564
FXUS66 KPDT 010428
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
928 PM PDT THU APR 30 2026
KEY MESSAGES
- ABOVE-NORMAL TEMPERATURES LIKELY (80-100 PERCENT CONFIDENCE)
INTO THE MIDDLE OF NEXT WEEK
- VERY LOW TO SLIGHT CHANCE (5-20 PERCENT) OF MOUNTAIN SHOWERS
AND THUNDERSTORMS LATE FRIDAY THROUGH EARLY NEXT WEEK
DISCUSSION
DAY CLOUD PHASE RGB IMAGERY REVEALS FEW TO SCATTERED FAIR
WEATHER CUMULUS OVER THE EAST SLOPES OF THE WASHINGTON CASCADES
AND ADJACENT RIDGES THAT EXTEND EASTWARD THROUGH KITTITAS,
YAKIMA, AND KLICKITAT COUNTIES. FARTHER EAST, FEW TO SCATTERED
CUMULUS ARE ALSO PRESENT OVER THE BLUE MOUNTAINS. CHANCES OF
SHOWERS ARE VERY LOW (5 PERCENT OR LESS) THIS AFTERNOON.
ZOOMING OUT TO EXAMINE THE BROADER PICTURE, A REX BLOCK LOOK-
ALIKE PATTERN HAS SET UP ACROSS THE REGION. AN AMPLIFIED UPPER-
LEVEL RIDGE IN THE NORTHEAST PACIFIC EXTENDS ACROSS THE PACIFIC
NORTHWEST POLE-WARD THROUGH THE CANADIAN ROCKIES AND INTO THE
PRAIRIES. MEANWHILE, A CLOSED LOW IS VISIBLE OVER BAJA
CALIFORNIA (ENSEMBLE GUIDANCE TAKES IT INLAND ACROSS THE
SOUTHWEST THIS EVENING 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.
BY FRIDAY AFTERNOON THROUGH SATURDAY MORNING, THE SECOND
SHORTWAVE WILL APPROACH THE PACIFIC NORTHWEST, DEEPENING INTO A
CLOSED LOW. ENSEMBLE AND DETERMINISTIC GUIDANCE SHOW SOME SLIGHT
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 (10-25 PERCENT)
OF SHOWERS AND SLIGHT CHANCE (5-20 PERCENT) OF THUNDERSTORMS
REMAINS IN THE FORECAST FOR PORTIONS OF 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, HAVE SEEN A CONTINUED SOUTHWARD TREND IN THE
LOCATION AND TRACK OF THE CLOSED LOW IN ENSEMBLE GUIDANCE OVER
THE LAST COUPLE RUNS, RESULTING IN LOWER CHANCES (5-20 PERCENT)
OF PRECIPITATION FOR OUR FORECAST AREA THAN PREVIOUSLY FORECAST
YESTERDAY. A NOTE ON UNCERTAINTY, ALL CLUSTERS TAKE THE CLOSED
LOW INLAND ACROSS CALIFORNIA, THE GREAT BASIN, AND THE SOUTHWEST
SOMETIME BETWEEN MONDAY AND TUESDAY, BUT DETAILS IN TIMING
VARY.
TO TOUCH ON FORECAST TEMPERATURES, WHILE THERE IS STILL SOME
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 WEDNESDAY, CHANCES OF REACHING 90
DEGREES ARE LOW-MEDIUM (20-65 PERCENT) FOR THE YAKIMA VALLEY
AND LOWER COLUMBIA BASIN AS WELL AS HEAT-PRONE PORTIONS OF THE
EASTERN COLUMBIA RIVER GORGE AS WELL AS CENTRAL AND NORTH-
CENTRAL OREGON. MOREOVER, SUNDAY THROUGH WEDNESDAY, 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 /06Z TAFS THROUGH 06Z SATURDAY/
CLOUDS ARE LIMITED IN COVERAGE AND ABOVE 12,000 FT FOR ALL OF
THE TERMINALS. WINDS WILL REMAIN UNDER 10 KNOTS AT ALL
TERMINALS. VFR CONDITIONS ARE ANTICIPATED FOR ALL TERMINALS
THROUGH FRIDAY.
PRELIMINARY POINT TEMPS/POPS
PDT 45 80 51 81 / 0 0 0 0
ALW 50 80 55 82 / 0 0 0 0
PSC 45 83 51 86 / 0 0 0 0
YKM 47 81 54 84 / 0 0 0 0
HRI 45 83 50 85 / 0 0 0 0
ELN 44 76 50 79 / 0 0 10 0
RDM 37 78 44 77 / 0 0 10 10
LGD 41 74 46 77 / 0 0 0 0
GCD 41 75 48 78 / 0 0 0 0
DLS 50 82 55 84 / 0 0 10 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...86
AVIATION...71
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