668
FXUS66 KOTX 161909
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
1109 AM PST SAT NOV 16 2024
SYNOPSIS
SNOW WILL RETURN TO THE CASCADES DURING THE DAY SATURDAY AND
SPREAD EASTWARD SATURDAY NIGHT AND SUNDAY. HEAVY SNOW
ACCUMULATIONS ARE EXPECTED ON THE MOUNTAIN PASSES. 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.
UPDATE
DENSE FOG ADVISORY FOR THE NORTHEAST MOUNTAINS EXPIRED AT 9AM.
DISCUSSION
SATURDAY AND SUNDAY: SCATTERED RAIN AND SNOW SHOWERS SOUTH OF
INTERSTATE 90 AND EAST OF US-395 WILL CONTINUE THROUGH AT LEAST
SUNRISE OUT OF THE SHALLOW STRATUS DECK CURRENTLY IN PLACE. TO THE
NORTH, AREAS OF SHALLOW DENSE FOG WILL CONTINUE THROUGH SUNRISE AS
WELL THANKS TO RADIATIONAL COOLING AND MOIST SURFACE CONDITIONS.
HIGH TEMPERATURES TODAY WILL REACH INTO THE UPPER 30S TO UPPER
40S. HIGH CLOUDS MOVING IN ARE INDICATIVE OF THE NEXT SYSTEM
MOVING INTO OUR AREA THIS AFTERNOON WHICH WILL BE THE FIRST
LOWLAND SNOW OF THE SEASON TO MUCH OF THE AREA.
A PLUME OF SUBTROPICAL MOISTURE IS HEADED OUR WAY THIS AFTERNOON THANKS
TO A SURFACE LOW CHURNING OFF THE ALASKA COAST. NORTHERLY FLOW
ALOFT WILL SLOWLY TURN WESTERLY THROUGH THE DAY AS A SHORTWAVE
TROUGH MOVES CLOSER TO SOUTHEAST BC. AS THIS OCCURS, WIDESPREAD
LIGHT TO MODERATE PRECIPITATION WILL SPREAD ACROSS CENTRAL AND
EASTERN WASHINGTON/NORTH IDAHO THIS AFTERNOON AND EVENING.
PRECIPITATION WILL START AS SNOW NORTHEAST OF RITZVILLE BUT WARM
AIR ADVECTION WILL QUICKLY CAUSE A CHANGEOVER TO RAIN BELOW 3000
FEET INTO SUNDAY MORNING AS FAR NORTH AS THE CANADIAN BORDER.
WINTER WEATHER ADVISORIES ARE IN PLACE IN NORTHEAST WASHINGTON AND
NORTH IDAHO FROM THIS AFTERNOON TO SUNDAY MORNING WHERE SNOW
TOTALS WILL RANGE FROM 1-4 INCHES. THE WARM AIR ADVECTION WILL
CAUSE A BRIEF CHANGEOVER TO RAIN AT STEVENS PASS AS WELL SUNDAY
MORNING, BUT A COLD FRONT PASSAGE WILL BRING SNOW LEVELS BELOW THE
PASS LEVEL. WINTER STORM WARNINGS ARE IN PLACE FOR THE CASCADE
PASSES AND LOOKOUT PASS THROUGH FROM TODAY TO MONDAY EVENING FOR 1
TO 2 FEET OF SNOW.
AT THE CASCADE PASSES THERE WILL BE 2 DISTINCT TIMES OF
PARTICULARLY CHALLENGING TRAVEL: SATURDAY AFTERNOON AND SUNDAY
AFTERNOON. THERE IS A 50-70% CHANCE OF SNOWFALL RATES 1” PER HOUR
OR MORE FROM 5 PM TO 10 PM SATURDAY BEFORE CHANGING OVER TO RAIN.
THIS ROUND OF HEAVIER SNOW CARRIES HIGH CONFIDENCE FOR STEVENS AND
WASHINGTON PASS. THE LESS CERTAIN ROUND OF HEAVIER SNOW IS A
PUGET SOUND CONVERGENCE ZONE THAT FORMS BEHIND THE FRONT PASSAGE
SUNDAY AFTERNOON. STEVENS PASS HAS A 30% CHANCE OF 1” PER HOUR
RATES THANKS TO THIS FEATURE FROM 2PM TO APPROXIMATELY 11PM
SUNDAY.
