715
FXUS66 KPDT 292238
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
338 PM PDT WED APR 29 2026
KEY MESSAGES
- ABOVE-NORMAL TEMPERATURES THURSDAY INTO NEXT WEEK
- UNCERTAINTY IN POTENTIAL FOR MOUNTAIN SHOWER AND THUNDERSTORM
ACTIVITY LATE FRIDAY THROUGH EARLY NEXT WEEK
DISCUSSION
DAY CLOUD PHASE RGB IMAGERY REVEALS FEW TO SCATTERED CUMULUS
OVER THE EAST SLOPES OF THE WASHINGTON CASCADES AND ADJACENT
RIDGES THAT EXTEND EASTWARD THROUGH KITTITAS, YAKIMA, KLICKITAT
COUNTIES. FARTHER EAST, FEW TO BROKEN CUMULUS ARE PRESENT OVER
THE BLUE MOUNTAINS. ASIDE FROM ISOLATED SHOWERS OVER THE HIGHER
SUB-RANGES OF THE BLUE MOUNTAINS, DRY CONDITIONS ARE FORECAST
REGION-WIDE THIS AFTERNOON.
ZOOMING OUT TO EXAMINE THE BROADER PICTURE, A REX BLOCK LOOK-
ALIKE PATTERN IS SETTING UP ACROSS THE REGION. AN AMPLIFIED
UPPER-LEVEL RIDGE IN THE NORTHEAST PACIFIC EXTENDS FROM OFF THE
COAST OF THE PACIFIC NORTHWEST POLE-WARD THROUGH BRITISH
COLUMBIA. MEANWHILE, A CLOSED LOW IS VISIBLE WELL OFF THE COAST
OF SOUTHERN CALIFORNIA (ENSEMBLE GUIDANCE TAKES IT INLAND
ACROSS THE SOUTHWEST LATER THURSDAY THROUGH FRIDAY, SO WILL
ARGUE THIS IS NOT A TRUE BLOCKING PATTERN). A COUPLE
SHORTWAVES ARE EVIDENT UPSTREAM OF THE RIDGE, THE LATTER OF
WHICH WILL BE THE MAIN FEATURE OF INTEREST FRIDAY THROUGH EARLY
NEXT WEEK.
THURSDAY, TEMPERATURES WILL WARM TO ABOVE NORMAL (LARGELY IN
THE 70S FOR MAJOR POPULATION CENTERS) AS THE AFOREMENTIONED
UPPER-LEVEL RIDGE SLIDES OVERHEAD. THE FIRST SHORTWAVE NOTED
EARLIER WILL ALMOST CERTAINLY (95 PERCENT CONFIDENCE) TRACK
NORTHEAST OF THE FORECAST AREA INTO BRITISH COLUMBIA AND NOT
SIGNIFICANTLY INFLUENCE OUR WEATHER.
BY FRIDAY AFTERNOON, THE SECOND SHORTWAVE WILL APPROACH THE
PACIFIC NORTHWEST, DEEPENING INTO A CLOSED LOW OR MORE AMPLIFIED
OPEN-WAVE TROUGH. ENSEMBLE AND DETERMINISTIC GUIDANCE SHOW SOME
SPREAD WITH REGARD TO ITS LOCATION, WHICH WILL MODULATE
CONVECTIVE POTENTIAL ACROSS THE CASCADE CREST AND WESTERN HALF
OF OUR FORECAST AREA. SOLUTIONS THAT ARE CLOSER TO THE COAST
PRESENT A BETTER CHANCE OF CONVECTION. CURRENTLY, HAVE A VERY
LOW CHANCE (5-15 PERCENT) OF SHOWERS AND THUNDERSTORMS FOR THE
WASHINGTON CASCADE CREST AND AREAS EAST OF THE CASCADE CREST,
WHILE THE CASCADE CREST OF OREGON HAS A 15-25 PERCENT CHANCE OF
SHOWERS AND 10-15 PERCENT CHANCE OF THUNDERSTORMS.
ALL CLUSTERS OF ENSEMBLE SOLUTIONS TAKE THE UPPER-LEVEL CLOSED
LOW SOUTH ALONG THE COAST OF OREGON AND CALIFORNIA OVER THE
WEEKEND. AS A RESULT, A SLIGHT CHANCE TO CHANCE (10-40 PERCENT)
OF SHOWERS AND SLIGHT CHANCE (10-20 PERCENT) OF THUNDERSTORMS
REMAINS IN THE FORECAST FOR THE CASCADES AND BLUES EACH DAY.
