928
FXUS66 KOTX 270546
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
1046 PM PDT SAT SEP 26 2026
KEY MESSAGES
- FROSTY MORNINGS SUNDAY AND MONDAY OVER EASTERN WASHINGTON AND
IDAHO PANHANDLE MOUNTAIN VALLEYS, AS WELL THE OUTLYING AREAS AROUND
THE SPOKANE AREA AND PALOUSE.
SYNOPSIS
CHILLY FALL LIKE OVERNIGHT TEMPERATURES WILL BRING THE POTENTIAL FOR
FROST TO THE VALLEYS THROUGH THE WEEKEND INTO MONDAY MORNING.
MOISTURE OFF THE PACIFIC WILL BRING RAIN TO THE CASCADE CREST ON
TUESDAY, BUT REMAINING MOSTLY DRY EAST OF THE CASCADES. TEMPERATURES
WILL MODERATE BACK TO NEAR NORMAL NEXT WEEK. SEASONAL TEMPERATURES
THEN CONTINUE THROUGH THE REST OF THE WORK WEEK.
DISCUSSION
TONIGHT THROUGH SUNDAY NIGHT: THE INLAND NORTHWEST WILL BE UNDER A
SPLIT FLOW REGIME AT UPPER LEVELS. MUCH DRIER AIR OVER THE REGION AS
WELL IN THE POST COLD FRONTAL AIR MASS. THERE WILL BE A WEAK
DISTURBANCE THAT PASSES THROUGH OVERNIGHT WITH SOME HIGH LEVEL CLOUD
COVER AND A LITTLE BIT OF NORTHERLY WINDS PICKING UP OVER THE
COLUMBIA BASIN LATE TONIGHT. THE ECMWF ENSEMBLE INDICATES A
SLIGHT COOL ANOMALY BECAUSE OF THE DRIER AIR AND POTENTIAL FOR
STRONG RADIATIONAL COOLING. THERE WERE A FEW AREAS THAT GOT
CHILLY OVERNIGHT LAST NIGHT, INCLUDING THE NORTHERN PORTIONS OF
THE UPPER COLUMBIA BASIN ACROSS THE HIGHWAY 2 CORRIDOR. THAT
WAS WITH WINDS ELEVATED AT LEAST FOR THE FIRST PART OF LAST
NIGHT. THE HIGH CLOUDS TONIGHT SHOULD HAVE MINIMAL IMPACTS ON
INSULATING THE SURFACE, AND I SUSPECT TEMPERATURES TO DROP QUITE
A BIT WITH A BETTER POTENTIAL FOR TEMPERATURES ACROSS THE MOSES
LAKE AREA, UPPER COLUMBIA BASIN, AND INTO THE SPOKANE/COEUR
D'ALENE AREA AND PALOUSE TO DROP INTO THE MID 30S. A FROST
ADVISORY HAS BEEN ISSUED FOR THESE AREAS AND ANYONE CONCERNED
ABOUT SENSITIVE VEGETATION TO FROST/FREEZE DAMAGE SHOULD TAKE
ACTION TO COVER THEM OR BRING THEM INDOORS. SUNDAY WILL BE
MOSTLY SUNNY, AND SUNDAY NIGHT WILL BE ANOTHER DRY, CLEAR NIGHT
WITH EVEN LIGHTER WINDS. THERE IS A GOOD CHANCE THAT THESE SAME
AREAS THAT SEE FROST TONIGHT WILL REPEAT SUNDAY NIGHT. THE
OKANOGAN VALLEY AND WATERVILLE PLATEAU WILL ALSO SEE THE
POTENTIAL FOR FROST, ESPECIALLY WITH LIGHTER WINDS SUNDAY NIGHT.
MONDAY THROUGH SATURDAY: A WEAK ATMOSPHERIC RIVER (AR) WILL BE
DIRECTED OVER THE NORTHWEST MONDAY NIGHT INTO TUESDAY. P-WATS
INCREASE UP TO AROUND AN INCH. THE SHORTWAVE DISTURBANCE THAT PUSHES
THROUGH ISN'T PARTICULARLY DYNAMIC. WITH HOW DRY IT IS LEADING INTO
THE AR'S ARRIVAL, IT'S GOING TO TAKE QUITE A BIT OF MOISTENING TO
SQUEEZE MUCH PRECIPITATION OUT EAST OF THE CASCADES. BEST POTENTIAL
WILL BE AT THE CASCADE CREST WHERE RAIN IS A NEAR CERTAINTY ON
TUESDAY. THE AIR MASS REMAINS TOO WARM FOR SNOW. TOTAL RAINFALL
ALONG THE CASCADE CREST WILL BE UP TO AROUND A HALF OF AN INCH.
