692
FXUS66 KOTX 151200
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
400 AM PST SUN DEC 15 2024
SYNOPSIS
SUNSHINE IS EXPECTED ACROSS MUCH OF CENTRAL AND EASTERN
WASHINGTON ON SUNDAY, BUT THE SUN WON'T LAST LONG. ON MONDAY A
SWATH OF LIGHT SNOW WILL SPREAD ACROSS THE INLAND NORTHWEST.
TUESDAY THROUGH THE WEEKEND WILL FEATURE TEMPERATURES IN THE 30S
AND 40S WITH PRECIPITATION MAINLY CONFINED TO THE MOUNTAINOUS
TERRAIN.
DISCUSSION
SUNDAY: SATELLITE IMAGERY EARLY THIS MORNING REVEALS HIGH LEVEL
CLOUDS CLEARING FROM WEST TO EAST AS DRIER AIR AND SURFACE PRESSURE
RISES BEHIND THIS EVENING’S COLD FRONT PASSAGE. BREEZY SOUTHWEST
SURFACE WINDS ARE BEING FELT ACROSS EXPOSED AREAS OF EASTERN
WASHINGTON EARLY THIS MORNING IN RESPONSE. EARLY TODAY, AN UPPER
LEVEL TROUGH WILL SHIFT OVER THE INLAND NORTHWEST WITH SNOW SHOWERS
CONTINUING OVER THE CASCADE CREST AND THE IDAHO PANHANDLE THROUGH
THE MORNING FOR THE CASCADES AND THROUGH THE AFTERNOON FOR THE IDAHO
PANHANDLE. BRIEF PERIODS OF MODERATE TO HEAVY SNOWFALL RATES WILL
BE POSSIBLE WITH THESE SNOW SHOWERS OVER STEVENS AND LOOKOUT
PASSES THIS MORNING.
BEHIND THE UPPER LEVEL TROUGH, A TRANSIENT UPPER LEVEL RIDGE WILL
MOVE IN THIS AFTERNOON AND EVENING WHICH WILL FOR A MAJORITY OF
CENTRAL AND PARTS OF EASTERN WASHINGTON TO SEE SUN TODAY.
SUNDAY NIGHT AND MONDAY: THE NEXT SYSTEM WILL MOVE IN QUICKLY
BEHIND THE FRONT SUNDAY NIGHT INTO EARLY MONDAY MORNING THAT WILL
BRING WIDESPREAD SNOW TO EASTERN WASHINGTON AND NORTH IDAHO. A
WARM FRONT ASSOCIATED WITH AN OCCLUDED LOW PRESSURE SYSTEM
OFFSHORE WILL LIFT NORTHWARD LATE TONIGHT. UPSLOPE EASTERLY FLOW
AT THE SURFACE THIS EVENING WILL ALLOW FOR PRECIPITATION TO BEGIN
FOR THE LEE OF THE CASCADES SUNDAY NIGHT WITH PRECIPITATION
SPREADING NORTHWARD THROUGH MONDAY MORNING.
THANKS TO THE COLD FRONT PASSAGE THIS EVENING, SNOW LEVELS DOWN TO
THE VALLEY FLOOR SHOULD SUPPORT A PRIMARILY SNOW EVENT ACROSS THE
REGION. THE EXCEPTION WILL BE FOR THE LOWER SPOTS IN THE COLUMBIA
BASIN AND THE L-C VALLEY WHERE MARGINAL TEMPERATURES WILL KEEP THEM
AS RAIN OR A WET SNOW. FOR THE SPOKANE AREA, MODELS ARE SHOWING
SNOW BEGINNING OVER THE METRO RIGHT AROUND THE MORNING COMMUTE
TIME. THERE IS SOME SOME UNCERTAINTY ON THE EXACT TIMING OF THE
PRECIPITATION ONSET WITH THE EARLIEST MEMBER OF HREF HAVING SNOW
BEGINNING AROUND SPOKANE AT 6AM AND THE LATEST MEMBER AT 1PM. THE
DIFFERENCE IN ONSET TIMES WILL PLAY A LARGE ROLE IN THE OVERALL
IMPACTS AS AN EARLIER ONSET WOULD RESULT IN A TRICKY MORNING
COMMUTE AND A LATER ONE BRINGING A TRICKY EVENING COMMUTE. WITH
ALL THAT SAID, OUR CURRENT FORECAST ALIGNS CLOSER WITH THE EARLIER
HREF MEMBERS WITH SNOW BEGINNING AROUND 6/7AM. THOSE HEADING OUT
EARLY MONDAY MORNING SHOULD ALLOW FOR EXTRA TIME TO GET TO YOUR
DESTINATION SAFELY.
