056
FXUS66 KOTX 180544
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
944 PM PST MON FEB 17 2025
SYNOPSIS
SNOW WILL BE FOCUSED OVER SOUTHEAST WASHINGTON INTO THE CENTRAL
PANHANDLE MOUNTAINS OF IDAHO THROUGH TUESDAY MORNING. THE
REMAINDER OF THE REGION WILL SEE DRIER CONDITIONS INTO TUESDAY.
THE NEXT WEATHER SYSTEM ARRIVES WEDNESDAY BRINGING WIDESPREAD
SNOW AND RAIN. WARMER TEMPERATURES AND RAIN ARRIVE LATE IN THE
WEEK INTO NEXT WEEKEND AS HIGH TEMPERATURES WARM INTO THE 40S.
THIS WILL RESULT IN MELTING SNOW ACROSS THE LOWER ELEVATIONS.
DISCUSSION
TONIGHT THROUGH TUESDAY NIGHT: DRIER AIR COMING DOWN FROM THE
NORTH HAS HELPED BRING THE SNOW TO AN END OVER MOST OF NORTHERN
WASHINGTON INTO THE N IDAHO PANHANDLE. MEANWHILE PERSISTENT WEST-
NORTHWEST UPSLOPE FLOW AND A WEAK MID LEVEL WAVE DROPPING DOWN
FROM BRITISH COLUMBIA WILL ALLOW LIGHT SNOW TO PERSIST TONIGHT
OVER SE WASHINGTON INTO THE CENTRAL PANHANDLE MOUNTAINS. THE ADDED
UPSLOPE WILL BE MOST PRONOUNCED ON THE CAMAS PRAIRIE WITH AN
ADDITIONAL 3 TO 6 INCHES FORECAST TONIGHT ABOVE 3000 FEET. WINTER
WEATHER ADVISORIES AND WINTER STORM WARNINGS REMAIN PLACE FOR
THESE AREAS. SNOW LEVELS CONTINUE TO BE AN ISSUE FOR THE
LEWISTON- CLARKSTON VALLEY WHERE THE SNOW LEVEL IS EXPECTED TO
REMAIN NEAR 2000 FEET. BREAKS IN THE CLOUDS THIS EVENING OVER
CENTRAL AND NE WASHINGTON AND THE N IDAHO PANHANDLE WILL ALLOW
RADIATIONAL FOG TO QUICKLY FORM IN THE VALLEYS AND ACROSS THE
COLUMBIA BASIN. AREAS OF FREEZING FOG IS EXPECTED OVERNIGHT, WHICH
COMBINED WITH WATER REFREEZING ON UNTREATED ROADS WILL RESULT IN
AREAS OF SLICK CONDITIONS.
LIGHT SNOW WILL GRADUALLY COME TO AN END TUESDAY MORNING OVER SE
WA INTO THE CENTRAL PANHANDLE MOUNTAINS WITH A DRY DAY ELSEWHERE.
INCREASING NORTHEAST BOUNDARY LAYER WINDS TUESDAY AFTERNOON OVER
NE WASHINGTON INTO THE N IDAHO PANHANDLE AHEAD OF AN APPROACHING
WEATHER SYSTEM SHOULD ALLOW FOR INCREASING SUNSHINE IN THE
AFTERNOON WHILE AREAS CLOSER TO THE CASCADES, MOSES LAKE/RITZVILLE
AREAS, PALOUSE, AND LC VALLEY LIKELY STAY UNDER STRATUS FOR MUCH
OF THE DAY. LATE TUESDAY NIGHT THE NEXT WEATHER SYSTEM BEGINS TO
SPREAD SNOW INTO THE CASCADES OVERNIGHT. JW
WEDNESDAY THROUGH MONDAY: SNOW WILL CONTINUE TO SPREAD EAST
WEDNESDAY MORNING AS THE SURFACE LOW PRESSURE APPROACHES THE
WASHINGTON/OREGON COAST. HIGHLY AMPLIFIED SOUTHERLY FLOW ALOFT AND
DOWNSLOPING EAST WINDS WILL CAUSE SNOW LEVELS TO RISE QUICKLY
WEDNESDAY AFTERNOON, ESPECIALLY ON THE PALOUSE. 0-4 KM WETBULB
TEMPERATURES STAY BELOW 0.5C FOR MUCH OF THE DAY IN CENTRAL
WASHINGTON FROM APPROXIMATELY QUINCY AND NORTHWESTWARD. THE 0.5C
LINE APPROACHES SPOKANE AREA IN THE EARLY AFTERNOON, WHICH WOULD
SIGNAL THE POTENTIAL TO CHANGE TO A RAIN-SNOW MIX (ESPECIALLY
DOWNTOWN). OVERALL THE LOWLANDS CAN EXPECT AROUND 0.5-2" OF NEW SNOW
WEDNESDAY (EXCEPT THE WARMER PALOUSE AND L-C VALLEY). THE BEST
CHANCES (40%) FOR 2+" OF NEW LOWLAND SNOW WEDNESDAY ARE ON THE
WATERVILLE PLATEAU AND LEAVENWORTH. PRECIPITATION RATES ARE NOT ALL
THAT IMPRESSIVE WITH LACKLUSTER DENDRITIC LAYER OMEGA AND OVERALL
ISENTROPIC LIFT. STEVENS PASS HAS A 50% CHANCE OF 4+" OF NEW SNOW
AND LOOKOUT PASS HAS A 20% CHANCE OF 4+" OF NEW SNOW WEDNESDAY
AFTERNOON THROUGH THURSDAY MORNING. DAYTIME HIGHS WEDNESDAY WILL BE
IN THE 30S.