THE REST OF THE INLAND NORTHWEST WILL MAINLY JUST SEE CLOUDY
SKIES. THE NORTHERN PANHANDLE WILL SEE A 40-50% CHANCE FOR RAIN
WITH LIGHT ACCUMULATIONS OF LESS THAN A TENTH OF AN INCH
EXPECTED. TEMPERATURES MODERATE AND WARM CLOSER TO NORMAL. THIS
WILL EFFECTIVELY ELIMINATE THE RISK FOR ADDITIONAL FROST
CONCERNS.
THE MOISTURE PLUME WITH THE AR DRIES UP ON WEDNESDAY FOR DRIER
WEATHER REGIONWIDE INTO THURSDAY. THERE IS MORE UNCERTAINTY
FRIDAY INTO NEXT WEEKEND. THE ENSEMBLES ARE IN GOOD AGREEMENT
WITH A RIDGE OF HIGH PRESSURE BUILDING UP FROM THE FOUR CORNERS
AREA. THERE ARE DIFFERENCES THOUGH WITH HOW QUICKLY THE RIDGE
BUILDS IN THOUGH. THERE ARE ENSEMBLE MEMBERS THAT BRINGS ACROSS
ANOTHER SHORTWAVE DISTURBANCE ON FRIDAY THAT KEEPS THIS RIDGE
RATHER FLAT. IT MAY EVEN BRING LIGHT RAIN TO AT LEAST THE
MOUNTAINS. THE NBM FORECAST KEEPS TEMPERATURES NEAR NORMAL FOR
THE END OF THE EXTENDED. IF THE ENSEMBLE MEMBERS THAT BUILDS THE
RIDGE UP EARLIER ARE CORRECT, THEN WE WILL SEE TEMPERATURES
INCREASING BACK INTO THE MID 70S BY NEXT WEEKEND. THERE IS A
GOOD BET THAT THE RIDGE WILL BE WELL ESTABLISHED OVER THE WEST
BY EARLY NEXT WEEK THOUGH WITH ABOVE AVERAGE TEMPERATURES AND
DRY CONDITIONS. /SVH
AVIATION
06Z TAFS: HIGH CIRRUS CLOUDS THEN INCREASE TONIGHT. PATCHY FOG
EXPECTED NEAR WATER BODIES IN THE MOUNTAIN VALLEYS OF NORTHEAST
WASHINGTON AND THE IDAHO PANHANDLE OVERNIGHT INTO SUNDAY
MORNING. LIGHT WINDS ARE EXPECTED THROUGH THE TAF PERIOD EXCEPT
INCREASING SLIGHTLY OUT OF THE NORTHEAST AROUND 10 KTS AT KCOE
NEAR 11Z SUNDAY.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: HIGH CONFIDENCE
IN THE FORECAST AND VFR CONDITIONS AT TAF SITES THROUGH SUNDAY.
JW
-----------------------
CONFIDENCE DESCRIPTORS:
LOW - LESS THAN A 30 PERCENT CHANCE
MODERATE - 30 TO 70 PERCENT CHANCE
HIGH - GREATER THAN A 70 PERCENT CHANCE
FOR ADDITIONAL PROBABILISTIC INFORMATION FOR NWS SPOKANE
AIRPORTS, PLEASE REFER TO THE AVIATION DASHBOARD ON OUR
WEBPAGE: HTTPS:/WWW.WEATHER.GOV/OTX/AVNDASHBOARD
PRELIMINARY POINT TEMPS/POPS
SPOKANE 36 64 36 67 44 68 / 0 0 0 0 0 0
COEUR D'ALENE 37 64 38 65 42 66 / 0 0 0 0 0 10
PULLMAN 34 64 38 64 40 67 / 0 0 0 0 0 0
LEWISTON 40 66 44 70 46 74 / 0 0 0 0 0 0
COLVILLE 30 67 31 69 35 67 / 0 0 0 0 0 10
SANDPOINT 34 63 34 65 38 62 / 0 0 0 0 0 10
KELLOGG 34 63 39 62 42 64 / 0 0 0 0 0 0
MOSES LAKE 36 68 36 69 44 72 / 0 0 0 0 0 0
WENATCHEE 44 66 45 69 51 70 / 0 0 0 0 0 10
OMAK 38 67 39 69 45 68 / 0 0 0 0 0 0
OTX WATCHES/WARNINGS/ADVISORIES
WA...FROST ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM PDT SUNDAY FOR
MOSES LAKE AREA-SPOKANE AREA-UPPER COLUMBIA BASIN-
WASHINGTON PALOUSE.
ID...FROST ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM PDT SUNDAY FOR
COEUR D'ALENE AREA-IDAHO PALOUSE.
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