409
FXUS66 KOTX 270812
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
112 AM PDT SUN SEP 27 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.
- MILD AND DRY PATTERN THIS WEEK, EXCEPT FOR RAIN NEAR THE CASCADE CREST
AND CHANCE OF RAIN NORTH IDAHO PANHANDLE ON TUESDAY
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
TODAY THROUGH MONDAY: A DRY AIR MASS WILL REMAIN OVER THE INLAND
NW THROUGH SUNDAY NIGHT WITH PRECIPITATABLE WATER VALUES RANGING
FROM NEAR 40-70 PERCENT OF NORMAL. THIS COMBINED WITH LIGHT WINDS
WILL PROMOTE STRONG RADIATIONAL COOLING WITH AREAS OF FROST. A
FROST ADVISORY REMAINS IN EFFECT THROUGH 9 AM THIS MORNING FOR AREAS
STILL WITHIN THEIR CLIMATOLOGICAL GROWING SEASON WHERE AREAS OF
FROST ARE FORECAST. FOR THE NORTHERN MOUNTAIN VALLEYS AND ID
PANHANDLE THE AVERAGE FIRST FROST OCCURS AROUND SEPTEMBER
15TH-25TH AND THUS THE REASON FOR NO ADVISORIES SINCE FROST IS
MORE COMMON THIS TIME OF YEAR, ALTHOUGH MANY AREAS STILL HAVE NOT
RECEIVED THEIR FIRST FROST YET, WITH ANOTHER COOL NIGHT IN STORE
FOR SUNDAY NIGHT. FOR HIGH TEMPERATURES GRADUAL WARMING IS
EXPECTED FOR SUNDAY AND MONDAY AS SOUTHWEST FLOW DEVELOPS AHEAD OF
THE NEXT SYSTEM. HIGH TEMPERATURES ON MONDAY WILL BE RIGHT NEAR
NORMAL VALUES WITH READINGS IN THE MID 60S TO LOW 70S.
MONDAY NIGHT AND TUESDAY: A WEAK ATMOSPHERIC RIVER TAKES AIM AT
THE REGION WITH AN INCREASE IN MOISTURE AS PRECIPITABLE WATER
INCREASES TO 150-200 PERCENT OF NORMAL. YET WITH THE STRONG
WESTERLY FLOW AND DRY AIR MASS TO START, PRECIPITATION WILL HAVE A
HARD TIME REACHING THE GROUND OTHER THAN POTENTIAL SPRINKLES, AND
A CHANCE FOR LIGHT RAIN OVER THE NORTHERN MOUNTAINS. UPSLOPE FLOW
INTO THE CASCADE CREST WILL LEAD TO WET CONDITIONS WITH AROUND
0.50-1.00 INCH OF RAIN, WITH LIGHT RAIN SPILLING OVER THE CREST
INTO THE UPPER REACHES OF THE METHOW VALLEY, LAKE CHELAN, AND LAKE
WENATCHEE.
WEDNESDAY THROUGH SATURDAY: FOLLOWING TUESDAY'S INFLUX OF CLOUDS
AND AREAS OF LIGHT RAIN OR SPRINKLES, THE WEATHER LOOKS VERY
QUIET FOR THE REST OF THE WEEK. A MILD WEST-SOUTHWEST FLOW
PATTERN OCCURS FOR THE REST OF THE WEEK WITH WEAK RIDGING BRINGING
NEAR TO SLIGHTLY ABOVE NORMAL TEMPERATURES. ABOUT 25 PERCENT OF
THE MODEL CLUSTERS SHOW THE STRONGER RIDGE BUILDING IN SOONER, BY
FRIDAY, WHICH WOULD RESULT IN A MORE RAPID WARMING TREND BY
SATURDAY IF REALIZED. JW
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
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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 63 36 67 43 67 48 / 0 0 0 0 0 0
COEUR D'ALENE 63 38 66 42 64 48 / 0 0 0 0 10 20
PULLMAN 63 38 65 39 67 46 / 0 0 0 0 0 10
LEWISTON 66 44 71 45 74 52 / 0 0 0 0 0 0
COLVILLE 66 31 68 36 67 40 / 0 0 0 0 0 10
SANDPOINT 62 34 64 37 61 44 / 0 0 0 0 10 20
KELLOGG 63 39 63 41 62 48 / 0 0 0 0 10 30
MOSES LAKE 68 36 70 43 71 47 / 0 0 0 0 0 0
WENATCHEE 67 45 70 50 69 53 / 0 0 0 0 10 10
OMAK 68 39 69 45 67 45 / 0 0 0 0 0 10
OTX WATCHES/WARNINGS/ADVISORIES
WA...FROST ADVISORY UNTIL 9 AM PDT THIS MORNING FOR MOSES LAKE AREA-
SPOKANE AREA-UPPER COLUMBIA BASIN-WASHINGTON PALOUSE.
ID...FROST ADVISORY UNTIL 9 AM PDT THIS MORNING FOR COEUR D'ALENE
AREA-IDAHO PALOUSE.
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