378
FXUS66 KOTX 160514
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
914 PM PST SUN DEC 15 2024
SYNOPSIS
LIGHT SNOW WILL INCREASE ACROSS THE REGION LATE TONIGHT INTO
MONDAY. SNOW WILL BEGIN BY EARLY MORNING IN THE CASCADES AND THEN
SPREAD INTO THE IDAHO PANHANDLE BY THE LATE MORNING HOURS. A
WETTER WEATHER SYSTEM IS EXPECTED TUESDAY INTO TUESDAY NIGHT WITH
RISING SNOW LEVELS. SNOW WILL MAINLY ACCUMULATE OVER HIGH MOUNTAINS
AND IN NORTH-CENTRAL WASHINGTON INCLUDING THE EASTERN CASCADE
VALLEYS. THIS WET SYSTEM WILL BE FOLLOWED BY BREEZY WINDS
WEDNESDAY AFTERNOON. THE REST OF THE WEEK WILL FEATURE MILD
TEMPERATURES AND INTERMITTENT LIGHT PRECIPITATION PRIMARILY
CONFINED TO THE NORTHERN MOUNTAINS.
DISCUSSION
KEY POINTS:
* LIGHT SNOW EXPECTED TONIGHT THROUGH MONDAY NIGHT WITH TRAVEL
IMPACTS THAT INCLUDES THE MORNING AND EVENING COMMUTING PERIODS.
* ATMOSPHERIC RIVER TUESDAY INTO WEDNESDAY BRINGING MOUNTAIN SNOW
AND VALLEY RAIN ACROSS THE INLAND NORTHWEST.
* FREEZING RAIN POSSIBLE FOR EASTERN CASCADE VALLEYS WEDNESDAY
MORNING.
TONIGHT THROUGH TUESDAY: A BRIEF BREAK IN PRECIPITATION THIS EVENING
BEFORE THE NEXT WEATHER SYSTEM BRINGS WIDESPREAD LIGHT SNOW ACROSS
MUCH OF THE REGION LATE TONIGHT THROUGH MONDAY. THE ABSENCE OF CLOUD
COVER OVER MUCH OF THE REGION WILL RESULT IN EFFICIENT RADIATIVE
COOLING WITH TEMPERATURES DROPPING INTO THE 20S TO LOWER 30S
ACROSS MUCH OF THE LOWLANDS. A WARM FRONT WILL THEN SPREAD
MOISTURE ACROSS THE REGION LATE TONIGHT INTO EARLY MONDAY.
EASTERLY FLOW AT LOWER LEVELS WILL FAVOR UPSLOPE FLOW INTO THE
EAST SLOPES OF THE CASCADES WITH PRECIPITATION BEGINNING BY THE
EARLY MORNING HOURS BETWEEN 1-4 AM FOR PLACES LIKE LEAVENWORTH,
PLAIN, LAKE WENATCHEE, AND TRAVEL UP AND OVER STEVENS PASS. I WILL
TAKE LONGER FOR THE ATMOSPHERE TO MOISTEN FROM THE TOP DOWN
ACROSS THE BASIN INTO THE IDAHO PANHANDLE. EASTERLY TO
NORTHEASTERLY WINDS OFF OF THE HIGHER TERRAIN IN THE IDAHO
PANHANDLE WILL COUNTERACT THE MOISTEN EFFECTS OF THE ISENTROPIC
ASCENT ALONG THE WARM FRONT. THERE IS MORE UNCERTAINTY WITH WHEN
SNOW MAY BEGIN ACROSS EXTREME EASTERN WASHINGTON AND IN THE IDAHO
PANHANDLE BECAUSE OF THE BROAD DOWNSLOPING EFFECTS. SOME OF THE
HIGH RESOLUTION MODEL GUIDANCE HAS SNOW BEGINNING RIGHT AROUND THE
TAIL END OF THE MORNING COMMUTE ACROSS SPOKANE TO COEUR D'ALENE,
WHEREAS OTHERS HAVE SNOW BEGINNING AFTER 10 AM. I TEND TO LEAN
TOWARD A LATER INITIATION TIME FOR SNOW CLOSER TO THE IDAHO
PANHANDLE DUE TO DOWNSLOPING FLOW PREVIOUSLY HIGHLIGHTED.
