146
FXUS66 KOTX 181140
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
340 AM PST MON NOV 18 2024
SYNOPSIS
PRECIPITATION WILL BE MORE SHOWERY THROUGH EARLY TUESDAY. WEATHER
WILL REMAIN UNSETTLED THROUGH THE WEEK WITH THE NEXT WINTER STORM
TUESDAY NIGHT INTO WEDNESDAY BRINGING ANOTHER ROUND OF WIDESPREAD
SNOW. THIS WILL RESULT IN MODERATE TO MAJOR IMPACTS ACROSS
CENTRAL WASHINGTON AND MINOR IMPACTS FOR EASTERN WASHINGTON AND
NORTH IDAHO. ADDITIONAL SYSTEMS PASSING THROUGH THURSDAY THROUGH
NEXT WEEKEND WILL BRING ADDITIONAL PERIODS OF LOWLAND RAIN AND
MOUNTAIN SNOW.
DISCUSSION
TODAY AND TONIGHT: MOUNTAIN SNOW SHOWERS WILL CONTINUE THROUGH
MUCH OF THE DAY TODAY ALONG US-2 AND I-90 WITH UPSLOPE WESTERLY
FLOW IN PLACE WITH MODERATELY STEEP LAPSE RATES. 500 MB
TEMPERATURES IN THE WAKE OF THE COLD FRONT PASSAGE ARE
IMPRESSIVELY COLD AT -36 TO -38C. SNOW/GRAUPEL SHOWERS WITH AN
ISOLATED LIGHTNING STRIKE CANNOT BE RULED OUT THIS AFTERNOON IN
THE EASTERN THIRD OF WASHINGTON AND THE NORTH IDAHO LOWLANDS IN
THIS TYPE OF WEATHER REGIME. HIGH TEMPERATURES WILL RANGE FROM THE
40S IN CENTRAL WASHINGTON AND MID TO UPPER 30S IN THE EASTERN
THIRD OF WASHINGTON AND THE NORTH IDAHO PANHANDLE TODAY.
TEMPERATURES WILL COOL OFF INTO THE 20S TONIGHT FAIRLY QUICKLY AS
A MUCH DRIER AIRMASS IS IN PLACE WITH FAIRLY MINIMAL CLOUD COVER
TO START THIS NIGHT. MODELS ARE HINTING AT SOME AREAS OF DENSE FOG
FORMING IN THE SHELTERED VALLEYS OF NORTHEAST WASHINGTON TONIGHT
BUT CONFIDENCE REMAINS LOW FOR THIS. A VORT MAX WILL PIVOT THROUGH
OUR AREA STARTING LATE THIS EVENING THAT WOULD BRING SOME LIGHT
SNOWFALL UP AN INCH AT STEVENS PASS BEFORE SUNRISE. /DB
..HEAVY SNOW TO IMPACT CENTRAL WA TUESDAY NIGHT INTO WEDNESDAY
TUESDAY: WIDELY SCATTERED SNOW SHOWERS WILL BE DRIFTING THROUGH THE
REGION TUESDAY MORNING AND EARLY AFTERNOON WITH THE DEPARTURE OF
A COLD UPPER-LEVEL TROUGH. MODELS ARE STRUGGLING ON THE EXACT
PLACEMENT OF THE SHOWERS GIVEN THE CHAOTIC CONVECTIVE NATURE. AS
SUCH, WE TURN TOWARD ENSEMBLES WHICH FAVOR AREAS NORTH AND EAST OF
A LINE FROM KELLOGG TO OMAK INCLUDING THE UPPER BASIN, SPOKANE-
CD'A AREA, SANDPOINT, COLVILLE, AND REPUBLIC. MAIN CONCERN WILL BE
LIGHT ACCUMULATIONS OF SNOW IMPACTING THE TUESDAY MORNING COMMUTE
RESULTING IN SLICK CONDITIONS. SHOWER ACTIVITY WILL WANE IN THE
AFTERNOON WITH TEMPERATURES IN THE 30S TO LOWER 40S. WINDS WILL BE
LIGHT AND BEGIN SHIFTING TO THE EAST AND SOUTHEAST DRAWN TO A
POWERFUL CYCLONE OFF THE WA COAST.