MONDAY: MOUNTAIN SNOW AND LOWLAND RAIN/SNOW SHOWERS WILL CONTINUE
INTO MONDAY THANKS TO THE COLD TROUGH ABOVE US. TEMPERATURES
DURING THE DAY MONDAY WILL BE IN THE UPPER 30S TO 40S. ADDITIONAL
LIGHT SNOW UP TO 1 INCH WILL FALL IN THE EASTERN THIRD OF
WASHINGTON AND THE IDAHO PANHANDLE OVERNIGHT MONDAY INTO TUESDAY
BUT WILL MOSTLY BE IN THE GRASSES THANKS TO MILD ROAD
TEMPERATURES. WITH THAT IN MIND, I TRIMMED THE WINTER WEATHER
ADVISORIES DOWN TO JUST CAPTURE THE SUNDAY SNOWFALL. /DB
..WIDESPREAD SNOW IN TUESDAY NIGHT INTO WEDNESDAY. SIGNIFICANT
SNOWFALL EXPECTED IN CENTRAL WA...
TUESDAY AND WEDNESDAY: CONFIDENCE CONTINUES TO INCREASE FOR AN
IMPACTFUL WINTER STORM TUESDAY NIGHT THROUGH WEDNESDAY. NUMEROUS
ENSEMBLE SOLUTIONS ARE ADVERTISING AN ANOMALOUS SNOW EVENT FOR
MUCH OF CENTRAL AND NORTHEASTERN WA. THE FLOW PATTERN IS RIGHT AND
THERE WILL BE COPIOUS AMOUNTS OF QPF. MIDLEVEL TEMPERATURES WILL
BE COLD ENOUGH; MILLION DOLLAR QUESTION IS WHAT WILL THE VALLEY
TEMPERATURES BE WHEN THE SNOW ARRIVES. NORTH IDAHO WILL ALSO BE
IMPACTED BUT WITH LIGHTER AMOUNTS. BOTTOM LINE...THIS STORM HAS
THE POTENTIAL TO HAVE SIGNIFICANT IMPACTS ON THE WEDNESDAY MORNING
COMMUTE FOR MANY COMMUNITIES AND TRAVEL ACROSS THE CASCADE
MOUNTAIN PASSES WILL BE CHALLENGING.
STARTING OFF TUESDAY MORNING, THERE WILL BE A FEW LIGHT SNOW SHOWERS
DRIFTING EASTWARD THROUGH THE IDAHO PANHANDLE. OTHERWISE, TUESDAY
WILL PROVIDE A BREAK IN THE UNSETTLED WEATHER PATTERN WITH CHILLY
TEMPERATURES. THIS COOLER AIR MASS WILL BE OVERRUN BY MOIST
ISENTROPIC ASCENT AIDED AHEAD OF A WARM FRONT TUESDAY NIGHT,
STARTING IN THE CASCADES AROUND SUNSET AND EXPANDING TO THE IDAHO
PANHANDLE NEAR SUNRISE WEDNESDAY MORNING. THE WARM FRONT WILL
EXTEND OFF AN EXTREMELY DEEP LOW TRACKING OFF WA COAST TOWARD
VANCOUVER ISLAND. THIS WILL DRAW GUSTY EAST TO SOUTHEAST WINDS
ACROSS THE AREA RESULTING IN COLD AIR DAMMING IN THE LEE OF THE
CASCADES AND A FAVORABLE WIND PATTERN FOR OROGRAPHIC ASCENT FOR
CENTRAL WA WITH A ZERO CHANCE FOR A RAIN SHADOW. COPIOUS AMOUNTS
OF QPF ARE FORECAST BY THE MODELS (0.50-1.50"), WHICH COULD FALL
IN THE FORM OF SNOW FOR MANY LOCATIONS. THIS IS A NEAR CERTAINTY
FOR THE MOUNTAINS. IN THE LOWLANDS, IT WILL BE A BIT MORE
CHALLENGING. 1) THERE WILL BE A PUNCH OF WARMER AIR COMING INTO
THE BASIN AND SOUTHEASTERN WA AND WORKING ITS WAY NORTHWARD. AS