A WARMING TREND WILL OCCUR THROUGH THE WEEKEND WITH RISING SNOW
LEVELS AND ADDITIONAL CHANCES FOR LIGHT PRECIPITATION, PARTICULARLY
IN THE CASCADES. BY SATURDAY, LOWLAND TEMPERATURES WILL BE IN THE
40S AND PERHAPS EVEN THE LOW 50S. LEWISTON HAS A 20% CHANCE OF
HITTING 50 DEGREES SATURDAY. AREAS ON THE COLUMBIA BASIN ALONG AND
SOUTH OF OTHELLO HAVE A 30-50% CHANCE OF 50+ DEGREES SATURDAY.
ENSEMBLE GUIDANCE SHOWS AN IMPRESSIVE ATMOSPHERIC RIVER SIGNAL BY
SUNDAY. WITH EVEN WARMER TEMPERATURES, THIS WOULD BRING THE
POTENTIAL FOR FLOODING FOR CREEKS AND SMALL STREAMS. THE ID PALOUSE
HAS A 30-50% CHANCE OF RAINFALL 0.75+" FROM SUNDAY TO TUESDAY.
COMBINED WITH SNOWMELT, PARADISE CREEK IS FORECASTED TO PEAK JUST
BELOW MINOR FLOOD STAGE SUNDAY. THIS WILL BE CLOSELY WATCHED OVER
THE NEXT SEVERAL DAYS. /DB
AVIATION
06Z TAFS: A WEAK WAVE DROPPING DOWN FROM THE NORTHWEST WILL BRING
ONE LAST ROUND OF SNOW SHOWERS MAINLY TO SE WA AND N ID WITH DRIER
WEATHER TO FOLLOW. SNOW ACCUM WILL MAINLY BE LIMITED TO THE CAMAS
PRAIRIE AROUND WINCHESTER. THE BOUNDARY LAYER REMAINS MOIST AND
ALTHOUGH SOME SITES ARE EXPERIENCING VFR SKIES, LIGHT WINDS AND
PARTIAL CLEARING WILL RESULT IN RETURN OF LOW STRATUS AND
RADIATIONAL FOG DEVELOPMENT. TIMING WHEN THIS SETS IN COMES WITH
LOW CONFIDENCE. INCREASING NORTHEAST BOUNDARY LAYER TUE MORNING
INTO THE AFTERNOON OVER NE WA/N IDAHO PANHANDLE SHOULD HELP THE
STRATUS BECOME SCATTERED AROUND KCOE-KGEG. NEXT STORM SYSTEM WILL
BRING TOP DOWN MOISTENING INTO THE CASCADES 00-06Z WITH -SN
DEVELOPING AROUND WINTHROP AND LEAVENWORTH. SNOW WILL EXPAND INTO
KEAT AND KOMK 6-12Z AND THEN INTO E WA AND N ID AFTER 12Z.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: THERE IS LOW
CONFIDENCE WITH EXACT RESTRICTIONS OF STRATUS VS FOG AT ANY
PARTICULAR SITE GIVEN THE MOIST BOUNDARY LAYER. PROBABILITIES ARE
NEAR 80-90% THAT CONDITIONS WILL NOT REMAIN VFR AND FAVOR LIFR
CONDITIONS FOR KPUW TO KGEG AND ACROSS THE UPPER COLUMBIA BASIN
BUT ONLY 40-50% FOR KSFF, KCOE, KMWH. GIVEN CEILINGS ARE ALREADY
500 FEET AGL AT PUW, THERE IS HIGH CONFIDENCE THAT KPUW WILL BE
IMPACTED BY IFR AND LIFR CONDITIONS FOR MUCH OF THE TAF PERIOD.
-----------------------
CONFIDENCE DESCRIPTORS:
LOW - LESS THAN A 30 PERCENT CHANCE
MODERATE - 30 TO 70 PERCENT CHANCE
HIGH - GREATER THAN A 70 PERCENT CHANCE
PRELIMINARY POINT TEMPS/POPS
SPOKANE 27 35 22 35 30 38 / 10 0 0 70 70 20
COEUR D'ALENE 25 35 20 36 31 39 / 20 0 0 60 80 40
PULLMAN 29 34 26 35 32 35 / 60 30 0 90 90 60
LEWISTON 34 39 30 40 36 42 / 70 40 0 80 80 40
COLVILLE 20 36 21 36 26 42 / 10 0 10 70 60 10
SANDPOINT 25 35 20 34 29 39 / 20 10 0 60 80 60
KELLOGG 27 34 20 37 32 38 / 50 20 0 70 80 80
MOSES LAKE 27 37 29 37 30 42 / 10 0 20 90 30 0
WENATCHEE 29 35 31 36 29 42 / 0 0 40 90 20 0
OMAK 24 36 29 37 28 41 / 0 0 30 90 30 0
OTX WATCHES/WARNINGS/ADVISORIES
ID...WINTER STORM WARNING UNTIL 4 AM PST TUESDAY FOR CENTRAL
PANHANDLE MOUNTAINS-IDAHO PALOUSE-LEWIS AND SOUTHERN NEZ
PERCE COUNTIES.
WA...WINTER STORM WARNING UNTIL 4 AM PST TUESDAY FOR NORTHEAST BLUE
MOUNTAINS.
WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING FOR LOWER
GARFIELD AND ASOTIN COUNTIES-WASHINGTON PALOUSE.
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