090
FXUS66 KPDT 121043
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
343 AM PDT SUN JUL 12 2026
KEY MESSAGES
- COOLER AND LESS DAY CONDITIONS TODAY.
- ABOVE NORMAL TEMPERATURES THIS WEEK, PEAKING TUESDAY AND
WEDNESDAY.
- ELEVATED FIRE WEATHER CONCERNS DUE TO DRY LIGHTNING THROUGH
MIDWEEK.
DISCUSSION
CURRENT RADAR AND INFRARED SATELLITE IMAGERY SHOWS LIGHT RETURNS
ACROSS GRANT COUNTY EXTENDING NORTHEAST THROUGH THE NORTHERN
BLUE MOUNTAINS AS HIGH LEVEL CLOUDS PASS SOUTH TO NORTH. THIS IS
IN RESPONSE TO THE STRONG UPPER LEVEL RIDGE OVER THE 4 CORNERS
REGION MOVING NORTHEAST INTO WYOMING AND THE DAKOTAS, MOVING
MOISTURE NORTH ORIGINATING FROM A REMNANT TROUGH OVER THE BAJA
PENINSULA. THE CLOUDS WILL SHIFT EAST AND BREAK UP THROUGH THE
DAY TODAY AS THE UPPER LEVEL LOW NEAR VANCOUVER ISLAND ADVECTS A
COOLER AIRMASS ONSHORE STRENGTHEN BY SURFACE HIGH PRESSURE.
COOLER TEMPERATURES ARE EXPECTED AS A RESULT, WITH AFTERNOON
TEMPERATURES AROUND 5 DEGREES COOLER THAN SATURDAY ACROSS THE
COLUMBIA BASIN, BLUE MOUNTAIN FOOTHILLS, AND JOHN DAY BASIN.
HIGHS WILL HOVER IN THE LOW TO MID-80S ACROSS THESE AREA, WHICH
IS ABOUT 6 DEGREES BELOW NORMAL.
THESE COOLER TEMPERATURES WILL BE SHORT-LIVED AS THE UPPER LEVEL
RIDGE ELONGATES OFF THE SOUTHERN CALIFORNIA COAST FROM THE
DAKOTAS AND ANOTHER UPPER LEVEL LOW PRESSURE DROPS ALONG THE
WASHINGTON/OREGON COASTS. THESE SYNOPTIC FEATURES GREATLY
INCREASE THE EFFICIENCY OF SOUTHWEST FLOW ALOFT AND FUNNELS
SUB-TROPICAL HEAT INTO THE PACIFIC NORTHWEST. HIGHS WILL
INCREASE ABOUT 10 DEGREES ON MONDAY, RETURNING AFTERNOON
TEMPERATURES BACK INTO THE LOW TO MID-90S ACROSS THE AREA.
THE OFFSHORE LOW CONTINUES TO DIG SOUTH ALONG THE CENTRAL
CALIFORNIA COAST TUESDAY AND WEDNESDAY TO FURTHER INCREASE HIGH
TEMPERATURES INTO THE MID-TO UPPER 90S. GUIDANCE DOES SUGGEST
SOME AREAS MAY REACH INTO THE TRIPLE DIGITS BOTH DAYS, AS THE
NBM ADVERTISES A 20-45% CHANCE ON TUESDAY AND A 30-55% CHANCE
WEDNESDAY FOR WALLA WALLA, TRI-CITIES, HERMISTON, MILTON-
FREEWATER AND YAKIMA, WITH WALLA WALLA HAVING THE BEST CHANCES
(43% AND 52%). ENSEMBLES ARE HINTING AT HIGHER TEMPERATURES FOR
SUBSEQUENT FORECASTS AS 61% OF MEMBERS SUGGEST HIGHER
TEMPERATURES THAN CURRENTLY FORECAST ON TUESDAY, AND 58% OF
MEMBERS ON WEDNESDAY. THIS QUICK WARMUP, COUPLED WITH HIGH
TEMPERATURES AROUND 100 DEGREES, WILL ALLOW FOR WIDESPREAD
MODERATE HEATRISK (2 OR 4) ACROSS THE COLUMBIA GORGE, LOWER
COLUMBIA BASIN, BLUE MOUNTAIN FOOTHILLS, NORTH-CENTRAL OREGON
AND THE YAKIMA/KITTITAS VALLEYS. BRIEF RELIEF LIKELY THURSDAY
AND FRIDAY AS ECMWF AI ENSEMBLES AND GFS AI ENSEMBLES BOTH SHOW
THE CONUS HIGH PRESSURE SHIFTING EAST AS THE OFFSHORE LOW
WEAKENS AND MOVES INLAND, CUTTING OFF THE ENHANCED SOUTHWEST
FLOW ALOFT.
