642
FXUS66 KPDT 250528
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1028 PM PDT WED JUN 24 2026
.UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- ISOLATED THUNDERSTORMS TODAY, MAINLY EAST SLOPES OF THE
WASHINGTON CASCADES
- MULTIPLE RED FLAG WARNINGS IN EFFECT THURSDAY DUE TO BREEZY
WINDS AND LOW RELATIVE HUMIDITY
- COOLER, BREEZY, AND SHOWERY WEATHER IS LIKELY (95 PERCENT
CONFIDENCE) FRIDAY INTO THE WEEKEND
DISCUSSION
WATER VAPOR IMAGERY SHOWS A WEAK SHORTWAVE MOVING OVER THE
PACIFIC NORTHWEST THIS AFTERNOON. WHILE SOME CIRRUS IS PRESENT,
THE MAIN FOCUS HAS BEEN ON CUMULUS FIELDS OVER THE MOUNTAINS.
THE MOST ROBUST OF WHICH DEVELOPED ACROSS THE EAST SLOPES OF THE
WASHINGTON CASCADES MID-MORNING AND HAS RESULTED IN SHOWERS AND
ISOLATED THUNDERSTORMS. ELSEWHERE, VERTICAL DEVELOPMENT HAS
REMAINED STUNTED OVER THE HIGHER TERRAIN OF THE OREGON CASCADES
AND BLUE MOUNTAINS, BUT SOME RECENT VERTICAL GROWTH HAS BEEN
NOTED IN WESTERN WASCO COUNTY EAST OF MT HOOD. THERE IS STILL A
VERY LOW TO SLIGHT CHANCE (5-15 PERCENT) OF HIGH-BASED SHOWERS
AND THUNDERSTORMS ACROSS THE EAST SLOPES OF THE OREGON CASCADES
AND BLUE MOUNTAINS THIS AFTERNOON AND EVENING.
WIDESPREAD MODERATE (LEVEL 2 OF 4) HEATRISK IS STILL EXPECTED
ACROSS THE LOWER ELEVATIONS OF THE FORECAST AREA TODAY, WITH
AFTERNOON TEMPERATURES PEAKING IN THE UPPER 80S TO MID-90S.
THIS LEVEL OF HEAT PRIMARILY AFFECTS THOSE WHO ARE SENSITIVE TO
HEAT, ESPECIALLY THOSE WITHOUT COOLING/HYDRATION.
BREEZY WESTERLY WINDS IN TANDEM WITH LOW RELATIVE HUMIDITY WILL
FACILITATE ANOTHER ROUND OF LOCALIZED FIRE WEATHER CONCERNS
THIS AFTERNOON AND EVENING (SEE FIRE WEATHER SECTION BELOW FOR
DETAILS).
BY THURSDAY, THE CLOSED LOW CURRENTLY LOCATED IN THE GULF OF
ALASKA IS EXPECTED (95 PERCENT CONFIDENCE) TO MOVE SOUTHEAST
ALONG THE COAST OF BRITISH COLUMBIA AND SOUTHEAST ALASKA. A
SHORTWAVE WRAPPING AROUND THE BASE OF THE LOW IS FORECAST TO
MOVE INLAND OVER THE PACIFIC NORTHWEST DURING THE AFTERNOON.
BREEZY TO WINDY WESTERLY WINDS AND LOW RELATIVE HUMIDITY ARE
ANTICIPATED AND RED FLAG WARNINGS HAVE BEEN ISSUED (SEE FIRE
WEATHER SECTION BELOW FOR DETAILS).
A TRANSITION TO A COOLER, WETTER PATTERN IS LIKELY (90 PERCENT
CONFIDENCE) BY THURSDAY NIGHT AS A SECOND SHORTWAVE MOVES
OVERHEAD, FOLLOWED BY THE PARENT CLOSED LOW OVER THE WEEKEND.
