066
FXUS66 KOTX 192257
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
257 PM PST TUE NOV 19 2024
SYNOPSIS
A WINTER STORM IS BEGINNING TO MOVE INLAND THIS AFTERNOON AND WILL
IMPACT THE INLAND NORTHWEST THIS EVENING THROUGH WEDNESDAY.
WIDESPREAD SNOW WILL BE FELT ACROSS MUCH OF EASTERN WASHINGTON
AND NORTH IDAHO. THIS WILL RESULT IN MODERATE TO MAJOR IMPACTS
ACROSS CENTRAL WASHINGTON WHERE PRECIPITATION WILL FALL MAINLY AS
SNOW AND MINOR IMPACTS FOR EASTERN WASHINGTON AND NORTH IDAHO
WHERE SNOW WILL CHANGEOVER TO RAIN BY THE MID MORNING IN THE
VALLEYS. ADDITIONAL SYSTEMS PASSING THROUGH THURSDAY THROUGH NEXT
WEEKEND WILL BRING ADDITIONAL PERIODS OF LOWLAND RAIN AND
MOUNTAIN SNOW.
DISCUSSION
KEY MESSAGES:
*MODERATE TO HEAVY SNOW ACROSS CENTRAL WASHINGTON TUESDAY EVENING
THROUGH WEDNESDAY MORNING.
*LIGHT SNOW ACROSS I-90 CORRIDOR FROM MOSES LAKE TO LOOKOUT PASS
TUESDAY NIGHT INTO WEDNESDAY MORNING IMPACTING THE WEDNESDAY MORNING
COMMUTE.
*BLIZZARD CONDITIONS RESULTING IN CHALLENGING TRAVEL OVER THE
CASCADES PASSES TUESDAY EVENING.
TUESDAY NIGHT THROUGH THURSDAY: A MID LEVEL WAVE THAT MOVED ACROSS
THE INLAND NORTHWEST AND BROUGHT LIGHT SNOW TO PARTS OF CENTRAL AND
EASTERN WASHINGTON THIS MORNING HAS MOVED OUT OF THE REGION TO THE
NORTHEAST AS AN UPPER LEVEL RIDGE BUILDS OVER FAR EASTERN WASHINGTON
AND NORTH IDAHO THIS AFTERNOON. AREAS THAT SAW SNOW THIS MORNING
SUCH AS WENATCHEE, MOSES LAKE, EPHRATA, AND OMAK SAW THEIR DEW
POINTS WARM INTO THE LOW 30S AS THE SURFACE BECAME SATURATED. THIS
WILL PLAY A ROLE IN THE OVERALL SNOW DEVELOPMENT LATER ON THIS
AFTERNOON AND EVENING.
FOCUS SHIFTS TO THE DEEP SURFACE LOW PRESSURE OFF THE WASHINGTON
COAST THIS EVENING. AS OF 2PM, THE PRESSURE HAS DROPPED TO 950MB OFF
THE WASHINGTON COAST. AS THIS STRONG SYSTEM SHIFTS TO THE NORTH-
NORTHWEST, AN AMPLIFYING RIDGE TO THE EAST WILL RESULT IN A DEEP
SOUTHWEST FLOW ALOFT AND DRAW WARM, MOIST AIR IN THE FORM OF AN
ATMOSPHERIC RIVER INTO THE INLAND NORTHWEST. WITH THE RIDGE TO THE
EAST AND THE DEEP LOW OFF SHORE, THIS HAS CREATED A STRONG EAST TO
SOUTHEAST PRESSURE GRADIENT ACROSS THE ENTIRETY OF THE NORTHWEST.
