588
FXUS66 KPDT 212353
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
452 PM PDT SAT MAR 21 2026
UPDATED AVIATION DISCUSSION
KEY MESSAGES
- MINOR RIVER FLOODING IN SOUTH-CENTRAL WASHINGTON THROUGH
MONDAY
- ELEVATED RIVER LEVELS IN SOUTH-CENTRAL WASHINGTON CONTINUE
THROUGH NEXT WEEK AFTER FLOODING SUBSIDES MONDAY
- AREAS OF FROST OVERNIGHT IN THE COLUMBIA BASIN AND ALONG THE
BLUE MOUNTAIN FOOTHILLS
DISCUSSION
CLEAR TO PARTLY CLOUDY SKIES ARE PRESENT ACROSS THE MAJORITY OF
THE FORECAST AREA THIS AFTERNOON. THE AIR MASS IS QUITE DRY,
PWATS OF 0.2-0.3", AND SOME OF THE DRY AIR FROM ALOFT IS MIXING
TO THE SURFACE. DEW POINTS IN THE SINGLE DIGITS TO TEENS HAVE
SURFACED IN PLACES, NOTABLY ALONG THE LEE OF THE WASHINGTON
CASCADES AS WELL AS NORTH-CENTRAL OREGON. ELSEWHERE, DEW POINTS
HAVE CRASHED RELATIVE TO THE EARLY MORNING, BUT ONLY IN THE
20S. ANTICIPATING THESE LOW DEW POINTS WILL BECOME MORE
WIDESPREAD THROUGH THE REMAINDER OF THE AFTERNOON AND EVENING AS
DRY AIR CONTINUES TO MIX TO THE SURFACE.
TONIGHT, MOSTLY CLEAR SKIES COUPLED WITH THE AFOREMENTIONED DRY
AIR MASS WILL FACILITATE CHILLY TEMPERATURES. AREAS OF NEAR- TO
SUB-FREEZING TEMPERATURES ARE FORECAST FOR THE LOWLANDS. WHILE
NOT ATYPICAL FOR LATE MARCH, THEY COME ON THE HEELS OF AN
ANOMALOUSLY WARM STRETCH. COUPLED WITH THE FACT THAT FLOWERS
AND TREES ARE BLOOMING AND BUDDING SEVERAL WEEKS EARLY ACROSS
PARTS OF THE FORECAST AREA, HAVE OPTED TO INJECT AREAS OF FROST
INTO THE GRIDDED FORECAST WHERE TEMPERATURES AND RELATIVE
HUMIDITY ARE SUPPORTIVE. WILL NOTE, THE VERY DRY AIR MASS HAS
THE POTENTIAL TO HINDER FROST FORMATION IF SURFACE DEW POINTS
REMAIN LOW ENOUGH, BUT THINKING THE RECENT PRECIPITATION WILL
KEEP ENOUGH MOISTURE NEAR THE SURFACE TO HAVE AT LEAST PATCHY TO
AREAS OF FROST IN COLD-PRONE LOCATIONS.
SUNDAY, MOSTLY DRY CONDITIONS ACCOMPANIED BY NEAR-SEASONAL
TEMPERATURES ARE ANTICIPATED BENEATH QUASI-ZONAL FLOW ALOFT.
VERY DRY AIR ALOFT (SINGLE DIGIT TO TEENS DEW POINTS) IS
EXPECTED TO MIX TO THE SURFACE IN PLACES, BUT THE LACK OF
SIGNIFICANT WIND SHOULD LIMIT FIRE WEATHER CONCERNS.
ENSEMBLE NWP GUIDANCE SHOWS A PLUME OF MOISTURE FROM THE PACIFIC
MOVING INTO THE PACIFIC NORTHWEST BY LATE MONDAY. PRECIPITATION
CHANCES INCREASE BY MONDAY NIGHT AS A STRONG OFFSHORE SURFACE
LOW TRACKS NORTHEAST TOWARDS BRITISH COLUMBIA. ITS ATTENDANT
FRONTAL SYSTEM WILL MOVE INLAND TUESDAY INTO WEDNESDAY, WITH
PERHAPS ANOTHER COLD FRONTAL BOUNDARY IN ITS WAKE LATER
WEDNESDAY INTO WEDNESDAY NIGHT AS A 500-MB SHORTWAVE MOVES
OVERHEAD.
THE EARLY-WEEK SYSTEM WILL ALSO USHER IN BREEZY TO WINDY
CONDITIONS ACROSS THE FORECAST AREA.
LOOKING AHEAD, THERE IS STILL SIGNIFICANT UNCERTAINTY IN DETAILS
OF THE 500-MB HEIGHT PATTERN, BUT A BUILDING RIDGE IS FAVORED
(60-70 PERCENT OF ENSEMBLE MEMBERS) AND MOSTLY DRY WEATHER IS
FORECAST LATER THURSDAY THROUGH FRIDAY. 86
AVIATION /00Z TAFS THROUGH 00Z MONDAY
VFR CONDITIONS PREVAIL
FOR ALL SITES. WINDS WILL BE GUSTING AT 20-25 KTS THROUGH 02Z THIS
EVENING FOR KRDM/KBDN AND 05-06Z TONIGHT FOR KDLS/KYKM. OTHERWISE,
THE REMAINING SITES WILL HAVE WINDS LESS THAN 12 KTS. FEASTER/97
HYDROLOGY
RIVER FLOODING FROM SNOWMELT AND PREVIOUS RAINFALL IS ONGOING
FOR THE YAKIMA AND NACHES RIVERS IN SOUTH-CENTRAL WASHINGTON.
THESE RIVERS HAVE CRESTED, OR WILL CREST THIS AFTERNOON, FOR
MOST LOCATIONS IN THE YAKIMA AND KITTITAS VALLEYS. LOCATIONS
DOWNSTREAM TOWARDS THE EASTERN END OF THE YAKIMA VALLEY AND THE
LOWER COLUMBIA BASIN HAVE YET TO CREST, AND THE YAKIMA AT KIONA
IS FORECAST TO CREST BETWEEN LATE SUNDAY AFTERNOON AND EARLY
MONDAY MORNING.
LOOKING AHEAD, SEVERAL FORECAST POINTS ALONG THE YAKIMA AND
NACHES RIVERS, INCLUDING THOSE AT EASTON, CLIFFDELL, NACHES, AND
PERHAPS UMTANUM, ARE THEN ANTICIPATED TO REMAIN ABOVE ACTION
STAGE THROUGH THE WEEK ACCORDING TO THE LATEST FORECASTS FROM
THE NORTHWEST RIVER FORECAST CENTER IN PORTLAND.
PRELIMINARY POINT TEMPS/POPS
PDT 31 56 34 60 / 0 0 0 0
ALW 35 56 38 60 / 0 0 0 0
PSC 34 60 35 63 / 0 0 0 0
YKM 29 56 34 59 / 0 0 0 0
HRI 33 59 34 62 / 0 0 0 0
ELN 29 52 31 55 / 0 0 0 0
RDM 23 60 30 63 / 0 0 0 0
LGD 28 58 35 64 / 0 0 0 0
GCD 28 61 35 66 / 0 0 0 0
DLS 34 60 38 62 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...86
AVIATION...97
HYDROLOGY...86
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