SNOWFALL OVER EXTREME EASTERN WASHINGTON INTO THE IDAHO PANHANDLE
LOOKS TO PICK UP FOR THAT LATE MORNING INTO EARLY AFTERNOON HOURS.
WESTERLY UPSLOPE FLOW WITH THE PASSAGE OF THE COLD FRONT WILL
KEEP SNOW GOING ACROSS THE CENTRAL PANHANDLE MOUNTAINS THROUGH
MONDAY NIGHT. OVERALL, SNOW AMOUNTS LOOK TO RANGE BETWEEN 1 TO 3
INCHES IN THE LOWLANDS. THE EXCEPTION WILL BE LEAVENWORTH AND
PLAIN WHERE MORE LIKE 2 TO 4 INCHES IS EXPECTED. THE MOUNTAIN
PASSES WILL SEE THE POTENTIAL FOR UP TO AROUND 5 INCHES THROUGH
THE COURSE OF THIS WEATHER SYSTEM. A WINTER WEATHER ADVISORY IS IN
EFFECT TO HIGHLIGHT THE LIGHT SNOW POTENTIAL WITH IMPACTS DURING
THE COMMUTING PERIODS TOMORROW. IMPACTS WILL BE MINOR, BUT EXPECT
THE POTENTIAL FOR SLICK TRAVEL CONDITIONS WITH SNOW: REDUCE SPEEDS
AND INCREASE FOLLOWING DISTANCE TO MITIGATE THE RISK FOR WINTER
RELATED ACCIDENTS TO OCCUR.
THE BOUNDARY LAYER WILL BE MOIST MONDAY NIGHT INTO TUESDAY WITH THE
POTENTIAL FOR LOW STRATUS OR FOG. SYNOPTICALLY, ITS NOT A GREAT SET
UP FOR FOG TO FORM, BUT THE NORTHERN PORTION OF THE BASIN INTO THE
NORTHERN MOUNTAIN VALLEYS WILL BE MORE FAVORED FOR FOG TO FORM.
ANOTHER WEAK SHORTWAVE DISTURBANCE WILL MOVE ACROSS MONDAY NIGHT
INTO EARLY TUESDAY REINFORCING LIGHT SNOW AT THE CASCADE CREST AND
OVER THE CENTRAL PANHANDLE MOUNTAINS. THIS WILL PRECEDE A WARM FRONT
THAT PUSHES NORTHWARD WITH A WEAK ATMOSPHERIC RIVER (AR) THAT WILL
POINT INTO THE NORTHWEST BY TUESDAY AFTERNOON AND FURTHER ON INTO
THE FORECAST PERIOD. READ ON FOR ADDITIONAL IMPACTS WITH THIS EVENT.
/SVH
TUESDAY NIGHT THROUGH SATURDAY: WE'LL REMAIN IN A PROGRESSIVE
WEATHER PATTERN THROUGH THE END OF THE FORECAST PERIOD WITH A SERIES
OF SHORTWAVES ON TRACK TO MOVE THROUGH THE REGION, BRINGING ABUNDANT
MOISTURE AND WARMER AIR UP FROM THE SOUTHWEST. CHANCES FOR SNOW WILL
LINGER THROUGH TUESDAY NIGHT FOR LOCATIONS JUST EAST OF THE CASCADES
INCLUDING THE OKANOGAN AND METHOW VALLEYS, LEAVENWORTH, AND
WENATCHEE WHERE LINGERING COLD AIR FROM MONDAY'S SYSTEM WILL BE
SHELTERED BY THE MOUNTAINS AND THEREFORE HARDER FOR THE INCOMING
WARMER AIR TO SCRUB OUT. AS WARM, SOUTHWESTERLY FLOW MOVES IN HIGHER
UP IN THE ATMOSPHERE, THE AFOREMENTIONED SHELTERED LOCATIONS COULD
SEE A BRIEF PERIOD OF FREEZING RAIN WEDNESDAY MORNING DUE TO COLD
AIR STILL BEING IN PLACE AT THE SURFACE. BY WEDNESDAY AFTERNOON, THE
WARMER AIR SHOULD BE ABLE TO MIX DOWN TO THE SURFACE, BRINGING
TEMPERATURES ABOVE FREEZING AND CHANGING THE PRECIPITATION TYPE OVER
TO RAIN REGIONWIDE. HEADING INTO WEDNESDAY NIGHT, CHANCES FOR PRECIP
WILL RECEDE TO THE MOUNTAINS, AND THE LOWLANDS WILL SEE MAINLY DRY
CONDITIONS FOR THE REMAINDER OF THE WORKWEEK. DAYTIME HIGH
TEMPERATURES WILL BE IN THE 30S TO MID 40S AND OVERNIGHT LOWS WILL
BE IN THE 20S AND 30S. MORE WIDESPREAD PRECIPITATION CHANCES LOOK TO
RETURN OVER THE WEEKEND. /FEWKES
AVIATION
06Z TAFS: VFR CONDITIONS CONTINUE BETWEEN WEATHER SYSTEMS. A
STRATUS DECK WITH CEILINGS BETWEEN 3-5 KFT AGL. WILL BECOME
PRESENT OVER NORTHEAST WASHINGTON INTO THE IDAHO PANHANDLE.