ON AVERAGE 24 HOUR SNOW AMOUNTS IN THE LOWLANDS ARE FORECAST TO
BETWEEN 1 TO 4 INCHES FOR THE CASCADE VALLEYS AND WATERVILLE
PLATEAU, 1 TO 3 INCHES IN THE NORTHEAST MOUNTAINS, SPOKANE/CDA
AREAS, AND THE IDAHO PANHANDLE VALLEYS. FOR THE SPOKANE AREA, THE
HIGHER END OF THE SNOW SPECTRUM WILL BE FELT ACROSS THE HIGHER
BENCHES. LOWER SPOTS IN DOWNTOWN SPOKANE THROUGH LIBERTY LAKE
WILL BE ON THE LOWER END OF THE SNOW SPECTRUM WITH TEMPERATURES
SUPPORTING A RAIN/SNOW MIX MONDAY AFTERNOON. /VMT
TUESDAY THROUGH SUNDAY: THE REGION WILL REMAIN UNDER A STEADY STREAM
OFF OF WEAK SHORTWAVES WIDESPREAD SHOWERS ACROSS THE INLAND
NORTHWEST. THESE WAVES WILL BE DRAWING WARMER AIR FROM THE SOUTH.
FOR TUESDAY, THERE IS BROAD COVERAGE OF SNOW ACROSS THE REGION.
ACCUMULATIONS ARE EXPECTED TO BE LESS THAN MONDAY. THE WARMER AIR
WILL LEAD TO PRECIP TYPE TO BECOME MAINLY LOW LAND RAIN AND MOUNTAIN
SNOW. HIGHEST PRECIP WILL BE ALONG THE CASCADES WITH STEVENS PASS
RECEIVING NEAR HALF AN INCH ON TUESDAY. THE REST OF THE REGION WILL
BE AROUND 2 TENTHS OF AN INCH. THE REST OF THE PERIOD PRECIP TOTALS
ARE EXPECTED TO BE AROUND A TENTH OF AN INCH OR LESS PER 24 HOUR
PERIOD. HIGHS FOR THE PERIOD WILL BE IN THE 30S TO LOW 40S. LOWS
WILL BE IN THE 20S TO LOW 30S. MODELS ARE HINTING AT A MORE ROBUST
SYSTEM WILL IMPACT THE REGION FOR NEXT WEEK. /JDC
AVIATION
12Z TAFS: AS OF 12Z, THE EDGE OF THE HIGH LEVEL CLOUDS IS
BEGINNING TO MOVE THROUGH GEG. ALTHOUGH A BIT EARLIER THAN WHAT
THE HREF WAS PROJECTING, MVFR CONDITIONS HAVE REDEVELOPED AT SFF-
COE-DEW THIS MORNING. FOLLOWING A SIMILAR TREND, A MVFR OR IFR
DECK SHOULD FILL INTO GEG IN THE NEXT 1-2 HOURS. THERE WILL BE A
SLIGHT CHANCE FOR SNOW SHOWERS OVER THE IDAHO PANHANDLE THIS
MORNING AND EARLY AFTERNOON WITH THE BEST CHANCES OVER COE.
BY AFTERNOON AND EVENING ALL SITES SHOULD IMPROVE TO VFR CONDITIONS,
HOWEVER SOME LOW CLOUDS IN THE VALLEYS NORTH AND EAST OF SPOKANE
COULD PERSIST. BREEZY SOUTHWEST WINDS WILL CONTINUE THROUGH THE
EARLY MORNING AND BEGIN TO DECLINE THIS AFTERNOON. WINDS WILL
SHIFT TO THE EAST TO SOUTHEAST THIS EVENING AHEAD OF AN APPROACHING
WARM FRONT. WARM FRONT WILL MOVE INTO THE AREA NEAR THE END OF
THE PERIOD WITH LIGHT SNOW BEGINNING AT EAT/MWH BEFORE 12Z. SNOW
WILL SPREAD NORTHEASTWARD THROUGH THE MORNING, REACHING GEG
BETWEEN 14-15Z.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: MODERATE
CONFIDENCE FOR MVFR/IFR CONDITIONS THROUGH THE EARLY AFTERNOON FOR
GEG/SFF/COE. THERE IS HIGH CONFIDENCE FOR CONDITIONS TO IMPROVE TO
VFR BUT THERE STILL EXISTS A 30-40 PERCENT CHANCE FOR MVFR
CEILINGS TO PERSIST.
-----------------------
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 36 30 33 31 37 33 / 10 10 90 50 30 50
COEUR D'ALENE 36 30 33 30 37 33 / 20 10 90 70 30 50
PULLMAN 37 30 34 30 36 32 / 20 20 100 60 40 30
LEWISTON 45 33 38 34 42 35 / 10 10 90 50 30 20
COLVILLE 35 26 32 24 34 28 / 0 20 90 40 40 60
SANDPOINT 35 28 31 29 34 32 / 40 10 90 80 50 70
KELLOGG 34 29 33 31 37 34 / 70 10 100 90 60 50
MOSES LAKE 39 31 36 31 37 32 / 0 40 100 40 30 40
WENATCHEE 37 30 33 29 35 32 / 0 50 90 30 30 50
OMAK 37 28 33 27 34 30 / 0 40 90 20 30 60
OTX WATCHES/WARNINGS/ADVISORIES
ID...NONE.
WA...WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING FOR WESTERN
CHELAN COUNTY.
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