170
FXUS66 KOTX 211215
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
415 AM PST FRI FEB 21 2025
SYNOPSIS
WARMER TEMPERATURES AND RAIN WILL ARRIVE THIS WEEKEND AS HIGH
TEMPERATURES WARM INTO THE 40S. RUNOFF FROM RAIN AND MELTING SNOW
WILL LEAD TO INCREASED FLOW AND MINOR FLOODING ACROSS SOUTHEAST
WASHINGTON AND THE CENTRAL AND SOUTHERN IDAHO PANHANDLE. ANOTHER
WEATHER SYSTEM MONDAY INTO TUESDAY WILL BRING MORE RAIN AND
POSSIBLY STRONGER WINDS.
DISCUSSION
FRIDAY: SOUTHWEST FLOW DIRECTED INTO THE PACIFIC NORTHWEST DUE TO A
WEAK RIDGE OVER THE WESTERN US COMBINED AND TROUGHING OVER THE
NORTHEAST PACIFIC WILL SET THE STAGE FOR THE NEXT SEVERAL DAYS AS A
SERIES OF SYSTEMS PASS THROUGH THE REGION. THE FIRST SYSTEM WILL
ARRIVE FRIDAY AFTERNOON INTO THE EVENING AS A SURFACE LOW MOVES INTO
THE SOUTHERN ALASKAN PANHANDLE AND THE ASSOCIATED FRONTAL BOUNDARY
SHIFTS INTO THE INLAND NORTHWEST. TEMPERATURES WILL BE COOL ENOUGH
AND SNOW LEVELS WILL BE LOW ENOUGH FOR LIGHT SNOW ACROSS THE
NORTHERN VALLEYS (METHOW VALLEY, REPUBLIC, DEER PARK) AND UPPER
COLUMBIA BASIN BETWEEN WILBUR AND DAVENPORT OVERNIGHT. HIGHER
BENCHES AROUND SPOKANE AND COEUR D’ALENE THROUGH BONNERS FERRY MAY
ALSO EXPERIENCE A MIX OF RAIN AND NON-ACCUMULATING SNOW.
SATURDAY AND SUNDAY: TWO SYSTEMS ARE PROGGED TO IMPACT THE PACIFIC
NORTHWEST BETWEEN SATURDAY AFTERNOON AND SUNDAY AND BRING A MODERATE
TO STRONG ATMOSPHERIC RIVER INTO THE REGION. MODELS CONTINUE TO BE
IN RELATIVELY GOOD AGREEMENT WITH THE RIDGE OVER THE WESTERN US TO
PROGRESSIVELY FLATTEN AS THE SYSTEMS RIDE OVERTOP. THE FIRST SYSTEM
WILL ARRIVE SATURDAY AFTERNOON AND EVENING AS A WARM FRONT LIFTS
NORTH ACROSS THE INLAND NORTHWEST. THERE STILL REMAIN DIFFERENCES IN
THE ONSET OF PRECIPITATION AND EXACT AMOUNTS. THE HIGHEST
PRECIPITATION TOTALS WITH THIS FIRST ROUND OF PRECIPITATION WILL BE
ACROSS THE CASCADES, FAR EASTERN WASHINGTON, AND NORTH IDAHO AS
STRONG WESTERLY FLOW ALOFT FAVORS OROGRAPHIC ENHANCEMENT. THAT BEING
SAID, THE LEE OF THE CASCADES WILL NOT BE COMPLETELY SHADOWED
INITIALLY WITH THE WARM FRONT. SNOW LEVELS WILL BE ON THE RISE
THROUGH THE DAY ON SATURDAY WITH PRECIPITATION FALLING MOSTLY AS
HIGH MOUNTAIN SNOW AND LOWLAND RAIN. THE EXCEPTION WILL BE FOR THE
METHOW VALLEY WHERE COLDER AIR LOOKS TO SUPPORT A WINTRY MIX
OVERNIGHT.