SUCH, THERE IS LOW CONFIDENCE FOR IMPACTFUL SNOW AT LOCATIONS LIKE
MOSES LAKE, RITZVILLE, AND LA CROSSE. AMOUNTS FOR CENTRAL WA FROM
REPUBLIC TO WENATCHEE AND POINTS WEST CARRY A HIGHER PROBABILITY
TO REMAIN ALL SNOW. AMOUNTS COULD BE QUITE IMPACTFUL WITH OVER A
FOOT IN THE MOUNTAINS AND 1 TO 10 INCHES IN THE VALLEYS. WHY SUCH
A BIG RANGE? THE UNCERTAINTY COMES WITH HOW MUCH OF THE TUESDAY
WARMTH IS TRAPPED BY THE INCOMING CLOUD SHIELD AND DOES THE SNOW
FALL WITH TEMPERATURES ABOVE FREEZING FOR THE LOWEST ELEVATIONS
ALONG THE COLUMBIA AND OKANOGAN RIVER. NBM IS GIVING LOCATIONS
LIKE WENATCHEE PROPER AN 80% CHANCE FOR RAIN AND 20% FOR SNOW AS
THE P-TYPE. HOWEVER, WHEN ANALYZING THE MAX WETBULB IN THE COLUMN,
IT LOOKS TO REMAIN BELOW 33F. CONSEQUENTLY, FORECAST HAS BEEN
TWEAKED TO SUPPORT MORE SNOW VS RAIN, ESPECIALLY WITH THE COLD AIR
DAMMING SIGNATURE AND HEAVIER PRECIPITATION INTENSITIES. ONCE YOU
GET ABOVE 1500 FEET ELEVATION, THE CHANCES FOR 5+ INCHES
INCREASES SIGNIFICANTLY SO GENERALLY SPEAKING, THE MAIN CHALLENGE
IS RIVER LEVEL TO 1500 FEET. FURTHER EAST INTO THE IDAHO
PANHANDLE, NORTHEASTERN WA, AND PALOUSE, LOWLAND SNOW AMOUNTS WILL
BE CLOSER TO THE 1-4" RANGE; HIGHER END OF THE RANGE IN THE
VALLEYS OF NE WA AND N ID AND LOWEST ON THE PALOUSE. THE MOUNTAINS
STAND A GOOD SHOT OF RECEIVING 6-10 INCHES.
GUSTY EAST TO SOUTHEAST WINDS WILL BE IN PLACE WITH SPEEDS ACROSS
THE BASIN ON THE ORDER OF 10-20 MPH WITH GUSTS UP TO 30 MPH.
STRONG EASTERLY WINDS WILL ALSO IMPACT THE RIDGELINES AND PASSES
IN THE CASCADES. THE ECMWF ENS HAS NUMEROUS MEMBERS ADVERTISING
WIND GUSTS OF 50 MPH AT STEVENS PASS. THE COMBINATION OF HEAVY
SNOW AND GUSTY WINDS COULD RESULT IN VERY CHALLENGING TRAVEL
CONDITIONS.
FORECAST SNOW LEVELS, SNOW RATIOS, AND QPF ARE LIKELY TO BE TWEAKED
SEVERAL TIMES AS WE GET CLOSER TO THE EVENT WHICH WILL IMPACT
SNOW AMOUNTS. THE MAIN MESSAGE AT THIS TIME IS TO BE PREPARED FOR
A POTENTIALLY SIGNIFICANT WINTER STORM TUE NT INTO WED IN CENTRAL
WA AND WINTER TRAVEL CONDITIONS FOR THE REMAINDER OF THE INLAND NW
OUTSIDE THE LOWER BASIN AND L-C VALLEY.
THURSDAY THROUGH SATURDAY: THERE IS AN 85% CHANCE FOR AN UNSETTLED
WEATHER PATTERN TO PERSIST THROUGHOUT THE WEEK. THE AXIS OF
MOISTURE THAT ARRIVES TUE-WED NEVER REALLY DISSIPATES. AT LEAST
TWO OTHER LOW PRESSURE SYSTEMS EJECTING THROUGH PAC NW WAVER THE
PLUME OF MOISTURE NORTH AND SOUTH WITH WARM/COLD FRONT PASSAGES.