TUESDAY NIGHT THROUGH WEDNESDAY: AN EXTREMELY INTENSE LOW PRESSURE
WILL BE TRACKING OFF THE WA COAST. STRONG CROSS CWFA PRESSURE
GRADIENTS WILL CREATE GUSTY EAST TO SOUTHEAST WINDS WHILE DEEP
MOISTURE FLOWS INLAND. THIS IS A CLASSIC SETUP FOR MODERATE TO
HEAVY SNOW FOR CENTRAL WA, ESPECIALLY WITH A COLDER AIR MASS
SETTLING IN AHEAD OF THE INCOMING SYSTEM. LIGHTER SNOW WILL SPREAD
INTO EASTERN WA AND NORTH IDAHO WEDNESDAY MORNING IMPACTING THE
WEDNESDAY MORNING COMMUTE. SNOW LEVELS TO BE NEAR VALLEY FLOORS
FOR MOST AREAS OUTSIDE THE EXTREME DEEP BASIN LEADING TO MODERATE
TO HIGH CONFIDENCE FOR SNOW AS THE MAIN P-TYPE AT THE START OF THE
EVENT. SNOW LEVELS WILL RISE THROUGH THE DAY WEDNESDAY NOSING
INTO THE EASTERN WA AND N IDAHO FIRST AND SLOWLY BLEEDING INTO THE
COLD AIR OVER CENTRAL WA.
THE FOCUS FOR SIGNIFICANT WINTER STORM AND AN ANOMALOUS SNOW
EVENT WILL BE OVER CENTRAL WASHINGTON INCLUDING THE CASCADES,
OKANOGAN HIGHLANDS, WATERVILLE PLATEAU, AND THE ENTIRE HIGHWAY 97
CORRIDOR FROM BLEWETT PASS TO SOUTHERN BC. WINTER STORM WATCHES
HAVE BEEN ISSUED GIVEN MODERATE TO HIGH CONFIDENCE AND CONSISTENT
SIGNAL IN THE ENSEMBLE GUIDANCE OVER 3 DAYS NOW. FOR THE REMAINDER
OF E WA AND NORTH ID, WE WILL BE LOOKING AT THE POTENTIAL FOR
WINTER WEATHER ADVISORIES GIVEN THE TIMING INTERSECTING THE
WEDNESDAY MORNING COMMUTE.
* IMPACTS:
TUESDAY: BE CAUTIOUS OF DEVELOPING SLICK CONDITIONS WITH SNOW SHOWERS
TUESDAY MORNING. BEST TO CHECK CONDITIONS OR RADAR IN THE MORNING
AND LEAVE A FEW EXTRA MINUTES TO REACH YOUR DESTINATION SAFELY.
TUESDAY EVENING: LIGHT SNOW WILL BE JUST DEVELOPING IN CENTRAL WA.
OVERALL, IMPACTS WILL BE MINOR DURING THE EVENING COMMUTE BUT
WINTER TRAVEL CONDITIONS AND POTENTIALLY SLICK CONDITIONS WILL BE
JUST STARTING TO DEVELOP.
TUESDAY NIGHT AND WEDNESDAY: RESIDENTS OF THE INLAND NW SHOULD PLAN
FOR A SLOW COMMUTE COME WEDNESDAY MORNING. IN CENTRAL WA, PERIODS
OF MODERATE TO HEAVY SNOW ACCUMULATIONS WILL HAVE FALLEN OR IN
PROCESS OF FALLING LEADING TO WINTER TRAVEL CONDITIONS. SNOWFALL
RATES OF 1-2" HOUR WILL BE POSSIBLE IN CENTRAL WA. GOOD TIME TO
MAKE SURE YOU HAVE YOUR WINTER EMERGENCY SAFETY KIT AND PREPARE
FOR SLOW TRAVEL. FOR EASTERN WA AND NORTH IDAHO, THE EVENT WILL
NOT BE OUT OF THE ORDINARY BUT PREPARED FOR A FEW INCHES OF SNOW
FALLING THROUGH THE MORNING HOURS AND SLICK TRAVEL. SNOW WILL
CONTINUE TO FALL WEDNESDAY AFTERNOON ACROSS THE NORTHERN
MOUNTAIN/MOUNTAIN VALLEYS WITH LIGHTER RATES AND COULD LEAD TO
CONTINUED WINTER TRAVEL CONDITIONS HEADING HOME DURING THE
WEDNESDAY EVENING COMMUTE. TEMPERATURES BY WEDNESDAY AFTERNOON
WILL HAVE WARMED ABOVE FREEZING FOR MUCH OF THE BASIN, SPOKANE-
CD'A, AND PALOUSE. THE VALLEYS OF CENTRAL WA ALONG HWY 97 ARE
EXPECTED TO WARM ABOVE FREEZING BUT THIS COMES WITH LOWER
CONFIDENCE AND DEPENDENT ON THE DURATION OF THE SNOW.
