186
FXUS66 KPDT 230518
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1018 PM PDT SAT AUG 22 2026
KEY MESSAGES
- RED FLAG WARNINGS IN EFFECT THROUGH 11 PM THIS EVENING FOR
ABUNDANT LIGHTNING AND GUSTY OUTFLOW WINDS FOR THE NORTHERN
BLUE MOUNTAINS.
- BREEZY TO WINDY WESTERLY WINDS TODAY WILL OVERLAP WITH LOW
RELATIVE HUMIDITY ACROSS MUCH OF THE FORECAST AREA. RED FLAG
WARNINGS AND WIND ADVISORIES ARE IN EFFECT THROUGH THIS
EVENING.
DISCUSSION
A LOW-PRESSURE SYSTEM CURRENTLY CENTERED NEAR THE OR/WA COAST
WILL CONTINUE TO DRIVE AN ACTIVE WEATHER DAY ACROSS THE REGION.
CROSS-CASCADE SURFACE PRESSURE DIFFERENCES HAVE BEEN A BIT
WEAKER THAN ANTICIPATED YESTERDAY; OBSERVED VALUES IN THE 7-8
MB RANGE (PORTLAND TO SPOKANE) ARE A FEW MILLIBARS SHY OF WHAT
WE WOULD LIKE TO SEE FOR WIDESPREAD WINDY CONDITIONS. THAT SAID,
NWP GUIDANCE SHOWS AN INCREASE TO 9-11 MB THROUGH THE REMAINDER
OF THE AFTERNOON AND INTO THE EVENING. COUPLED WITH A 25-35 KT
850-MB JET THROUGH THE CASCADE GAPS AND ACROSS THE COLUMBIA
BASIN, STILL ANTICIPATING WIDESPREAD BREEZY CONDITIONS, SO HAVE
RETAINED THE PREVIOUSLY ISSUED WIND ADVISORIES WHICH REMAIN IN
EFFECT THROUGH THIS EVENING. ADDITIONALLY, HAVE ADDED PATCHY
BLOWING DUST TO THE FORECAST FOR DUST-PRONE LOCATIONS WITHIN THE
COLUMBIA BASIN REGION. CONFIDENCE IS LOW IN TIMING, MAGNITUDE,
AND DURATION OF ANY VISIBILITY REDUCTIONS, BUT GIVEN THE
EXTENDED DRY CONDITIONS, FORECAST WINDS WILL BE CAPABLE OF
LOFTING DUST.
HIGH-BASED SHOWERS ARE ONGOING ACROSS THE EASTERN THIRD OF OUR
FORECAST AREA, ROUGHLY ALONG AND EAST OF A LINE EXTENDING FROM
GRANT COUNTY THROUGH UMATILLA, WALLA WALLA, AND FRANKLIN
COUNTIES. GUSTY OUTFLOW WINDS IN EXCESS OF 45 MPH HAVE BEEN
OBSERVED WITH SHOWER ACTIVITY IN WALLOWA COUNTY. ADDITIONAL
SHOWER AND THUNDERSTORM DEVELOPMENT WILL BE CAPABLE OF PRODUCING
STRONG, GUSTY OUTFLOW WINDS DUE TO A DEEP, WELL-MIXED BOUNDARY
LAYER; DCAPE VALUES OF ROUGHLY 1000-1400 J/KG ARE IN PLACE OVER
THE REGION. CAMS HAVE LOOSELY CLUSTERED AROUND THE NORTHEASTERN
PORTION OF THE BLUE MOUNTAINS FROM THE ELKHORNS NORTH THROUGH
THE NORTHERN BLUE MOUNTAINS FOR ADDITIONAL THUNDERSTORM
DEVELOPMENT THIS AFTERNOON. A WIDE RANGE OF SOLUTIONS REMAINS
PRESENT AMONG CAMS, MANY OF WHICH PRODUCE NO SIGNIFICANT
CONVECTION WHILE OTHERS INITIATE AND MAINTAIN RATHER ROBUST
CELLS OVER THE AFOREMENTIONED AREA. SHOULD ROBUST CONVECTION
DEVELOP, AN ENVIRONMENT CHARACTERIZED BY AMPLE EFFECTIVE SHEAR
(30-45 KTS) AND MUCAPE IN EXCESS OF 500 J/KG WILL BE CAPABLE OF
MAINTAINING A FEW STRONG THUNDERSTORMS. MOREOVER, STRONGER
STORMS WILL BE CAPABLE OF PRODUCING SMALL HAIL AND SEVERE
OUTFLOW WINDS IN EXCESS OF 60 MPH.
THE LOW-PRESSURE SYSTEM WILL TRACK INLAND ACROSS NORTHERN
WASHINGTON THIS EVENING THROUGH SUNDAY, WITH LOW (5-10 PERCENT)
PRECIPITATION CHANCES INTO TONIGHT. BREEZY WESTERLY WINDS WILL
CONTINUE INTO SUNDAY, THOUGH NOT ANTICIPATING THE NEED FOR
ADDITIONAL HEADLINES FOR WIND OR FIRE WEATHER.
