055
FXUS66 KOTX 170514
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
914 PM PST SAT NOV 16 2024
SYNOPSIS
A WINTER STORM WILL PUSH ACROSS THE REGION OVER THE WEEKEND WITH HEAVY
SNOW ACCUMULATIONS IMPACTING TRAVEL ACROSS THE CASCADE CREST AND
OVER LOOKOUT PASS. LIGHT TO MODERATE SNOW IS EXPECTED OVERNIGHT IN
THE VALLEYS OF NORTHEAST WASHINGTON AND IDAHO PANHANDLE. THE
WEATHER PATTERN FOR NEXT WEEK IS TRENDING WETTER WITH POTENTIAL
FOR WIDESPREAD SNOW TUESDAY NIGHT INTO WEDNESDAY THEN RAIN AND
SNOW THROUGH THE REMAINDER OF THE WEEK.
DISCUSSION
TONIGHT THROUGH MONDAY NIGHT: ACTIVE WEATHER WILL RETURN TO THE
NORTHWEST OVER THE WEEKEND WITH A WEAK ATMOSPHERIC RIVER BEING
DIRECTED INTO THE REGION AHEAD OF AN APPROACHING UPPER LEVEL TROUGH
OF LOWER PRESSURE. THE WARM FRONT AND ASSOCIATED OVERRUNNING
PRECIPITAITON IS PUSHING ACROSS THE CASCADES THIS AFTERNOON WITH
LIGHT PRECIPITAITON IN THE FORM OF A MIX OF RAIN AND SNOW ACROSS THE
WENATCHEE AREA UP TO THE OKANOGAN VALLEY/HIGHLANDS. THE PROGNOSES
IS FOR THE ATMOSPHERE TO CONTINUE TO MOISTEN IN THE WARM SECTOR,
AND FOR RADAR TO FILL IN ACROSS THE REST OF EASTERN WASHINGTON
INTO THE IDAHO PANHANDLE THIS EVENING. THIS WILL RESULT IN
WIDESPREAD PRECIPITATION ACROSS THE REGION BY AROUND 8-10PM THIS
EVENING. TEMPERATURES ARE RUNNING IN THE MID TO UPPER 30S WITH
DEW POINTS IN THE UPPER 20S IN THE NORTHERN MOUNTAIN VALLEYS.
CONFIDENCE IS HIGH THAT THESE AREAS WILL WETBULB DOWN TO FREEZING
AND PRECIPITATION FALL AS SNOW ONCE THE ATMOSPHERE MOISTENS DOWN
TO THE SURFACE. THEN THERE WILL BE A TRANSITION ZONE FROM THE
HIGHWAY 2 CORRIDOR ACROSS THE BASIN DOWN TO MOSES LAKE-RITZVILLE-
ROSALIA WHERE PRECIPITATION TYPE WILL START OUT AS A MIX OF RAIN
AND SNOW. IN GENERAL, WE ARE LOOKING AT WET SNOW ACROSS THE
HIGHWAY 2 CORRIDOR AND ON THE HIGHER BENCHES AROUND SPOKANE TO A
RAIN/SNOW MIX INTO DOWNTOWN SPOKANE; THEN BECOMING RAIN AS FAR
SOUTH AS MOSES LAKE TO RITZVILLE. PULLMAN/MOSCOW AREAS ALSO LOOK
TO WETBULB DOWN TO SNOW WITH LIGHT SLUSHY ACCUMULATIONS EXPECTED
LATE IN THE EVENING INTO THE EARLY OVERNIGHT HOURS.
WARM AIR ADVECTION WITH THE WARM FRONT WILL PUSH SNOW LEVELS
HIGHER OVERNIGHT INTO SUNDAY MORNING WITH A TRANSITION TO RAIN
FROM SOUTH TO NORTH. THIS TRANSITION LOOKS TO OCCUR FROM WILBUR TO
SPOKANE AROUND MIDNIGHT TONIGHT AND THEN ACROSS THE NORTHERN
MOUNTAIN VALLEYS EARLY TOMORROW MORNING AROUND 4-6 AM OR SO. BY
SUNDAY MORNING, SNOW LEVELS LOOK TO INCREASE UP TO AROUND
3500-4000 FEET FROM THE CASCADES, ACROSS THE NORTHERN MOUNTAINS
AND INTO THE IDAHO PANHANDLE. MOUNTAIN PASSES WILL REMAIN WITH
SNOW AND STEVENS PASS AND LOOKOUT PASS LOOK TO RECEIVE HEAVY SNOW
ACCUMULATIONS. WESTERLY FLOW ACROSS THE CASCADES WILL RESULT IN A
PRECIPITATION SHADOW ACROSS MUCH OF CENTRAL WASHINGTON IN THE LEE
OF THE CASCADES BY SUNDAY MORNING, AND THIS WILL LIMIT
ACCUMULATIONS AT BLEWETT, LOUP LOUP, AND SHERMAN PASS WITH LIGHT
TO MODERATE SNOW EXPECTED.
