710
FXUS66 KOTX 151103
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
303 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. SNOW SHOWERS MAY RESULT IN PERIODS OF INTENSE BURSTS OF
SNOW, ESPECIALLY FOR STEVENS PASS AND LOOKOUT PASS.
BEHIND THE UPPER LEVEL TROUGH, A TRANSIENT UPPER LEVEL RIDGE WILL
MOVE IN THIS AFTERNOON AND EVENING WHICH MAY ALLOW 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 NON-ACCUMULATING SNOW. FOR THE SPOKANE AREA, MODELS ARE
SHOWING SNOW BEGINNING OVER THE METRO RIGHT AROUND THE MORNING
COMMUTE TIME, WITH SOME UNCERTAINTY ON THE EXACT TIMING WITH THE
HREF GIVING THE EARLIEST ONSET OF SNOW FOR SPOKANE AS 6AM AND THE
LATEST AT 1PM.
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. THOSE HEADING OUT
MONDAY MORNING SHOULD ALLOT EXTRA TIME TO GET TO THEIR
DESTINATIONS. /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
06Z TAFS: COLD FRONT IS CURRENTLY PASSING THROUGH THE CASCADES AND
WILL PUSH THE WIDESPREAD STRATIFORM PRECIPITATION OVER EXTREME SE WA
AND NC ID (INCLUDING PUW AND LWS)EAST OF THESE SITES OVER THE NEXT
FEW HOURS. BRIEF MVFR CIGS ARE POSSIBLE AT THESE SITES, BUT FAR FROM
LIKELY. WHAT HAPPENS AS THE COLD FRONT MOVES IN IS TOUGHER TO
FIGURE. MANY OF THE HREF MODEL MEMBERS SUGGEST THAT AS THE HIGH
CLOUDS PUSH INTO MT TONIGHT, THAT WE WILL SEE LOW CLOUDS (IFR/MVFR)
FORMING BETWEEN PUW AND GEG AND EXTENDING EAST INTO NORTH ID. IF
THESE CLOUDS IN FACT FORM, THE LOW LEVEL S-SW WINDS COULD PUSH THESE
INTO GEG-SFF-COE SOMETIME AFTER 12Z, BUT WHETHER THEY MAKE IT THIS
FAR ISN'T CERTAIN. ADDING SLIGHTLY TO THE CHANCES WILL BE A WEAK
DISTURBANCE MOVING IN FROM THE SW AROUND THIS TIME WHICH MAY RESULT
IN SOME LIGHT SNOW SHOWERS. BY AFTERNOON AND EVENING WE THINK ALL
SITES SHOULD SEE VFR CONDITIONS, HOWEVER SOME LOW CLOUDS IN THE
VALLEYS NORTH AND EAST OF SPOKANE COULD PERSIST OF THE COLD FRONT
PASSAGE TONIGHT DOESN'T MIX THEM OUT. THE NEXT SYSTEM WILL MOVE OVER
THE AREA LATE IN THE PERIOD BRINGING INCREASING HIGH CLOUDS, BUT ANY
CHANCE OF PRECIPITATION (LIKELY SNOW) WILL HOLD OFF UNTIL AFTER
06Z.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: REDEVELOPMENT OF
STRATUS TOWARDS SUNRISE SUNDAY MORNING BETWEEN PULLMAN, SPOKANE, AND
COEUR D'ALENE IS MODERATE HOWEVER WHETHER OR NOT THIS MOVES INTO GEG-
SFF-COE IS FAR LESS CERTAIN. IF IT DOES MOVE IN AND AFFECT THESE
LOCATIONS IT COULD PERSIST INTO THE AFTERNOON RESULTING IN IFR/MVFR
CONDITIONS. FX
-----------------------
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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