968
FXUS66 KOTX 201054
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
254 AM PST THU FEB 20 2025
SYNOPSIS
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 AND FRIDAY: A HIGH PRESSURE CENTER OFF THE COAST OF
CALIFORNIA WILL SUPPORT A SHALLOW RIDGE PATTERN INTO THE PACIFIC
NORTHWEST. IT WILL BRING A DRYING, WARMING PATTERN INTO THE INLAND
NORTHWEST. LINGERING MOISTURE WILL BRING SOME ISOLATED SNOW TO
THE CASCADES AND HIGH TERRAIN OF THE NORTHEAST WA AND ID
PANHANDLE. ANY NEW ACCUMULATIONS ARE EXPECTED TO BE LESS THAN
INCH. FOR THE LOWLAND AREAS, FOG WILL BE THE MAIN CONCERN FOR THE
PERIOD. WITH ABUNDANT MOISTURE IN THE BOUNDARY LAYER, AREAS IN THE
BASIN AND VALLEYS CAN EXPECT PERIODS OF DENSE FOG WITH VISIBILITY
OF A QUARTER MILE OR LESS MAINLY DURING THE EARLY MORNING HOURS.
BY LATE FRIDAY AFTERNOON, A LOW BEGINS TO PRESS INTO THE REGION
THROUGH SOUTHERN BC. IT WILL MAINLY BRING INCREASING PRECIP INTO
THE NORTH CASCADES BEFORE SPREADING EAST ACROSS NORTH WA. IT WILL
BE THE START OF WHAT IS EXPECTED TO BE A SOGGY WEEKEND FOR THE
REGION. STRATUS CLOUDS WILL KEEP TEMPERATURES FROM FLUCTUATING TOO
MUCH. HIGH WILL BE IN THE UPPER 30S AND LOW 40S. LOWS WILL BE IN
THE 20S. /JDC
SATURDAY AND SUNDAY: THE INLAND NORTHWEST WILL TRANSITION TO A
PERIOD OF WARMER AND WETTER WEATHER AS A SERIES OF SYSTEMS PASS
THROUGH SATURDAY AND TUESDAY. MODELS ARE IN RELATIVELY GOOD
AGREEMENT ON THE OVERALL SYNOPTIC SETUP WITH A FLAT RIDGE OVER THE
WESTERN US AND SOUTHWEST FLOW DIRECTED INTO THE WEST COAST. THE
FIRST SYSTEM WILL ARRIVE SATURDAY AFTERNOON AND EVENING AS A WARM
FRONT AIDED BY A ROBUST MOISTURE PLUME ADVECTS NORTH. WHILE THERE
ARE SUBTLE DIFFERENCES IN THE STRENGTH OF THE RIDGE, TIMING, AND THE
PLACEMENT OF THE AXIS OF MOISTURE, THERE IS HIGH CONFIDENCE FOR
WIDESPREAD PRECIPITATION WITH THIS SYSTEM. BOTH THE EPS AND GEFS
MEANS DEPICT AN ATMOSPHERIC RIVER IN THE 99TH+ PERCENTILE RANGE
COMPARED TO CLIMATOLOGY SATURDAY EVENING AS THIS FRONT MOVES
THROUGH. 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 COLD AIR WHERE COLDER AIR MAY SUPPORT
A WINTRY MIX DURING THE EVENT.
A SECOND SURGE OF WIDESPREAD PRECIPITATION WILL OCCUR SUNDAY AS
DETERMINISTIC MODELS SHOW A MORE COMPACT SHORTWAVE TO MOVE THROUGH
THE NORTHWEST. ALTHOUGH THERE ARE SOME DIFFERENCES IN THE EXACT
STRENGTH AND PLACEMENT, BETTER DYNAMICS WITH THIS SECOND ROUND WOULD
SUPPORT HIGHER RAIN TOTALS COMPARED TO THE FIRST. BY THE END OF THIS
TWO DAY PERIOD, THE NBM IS CURRENTLY PROJECTING PRECIPITATION TOTALS
IN THE 0.60 TO 1.5 INCH RAIN ACROSS FAR EASTERN WASHINGTON AND NORTH
IDAHO AND 0.15 TO 0.50 INCHES FOR CENTRAL WASHINGTON.