MODELS DEPICT THIS PRESSURE GRADIENT PEAKING BETWEEN 6 PM AND 10 PM
THIS EVENING. THIS LOW LEVEL FLOW PATTERN IS CONDUCIVE TO A MODERATE
TO HEAVY SNOWFALL EVENT ACROSS CENTRAL WASHINGTON DUE TO THE
COMBINATION OF UPSLOPE FLOW AND STRONG ISENTROPIC ASCENT AS THE
WARM, MOIST AIR OVERRUNS THE COLDER AIR AT THE SURFACE. THERE STILL
REMAINS SOME UNCERTAINTY ON HOW MUCH SNOW WILL ACCUMULATE AT THE
SURFACE, ESPECIALLY FOR THE LOWER ELEVATIONS SPOTS SUCH AS DOWNTOWN
WENATCHEE AND THE LOWER AREAS AROUND OMAK AS SURFACE TEMPERATURES
TRY TO WARM ABOVE FREEZING. WITH DEWPOINTS IN CENTRAL WASHINGTON
INTO THE LOW 30S THIS AFTERNOON AND NOT MUCH DRYING EXPECTED TODAY,
THERE WILL BE LESS WIGGLE ROOM FOR COOLING AT THE ONSET OF
PRECIPITATION. HOWEVER, OVERCAST SKIES ARE EXPECTED TO CONTINUE
WHICH WILL ALLOW TEMPERATURES TO REMAIN IN THE LOW 30 TO MID 30S.
PRECIPITATION LOOKS TO BEGIN IN CENTRAL WASHINGTON THIS EVENING
AROUND 6-7PM. WITH TEMPERATURES A COUPLE DEGREES ABOVE FREEZING AND
AFTERNOON AND SOME DRY AIR TO OVERCOME AT THE ONSET FOR AREAS ALONG
THE COLUMBIA RIVER FROM WENATCHEE TO OMAK, PRECIPITATION DOES LOOK
TO BEGIN AS A WET SNOW OR A RAIN/SNOW MIX. STRONGER ASCENT WITHIN
THE DENDRITIC GROWTH ZONE BETWEEN 10PM-2AM SUGGEST HEAVIER SNOWFALL
RATES MAY BE ENOUGH TO OVERCOME THE WARMER AIR AT THE SURFACE, BUT
THIS WILL BE A TRICKIER ONE. FOR ELEVATIONS ABOVE 1000-1500 FEET,
COLDER TEMPERATURES WILL SUPPORT ALL SNOW ACROSS CENTRAL WASHINGTON.
WHEN THIS IS ALL SAID AND DONE, MOST LIKELY SNOW AMOUNTS FOR LOWER
ELEVATIONS ALONG THE COLUMBIA RIVER WILL BE IN THE 2 TO 5 INCH
RANGE. THE HIGHER BENCHES IN CENTRAL WASHINGTON'S MOST LIKELY RANGE
WILL BE IN THE 4 TO 8 INCH RANGE. FURTHER UP THE VALLEYS INTO
LEAVENWORTH, PLAIN, WINTHROP, MAZAMA WILL SEE 7+ INCHES THROUGH
EARLY WEDNESDAY.
AROUND THE LOWER COLUMBIA BASIN AND THE MOSES LAKE AREA, THE INFLUX
OF WARM AIR MAY ALLOW FOR A QUICK TENTH OR SO, BUT TEMPERATURES WELL
ABOVE FREEZING THIS AFTERNOON WITH A BREAK IN THE CLOUDS WILL BE
HARD TO SEE ACCUMULATIONS OVER THE ROAD SURFACES. MODELS DO SUGGEST
A SHARP GRADIENT OF SNOW TOTALS ON THE ORDER OF 0.5 TO 6 INCHES
BETWEEN MOSES LAKES AND PALISADES ON THE WATERVILLE PLATEAU WHERE
PLACES SUCH AS QUINCY, EPHRATA, SOAP LAKE HAVE A BETTER CHANCE OF
HOLDING ONTO COLD AIR LONGER AS THE WARM AIR SURGES IN AND ARE
FORECASTED TO SEE 2 TO 4 INCHES.
FURTHER EAST INTO THE SPOKANE AREA, COEUR D’ALENE AREAS, MODELS HAVE
COME INTO BETTER AGREEMENT THAT PRECIPITATION WILL MAKE IT HERE
BETWEEN 3-5AM AS SNOW. CAMS CONTINUE TO SHOW A BAND OF MODERATE
SNOWFALL RATES AROUND THE EARLY COMMUTE TIME BEFORE SWITCHING OVER
THE RAIN. ROAD TEMPERATURES ACROSS THE SPOKANE AREA HAVE WARMED INTO
THE LOWER 50S THIS AFTERNOON, WHICH WILL HELP TO MITIGATE
SIGNIFICANT ROAD ACCUMULATIONS ALONG I-90, BUT LESSER TRAVELED AND
UNTREATED ROADS MAY SEE TRICKIER CONDITIONS. USE CAUTION IF YOU HEAD
OUT EARLY TOMORROW MORNING.