GUSTY EAST WINDS WILL HAVE THE POTENTIAL TO CREATE BLOWING AND
DRIFTING SNOW IN THE EAST SLOPES, ESPECIALLY AT STEVENS PASS. THE
WATERVILLE PLATEAU COULD ALSO BE COPING WITH ADVERSE CONDITIONS
FROM DRIFTING SNOW WITH A STEADY 15-20 MPH WIND. ISOLATED POWER
OUTAGES CANNOT BE RULED OUT IN THE EAST SLOPES FROM THE SNOW AND
GUSTY WINDS.
STRONG WINDS IN THE LEE OF THE BLUE MOUNTAINS, ALONG THE SNAKE RIVER
VALLEY COULD RESULT IN SOME TREE DAMAGE AND ISOLATED POWER OUTAGES.
* SNOW AMOUNTS:
SNOW AMOUNTS COULD CONTINUE TO CHANGE AS THE FORECAST BECOMES
FINE TUNED. AT THIS TIME, FORECAST IS CALLING FOR 6-10 INCHES FOR
THE VALLEYS OF CENTRAL WA INCLUDING WENATCHEE, CHELAN, OMAK, AND
REPUBLIC. UPPER CASCADE VALLEYS LIKE LEAVENWORTH, ARDENVOIR, AND
WINTHROP CARRY HIGHER PROBABILITIES FOR 8 TO 14 INCHES. AREAS
ALONG THE COLUMBIA RIVER SUCH AS CHELAN, CITY OF WENATCHEE, ROCK
ISLAND, AND INTO THE W BASIN AROUND MOSES LAKE AND EPHRATA CARRY
SOME UNCERTAINTY DUE TO A POTENTIAL FOR SNOW TO BE FALLING WITH
TEMPERATURES 32-36F. THERE IS MODERATE CONFIDENCE FOR SNOW TO FALL
AT THESE TEMPERATURES GIVEN DRIER DEWPOINTS BUT IT DEFINITELY IS
SOMETHING THAT COULD ALTER ACCUMULATIONS. WENATCHEE PROPER WILL
ALSO BE IMPACTED FROM THE TIMING OF DOWNSLOPING MIDLEVEL WINDS OFF
MISSION RIDGE AT SOME POINT. SOME MODELS DELAY THIS 6 HOURS FROM
THE OTHER. IF THIS IS DELAYED, AMOUNTS COULD BE > 7". IF THE TEMPS
REMAIN 35F AND DOWNSLOPING OCCURS EARLIER, COULD BE CLOSER TO 4".
THE MOUNTAINS IN CENTRAL WA WILL BE MORE IN THE RANGE OF 1-2
FEET. SNOW AMOUNTS TAPER OFF CLOSER TO 2-4 INCHES FOR THE VALLEYS
OF NE WA AND N ID AND 5-10 INCHES IN THE MOUNTAINS. AMOUNTS ARE
NEAR OR LESS THAN 2 INCHES FOR THE LOWER BASIN, PALOUSE, AND CAMAS
PRAIRIE. LESS THAN AN INCH IS EXPECTED IN THE L-C VALLEY, LA
CROSSE, AND SOUTH OF MOSES LAKE. SPEAKING OF MOSES LAKE, THIS HAS
BEEN ONE OF THE GREATER CHALLENGES AND WOULD NOT RULE OUT A SHARP
GRADIENT OF SNOW AMOUNTS ACROSS GRANT COUNTY FROM A TRACE NEAR
OTHELLO TO 4 INCHES OR MORE BY COULEE CITY/HARLTINE.
* WINDS:
WITH BOMB CYCLOGENESIS EXPECTED OF THE WA COAST PRODUCING
HURRICANE FORCE WINDS, WE ARE LOOKING AT 16-20 MB EAST TO WEST
PRESSURE GRADIENT FROM LEWISTON TO SEATTLE. THIS WILL NO DOUBT
MANIFEST INTO GUSTY EAST WINDS ACROSS OUR NECK OF THE WOODS WITH
SPEEDS OF 10-25 MPH AND GUSTS TO 30-40 MPH. STRONGEST WINDS WILL
BE CHANNELING UP THROUGH THE SNAKE RIVER AND DOWN THE FOOTHILLS
OF THE BLUE MOUNTAINS BEFORE SPILLING INTO THE PALOUSE, COLUMBIA
BASIN, AND WATERVILLE PLATEAU. LOCALLY STRONGER WINDS ARE EXPECTED WILL
BE POSSIBLE CHANNELING THROUGH THE CASCADE RIDGES AND PASSES
WHICH COULD GUST UPWARDS OF 50+ MPH. MAY NEED TO CONSIDER A
WIND ADVISORY FOR LOCATIONS BETWEEN LA CROSSE AND LEWISTON WITH
THE POTENTIAL FOR GUSTS 40+ MPH. /SB
THURSDAY THROUGH MONDAY: THE ENSEMBLE CLUSTERS ARE IN EXCELLENT
AGREEMENT WITH THE 500 MB PATTERN AFTER THE WEDNESDAY STORM. THE
PARENT TROUGH SLOWLY MOVES EAST TOWARDS THE WASHINGTON COAST WHICH
WILL MAKE FOR MANY MORE CHANCES FOR UNSETTLED WEATHER.