EASTERLY TO NORTHEASTERLY WINDS OVER THIS PORTION OF THE REGION
WILL KEEP CEILINGS FROM LOWER THROUGH THE EVENING THOUGH. A WARM
FRONT AND SPREAD LIGHT SNOW ACROSS THE REGION STARTING KEAT TO
KMWH BETWEEN 09-13Z, AND MAY SEE MODERATE SNOW INTENSITY AT TIMES
INTO THE EAST SLOPES OF THE CASCADES AS EASTERLY FLOW WILL CREATE
MORE FAVORABLE UPSLOPE FLOW. SNOW MAY START NEAR 15-18Z NEAR KGEG
AND VICINITY. EXPECT SNOW TO BE LIGHT, BUT DETERIORATING
CONDITIONS WITH IFR TO LOW IFR CONDITIONS THROUGH THE DAY MONDAY.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: THERE IS HIGH
CONFIDENCE ON IFR TO LOW IFR CONDITIONS WITH SNOW ON MONDAY.
CONFIDENCE REMAINS HIGH THAT WIDESPREAD FOG OR LOW STRATUS WITH
IFR CONDITIONS PREVAILING ACROSS MUCH OF THE REGION AS SNOW ENDS
INTO MONDAY EVENING.
-----------------------
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 30 34 31 37 35 47 / 10 90 60 60 60 70
COEUR D'ALENE 29 34 31 37 35 45 / 10 90 80 60 70 80
PULLMAN 30 34 32 37 34 46 / 10 100 70 60 50 60
LEWISTON 33 39 35 43 39 52 / 10 90 50 40 30 40
COLVILLE 26 32 29 34 30 42 / 10 90 60 60 80 80
SANDPOINT 28 32 30 35 31 41 / 10 90 80 60 70 90
KELLOGG 29 34 32 37 36 43 / 10 100 90 70 70 80
MOSES LAKE 31 36 32 38 35 45 / 40 100 40 50 40 40
WENATCHEE 30 34 30 35 34 43 / 60 90 30 50 60 60
OMAK 28 34 28 34 30 39 / 30 90 10 50 70 70
OTX WATCHES/WARNINGS/ADVISORIES
ID...WINTER WEATHER ADVISORY FROM 7 AM TO 10 PM PST MONDAY FOR COEUR
D'ALENE AREA-IDAHO PALOUSE-NORTHERN PANHANDLE.
WINTER WEATHER ADVISORY FROM 10 AM MONDAY TO 7 AM PST TUESDAY
FOR CENTRAL PANHANDLE MOUNTAINS.
WA...WINTER WEATHER ADVISORY FROM 7 AM TO 10 PM PST MONDAY FOR
NORTHEAST MOUNTAINS-SPOKANE AREA-WASHINGTON PALOUSE.
WINTER WEATHER ADVISORY FROM 7 AM TO 5 PM PST MONDAY FOR
OKANOGAN HIGHLANDS-UPPER COLUMBIA BASIN.
WINTER WEATHER ADVISORY FROM 1 AM TO 1 PM PST MONDAY FOR CENTRAL
CHELAN COUNTY-OKANOGAN VALLEY-WATERVILLE PLATEAU-WENATCHEE
AREA-WESTERN CHELAN COUNTY-WESTERN OKANOGAN COUNTY.
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