UP INTO NORTHEAST WASHINGTON AND NORTH IDAHO, THESE PLACES WILL HOLD
ONTO COLDER AIR LONGER WITH SNOW CONTINUING THROUGH MUCH OF THE
MORNING WITH 2 TO 5 INCHES EXPECTED IN THE VALLEY LOCATIONS. SHERMAN
PASS IS FORECASTED TO RECEIVE 8 TO 12 INCHES THROUGH WEDNESDAY. WHILE
WINDS DO NOT LOOK TO BE AS STRONG AS ACROSS THE CASCADES, BREEZY
WINDS WILL RESULT IN REDUCED VISIBILITIES FOR THIS PASS.
WITH REGARDS TO WINDS, THE STRONG EAST TO SOUTHEASTERLY PRESSURE
GRADIENT WILL SUPPORT BREEZY EAST WINDS ACROSS MUCH OF THE REGION.
THE STRONGEST WINDS WILL BE WHERE THE GRADIENTS BECOME PARALLEL TO
THE VALLEYS AND ALLOW FOR GAP WIND ENHANCEMENT. THE BEST CHANCES TO
SEE WIND GUSTS 50+ MPH WILL ALONG US 2 FROM COLES CORNER TO STEVENS
PASS AND ALONG THE SNAKE RIVER VALLEY WHERE THERE IS A 50-60 PERCENT
CHANCE.
WINDS WILL DECREASE THROUGH THE DAY ON WEDNESDAY AND SETTLE
OVERNIGHT. PERSISTENT MOIST, SOUTHWEST FLOW ALONG WITH THE ARRIVAL OF
ANOTHER SYSTEM ON THURSDAY WILL ALLOW LIGHT PRECIPITATION TO
CONTINUE OVERNIGHT WEDNESDAY INTO EARLY THURSDAY ACROSS EASTERN
WASHINGTON AND NORTH IDAHO AS MOUNTAIN SNOW AND LOWLAND RAIN. THE
EXCEPTION WILL BE FOR THE METHOW VALLEY WHERE MODELS SUGGEST WILL
HOLD ON TO THE COLDER AIR THROUGH THURSDAY. THIS WILL ALLOW
PRECIPITAITON TO FALL AS SNOW. /VMT
THURSDAY NIGHT THROUGH TUESDAY: THE CONTINUOUS PRESENCE OF THE THE
LOW OFF THE PACIFIC NORTHWEST COAST WILL KEEP THE REGION UNDER A
WARM, WET PATTERN. SNOW LEVELS WILL RISE FROM 3500FT TO 5000FT. IT
WILL GENERATE ANOTHER MOUNTAIN SNOW AND LOW LAND RAIN EVENT THROUGH
FRIDAY. RAIN AMOUNTS WILL BE IN THE 0.5-1.0". ENSEMBLES BEGIN TO
BRING THE LOW THROUGH THE REGION EARLY SATURDAY MORNING AND PUSH A
COLD FRONT ACROSS THE REGION. BY SUNDAY MORNING, IT WILL LOWER THE
SNOW LEVELS BACK TO THE SURFACE BUT USHER IN DRIER AIR FOR THE REST
OF THE PERIOD. WITH PRECIPITABLE WATER AMOUNTS RANGING FROM 0.25-
0.5", SNOW SHOWERS ARE EXPECTED ACROSS THE REGION THROUGH REST OF
THE PERIOD. SNOW AMOUNTS FOR THE PERIOD WILL BE 3-6" FOR THE HIGHER
TERRAINS AND UP TO 3 INCHES FOR THE LOWLANDS. HIGHS WILL BE WARMEST
ON FRIDAY WITH 40S AND LOW 50S EXPECTED. THEY WILL DROP DOWN TO 30S
BY EARLY NEXT WEEK. LOWS WILL BE IN THE 30S FOR FRIDAY AND DROP INTO
THE 20S BY EARLY NEXT WEEK. /JDC
AVIATION
18Z TAFS: DEEP LOW PRESSURE OFF THE COAST OF NORTHWEST WASHINGTON
WILL DELIVER WIDESPREAD RAIN AND SNOW EAST OF THE CASCADES
BEGINNING THIS EVENING. THE HEAVIEST BAND IS PROJECTED TO ARRIVE
AT WENATCHEE BETWEEN 04-06Z AND PERSIST THROUGH 12-15Z WITH THE
POTENTIAL FOR 4 TO 6 INCHES OF SNOW ACCUMULATION. SIMILAR