THE WARM FRONT PASSAGE TONIGHT INTO EARLY SUNDAY IS JUST THE FIRST
WAVE. THE SECOND WAVE WILL COME WITH THE COLD FRONT PASSAGE SUNDAY
AFTERNOON INTO SUNDAY EVENING. DYNAMICS ALONG THE COLD FRONT WILL
RESULT IN PRECIPITATION REFORMING BACK INTO THE BASIN, BUT
PRECIPITATION TYPE WILL BE AS RAIN ACROSS THE LOWLANDS BY THIS
POINT. FRONTAL PASSAGE WILL COME WITH A PERIOD OF MODERATE
PRECIPITATION INTENSITY. LAPSE RATES ALSO WILL STEEPEN IN THE POST
FRONTAL AIR MASS WITH MORE CONVECTIVELY DRIVEN SHOWERS EXPECTED
OVER THE CASCADE CREST AND INTO THE IDAHO PANHANDLE SUNDAY NIGHT.
THIS MAY RESULT IN SOME HEAVIER BURSTS OF SNOW OVER STEVENS PASS
AND LOOKOUT PASS INTO AT LEAST MONDAY MORNING BEFORE THESE SHOWERS
START TO WIND DOWN BY MONDAY AFTERNOON. TOTAL SNOW THAT WITH THE
WARM FRONT TONIGHT, COLD FRONT PASSAGE ON SUNDAY, AND POST FRONTAL
CONVECTIVE SHOWERS MONDAY NIGHT, STEVENS PASS LOOKS TO PICK UP
CLOSE TO 2 FEET OF NEW SNOW, LOOKOUT PASS BETWEEN 10 TO 18 INCHES
(OR A FOOT TO A FOOT AND A HALF), AND SHERMAN PASS BETWEEN 4 TO 7
INCHES. THE NORTHERN MOUNTAIN VALLEYS LOOK TO PICK UP BETWEEN 1 TO
4 INCHES AND LOCALLY UP TO 6 INCHES IN SPOTS NEAR THE CANADIAN
BORDER IN THE NORTHEAST MOUNTAINS AND NEAR PRIEST LAKE. SNOW
LEVELS WILL CRASH BEHIND THE COLD FRONT SUNDAY NIGHT, BUT SO WILL
THE AVAILABLE MOISTURE. RAIN MAY BRIEFLY TURN OVER TO SNOW FOR THE
VALLEYS IN THE NORTHERN PANHANDLE, BUT ANY ADDITIONAL
ACCUMULATIONS FOR THESE AREAS WILL BE LIGHT AND GENERALLY BELOW A
HALF INCH OF ADDITIONAL SNOW SUNDAY NIGHT INTO MONDAY MORNING. THE
CURRENT CAST OF WINTER STORM WARNINGS AND WINTER WEATHER
ADVISORIES LOOK ON TRACK AND NO UPDATES ARE NEEDED AT THIS TIME.
WINDS WILL BECOME BREEZY WITH THE COLD FRONT PASSAGE PRIMARILY
ACROSS THE WEST PLAINS, ON THE PALOUSE, AND ACROSS HIGHWAY 12 OVER
ALPOWA SUMMIT SUNDAY EVENING. STRONGEST WIND GUSTS LOOK TO BE UP
AROUND 30 MPH FROM THE WEST PLAINS DOWN ONTO THE PALOUSE, AND
POTENTIALLY UP TO AROUND 40 MPH OVER ALPOWA SUMMIT. THESE WINDS
ARE BELOW ADVISORY CRITERIA AND SHOULD HAVE MINIMAL IMPACTS.
THE ATMOSPHERE REMAINS CONDITIONALLY UNSTABLE THROUGH MONDAY NIGHT.
