946
FXUS66 KOTX 191203
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
403 AM PST WED FEB 19 2025
SYNOPSIS
AN INCOMING WEATHER SYSTEM ARRIVES TODAY BRINGING WIDESPREAD SNOW
AND RAIN. WARMER TEMPERATURES AND RAIN ARRIVE LATE IN THE WEEK
INTO NEXT WEEKEND AS HIGH TEMPERATURES WARM INTO THE 40S. THIS
WILL RESULT IN MELTING SNOW ACROSS THE LOWER ELEVATIONS. RAIN AND
SNOWMELT EXPECTED TO LEAD TO LOCAL HYDRO ISSUES FOR LOW LYING AND
POOR DRAINAGE AREAS.
DISCUSSION
TODAY THROUGH THURSDAY: THE MOISTURE ASSOCIATED WITH THE INCOMING
LOW IS BEGINNING TO PRESS INTO THE INLAND NORTHWEST. ENSEMBLES
HAVE ADJUSTED THE TRACK FURTHER NORTH THAN PREVIOUS RUNS. IT IS
ALLOWING SLIGHTLY WARMER TEMPERATURES INTO THE LOW LEVELS FROM
PREVIOUS RUNS AND MUTING THE COLD AIR INTRUSION INTO NORTH
WASHINGTON AND IDAHO. IT HAS ALSO BROUGHT MORE MOISTURE INTO THE
METHOW VALLEY INCREASING EXPECTED SNOW AMOUNTS TO 2-4 INCHES. THE
REST OF THE REGION IS NEAR THE SAME PREVIOUS FORECAST WITH THE
HIGHER TERRAINS COULD SEE ANOTHER 4-9 INCHES THROUGH THURSDAY. THE
LOW LANDS COULD SEE ANOTHER 1-4 INCHES. THE BEST POTENTIAL THESE
AMOUNTS IS OVER THE WATERVILLE PLATEAU DOWN TO WENATCHEE AND
LEAVENWORTH. THE TIMING OF THE SNOW IS IS EXPECTED TO CAUSE
MORNING COMMUTE ISSUES FOR THE CASCADES VALLEYS THROUGH THE
MORNING. POCKETS OF FREEZING PRECIP ARE POSSIBLE SOUTH OF I-90
NEAR MOSES LAKE THROUGH THE MORNING. AS THE SYSTEM CONTINUES EAST,
WARMING TEMPERATURES COULD LIMIT THE SNOW AMOUNTS FOR EASTERN
WASHINGTON AND THE IDAHO PANHANDLE FOR THIS AFTERNOON WITH AREAS
SEEING AN INCH OR TWO. BY THURSDAY REMNANTS OF THE WAVE WILL
CONTINUE TO BRING LIGHT SNOW SHOWERS TO THE IDAHO PANHANDLE WITH
AMOUNTS UP TO INCH POSSIBLE. HIGHS FOR THE PERIOD WILL BE IN THE
UPPER 20S TO LOW 40S. OVERNIGHT LOWS WILL BE IN THE UPPER TEENS TO
20S. /JDC
FRIDAY THROUGH TUESDAY: THE INLAND NORTHWEST WILL BEGIN A TRANSITION
INTO A WARMER AND WET PERIOD AS A FLAT UPPER LEVEL RIDGE SHIFTS INTO
THE REGION. AN ACTIVE WEATHER PATTERN WITHIN THE GULF OF ALASKA WILL
KEEP A SOUTHWEST FLOW ALOFT AIMED AT THE NORTHWEST WITH SEVERAL
EMBEDDED SYSTEMS TO PASS THROUGH THE REGION.
MODELS CONTINUE TO BRING A WEAK FRONT THROUGH THE PACIFIC NORTHWEST
FRIDAY NIGHT, WITH LOW CONFIDENCE IN MEASURABLE PRECIPITATION ACROSS
THE INLAND NORTHWEST. MOST MODELS KEEP PRECIPITATION OVER THE
MOUNTAINS, BUT SEVERAL MEMBERS OF THE GEFS WANT TO BRING
PRECIPITATION AS FAR SOUTH AS THE SPOKANE AREA. REGARDLESS,
PRECIPITATION TOTALS WOULD BE LIGHT.
THE MOST SIGNIFICANT PERIOD OF THE EXTENDED FORECAST WILL BE
SATURDAY EVENING THROUGH SUNDAY AS A MODERATE TO STRONG ATMOSPHERIC
RIVER TAKES AIM AT THE NORTHWEST. WITH BOTH THE GEFS AND ECMWF
ENSEMBLES SHOWING PWATS OVER THE INLAND NORTHWEST INCREASING TO
0.75+ INCHES, THERE IS HIGH CONFIDENCE IN WIDESPREAD PRECIPITATION
AS A WARM FRONT LIFTS NORTH SATURDAY NIGHT. PRECIPITATION WILL FALL
PRIMARILY AS LOWLAND RAIN AND MOUNTAIN SNOW, ALTHOUGH SNOW WILL BE
FAVORED FOR THE METHOW VALLEY WHERE COLD AIR WILL TAKE LONGER TO
FULLY SCRUB OUT.