SNOW LEVELS WILL RISE ON WEDNESDAY AND DO NOT LOOK TO LOWER BACK
TO VALLEY FLOORS FOR MOST AREAS SOUTH OF HIGHWAY 2 UNTIL THE
WEEKEND. THE NORTHERN VALLEYS WILL BE THE CHALLENGE AND HAVE THE
POTENTIAL TO EXPERIENCE AT LEAST ONE MORE ROUND OF LIGHT TO
MODERATE SNOW WITH SNOW LEVELS NEAR 1500-2000 FEET. HIGHEST
CONFIDENCE WOULD BE IN THE METHOW VALLEY AND ALONG THE IMMEDIATE
CANADIAN BORDER INCLUDING REPUBLIC, LAURIER, NORTHPORT, AND
PORTHILL. IT IS CONCEIVABLE THAT SOME OF THESE LOCATIONS REMAIN
SNOW UNTIL FRIDAY BUT THESE DETAILS WILL NEED TO BE IRONED OUT AS
WE GET CLOSER TO THE EVENT. /SB
AVIATION
18Z TAFS: LOW CLOUDS WILL HANG AROUND IN THE VALLEYS OF NORTHEAST
WASHINGTON AND IN THE IDAHO PANHANDLE INTO THE EARLY AFTERNOON
UNTIL THEY START TO LIFT AND DISSIPATE WITH VFR CONDITIONS
PREVAILING IN THE AFTERNOON. HOWEVER, A WINTER STORM MOVING IN
TONIGHT WILL RESULT IN DETERIORATING CONDITIONS WITH WIDESPREAD
PRECIPITATION ACROSS THE INLAND NORTHWEST STARTING AROUND 00Z FROM
KEAT-KMWH-KOMK-KCQV TO AROUND 03Z-05Z FROM KLWS-KGEG-KSFF-KCOE-
KDEW-KSZT. PRECIPITATION IS EXPECTED TO BEGIN AS SNOW OR A MIX
ACROSS THE SPOKANE/COEUR D'ALENE CORRIDOR TO SNOW FROM KCQV-KDEW-
KSZT. SNOW LEVELS WILL BE RISING THROUGH THE NIGHT WITH A CHANCE
OVER TO RAIN FROM SOUTH TO NORTH INTO SUNDAY MORNING.
PRECIPITATION INTENSITY MAY BE MODERATE AT TIMES WITH WIDESPREAD
IFR CONDITIONS (AT TIMES LOW IFR CONDITIONS) ACROSS THE NORTHERN
HALF OF THE REGION TO MVFR CONDITIONS FROM KEAT-KMWH-KPUW-KLWS.
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 IS ONLY MODERATE FOR PRECIPITATION TYPE AND TIMING OF
CHANGE OVER FROM SNOW TO RAIN ACROSS KGEG-KSFF-KCOE BETWEEN THE
06Z-12Z PERIOD TONIGHT. /SVH
-----------------------
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 40 32 45 30 40 25 / 10 100 100 70 40 40
COEUR D'ALENE 39 32 43 31 39 25 / 10 100 100 90 80 70
PULLMAN 40 31 43 30 38 23 / 0 100 100 90 80 70
LEWISTON 47 39 51 34 45 29 / 0 90 90 80 50 40
COLVILLE 37 27 43 21 38 16 / 40 100 100 60 40 40
SANDPOINT 38 30 41 30 36 23 / 20 100 100 90 90 80
KELLOGG 37 33 40 31 35 27 / 20 100 100 100 90 80
MOSES LAKE 42 34 50 28 45 22 / 20 80 50 20 0 10
WENATCHEE 42 34 48 30 44 26 / 30 80 60 20 10 20
OMAK 41 32 46 25 42 22 / 40 80 50 20 0 10
OTX WATCHES/WARNINGS/ADVISORIES
ID...WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 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 FROM 4 PM THIS AFTERNOON TO 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.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page