332
FXUS66 KPDT 042205
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
305 PM PDT SAT JUL 4 2026
KEY MESSAGES
- CRITICAL FIRE WEATHER CONDITIONS STEMMING FROM LOW HUMIDITY
AND BREEZY WINDS TODAY ACROSS THE KITTITAS VALLEY AND OREGON
LOWER BASIN.
- ELEVATED TO CRITICAL FIRE WEATHER CONDITIONS TUESDAY AND
WEDNESDAY.
- LOW THUNDERSTORM CHANCES IN THE CENTRAL OREGON MOUNTAINS
MONDAY SHIFTING TO THE EASTERN MOUNTAINS TUESDAY.
DISCUSSION
LATEST SATELLITE IMAGERY SHOWS CLEAR SKIES THOUGH
SOME CU APPARENT IN EAST CENTRAL OR WITH ERODING STRATUS WEST
OF THE CASCADES. WATER VAPOR SHOWS CYCLONIC FLOW ALOFT AT MID-
LEVELS WITH A WESTERLY MID-LEVEL JET CENTERED ROUGHLY ACROSS THE
WA/BC BORDER. A SHARPENING THERMAL LOW IS DEVELOPING IN THE
COLUMBIA BASIN/INTERIOR NW TODAY WHEREIN THE DEVELOPING CROSS-
CASCADE PRESSURE GRADIENT AND MODEST LOW-LEVEL WINDS ARE
CONTRIBUTING TO GUSTS COMMONLY 20-30 MPH ALONG GAPS OF THE
CASCADES, EASTERN GORGE SPILLING INTO THE LOWER OR BASIN, AND
THE KITTITAS VALLEY. THE LATTER SEEING THE HIGHEST GUSTS WITH
GUSTS REACHING 40 MPH. WINDS WILL LESSEN TONIGHT WITH LOSS OF
SOLAR HEATING AND COOLING. THE LARGE SCALE PATTERN WILL SEE A
SIMILAR ZONAL PATTERN TOMORROW AS TODAY, AND SIMILAR CONDITIONS
WITH RESPECT TO TEMPERATURES AND HUMIDITY WITH WEAK HEIGHT
RISES OWING TO A SHORTWAVE RIDGE WORKING INTO WA/BC. A LOWER
SURFACE PRESSURE GRADIENT WILL BE IN PLACE THOUGH, THUS LIMITED
WEATHER CONCERNS OVERALL WITH LIGHT WINDS EXPECTED AND HIGHS
LARGELY 3-8 DEGREES ABOVE AVERAGE FOR THIS TIME OF YEAR.
LOOKING AHEAD, AN UPPER-LEVEL CLOSED LOW WILL BE DEVELOPING
SOUTHWARD ACROSS THE GULF OF ALASKA PROMOTING LARGE-SCALE
TROUGHING IN THE NORTHERN EASTERN NORTH PACIFIC WITH ANOTHER
CLOSED LOW DEVELOPING NORTHEAST OF HAWAII. THIS WILL WORK TO
PROMPT A SOUTHWEST FLOW ALOFT WITH INCREASING 850 HPA
TEMPERATURES MOVING IN, AND INCREASING MOISTURE INTO SOUTHERN
AND EASTERN OR. THE LATEST ENSEMBLE GUIDANCE SHOWS PRECIPITABLE
WATERS AROUND 125-175% OF NORMAL IN PLACE BY MONDAY ACROSS THE
SOUTHERN-THIRD OF THE FORECAST AREA. THE COMBINATION OF
OROGRAPHIC LIFT AND LARGE SCALE ASCENT WITH THIS REINFORCING
MOISTURE AND MODERATE INSTABILITY (WITH DETERMINISTIC GUIDANCE
SHOWING 500-800 J/KG OF MUCAPES AND MLCAPES OF 400-600 J/KG)
WILL PROMOTE THUNDER CHANCES ACROSS THE CENTRAL OR MOUNTAINS
AND SOUTHERN EASTERN MOUNTAINS. THE WEAK FORCING REGIME AND
QUANTITY OF MOISTURE LOWERS THE OVERALL CONFIDENCE THOUGH WITH
PRESENT THUNDER CHANCES AROUND 10-20%, HIGHEST ACROSS SOUTHERN
DESCHUTES, CROOK, AND GRANT COUNTIES.
THIS MID-LEVEL TROUGH IS FORECAST TO BECOME MORE AMPLIFIED
TUESDAY WITH HIGHS 6-12 ABOVE AVERAGE UNDER THE SOUTHERLY FLOW
AND THE SHOWER/THUNDERSTORM THREAT SHIFTING MORE TO THE EASTERN
MOUNTAINS/BLUES AND WALLOWAS. HOWEVER, MOISTURE REMAINS A
CONCERN AND THE LACK THEREOF UNDER THE WEAK FORCING PATTERN
AGAIN. MEANTIME, SHARPENING PRESSURE DIFFERENCES WILL PROMPT
BREEZY WINDS UNDER HOT, DRY CONDITIONS ON TUESDAY WITH THE THE
UPPER-LEVEL TROUGH’S MID-LEVEL JET SPREADING INTO THE REGION.
THIS WILL PROMOTE GUSTS 25-40 MPH ACROSS THE CASCADE GAPS,
KITTITAS VALLEY, AND THE EASTERN GORGE SPILLING INTO THE LOWER
BASIN. CHANCE FOR PEAK DAILY GUSTS EXCEEDING 30 MPH IS 70% OR
HIGHER ACROSS THESE AFOREMENTIONED AREAS; CHANCES FOR 40 MPH OR
HIGHER AROUND 50-90% LOCALIZED ACROSS THE KITTITAS VALLEY AND
PARTS OF THE EASTERN GORGE. THE UPPER TROUGH’S ATTENDANT COLD
FRONT WILL THEN MOVE THROUGH EARLY WEDNESDAY PROMOTING WINDY
CONDITIONS AND HIGHS ABOUT 8-15 DEGREES COOLER THAN TUESDAY.