CLUSTER ANALYSIS OF 00Z ENSEMBLE MEMBERS SHOWS RELATIVELY SMALL
DIFFERENCES IN TIMING/LOCATION AND MAGNITUDE OF THE LOW DURING
THE PERIOD, SO CONFIDENCE IS HIGH IN THE CURRENT FORECAST OF
BELOW-NORMAL TEMPERATURES FRIDAY THROUGH THE WEEKEND. HOWEVER,
EVEN SMALL DIFFERENCES IN THE TRACK/TIMING OF THE LOW CAN HAVE A
SIGNIFICANT IMPACT ON PRECIPITATION; THE TREND IN ENSEMBLE
GUIDANCE HAS BEEN TO KEEP THE LOWER ELEVATIONS RELATIVELY DRY
WITH PRECIPITATION FOCUSED OVER THE MOUNTAINS.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
VFR CONDITIONS CURRENTLY ACROSS ALL SITES, WHICH WILL STAY THE
COURSE THROUGH THE PERIOD. BREEZY WINDS HAVE SUBSIDED, BUT WILL
RETURN ACROSS ALL SITES EARLY IN THE AFTERNOON WITH SUSTAINED
WINDS OF 10-15KTS AND GUSTS OF 20-25KTS. 25KFT CEILINGS WILL
DROP TO 10KFT LATE THURSDAY AFTERNOON, AS A SYSTEM BRINGS LIGHT
RAIN TO KDLS/KRDM/KBDN NEAR THE END OF THE PERIOD. 75
FIRE WEATHER
WINDS WILL TRANSITION TO ONSHORE (WESTERLY) AND BECOME BREEZY
DURING THE MID/LATE AFTERNOON HOURS AS A WEAK SHORTWAVE TROUGH
MOVES OVER THE PACIFIC NORTHWEST. 12Z HREF AND REFS NWP GUIDANCE
BOTH SHOW MEDIUM PROBABILITIES (30-70 PERCENT) OF REACHING
LOCALIZED RED FLAG CONDITIONS ACROSS OR691 (LOWER COLUMBIA BASIN
OF OREGON), WA691 (LOWER COLUMBIA BASIN OF WASHINGTON), WA690
(KITTITAS VALLEY), AND OR703 (WARM SPRINGS RESERVATION) THIS
AFTERNOON AND EVENING. HAVE HELD OFF ON ISSUING ANY FIRE WEATHER
HEADLINES DUE TO INSUFFICIENT CONFIDENCE (NEED 80 PERCENT OR
HIGHER).
SHOWERS AND ISOLATED THUNDERSTORMS ARE ONGOING ALONG THE EAST
SLOPES OF THE WASHINGTON CASCADES THIS AFTERNOON. ELSEWHERE,
THERE IS A VERY LOW TO SLIGHT CHANCE (5-15 PERCENT) OF SHOWERS
AND THUNDERSTORMS FOR THE EAST SLOPES OF THE OREGON
CASCADES AND PORTIONS OF THE BLUE MOUNTAINS.
THURSDAY, FIRE WEATHER CONCERNS INCREASE ACROSS OR691, WA691,
WA690, AND OR703 AS BREEZY TO WINDY WESTERLY WINDS (10-20 MPH
WITH GUSTS OF 20-30 MPH) OVERLAP WITH LOW RELATIVE HUMIDITY OF
10-20 PERCENT. 12Z REFS, 12Z HREF, AND NBM PROBABILITIES PAINT
A 60-100 PERCENT CHANCE OF REACHING RFW CRITERIA ACROSS A GOOD
PORTION OF THESE ZONES. HAVE OPTED TO ISSUE RED FLAG WARNINGS,
VALID BETWEEN 10 AM AND 9 PM PDT THURSDAY DUE TO WIND AND LOW
RELATIVE HUMIDITY.
COOLER, BREEZY, AND SHOWERY WEATHER WITH ISOLATED THUNDERSTORMS
(MAINLY FOR THE MOUNTAINS) IS THEN FORECAST FRIDAY THROUGH THE
WEEKEND AS AN UPPER-LEVEL CLOSED LOW PRESSURE SYSTEM MOVES OVER
THE PACIFIC NORTHWEST.
PRELIMINARY POINT TEMPS/POPS
PDT 61 85 52 75 / 0 0 40 40
ALW 64 87 57 76 / 0 0 30 40
PSC 64 89 56 80 / 0 0 20 20
YKM 61 86 56 78 / 10 0 30 20
HRI 64 87 55 78 / 0 0 40 20
ELN 59 81 51 70 / 10 0 30 50
RDM 52 82 47 71 / 0 0 40 30
LGD 58 85 54 71 / 0 0 40 80
GCD 54 86 51 72 / 0 0 60 80
DLS 62 83 57 74 / 0 0 50 40
PDT WATCHES/WARNINGS/ADVISORIES
WA...RED FLAG WARNING FROM NOON TO 9 PM PDT THURSDAY FOR WAZ690-691.
OR...RED FLAG WARNING FROM 10 AM TO 9 PM PDT THURSDAY FOR ORZ691.
RED FLAG WARNING FROM NOON TO 8 PM PDT THURSDAY FOR ORZ703.
DISCUSSION...86
AVIATION...75
FIRE WEATHER...86
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