FOLLOWING A PERIOD OF COLD AND SNOW, THESE CONDITIONS RAISE CONCERNS
FOR RAPID SNOWMELT ACROSS THE LOWLANDS, POTENTIALLY LEADING TO RISES
IN SMALLER CREEKS AND STREAMS AND LOCALIZED FIELD FLOODING. AREAS OF
CONCERN INCLUDE SPOKANE COUNTY AND THE WASHINGTON AND IDAHO PALOUSE,
WHERE THERE IS AMPLE LOWLAND SNOW AND THE GFS AND NBM ARE INDICATING
A 30 TO 60% CHANCE OF RAPID ONSET FLOODING DURING THIS TIME PERIOD.
PARADISE CREEK IN MOSCOW CONTINUES TO BE FORECASTED TO EXCEED MINOR
FLOOD STAGE SUNDAY NIGHT.
PREPARATION AHEAD OF THIS EVENT IS ADVISED, SUCH AS CLEARING GUTTERS
AND STORM DRAINS OF COMPACTED SNOW AND DEBRIS TO HELP MINIMIZE
FLOODING IMPACTS.
ACTIVE WEATHER WILL CONTINUE INTO EARLY NEXT WEEK WITH MODELS
SHOWING THE NEXT SYSTEM TO MOVE INTO THE PNW SOMETIME BETWEEN MONDAY
AND TUESDAY. THERE ARE SIGNIFICANT DIFFERENCES AMONG ENSEMBLES IN
THE EXACT TIMING THOUGH, BUT THIS WILL CONTINUE TO BE MONITORED.
/VMT
AVIATION
12Z TAFS: THE LINE OF MOSIUTRE ASSOCIATED ITH THE INCOMING SYSTEM
IS BEGINNING TO IMPACT KEAT. IT WILL CONTINUE TO SPREAD EAST AND
NORTH THROUGH THE TAF PERIOD. P-TYPE AT KEAT, KMWH, AND KOMK
COULD START AS WET SNOW OR RAIN/SNOW MIX WITH TRANSITION
-SN WITH BRIEF PERIODS OF SN AS THERMAL PROFILES COOL. LOWEST
CONFIDENCE AROUND KMWH AND POINTS SOUTH WHICH WILL BE CLOSER TO
THE RAIN/SNOW LINE. POCKETS OF -FZRA ALSO POSSIBLE BUT WITH LOW
CONFIDENCE. TIMING BRINGS STEADY PRECIPITATION TO KEAT- KOMK
11-13Z, KCQV- RITZVILLE 14-15Z, AND KGEG, KCOE, AND KPUW 17-19Z. A
WEDGE OF WARMER AIR WILL BRING 80% CHANCE FOR TRANSITION TO RAIN
INTO THE CENTRAL- EASTERN BASIN AND AS FAR NORTH AS THE SPOKANE-
CD'A AREA. THE WARMER AIR OVERRUNNING THE SNOWPACK HAS A HISTORY
OF PRODUCING VERY LOW CEILINGS AROUND SPOKANE AND LOW VISIBILITY.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: THE HREF COMES
WITH HIGH PROBABILITIES > 70-80% FOR CEILINGS BELOW 1000 FEET AGL
AND VISIBILITY LESS THAN 1SM. THERE IS CONSIDERABLE UNCERTAINTY
WITH SNOW ACCUM AT KEAT, KMWH, KOMK DUE TO MARGINAL TEMPERATURES
NEAR 32-34F WHEN SNOW IS FALLING. WOULD NOT RULE OUT P-TYPE
REMAINING ALL SNOW FOR KPUW AND KGEG AS WELL BUT WITH SIMILAR,
MARGINAL TEMPS.
-----------------------
CONFIDENCE DESCRIPTORS:
LOW - LESS THAN A 30 PERCENT CHANCE
MODERATE - 30 TO 70 PERCENT CHANCE
HIGH - GREATER THAN A 70 PERCENT CHANCE
PRELIMINARY POINT TEMPS/POPS
SPOKANE 34 30 37 26 40 33 / 90 80 20 10 10 30
COEUR D'ALENE 34 31 36 27 42 34 / 90 90 30 20 10 30
PULLMAN 36 31 35 25 38 34 / 100 90 40 10 0 20
LEWISTON 40 34 42 25 42 36 / 90 80 30 10 0 10
COLVILLE 34 27 39 28 40 30 / 90 60 10 10 30 50
SANDPOINT 34 30 37 28 40 33 / 80 90 40 30 30 50
KELLOGG 36 31 35 27 42 35 / 90 100 70 20 10 40
MOSES LAKE 38 29 43 28 41 30 / 100 10 0 0 10 10
WENATCHEE 34 29 41 29 37 31 / 100 10 0 0 10 10
OMAK 35 28 38 29 39 31 / 90 20 0 0 20 30
OTX WATCHES/WARNINGS/ADVISORIES
ID...WINTER WEATHER ADVISORY FROM NOON TODAY TO 4 AM PST THURSDAY FOR
CENTRAL PANHANDLE MOUNTAINS.
WA...WINTER WEATHER ADVISORY UNTIL 1 PM PST THIS AFTERNOON FOR MOSES
LAKE AREA-UPPER COLUMBIA BASIN.
WINTER WEATHER ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR
CENTRAL CHELAN COUNTY-WATERVILLE PLATEAU-WENATCHEE AREA-
WESTERN OKANOGAN COUNTY.
WINTER WEATHER ADVISORY UNTIL 4 AM PST THURSDAY FOR WESTERN
CHELAN COUNTY.
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