964
FXUS66 KPDT 222044
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
144 PM PDT SUN MAR 22 2026
KEY MESSAGES
- MINOR RIVER FLOODING IN SOUTH-CENTRAL WASHINGTON THROUGH
MONDAY
- ELEVATED RIVER LEVELS IN SOUTH-CENTRAL WASHINGTON CONTINUE
THROUGH THIS WEEK AFTER FLOODING SUBSIDES MONDAY
- ACTIVE WEATHER RETURNS EARLY TUESDAY
DISCUSSION
TODAY, DRY CONDITIONS ACCOMPANIED BY NEAR-SEASONAL TEMPERATURES
ARE ONGOING BENEATH ZONAL FLOW ALOFT. VERY DRY AIR ALOFT (SEE
12Z SOUNDINGS AT SLE, UIL, AND BOI) HAS PARTIALLY MIXED TO THE
SURFACE ACROSS PORTIONS OF THE BLUE AND CASCADE MOUNTAINS, BUT
THE LACK OF SIGNIFICANT WIND SHOULD LIMIT FIRE WEATHER CONCERNS.
ENSEMBLE NWP GUIDANCE SHOWS A ROBUST PLUME OF MOISTURE (PWATS
150-250 PERCENT OF NORMAL) ARRIVING FROM THE PACIFIC 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 SECONDARY
SHORTWAVE MOVES OVERHEAD.
WHILE SOME LIGHT SNOWFALL IS FORECAST LATE MONDAY NIGHT INTO
EARLY TUESDAY MORNING FOR THE WASHINGTON CASCADE PASSES, STRONG
WARM ADVECTION SHOULD PUSH SNOW LEVELS ABOVE THE PASSES BY LATE
TUESDAY MORNING (90 PERCENT CONFIDENCE) AND LIMIT WINTER WEATHER
CONCERNS. SNOW LEVELS WILL DROP AGAIN TUESDAY NIGHT INTO
WEDNESDAY WITH THE PASSAGE OF A DECAYING COLD FRONT, THOUGH
PROBABILITIES OF SNOWFALL ARE QUITE LOW. FOR EXAMPLE, THE NBM
SHOWS A MODEST 30-70 PERCENT CHANCE OF REACHING OR EXCEEDING 2
INCHES OF SNOWFALL BETWEEN EARLY WEDNESDAY MORNING AND EARLY
THURSDAY MORNING FOR THE WASHINGTON CASCADE PASSES, WITH EVEN
LOWER 10-30 PERCENT CHANCES FOR THE OREGON CASCADE PASSES.
THE EARLY-WEEK SYSTEM WILL ALSO USHER IN BREEZY TO WINDY
CONDITIONS ACROSS THE FORECAST AREA. HOWEVER, ISENTROPIC
ANALYSIS OF LATEST DETERMINISTIC GUIDANCE DOES NOT SUGGEST THE
ADVERTISED 35-55 KT 850-MB JET WILL MIX UNIFORMLY TO THE
SURFACE ACROSS THE MAJORITY OF OUR LOWLANDS TUESDAY INTO
WEDNESDAY. RIDGES AND ESPECIALLY WIND-PRONE LOCATIONS WILL
LIKELY (60-80 PERCENT CONFIDENCE) SEE ADVISORY-LEVEL GUSTS (45
MPH OR GREATER), BUT CONFIDENCE IS STILL LOW-MEDIUM (20-50
PERCENT) IN ADVISORY-LEVEL GUSTS FOR OUR POPULATION CENTERS.
LOOKING AHEAD, PER ANALYSIS OF ENSEMBLE CLUSTERS, THERE IS
STILL SIGNIFICANT UNCERTAINTY IN DETAILS OF THE 500-MB HEIGHT
PATTERN. THAT SAID, A BUILDING UPPER-LEVEL RIDGE IS FAVORED
(60-80 PERCENT OF ENSEMBLE MEMBERS), AND MOSTLY DRY WEATHER IS
FORECAST LATER THURSDAY THROUGH SATURDAY. 86
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
VFR CONDITIONS CURRENTLY ACROSS ALL SITES, WHICH WILL STAY THE
COURSE THROUGH THE PERIOD. WINDS WILL STAY LIGHT AND BELOW
10KTS, WITH MORE BKN CEILINGS EARLY MONDAY MORNING. 75
HYDROLOGY
MINOR RIVER FLOODING FROM SNOWMELT AND PREVIOUS RAINFALL IS
ONGOING FOR THE YAKIMA AND NACHES RIVERS IN SOUTH-CENTRAL
WASHINGTON. THESE RIVERS HAVE CRESTED FOR MOST LOCATIONS IN THE
YAKIMA AND KITTITAS VALLEYS. HOWEVER, DOWNSTREAM LOCATIONS
TOWARDS THE LOWER COLUMBIA BASIN HAVE YET TO CREST, AND THE
YAKIMA RIVER AT KIONA IS FORECAST TO CREST MONDAY MORNING. THE
ONLY CHANGE TO HEADLINES THIS AFTERNOON WAS TO EXTEND THE FLOOD
WARNING FOR THE YAKIMA RIVER AT EASTON INTO MONDAY MORNING;
PREVIOUSLY, THE WARNING WAS SET TO END THIS AFTERNOON.
LOOKING AHEAD, SEVERAL FORECAST POINTS ALONG THE YAKIMA AND
NACHES RIVERS, INCLUDING THOSE AT EASTON, CLIFFDELL, NACHES, AND
PERHAPS UMTANUM, ARE 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 35 60 43 63 / 0 0 10 70
ALW 38 60 47 61 / 0 0 10 80
PSC 36 64 46 62 / 0 0 10 70
YKM 34 61 42 61 / 0 0 10 70
HRI 35 63 44 63 / 0 0 10 60
ELN 30 57 38 53 / 0 0 10 80
RDM 30 64 40 63 / 0 0 0 30
LGD 35 64 43 61 / 0 0 10 70
GCD 36 65 42 67 / 0 0 10 50
DLS 38 63 44 60 / 0 0 10 80
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...86
AVIATION...75
HYDROLOGY...86
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