ACCUMULATIONS ARE FORECAST FOR CHELAN, OMAK, GRAND COULEE, AND
REPUBLIC. LESSER AMOUNTS ARE EXPECTED FOR SPOKANE, COUER D'ALENE,
PULLMAN, AND KELLOGG WITH UP TO 2 INCHES OF ACCUMULATION IN THE
FORECAST WHERE A SHORTER DURATION OF SNOW IS ANTICIPATED. LOW
LEVEL EASTERLY FLOW WILL FAVOR PROLONGED LOW CEILINGS ALONG THE
CASCADES AS THE PRECIPITATION ARRIVES INTO WEDNESDAY MORNING.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
CONFIDENCE IS HIGH FOR HEAVY SNOW IN THE CASCADES OVERNIGHT INTO
EARLY WEDNESDAY MORNING. MARGINALLY WARM TEMPERATURES MAKE THE
ACCUMULATION FORECAST DIFFICULT REGIONWIDE SO OUR CONFIDENCE
RANGES FROM LOW TO MODERATE. ACCUMULATION EFFICIENCY WILL DECREASE
SIGNIFICANTLY AFTER 16Z WEDNESDAY FOLLOWING SUNRISE. /GKOCH
-----------------------
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 29 42 32 42 36 48 / 80 90 90 40 90 100
COEUR D'ALENE 26 42 32 41 37 46 / 50 100 100 50 100 100
PULLMAN 29 42 34 43 39 50 / 90 90 80 60 100 100
LEWISTON 34 51 38 47 45 57 / 80 80 60 40 90 90
COLVILLE 24 37 27 39 28 41 / 60 100 80 40 90 100
SANDPOINT 22 36 30 39 34 40 / 40 90 100 70 100 100
KELLOGG 23 40 34 40 38 46 / 50 100 90 80 100 100
MOSES LAKE 33 48 34 45 38 49 / 100 70 60 40 100 80
WENATCHEE 31 39 33 38 38 43 / 100 80 60 40 90 80
OMAK 29 42 32 39 35 45 / 100 100 50 30 90 90
OTX WATCHES/WARNINGS/ADVISORIES
ID...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 10 PM PST
WEDNESDAY FOR NORTHERN PANHANDLE.
WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 10 AM PST
WEDNESDAY FOR COEUR D'ALENE AREA-IDAHO PALOUSE.
WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 7 AM PST
THURSDAY FOR CENTRAL PANHANDLE MOUNTAINS.
WA...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 10 PM PST
WEDNESDAY FOR NORTHEAST MOUNTAINS.
WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 10 AM PST
WEDNESDAY FOR NORTHEAST BLUE MOUNTAINS-SPOKANE AREA-UPPER
COLUMBIA BASIN-WASHINGTON PALOUSE.
WIND ADVISORY FROM 7 PM THIS EVENING TO 10 AM PST WEDNESDAY FOR
LOWER GARFIELD AND ASOTIN COUNTIES.
WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 8 AM PST
WEDNESDAY FOR MOSES LAKE AREA.
WINTER STORM WARNING FROM 10 PM THIS EVENING TO 4 PM PST
WEDNESDAY FOR OKANOGAN HIGHLANDS-OKANOGAN VALLEY.
WINTER STORM WARNING UNTIL 10 AM PST WEDNESDAY FOR CENTRAL
CHELAN COUNTY-WATERVILLE PLATEAU-WENATCHEE AREA.
BLIZZARD WARNING UNTIL 10 AM PST WEDNESDAY FOR WESTERN CHELAN
COUNTY.
WINTER STORM WARNING UNTIL 4 PM PST WEDNESDAY FOR WESTERN
OKANOGAN COUNTY.
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