A SECOND SURGE OF WIDESPREAD PRECIPITATION WILL OCCUR SUNDAY AS
DETERMINISTIC MODELS SHOW A MORE COMPACT LOW TO MOVE THROUGH THE
NORTHWEST. NOTABLE DIFFERENCES IN THE PRECIPITATION AMOUNTS
BETWEEN MODELS STEMMING FROM THE STRENGTH AND TIMING OF THIS LOW.
THE DETERMINISTIC GFS HAS BEEN TRENDING MUCH WETTER WITH A
STRONGER, SLOWER MOVING LOW ALLOWING THE MOISTURE AXIS TO PERSIST
INTO THE REGION, WHILE THE DETERMINISTIC ECMWF DEPICTS A WEAKER
LOW WITH A QUICKER MOVING UPPER LEVEL SHORTWAVE AND LOWER RAINFALL
TOTALS. THE ENSEMBLE MEANS ARE MORE SIMILAR TO EACH OTHER, WITH A
LARGE SPREAD BETWEEN THE 10TH AND 90TH PERCENTILE VALUES. OUR
CURRENT FORECAST LEANS CLOSER TO THE WETTER FORECAST WITH 48 HOUR
TOTALS BETWEEN 0.80 TO 1.25 INCHES FOR THE LOWLANDS OF FAR EASTERN
WASHINGTON AND 1.5 TO 2.5 INCHES OVER THE MOUNTAINS.
IMPACTS: THE COMBINATION OF WARMER TEMPERATURES, RAIN, AND BREEZY
WINDS WILL RESULT IN RAPID SNOWMELT ACROSS THE LOWLANDS WHERE RECENT
OBSERVATIONS SHOW AROUND 4 TO 9 INCHES OF LOWLAND SNOWPACK. SEVERAL
OBSERVATIONS ACROSS THE SPOKANE COUNTY AND THE WASHINGTON AND IDAHO
PALOUSE ARE SHOWING 1.3 TO 1.8 INCHES OF LIQUID WITHIN THE SNOWPACK.
IF THE WETTER SCENARIO VERIFIES, RISES IN OUR FLASHIER CREEKS AND
STREAMS WILL BE COMMON ACROSS SPOKANE COUNTY AND THROUGH THE
WASHINGTON AND IDAHO PALOUSE. PONDING OF WATER IN URBAN AREAS WITH
POOR OR CLOGGED DRAINAGE AND FIELD FLOODING WILL BE OF CONCERN. IT
IS ADVISED TO TAKE PROPER PRECAUTIONS TO MITIGATE FLOOD IMPACTS.
PARADISE CREEK AT MOSCOW IS CURRENTLY FORECASTED TO REACH MINOR
FLOOD STAGE BY LATE SUNDAY MORNING. THE SOUTH FORK PALOUSE RIVER AT
PULLMAN, HANGMAN/LATAH CREEK AT SPOKANE, AND LITTLE SPOKANE RIVER AT
DARTFORD ARE ALL FORECASTED TO RISE NEAR BANKFULL CONDITIONS SUNDAY
NIGHT INTO MONDAY.
MONDAY: DETERMINISTIC MODELS HAVE BEEN COMING INTO BETTER AGREEMENT
WITH A DEEPENING SURFACE LOW TO SLIDE NORTHWARD ALONG THE PACIFIC
NORTHWEST COAST ON MONDAY. THERE ARE STILL DIFFERENCES IN THE EXACT
DETAILS, BUT THIS WOULD BRING ANOTHER ROUND OF PRECIPITATION AND
POSSIBLY STRONGER WINDS MONDAY NIGHT INTO TUESDAY. /VMT
TUESDAY THROUGH FRIDAY: AN EARLY MORNING TROUGH WILL BE PUSHING
THROUGH THE INLAND NORTHWEST ON TUESDAY. IT IS EXPECTED TO BE THE
END OF THE WET WEATHER PATTERN FOR THE REGION. IT WILL CONTINUE TO
BRING LOWLAND RAIN AND MOUNTAIN SNOW INTO TUESDAY AFTERNOON BEFORE
MOVING INTO SOUTHERN BC. PORTIONS OF THE BASIN, SOUTHWEST WA, AND
LOWER ID PANHANDLE CAN EXPECT GUSTY WINDS WITH THE PASSAGE. 850MB
WIND SPEEDS REACH INTO THE UPPER 30 TO 50 KNOTS RANGE. THERE IS
CURRENTLY A NEAR 30% PROBABILITY OF WIND GUSTS OF 35 MPH OR ABOVE.