THE PRESENCE OF THE INLAND HIGH AND OFFSHORE LOW PRESSURE
SYSTEMS SETS UP AN EXTENDED 'RIDGE BREAKDOWN' WEATHER PATTERN
THAT WILL ENHANCE DRY THUNDERSTORM POTENTIAL DURING THE
AFTERNOON HOURS. THIS POTENTIAL PEAKS TUESDAY AND WEDNESDAY AS
THE OFFSHORE LOW DIGS SOUTH AND TAPS INTO MONSOONAL MOISTURE.
ECMWF AND GFS ENSEMBLES SHOWCASE PRECIPITABLE WATER AMOUNTS OF
0.85-1.1" WHICH IS 150-180% ABOVE NORMAL. HOWEVER, THE NAM
ADVERTISES MARGINAL DEWPOINT DEPRESSION AT THE 850MB LEVEL, AND
THERE IS OVERALL CONCENSUS BETWEEN THE NAM, GFS, AND ECMWF WITH
A VERTICAL TEMPERATURE DIFFERENCE BETWEEN 850-500 MB OF 30-35C.
THIS LARGE TEMPERATURE DIFFERENCE ABOVE 30C WILL PROMOTE THE DRY
LIGHTNING RISK AS COOLER AIR ALOFT WILL PRODUCT CLOUDS AND
WARMER/DRIER AIR CLOSER TO THE SURFACE WILL EVAPORATE ANY
MOISTURE BEFORE REACHING THE GROUND SURFACE. THIS WILL ALSO LEAD
TO EXCEPTIONAL INSTABILITY DUE TO THE LESS DENSE AIR MASS AT THE
SURFACE BEING ABLE TO RISE RAPIDLY, LEADING TO THUNDERSTORM
POTENTIAL. 75
AVIATION /12Z TAFS THROUGH 12Z MONDAY/
VFR CONDITIONS CURRENTLY ACROSS ALL SITES, WHICH WILL STAY THE
COURSE THROUGH THE PERIOD. BREEZY WINDS OF 10-15KTS WITH GUSTS
OF 20-25KTS WILL BE POSSIBLE ACROSS KDLS/KRDM/KBDN, WITH WINDS
OF 10KTS OR LOWER FOR ALL REMAINING TERMINALS. 25KFT CEILINGS
WILL BREAK UP SLIGHTLY THROUGH THE DAY. 75
FIRE WEATHER
DRY CONDITIONS WILL STILL BE PRESENT TODAY WITH AFTERNOON
HUMIDITIES OF 20-25% AFTER MORNING RECOVERIES OF 50-70%. THESE
VALUES SHOULD NOT WAVER TO MUCH THROUGH THE WEEK, AS WINDS STAY
RELATIVELY LIGHT.
THE PRIMARY FIRE WEATHER CONCERN THIS WEEK INVOLVE THE
POTENTIAL FOR DRY LIGHTNING, PRIMARILY TUESDAY AND WEDNESDAY
ACROSS WA692, OR692-700, AND OR705. AS MENTIONED EARLIER WITH
THE PRESENCE OF THE HIGH PRESSURE TO THE SOUTHEAST, LOWER LEVELS
OF THE ATMOSPHERE WILL BE DRY AS COOLER, MORE MOIST AIR SLIDES
OVER THIS LAYER. THIS WILL LEAD TO MOISTURE EVAPORATING THROUGH
THE LOWER, DRY LAYER AS SUBSTANTIAL INSTABILITY IS PRESENT.
THIS INSTABILITY WILL ALSO LEAD TO THE POTENTIAL FOR PLUME-
DOMINATED FIRES FOR ANY THAT ARE ALREADY ON THE LANDSCAPE. THERE
IS ALSO POTENTIAL FOR ERRATIC DOWNDRAFTS AND MICROBURSTS AS THE
EVAPORATIVE COLUMN OF VIRGA WILL STILL REACH THE GROUND SURFACE
AS COOLER AIR, ACCELERATING TOWARD THE GROUND AS IT NEARS AND
EXTENDING OUTWARD WHEN REACHED. 75
PRELIMINARY POINT TEMPS/POPS
PDT 82 56 91 61 / 0 0 0 10
ALW 84 60 93 65 / 0 0 0 0
PSC 86 57 94 62 / 0 0 0 0
YKM 87 56 94 61 / 0 0 0 0
HRI 85 58 93 64 / 0 0 0 0
ELN 81 52 90 58 / 0 0 0 0
RDM 87 52 92 56 / 0 0 0 0
LGD 88 58 93 63 / 0 0 0 0
GCD 90 58 93 60 / 0 0 0 0
DLS 87 58 94 62 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...HEAT ADVISORY UNTIL 7 PM PDT THIS EVENING FOR ORZ050.
DISCUSSION...75
AVIATION...75
FIRE WEATHER...75
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