEVELOP
OVER THE EASTERN MOUNTAINS AND OR CASCADES. THIS WILL LEAD TO
SLIGHT CHANCES (15-20%) OF ISOLATED SHOWERS DEVELOPING WITH A
SLIGHT CHANCE (~15%) OF ISOLATED THUNDERSTORMS AS WELL.
SUNDAY THROUGH TUESDAY, WHILE OVERALL AGREEMENT IN THE
DEVELOPMENT OF THE CLOSED LOW AND IT'S EVENTUAL PUSH INLAND IS
HIGH AMONGST ENSEMBLE MEMBERS OF THE ECMWF, GFS, AND CANADIAN,
THERE IS DISAGREEMENT SURROUNDING THE LOCATION OF THE LOW
OFFSHORE, THE EXTENT OF THE LOW, AND THE TIMING OF IT'S TRANSIT
INLAND. SCENARIOS RANGE FROM A SMALLER LOW FURTHER OFFSHORE THAT
WOULD KEEP CENTRAL OR AND ADJACENT MOUNTAIN AREAS DRY, WHILE A
LARGER LOW CIRCULATION AND/OR A LOW CENTERED CLOSER TO NORTHERN
CA WOULD PRODUCE ISOLATED TO SCATTERED SHOWER CHANCES WITH
ISOLATED THUNDERSTORMS FOR SUNDAY. MONDAY AND TUESDAY, THERE IS
MODERATE CONFIDENCE (40-55%) THAT THE LOW'S PASSAGE INLAND WILL
BRING SHOWER AND ISOLATED THUNDERSTORM CHANCES ACROSS PORTIONS
OF CENTRAL OR AND THE EASTERN MOUNTAINS, HOWEVER THERE IS LOW
CONFIDENCE (15-25%) IN TIMING AND LOCATION OF BEST CHANCES OF
SHOWERS/THUNDERSTORMS OWING TO TIMING DIFFERENCES IN THE LOW
MOVING INLAND.
IN ADDITION TO IMPACTS FROM THE CLOSED LOW, ENSEMBLE CLUSTER
SOLUTIONS DEPICT UPPER LEVEL RIDGING DEVELOPING POLEWARD OF THE
LOW, RESULTING IN CONTINUED ABOVE NORMAL TEMPERATURES FOR THE
INLAND PACNW. BY MONDAY, THERE WILL BE A 50-70% CHANCE FOR HIGH
TEMPERATURES TO EXCEED 90 DEGREES ACROSS PORTIONS OF YAKIMA
VALLEY AND THE WA COLUMBIA BASIN. ACROSS THE REMAINDER OF THE
LOWER COLUMBIA BASIN, THE GORGE, KITTITAS VALLEY, AND THE JOHN
DAY BASIN THERE IS A 45-70% CHANCE OF EXCEEDING 85 DEGREES
MONDAY AFTERNOON. LAWHORN/82
AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
VFR CONDITIONS TO
PREVAIL THROUGH PERIOD. WINDS WILL BE LIGHT, 12KTS OR LESS, AT
ALL SITES. LAWHORN/82
PRELIMINARY POINT TEMPS/POPS
PDT 68 42 75 45 / 0 0 0 0
ALW 69 46 75 49 / 10 0 0 0
PSC 74 44 80 45 / 0 0 0 0
YKM 73 44 77 47 / 0 0 0 0
HRI 72 42 78 44 / 0 0 0 0
ELN 68 42 73 43 / 0 0 0 0
RDM 66 34 72 37 / 0 0 0 0
LGD 66 38 71 41 / 10 0 0 0
GCD 65 37 71 42 / 20 10 0 0
DLS 73 47 80 50 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...82
AVIATION...82
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