873
FXUS66 KOTX 201153
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
353 AM PST FRI DEC 20 2024
SYNOPSIS
A RIDGE OF HIGH PRESSURE WILL RESULT IN A DRYING TREND AND CALMER
WINDS THROUGH FRIDAY WITH A RETURN OF AREAS OF STRATUS AND FOG.
UNSETTLED WEATHER WILL RETURN THIS WEEKEND AND CONTINUE INTO
NEXT WEEK. MILD TEMPERATURES WILL RESULT IN PRECIPITATION
FALLING PRIMARILY AS VALLEY RAIN AND MOUNTAIN SNOW. CHECK
MOUNTAIN PASS FORECASTS AND CONDITIONS OFTEN BEFORE TRAVELING.
DISCUSSION
TODAY THROUGH SUNDAY: RIDGING TO OUR EAST WILL KEEP US IN AN ACTIVE
SOUTHWESTERLY FLOW REGIME WITH THREE DISTINCT SHORTWAVES ON TRACK TO
RIPPLE THROUGH THE INLAND NORTHWEST BY THE END OF THE WEEKEND. THE
FIRST OF THE THREE WAVES WILL BE THE WEAKEST AND WILL PASS THROUGH
DURING THE DAY TODAY. THIS WAVE WILL BRING WINTRY PRECIPITATION TO
THE CASCADE CREST WHILE THE REST OF THE REGION STAYS DRY.
OUR SECOND WAVE WILL MOVE IN TOMORROW AND WILL BRING MORE WIDESPREAD
PRECIPITATION. FOR THE CASCADE CREST AND NORTHERN MOUNTAINS
PRECIPITATION WILL BE IN THE FORM OF SNOW, AND FOR VALLEYS JUST EAST
OF THE CASCADES AND MORE SHELTERED NORTHERN VALLEYS WHERE COLD AIR
HAS A HARDER TIME MIXING AWAY FROM THE SURFACE, PERIODS OF FREEZING
RAIN WILL BE POSSIBLE. LOWLANDS/VALLEYS ELSEWHERE WILL SEE RAIN.
THE THIRD WAVE WILL ARRIVE LATE SUNDAY MORNING AND WILL BRING
PRECIPITATION OVERNIGHT INTO MONDAY. HEAVIER SNOW IN THE CASCADES IS
EXPECTED WITH THIS WAVE, WITH 6 TO 9 INCHES IN THE FORECAST FOR
STEVENS PASS. FREEZING RAIN WILL ONCE AGAIN BE POSSIBLE FOR THE
CASCADE VALLEYS AND NORTHERN VALLEYS WITH ACCUMULATIONS UP TO 0.15
INCHES POSSIBLE. DAYTIME HIGHS WILL BE IN THE 30S TO LOW 40S, AND
LOWS WILL BE IN THE 20S TO LOW 30S. /FEWKES
MONDAY AND TUESDAY: THE PERIOD STARTS UNDER WEEKEND TROUGH
CONTINUING TO BRING MOUNTAIN SNOW AND VALLEY RAIN TO THE REGION.
THE ACTIVITY WILL SLOWLY TAPER OFF THROUGH THE MORNING. MONDAY
AFTERNOON IS EXPECTED TO BE RELATIVELY QUIET. THE NEXT ROUND OF
PRECIP IS EXPECTED ARRIVE EARLY TUESDAY MORNING. IT WILL BRING
ANOTHER ROUND OF WIDESPREAD MOUNTAIN SNOW AND VALLEY RAIN TO THE
REGION. SNOW AMOUNTS FOR THE WILL BE HIGHEST IN THE CASCADES WITH
STEVENS PASS RECEIVING 4 TO 8 INCHES. HIGHS WILL CONTINUE TO BALMY
WITH THE SOUTHERN FLOW PATTERN. THE RANGE WILL BE IN 30S TO MID 40S.
OVERNIGHT LOWS WILL BE IN THE UPPER 20S AND 30S.
WEDNESDAY THROUGH FRIDAY: WEDNESDAY WILL START RELATIVELY CALM AS A
BRIEF SHORTWAVE RIDGE BUILDS IN BEHIND THE EXITING SYSTEM. IT WILL
BE SHORT LIVED AS ENSEMBLES BRING A MORE ROBUST COLDER WAVE ACROSS
THE PACIFIC NORTHWEST. WITH THE COLDER AIR MASS, MOUNTAIN SNOW WILL
CONTINUE WITH STEVENS PASS HAVING A 70% PROBABILITY OF 6 INCHES AND
20% OF ONE FOOT. REST OF THE MOUNTAIN AREAS RANGE FROM 4 TO 8
INCHES. THE COLDER AIR CAN BRING SNOW TO THE VALLEYS AND NORTHERN
PORTION OF THE BASIN. THE PROBABILITY OF AN INCH RANGE FROM 60 TO 80
PERCENT FOR WEDNESDAY NIGHT INTO THURSDAY MORNING. SPOKANE IS AROUND
20 PERCENT FOR ONE INCH OF SNOW. BY FRIDAY, THE REGION WILL BE UNDER
A ZONAL FLOW PATTERN WITH SEVERAL WAVES OF MOISTURE. WHILE IT IS
EXPECTED TO CONTINUE TO BE MOUNTAIN SNOW, THERE IS LOW CONFIDENCE ON
THE PRECIP TYPE FOR THE LOWER ELEVATIONS. TEMPERATURES IN THE AREA
LEAN MORE TOWARD RAIN AND WINTRY MIX. HIGHS WILL BE IN THE 30S.
OVERNIGHT LOWS WILL BE IN THE UPPER 20S AND 30S. /JDC
AVIATION
12Z TAFS: PATCHY FOG AND LOW CEILINGS HAVE RETURNED IN THE VALLEYS
OF NORTHERN WA AND THE ID PANHANDLE AS WELL AS AROUND KMWH.
SATELLITE IMAGERY IS SHOWING FOG ATTEMPTING TO CREEP INTO THE
GEG/COE AREA, SO DEVELOPMENT OF IFR CEILINGS AND REDUCED
VISIBILITIES WILL BE POSSIBLE FOR THOSE SITES THROUGH THE MORNING.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
THERE IS HIGH CONFIDENCE FOR IFR CONDITIONS PERSISTING AT MWH
THROUGH 14Z. LOW CONFIDENCE ON IF/WHEN IFR CONDITIONS WILL DEVELOP
AT GEG/COE.
-----------------------
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 42 31 43 33 43 36 / 10 0 70 80 0 90
COEUR D'ALENE 45 32 43 34 42 36 / 10 10 60 90 0 90
PULLMAN 46 35 45 31 42 36 / 10 0 60 80 0 100
LEWISTON 51 38 47 36 47 39 / 0 0 40 50 0 90
COLVILLE 40 29 39 31 38 33 / 10 10 70 80 20 100
SANDPOINT 42 33 40 32 42 30 / 10 10 50 100 10 90
KELLOGG 46 36 48 36 43 37 / 10 10 60 100 10 90
MOSES LAKE 43 31 40 32 43 34 / 10 0 90 20 30 80
WENATCHEE 41 34 40 33 38 33 / 10 0 90 10 50 90
OMAK 40 37 41 32 41 32 / 10 0 80 30 30 90
OTX WATCHES/WARNINGS/ADVISORIES
ID...NONE.
WA...NONE.
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