DETERMINISTIC MODELS EVEN SHOW THE POSSIBILITY OF A FUJIWHARA
EFFECT WITH A COUPLE OF LOW PRESSURES OFF THE WASHINGTON COAST.
SNOW LEVELS LOOK TO REMAIN ABOVE THE VALLEY FLOOR UNDER THE WARM,
SOUTHWEST FLOW ALOFT WITH SNOW REMAINING IN THE MOUNTAINS AND RAIN
FOR THE LOWLANDS. /DB
AVIATION
12Z TAFS: OFF AND ON SHOWERS WILL CONTINUE INTO AT LEAST THE
EARLY AFTERNOON HOURS ON MONDAY FOR THESE AREAS IN THE VICINITY OF
KDEW-KSZT-KCOE. LOW STRATUS IS EXPECTED TO EXPAND OVERNIGHT
ACROSS THE SPOKANE/COEUR D'ALENE CORRIDOR DOWN ON THE PALOUSE WITH
MVFR CONDITIONS EXPECTED AT KPUW-KGEG-KSFF-KCOE. LOW CLOUDS WILL
CONTINUE TO BE PRESENT THROUGH THE MORNING ON MONDAY BEFORE SEEING
CEILINGS GRADUALLY LIFTING IN THE AFTERNOON. MODELS SHOW A
RESURGENCE OF MVFR STRATUS INTO THE SPOKANE/COEUR D'ALENE CORRIDOR
OVERNIGHT INTO TUESDAY.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
MODERATE TO HIGH CONFIDENCE FOR MVFR CONDITIONS DUE TO LOW STRATUS
THROUGH MONDAY MORNING AT KGEG-KSFF-KCOE-KPUW. LOW CEILINGS
BETWEEN 1-4 KFT AGL LOOK TO CONTINUE INTO THE AFTERNOON HOURS WITH
CONVECTIVE SHOWERS IN THE VICINITY, BUT CONFIDENCE INCREASES FOR
CEILINGS LIFTING AND VFR CONDITIONS PREVAILING BY THE LATE
AFTERNOON.
-----------------------
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 39 26 37 29 40 31 / 40 20 30 50 90 80
COEUR D'ALENE 37 27 36 26 39 32 / 60 30 30 40 100 90
PULLMAN 37 27 38 29 40 33 / 60 30 20 60 80 90
LEWISTON 45 31 43 32 48 38 / 40 20 10 50 60 70
COLVILLE 37 21 34 24 35 23 / 40 20 30 50 100 80
SANDPOINT 36 25 34 22 35 29 / 80 60 50 30 100 90
KELLOGG 35 27 34 23 39 34 / 90 70 40 40 100 100
MOSES LAKE 45 27 41 33 46 31 / 10 10 30 90 70 60
WENATCHEE 43 29 36 30 39 32 / 10 10 20 100 70 50
OMAK 41 24 36 29 38 29 / 0 10 20 90 100 50
OTX WATCHES/WARNINGS/ADVISORIES
ID...WINTER WEATHER ADVISORY UNTIL 6 PM PST THIS EVENING FOR CENTRAL
PANHANDLE MOUNTAINS.
WA...WINTER STORM WATCH FROM TUESDAY EVENING THROUGH WEDNESDAY
EVENING FOR OKANOGAN HIGHLANDS-OKANOGAN VALLEY.
WINTER STORM WATCH FROM TUESDAY AFTERNOON THROUGH WEDNESDAY
EVENING FOR CENTRAL CHELAN COUNTY-WATERVILLE PLATEAU-
WENATCHEE AREA-WESTERN CHELAN COUNTY-WESTERN OKANOGAN
COUNTY.
WINTER STORM WARNING UNTIL 4 PM PST THIS AFTERNOON FOR WESTERN
CHELAN COUNTY.
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