BEST CHANCE IS SOUTHEAST WASHINGTON AND LOWER ID PANHANDLE AS THESE
REACH A 50% PROBABILITY. AS THE WAVE EXITS WARM, DRY AIR FILLS IN
BEHIND IT. IT WILL BRING A TASTE OF SPRING TO THE REGION WITH HIGHS
REACHING INTO THE MID 40S TO 50S. OVERNIGHT LOWS WILL BE BE IN THE
30S. THE DRY PATTERN WILL BRING A GRADUAL DECLINE TO FLOOD/HYDRO
CONCERNS FOR THE INLAND NORTHWEST. STARTING OVER THE WEEKEND, A
ZONAL FLOW PATTERN WILL BRING A GENERAL COOL, WET PATTERN FOR THE
START OF MARCH. /JDC
AVIATION
12Z TAFS: WIDESPREAD FOG AND STRATUS ARE BRINGING IFR CONDITONS TO
MOST TAF SITES WITH THE EXCEPTION BEING PUW. THE EASTERLY FLOW IS
KEEPING PUW IN VFR CONDITIONS. CONDITIONS ARE EXPECTED TO
CONTINUE THROUGH LAST THROUGH 17-18Z. AS ANOTHER SYSTEM MOVES
INTO THE AREA, RAIN AND SNOW WILL BEGIN IMPACTING THE CASCADES
AROUND 18Z. PRECIP EXPECTED AROUND 23Z FOR KGEG- KSFF- KCOE. FOR
KMWH- KEAT, THE PRECIPITATION WILL MOVE IN AROUND 17-20Z. THIS
PRECIPITATION COULD BE A MIX OF RAIN AND SNOW. AFTER THE
PRECIPITATION MOVES OUT OF THE AREA, TAF SITES WILL OVERALL BEGIN
TO IMPROVE THROUGH 05Z. STRATUS AND FOG IS EXPECTED TO RETURN
AROUND 06Z. MVFR TO IFR CONDITIONS EXPECTED OVERNIGHT.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: MODERATE TO HIGH
CONFIDENCE FOR IFR CONDITIONS FOR TAF SITES EXCLUDING PUW.
MODERATE TO LOW CONFIDENCE IN PRECIPITATION OCCURRENCE AND TIMING.
FOR KLWS- KMWH- KEAT, CEILINGS COULD TAKE LONGER TO IMPROVE AFTER
ANY RAIN OR SNOW FALLS. MODERATE CONFIDENCE ON THE RETURN OF IFR
FOR TONIGHT. /JDC
-----------------------
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 39 36 43 40 48 39 / 20 70 40 100 90 70
COEUR D'ALENE 41 34 44 39 47 38 / 20 70 50 100 90 80
PULLMAN 37 34 41 38 45 38 / 10 50 30 100 100 90
LEWISTON 42 36 48 42 52 42 / 0 40 20 90 90 80
COLVILLE 39 33 43 38 46 33 / 40 80 70 100 80 70
SANDPOINT 39 34 41 39 44 38 / 30 80 80 100 90 90
KELLOGG 42 36 43 41 44 41 / 20 60 60 100 100 90
MOSES LAKE 41 31 48 40 55 37 / 20 30 20 70 60 30
WENATCHEE 38 34 42 38 48 38 / 20 40 50 70 70 40
OMAK 39 34 42 36 46 35 / 30 50 50 90 60 50
OTX WATCHES/WARNINGS/ADVISORIES
ID...NONE.
WA...NONE.
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