348
FXUS66 KOTX 201835
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
1035 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 BETWEEN 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 SNOW WATER EQUIVALENT (SWE) OBSERVATIONS ACROSS 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 FROM
THE COMBO OF RAIN AND SNOWMELT. 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 EPS ENSEMBLE
MEAN CURRENTLY HAS WIND GUSTS FOR TUESDAY AFTERNOON BELOW 40 MPH
FOR SPOKANE, BUT THERE ARE A HANDFUL OF MEMBERS WITH GUSTS ABOVE
40 MPH AND 3 MEMBERS ABOVE 50 MPH. 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
18Z TAFS: THERE ARE SEVERAL LOW CLOUD BANKS ACROSS CENTRAL/EASTERN
WASHINGTON AND NORTH IDAHO FOLLOWING THE PASSAGE OF YESTERDAY'S
ROUND OF PRECIPITATION. WITH WEAK SOUTH WINDS JUST ABOVE THE
SURFACE AND WIDESPREAD SNOW COVER, ANY IMPROVEMENT IN CEILINGS
AND VISIBILITY AT SPOKANE INTERNATIONAL WILL BE GRADUAL THROUGH
THE DAY AND NIGHT DUE TO LIGHT UPSLOPE FLOW. WITH SUNSHINE AT TRI
CITIES AND WALLA WALLA, SURFACE WARMING IN THE DEEP COLUMBIA
BASIN SHOULD HELP ERODE AND LIFT THE LOW CLOUDS AROUND MOSES LAKE
AND EPHRATA, BUT THE HREF SUGGESTS THAT AFTERNOON IMPROVEMENTS AT
MWH AND EPH WILL BE LOST BY FRIDAY MORNING WITH THE EXPANSION OF
CLOUDS THROUGH THE NIGHT.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: OVERALL,
CONFIDENCE IN THE CEILINGS IS MODERATE TO LOW. IT IS NOT UNUSUAL
FOR LOW CLOUD LAYERS TO VARY ACROSS THE INLAND NORTHWEST FOLLOWING
A PRECIPITATION EVENT. AFTER ABOUT 24 TO 36 HOURS, CLOUD LAYERS
OFTEN CONSOLIDATE AS THE INVERSION LAYER STABILIZES. THE
WENATCHEE AND LEWISTON TAFS WILL LIKELY BE ESPECIALLY PROBLEMATIC
THIS AFTERNOON AND EVENING WITH FOG AND LOW CLOUDS BEING
CHANNELED THROUGH THE COLUMBIA AND SNAKE/CLEARWATER VALLEYS. WILL
THERE BE ENOUGH WARMING OF THE VALLEY WALLS TO DISPERSE THE
FOG/CLOUDS OR WILL THE LOW CLOUDS BE TRAPPED LATE INTO THE DAY?
TOUGH CALL. /GKOCH
-----------------------
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 36 27 38 34 44 39 / 0 0 10 50 40 100
COEUR D'ALENE 38 27 40 33 44 38 / 30 0 10 50 50 100
PULLMAN 36 26 37 33 43 39 / 10 0 0 40 30 100
LEWISTON 41 27 41 35 47 41 / 0 0 0 30 20 90
COLVILLE 36 27 38 32 42 36 / 0 10 40 70 50 100
SANDPOINT 35 29 39 33 42 38 / 30 10 40 80 70 100
KELLOGG 36 25 40 33 43 39 / 40 0 10 50 60 100
MOSES LAKE 39 29 39 31 47 38 / 0 0 10 10 20 60
WENATCHEE 39 30 36 32 42 37 / 0 0 10 20 30 70
OMAK 37 29 37 31 41 34 / 0 0 30 40 40 90
OTX WATCHES/WARNINGS/ADVISORIES
ID...NONE.
WA...NONE.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page