ENSEMBLE NWP GUIDANCE IS IN SUBJECTIVELY EXCELLENT AGREEMENT
THAT A RIDGE OF HIGH PRESSURE WILL REBUILD OVER THE PACIFIC
NORTHWEST BY MONDAY, WHILE A PAIR OF CLOSED LOWS (ONE IN THE
GULF OF ALASKA, AND THE OTHER FARTHER SOUTH IN THE EASTERN
PACIFIC) ATTEMPT TO MERGE. A LOW (5-15 PERCENT) CHANCE OF
SHOWERS AND THUNDERSTORMS IS FORECAST FOR THE SOUTHERN BLUE
MOUNTAINS ON MONDAY, WITH OTHERWISE ABOVE-NORMAL TEMPERATURES
AND DRY CONDITIONS.
LATER TUESDAY THROUGH FRIDAY, THE THEN-MERGED LOWS (PER ENSEMBLE
MEAN 500-HPA HEIGHTS/VORTICITY AND DETERMINISTIC SOLUTIONS)
WILL LIKELY (90 PERCENT CONFIDENCE) TRACK TOWARDS THE PACIFIC
NORTHWEST (LATER TUESDAY OR WEDNESDAY) AND EVENTUALLY INLAND
(THURSDAY OR FRIDAY). THIS SCENARIO WOULD RESULT IN BREEZY
WESTERLY WINDS THROUGH THE CASCADE GAPS AND LOW CHANCES (20
PERCENT OR LESS) OF SHOWERS AND THUNDERSTORMS.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
VFR CONDITIONS INITIATE AND MAINTAIN THROUGH THE FORECAST
PERIOD. DLS/PDT/ALW WILL SEE PERIODS OF BREEZY CONDITIONS
THROUGHOUT THE FORECAST PERIOD WITH 15 TO 25 KNOT GUSTS. ALW IS
FORECASTED TO IMPROVE BY 00Z WHILE PDT/DLS WILL SEE GENERAL
BREEZY WINDS, THOUGH NOT AS STRONG AS PRIOR. THIS SHOULD HELP
KEEP SMOKE LIFTED, BUT ALW/PSC COULD SEE A SMALL CHANCE (5 TO 15
PERCENT) OF MVFR CONDITIONS DEVELOPING OVERNIGHT WITH SMOKE
MAKING ITS WAY DOWN TO THE SURFACE.
FIRE WEATHER
A LOW-PRESSURE SYSTEM CURRENTLY CENTERED NEAR THE OR/WA COAST
WILL CONTINUE TO PRODUCE WIDESPREAD BREEZY TO WINDY WESTERLY
WINDS OF 15-25 MPH WITH GUSTS OF 25-40 MPH, LOCALLY STRONGER,
THROUGH THIS EVENING. MOREOVER, A VERY LOW TO SLIGHT CHANCE
(5-20%) OF HIGH-BASED SHOWERS AND THUNDERSTORMS WILL CONTINUE
ROUGHLY FROM GRANT AND UMATILLA COUNTIES EASTWARD TO WALLOWA
COUNTY THROUGH THIS EVENING. ANY SHOWERS AND THUNDERSTORMS WILL
BE CAPABLE OF PRODUCING STRONG, GUSTY OUTFLOW WINDS OF 40-60
MPH. RED FLAG WARNINGS REMAIN IN EFFECT FOR WIND AND LOW
RELATIVE HUMIDITY (WA690, WA691, OR691, OR696, OR698, OR700, AND
OR703) AS WELL AS ABUNDANT LIGHTNING AND GUSTY OUTFLOW WINDS
(OR/WA692) THROUGH THIS EVENING.
BREEZY WINDS WILL CONTINUE OVERNIGHT INTO SUNDAY AS THE LOW-
PRESSURE SYSTEM EXITS TO THE NORTHEAST, BUT OVERLAP OF CRITICAL
WIND/RH THRESHOLDS IS UNLIKELY (<30% CHANCE).
PRELIMINARY POINT TEMPS/POPS
PDT 49 82 48 89 / 0 0 0 0
ALW 57 84 55 92 / 0 0 0 0
PSC 58 86 52 92 / 0 0 0 0
YKM 59 86 56 90 / 0 0 0 0
HRI 58 85 52 91 / 0 0 0 0
ELN 54 77 50 86 / 0 0 0 0
RDM 45 83 45 90 / 0 0 0 0
LGD 51 85 48 93 / 10 0 0 0
GCD 53 87 51 95 / 0 0 0 0
DLS 61 83 58 92 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...AIR QUALITY ALERT UNTIL NOON PDT MONDAY FOR WAZ026-522-523.
OR...AIR QUALITY ALERT UNTIL NOON PDT MONDAY FOR ORZ041-044-049-050-
502-503-505>507-509>511.
DISCUSSION...86
AVIATION...95
FIRE WEATHER...86
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