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.
THE GREATEST IMPACTS WILL BE RISES IN OUR FLASHIER CREEKS AND
STREAMS IN THESE AREAS. ADDITIONALLY, 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. THE FORECAST FOR PARADISE CREEK IN MOSCOW CONTINUES TO
BRING IT ABOVE MINOR FLOOD STAGE BY SATURDAY AFTERNOON.
MONDAY THROUGH WEDNESDAY: MODELS ARE COMING INTO BETTER AGREEMENT ON
A THIRD SYSTEM TO PASS THROUGH THE REGION BETWEEN MONDAY AND TUESDAY
AND BRING MORE PRECIPITATION AND POSSIBLY STRONGER WINDS. WHILE NOT
BACKED BY THE FULL SUITE YET, THE ECMWF EXTREME FORECAST INDEX IS
HIGHLIGHTING THIS PERIOD FOR WINDS AND WIND GUSTS. THE ENSEMBLE MEAN
STILL KEEPS WIND GUSTS BELOW 40 MPH FOR SPOKANE, BUT THERE ARE A
HANDFUL OF MEMBERS WITH GUSTS ABOVE 40 AND 3 MEMBERS ABOVE 50. WE
WILL CONTINUE TO MONITOR THIS PERIOD AS WELL.
THE FORECAST TRENDS DRIER BY WEDNESDAY WITH GENERAL AGREEMENT FOR A
HIGH AMPLITUDE RIDGE TO SHIFT OVER THE WESTERN US. /VMT
AVIATION
06Z TAFS: ASIDE FROM KCOE, ALL OTHER TAF SITES ARE NO LONGER
SEEING PRECIPITATION. KCOE'S MOISTURE AND UPSLOPE FLOW WILL ALLOW
LIGHT SNOW TO CONTINUE THROUGH AROUND 09Z. NOW THAT THE
PRECIPITATION HAS MOVED OUT OF MOST OF THE AREA, VERY LOW STRATUS
OR FOG WILL DOMINATE MUCH OF THE SITES. ALL TAF SITES ARE AT IFR
OR LOWER, WITH KGEG-KSFF-KPUW-KMHW-KLWS-KEAT ALL AT LIFR. CEILINGS
ARE EXPECTED TO IMPROVE BY AROUND 18-20Z BUT LOW CLOUDS PERSIST
WITH MVFR TO IFR CONDITIONS CONTINUING INTO THURSDAY AFTERNOON.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: HIGH CONFIDENCE
IN VERY LOW CEILINGS THROUGH AT LEAST 17-18Z TODAY.
-----------------------
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 35 27 38 34 44 39 / 10 0 10 50 40 100
COEUR D'ALENE 36 26 40 33 44 38 / 20 10 10 50 50 100
PULLMAN 36 25 37 33 43 39 / 10 0 0 40 30 100
LEWISTON 40 25 41 35 47 41 / 0 0 0 30 20 90
COLVILLE 38 28 38 32 42 36 / 10 10 40 70 50 100
SANDPOINT 36 28 39 33 42 38 / 40 10 40 80 70 100
KELLOGG 34 24 40 33 43 39 / 50 10 10 50 60 100
MOSES LAKE 42 29 39 31 47 38 / 0 0 10 10 20 60
WENATCHEE 41 29 36 32 42 37 / 0 0 10 20 30 70
OMAK 39 27 37 31 41 34 / 10 0 30 40 40 90
OTX WATCHES/WARNINGS/ADVISORIES
ID...WINTER WEATHER ADVISORY UNTIL 4 AM PST EARLY THIS MORNING FOR
CENTRAL PANHANDLE MOUNTAINS.
WA...WINTER WEATHER ADVISORY UNTIL 4 AM PST EARLY THIS MORNING FOR
WESTERN CHELAN COUNTY.
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