MOIST UPSLOPE FLOW ACROSS THE CASCADE CREST AND INTO THE IDAHO
PANHANDLE WILL KEEP SHOWERS GOING FOR THESE AREAS, BUT A LACK OF
MOISTURE WILL LIMIT ACCUMULATIONS. ANY ADDITIONAL SNOW ACCUMULATIONS
OVER THE MOUNTAIN PASSES WILL BE LIGHT. THERE WILL BE A RELATIVE
BREAK PERIOD BETWEEN WINTER STORMS MONDAY NIGHT INTO TUESDAY BEFORE
THE NEXT ONE. READ ON MORE FOR WHAT IS EXPECTED WITH THE NEXT WINTER
STORM. /SVH
TUESDAY THROUGH FRIDAY: FOR THE LATTER PART OF THE WEEK AND INTO
NEXT WEEKEND, MODELS HAVE CONSISTENTLY SHOWN AN EXTENDED PERIOD OF
ACTIVE WEATHER AS AN OMEGA BLOCK SETS UP OVER THE US. OUR FIRST
SYSTEM WILL ARRIVE TUESDAY EVENING AS A LOW PRESSURE SYSTEM
RAPIDLY STRENGTHENS OFF THE WASHINGTON COAST BETWEEN EARLY TUESDAY
MORNING AND TUESDAY AFTERNOON. WHILE THERE STILL REMAINS SOME
DIFFERENCES ON THE EASTERN PLACEMENT OF THE UPPER LEVEL RIDGE OVER
THE INTERIOR WESTERN US BY THURSDAY, MODELS CONTINUE TO SHOW A
PERSISTENT STREAM OF MOISTURE TAKING AIM INTO THE PNW FROM TUESDAY
INTO NEXT WEEKEND/EARLY NEXT WEEK WITH MULTIPLE SYSTEMS PASSING
THROUGH. UNCERTAINTY IN THE FORECAST GROWS FOR THURSDAY AND BEYOND
AS THE PLACEMENT OF THE RIDGE PLAYS THE PRIMARY ROLE IN THE
TEMPERATURES AND PRECIPITATION CHANCES FOR EASTERN WASHINGTON AND
NORTH IDAHO.
TUESDAY INTO WEDNESDAY, MODELS ARE IN SOLID AGREEMENT THAT A WARM
FRONT WILL SPREAD NORTH INTO EASTERN WASHINGTON AND NORTH IDAHO AS
THE STRONG LOW OFF THE COAST BEGINS TO OCCLUDE. WITH HIGH
PRESSURE TO THE EAST AND DEEP LOW PRESSURE TO THE WEST, SEVERAL
MODELS ARE SHOWING A STRONG PRESSURE GRADIENT OF -18 TO -14MB
BETWEEN SEA- GEG TUESDAY NIGHT. THIS WILL RESULT IN GUSTY EAST TO
SOUTHEAST WINDS ACROSS EASTERN WASHINGTON AND PROVIDE FAVORABLE
UPSLOPE FLOW INTO THE EAST SLOPES OF THE CASCADES. AS THE WARM
FRONT SPREADS NORTHWARD AND OVERRUNS THE COLD AIR AT THE SURFACE,
PRECIPITATION LOOKS TO BEGIN AS SNOW TUESDAY EVENING. A BIG
CHALLENGE THOUGH IS HOW QUICKLY THIS COLD AIR WILL SCRUB OUT OF
PLACES SUCH AS WENATCHEE, LEAVENWORTH, WINTHROP, OMAK. WITH THE
STRONG EASTERLY GRADIENT AND MODELS TYPICALLY WARMING THESE AREAS
UP TOO QUICKLY, I SUSPECT PRECIPITATION TO REMAIN AS SNOW IN THESE
AREAS THROUGH EARLY WEDNESDAY. THIS COULD RESULT IN QUITE AN
IMPACTFUL LOWLAND SNOW EVENT FOR THE CASCADE VALLEYS, THE
WATERVILLE PLATEAU, AND THE OKANOGAN VALLEY IF SO. RIGHT NOW, OUR
FORECAST IS GIVING THESE AREAS 5 TO 8 INCHES OF SNOW TUESDAY NIGHT
INTO WEDNESDAY BEFORE CHANGING OVER TO RAIN WEDNESDAY AFTERNOON.
THIS WILL CONTINUE TO BE CLOSELY MONITORED OVER THE NEXT COUPLE OF
DAYS.
ACROSS NORTHEAST WASHINGTON, THE SPOKANE AREA, AND IDAHO PANHANDLE
VALLEYS, WHILE PRECIPITATION ALSO LOOKS TO BEGIN AS SNOW, THERE WILL
LIKELY BE A SMOOTHER TRANSITION TO RAIN AS SNOW LEVELS RISE
WEDNESDAY AFTERNOON. THE NBM IS CURRENTLY GIVING SPOKANE-COEUR
D’ALENE AREAS A 40 TO 50 PERCENT CHANCE FOR OVER 1 INCH OF SNOW,
ALTHOUGH EXAMINING INDIVIDUAL ENSEMBLE MEMBERS BETWEEN THE ECMWF,
GFS, AND CANADIAN MODEL WOULD PUT THE MOST LIKELY RANGE BETWEEN 2 TO
4 INCHES FOR SPOKANE AND 4 TO 6 INCHES FOR COEUR D’ALENE BEFORE
TRANSITIONING TO RAIN WEDNESDAY AFTERNOON. THIS WOULD LIKELY RESULT
IN A SLIPPERY WEDNESDAY MORNING COMMUTE.