BY SUNDAY, THE UPPER-LEVEL PATTERN RESEMBLES MORE OF A TRUE REX
BLOCK WITH THE CLOSED LOW ALONG THE COAST OF CALIFORNIA AND AN
AMPLIFYING RIDGE POLE-WARD IN THE NORTHEAST PACIFIC, PACIFIC
NORTHWEST, AND CANADIAN ROCKIES. THIS WILL LEAD TO CONTINUED
ABOVE-NORMAL TEMPERATURES ACROSS THE FORECAST AREA, ESPECIALLY
NORTH OF CENTRAL OREGON AND THE SOUTHERN BLUE MOUNTAINS.
MONDAY AND TUESDAY, ALL ENSEMBLE CLUSTERS TAKE THE CLOSED LOW
INLAND ACROSS CALIFORNIA, THE GREAT BASIN, AND THE SOUTHWEST.
AS IT BEGINS ITS INLAND TREK ON MONDAY, THE BEST CHANCES (15-50
PERCENT) OF SHOWERS AND THUNDERSTORMS (10-25 PERCENT) WILL BE
OVER THE OREGON CASCADES AND BLUE MOUNTAINS. ANALYSIS OF QPF
CLUSTERS SUGGESTS A ROUGHLY 35 PERCENT CHANCE OF A WIDESPREAD
WETTING RAIN FOR THE OREGON CASCADES AND BLUE MOUNTAINS WHILE
THE REMAINING MEMBERS SHOW A MORE PATCHY PRECIPITATION SIGNAL.
TO TOUCH ON FORECAST TEMPERATURES, WHILE THERE IS STILL
UNCERTAINTY IN HOW HOT CONDITIONS WILL BE UNDER THE RIDGE FRIDAY
INTO EARLY NEXT WEEK (PARTLY DUE TO THE AFOREMENTIONED
UNCERTAINTY IN SHOWER AND THUNDERSTORM CHANCES AND RESULTANT
CLOUD COVER), CHANCES OF AFTERNOON HIGHS EXCEEDING 80 DEGREES
ACROSS ALL MAJOR POPULATION CENTERS ARE MEDIUM TO VERY HIGH
(50-99 PERCENT) EACH DAY PER LATEST NBM CALIBRATED
PROBABILITIES. SUNDAY THROUGH TUESDAY, CHANCES OF REACHING 90
DEGREES ARE LOW-MEDIUM (20-60 PERCENT) FOR THE YAKIMA VALLEY
AND LOWER COLUMBIA BASIN. MOREOVER, ON MONDAY AND TUESDAY, THERE
IS A LOW-MEDIUM (20-60 PERCENT) CHANCE OF HEATRISK REACHING
MODERATE (LEVEL 2 OF 4) IN THE YAKIMA VALLEY, LOWER COLUMBIA
BASIN, AND HEAT-PRONE PORTIONS OF THE EASTERN COLUMBIA RIVER
GORGE AS WELL AS CENTRAL TO NORTH-CENTRAL OREGON. FOR CONTEXT,
THIS LEVEL OF HEAT AFFECTS THOSE WHO ARE SENSITIVE TO HEAT,
ESPECIALLY THOSE WITHOUT COOLING/HYDRATION. 86
AVIATION /00Z TAFS THROUGH 00Z FRIDAY/
VFR CONDITIONS WILL PERSIST THROUGH THE FORECAST PERIOD. WINDS
WILL BE LIGHT BELOW 10 KTS AND VARIABLE. 90
PRELIMINARY POINT TEMPS/POPS
PDT 43 74 45 80 / 0 0 0 0
ALW 46 75 49 79 / 0 0 0 0
PSC 43 79 44 84 / 0 0 0 0
YKM 45 77 47 80 / 0 0 0 0
HRI 42 78 44 82 / 0 0 0 0
ELN 42 73 44 76 / 0 0 0 0
RDM 33 72 37 78 / 0 0 0 0
LGD 38 70 41 75 / 0 0 0 0
GCD 37 71 42 76 / 0 0 0 0
DLS 47 79 50 82 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...86
AVIATION...90
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page