WHILE PRECIPITATION LOOKS LIMITED WITH MOSTLY DRY CONDITIONS
ANTICIPATED, HIGHER GUSTS ARE MORE LIKELY THAN TUESDAY WITH
30-45 MPH GUSTS FORECAST. THERE ARE BETTER CHANCES FOR AREAS
SEEING 40 MPH ACROSS THE LOWER BASIN AND NORTH CENTRAL OR
(50-60%) WEDNESDAY THAN TUESDAY. THE COMBINATION OF WINDY
CONDITIONS AND LOW HUMIDITIES WILL PROMPT POTENTIAL ELEVATED TO
CRITICAL FIRE WEATHER CONDITIONS TUESDAY AND WEDNESDAY.
INCREASING LARGE-SCALE TROUGHING IN THE EASTERN NORTH PACIFIC
LOOKS LIKELY THEN LATE THIS WEEK WITH CHANCES AROUND 70-80% FOR
THIS SCENARIO. THIS WILL PROMPT SIMILAR TO A SLIGHT RISE IN
HIGHS GOING INTO THE EARLY WEEKEND WITH NEAR-AVERAGE HIGHS
FORECAST WEDNESDAY-FRIDAY. OVERALL DRY CONDITIONS LOOK MORE
LIKELY THAN NOT WITH AN INCREASING CROSS-CASCADE GRADIENT
ALONGSIDE DIURNAL BREEZES ON FRIDAY AND SATURDAY.
AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
LATEST SATELLITE SHOWS
ONSHORE FLOW AND STRATUS WEST OF THE CASCADES WITH LARGELY CLEAR
SKIES IN THE NORTHWEST INTERIOR/EAST OF THE CASCADES. VFR CONDITIONS
EXPECTED TO CONTINUE THROUGH THE TAF PERIOD AT ALL SITES. MAIN
AVIATION CHALLENGE REVOLVES AROUND WINDS THIS AFTERNOON WITH
SHARPENING SURFACE PRESSURE GRADIENT DEVELOPING TODAY SUPPORTING
MODEST BREEZES AND GUSTS AT TAF SITES THIS AFTERNOON-EVENING, EXCEPT
KDLS WITH PEAK GUSTS TODAY LIKELY EXCEEDING 25 KTS (CONFIDENCE 60-
80%). WINDS WILL THEN LESSEN WITH GUSTS SUBSIDING BY EARLY
MORNING.
FIRE WEATHER
CRITICAL FIRE WEATHER CONDITIONS ARE IN PLACE
WITH LOW RH AND GUSTY WINDS SEEN ACROSS KITTITAS VALLEY AND
THE OR LOWER BASIN. THE FORMER DIPPING DOWN TO AROUND 15% WITH
GUSTS 30-40 MPH EARLY THIS AFTERNOON WHILE THE LATTER HAS SEEN
WINDS 15-20 MPH AND RH 10-15%. CONDITIONS WILL REMAIN FAVORABLE
FOR RAPID FIRE SPREAD INTO THE EVENING WITH A SHARP CROSS-
CASCADE PRESSURE GRADIENT EVOLVING THIS AFTERNOON. LOOKING
AHEAD, WEAKER PRESSURE DIFFERENCES ARE EXPECTED TOMORROW WITH
LOW HUMIDITY AGAIN BUT LIGHTER WINDS. THUS FIRE WEATHER
CONCERNS ARE LOWER COMPARED TO TODAY, AND THIS WILL CONTINUE
MONDAY. THAT SAID, THERE ARE LOW THUNDERSTORM CHANCES MONDAY
ACROSS THE CENTRAL OR MOUNTAINS.
TUESDAY AND WEDNESDAY HOLD THE NEXT WEATHER CONCERNS WITH BROAD
TROUGHING IN THE EASTERN NORTH PACIFIC. THIS WILL PROMOTE HOT,
DRY, AND WINDY CONDITIONS WITH A SHARP CROSS-CASCADE GRADIENT
DEVELOPING WITH INCREASING WESTERLY FLOW. MAIN AREAS OF CONCERN
IS ACROSS CASCADE GAPS, EASTERN GORGE INTO NORTH CENTRAL OR,
KITTITAS VALLEY, AND SIMCOE HIGHLANDS. A COLD FRONT WILL CROSS
THE AREA THEN EARLY WEDNESDAY KNOCKING TEMPERATURES DOWN SOME
WITH HUMIDITY INCREASING AS MUCH AS 10% IN THE NORTH. HOWEVER,
MORE WIDESPREAD BREEZY CONDITIONS ARE EXPECTED WITH HIGHER-END
GUSTS MORE LIKELY ON WEDNESDAY.
PRELIMINARY POINT TEMPS/POPS
PDT 53 88 55 90 / 0 0 0 0
ALW 58 89 59 92 / 0 0 0 0
PSC 56 91 56 94 / 0 0 0 0
YKM 55 91 58 95 / 0 0 0 0
HRI 56 90 56 93 / 0 0 0 0
ELN 51 87 54 91 / 0 0 0 0
RDM 49 89 54 89 / 0 0 0 10
LGD 53 88 56 89 / 0 0 0 10
GCD 52 92 56 91 / 0 0 0 20
DLS 57 92 60 95 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...RED FLAG WARNING UNTIL 7 PM PDT THIS EVENING FOR WAZ690.
OR...RED FLAG WARNING UNTIL 10 PM PDT THIS EVENING FOR ORZ691.
DISCUSSION...80
AVIATION...80
FIRE WEATHER...80
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