OVER THE CASCADE PASSES, THE NBM IS GIVING STEVENS AND WASHINGTON
PASSES A 70 TO 80 PERCENT CHANCE FOR 1 INCH PER HOUR SNOWFALL RATES
TUESDAY NIGHT INTO WEDNESDAY MORNING. ADDITIONALLY, IT IS GIVING A
60 TO 70 PERCENT CHANCE FOR OVER 18 INCHES OF SNOW IN 24 HOURS FOR
THESE PASSES. THIS IN COMBINATION WITH GUSTY EAST TO SOUTHEAST WINDS
WILL LIKELY RESULT IN VERY CHALLENGING TRAVEL OVER THE PASSES
TUESDAY NIGHT THROUGH WEDNESDAY MORNING.
THURSDAY AND BEYOND, MODELS CONTINUE TO SHOW THE INLAND NORTHWEST
REMAINING IN AN UNSETTLED PATTERN UNDER THE PERSISTENT STREAM OF
MOISTURE. SNOW LEVELS INCREASING UNDER THE SOUTHWEST FLOW ALOFT LOOK
TO KEEP SNOW PRIMARILY IN THE MOUNTAINS WITH RAIN FOR THE LOWLANDS.
HOWEVER, THERE STILL DOES REMAIN SOME UNCERTAINTY IN THE OVERALL
UPPER LEVEL FLOW PATTERN WHICH WILL LIKELY RESULT IN MANY CHANGES TO
THE EXTENDED FORECAST OVER THE NEXT SEVERAL DAYS. /VMT
AVIATION
06Z TAFS: WINTER STORM SYSTEM BRINGING RAIN AND SNOW TO AVIATION
AREA ALLOWING FOR LIFR/IFR CONDITIONS TO PREVAIL FOR LOCATIONS
NEAR KGEG AND VICINITY BETWEEN NOW AND 10Z WITH SOME TENDENCY TO
RAISE TO IFR/MVFR AFTERWARD. LOW LEVEL WIND SHEAR A GOOD
POSSIBILITY AS THE BACK EDGE OF THE SYSTEM MOVES THROUGH AS A COLD
FRONT WITH SURFACE GUSTS TO 40KTS A POSSIBILITY WITH PREVAILING
WIND DIRECTION FROM THE SOUTHWEST. /PELATTI
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
CONFIDENCE IS HIGH FOR IFR CONDITIONS WITH THE WINTER STORM
OVERNIGHT INTO SUNDAY FOR KGEG-KSFF-KCOE. THE STRATIFORM NATURE OF
THE PRECIPITATION IS TYPICALLY WELL HANDLED BY MODEL GUIDANCE.
-----------------------
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 32 46 30 40 25 39 / 100 90 80 50 40 10
COEUR D'ALENE 32 44 31 39 25 37 / 100 100 100 90 80 30
PULLMAN 33 43 30 38 23 36 / 100 100 100 80 70 20
LEWISTON 39 51 34 45 29 42 / 90 100 90 60 50 10
COLVILLE 29 43 21 38 16 35 / 100 80 70 50 40 20
SANDPOINT 31 41 30 36 23 34 / 100 100 100 90 80 40
KELLOGG 31 40 31 35 27 34 / 100 100 100 100 90 40
MOSES LAKE 36 50 28 45 22 41 / 90 70 20 10 10 10
WENATCHEE 33 48 30 44 26 36 / 90 70 30 10 20 20
OMAK 33 46 25 42 22 38 / 80 40 30 10 10 10
OTX WATCHES/WARNINGS/ADVISORIES
ID...WINTER WEATHER ADVISORY UNTIL 10 AM PST SUNDAY FOR NORTHERN
PANHANDLE.
WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO 10 AM PST
SUNDAY FOR IDAHO PALOUSE.
WINTER STORM WARNING FROM 10 PM THIS EVENING TO 10 PM PST MONDAY
FOR CENTRAL PANHANDLE MOUNTAINS.
WA...WINTER WEATHER ADVISORY UNTIL 10 AM PST SUNDAY FOR NORTHEAST
MOUNTAINS-OKANOGAN HIGHLANDS.
WINTER WEATHER ADVISORY UNTIL 10 PM PST SUNDAY FOR CENTRAL
CHELAN COUNTY.
WINTER STORM WARNING UNTIL 10 PM PST MONDAY FOR WESTERN CHELAN
COUNTY-WESTERN OKANOGAN COUNTY.
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