720
FXUS66 KOTX 152212
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
1013 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.
UPDATE
THE WINTER WEATHER ADVISORY FOR WESTERN CHELAN COUNTY WILL EXPIRE AT
10 AM.
DISCUSSION
REGIONAL RADAR RETURNS SHOW A DECREASING TREND IN SHOWER ACTIVITY
OVER THE CASCADE CREST AND STEVENS PASS. THE WEB CAM OVER STEVENS
PASS ALSO CONFIRMS THIS TREND WITH LITTLE IN THE WAY OF ADDITIONAL
SNOW EXPECTED TO ACCUMULATE THROUGH THE REST OF TODAY. THIS IS IN
RESPONSE TO A SHORTWAVE RIDGE OF HIGHER PRESSURE MOVING IN OVER THE
REGION WITH HIGHER HEIGHTS SUPPRESSING UPWARD MOTION. SCATTERED
SNOW SHOWERS WILL CONTINUE OVER THE IDAHO PANHANDLE TODAY. THESE
SHOWERS WILL BE LIGHT WITH MINIMAL ADDITIONAL SNOW ACCUMULATIONS
AND LITTLE TO NO IMPACTS. THE NEXT ROUND OF APPRECIABLE SNOW
ACCUMULATIONS WILL COME LATE TONIGHT INTO MONDAY WITH THE NEXT LOW
PRESSURE SYSTEM. SNOW WILL BEGIN TO FALL AROUND THE MORNING
COMMUTE, AND DISCUSSIONS ARE ONGOING FOR MESSAGING IMPACTS WITH
THIS NEXT WEATHER SYSTEM. /SVH
PREV DISCUSSION
/ISSUED 400 AM PST SUN DEC 15 2024/
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
18Z TAFS: AN MVFR DECK REMAINS OVER GEG, SFF, AND COE THIS MORNING,
BUT IS EXPECTED TO SCATTER OUT BY 20-22Z. LIGHT SNOW SHOWERS WILL
CONTINUE OVER PARTS OF THE IDAHO PANHANDLE INCLUDING SANDPOINT AND
MULLAN PASS THROUGH EARLY AFTERNOON WITH THE BEST CHANCES. BY LATE
AFTERNOON 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 INTO THE AFTERNOON BEFORE
SLOWING THIS EVENING. WINDS WILL SHIFT TO THE EAST TO SOUTHEAST THIS
EVENING AHEAD OF AN APPROACHING WARM FRONT. THE WARM FRONT WILL MOVE
INTO THE AREA NEAR THE END OF THE PERIOD WITH LIGHT SNOW BEGINNING
AT EAT/MWH AROUND 12Z. SNOW WILL SPREAD NORTHEASTWARD THROUGH THE
MORNING, REACHING GEG BETWEEN 14-15Z.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: THERE IS MODERATE
CONFIDENCE FOR CONDITIONS TO IMPROVE TO VFR THIS AFTERNOON FOR GEG,
SFF, AND 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 36 30 33 31 39 35 / 0 10 90 50 60 70
COEUR D'ALENE 36 30 33 30 38 35 / 10 10 90 70 60 70
PULLMAN 37 30 34 30 37 34 / 10 20 100 60 60 60
LEWISTON 45 33 38 34 44 39 / 0 10 90 50 40 30
COLVILLE 35 26 32 24 35 30 / 0 20 90 40 60 90
SANDPOINT 35 28 31 29 36 33 / 40 10 90 80 60 80
KELLOGG 34 29 33 31 38 36 / 60 10 100 90 70 80
MOSES LAKE 39 31 36 31 38 35 / 0 40 100 40 50 50
WENATCHEE 37 30 33 29 36 34 / 0 50 90 30 50 60
OMAK 37 28 33 27 35 33 / 0 40 90 20 50 80
OTX WATCHES/WARNINGS/ADVISORIES
ID...NONE.
WA...NONE.
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