757
FXUS66 KOTX 181200
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
500 AM PDT MON MAY 18 2026
KEY MESSAGES
- POP UP SHOWERS AND ISOLATED THUNDERSTORMS PRIMARILY OVER THE
HIGHER TERRAIN WILL RETURN MONDAY AFTERNOON.
- COLD OVERNIGHT TEMPERATURES WILL BRING A THREAT OF MORNING FROST
MONDAY. THIS COULD IMPACT SENSITIVE PLANTS OR CROPS.
- CONDITIONS TREND DRIER AND WARMER THROUGH THE WORKWEEK REGIONWIDE,
WITH PERIODIC BREEZY WINDS FOR THE CASCADES AND CENTRAL WA.
SYNOPSIS
DIURNALLY FORCED SHOWERS WITH ISOLATED AFTERNOON THUNDERSTORMS
WILL CONTINUE TODAY MONDAY. PRECIPITATION CHANCES DECREASE AND
AFTERNOON HIGHS TREND WARMER THROUGH THE WORKWEEK, CLIMBING BACK
INTO THE 70S AND 80S BY THURSDAY AND CONTINUING THROUGH NEXT
WEEKEND. BREEZY WINDS ARE EXPECTED AT TIMES THROUGH THE CASCADE GAPS
AND ACROSS THE WESTERN COLUMBIA BASIN.
DISCUSSION
TODAY THROUGH FRIDAY NIGHT: A DEEP LONGWAVE TROUGH OF LOWER
PRESSURE WILL REMAIN OVER THE CONUS FOR THIS WEEKEND THROUGH THE
WORKWEEK. THE AXIS OF THIS LONGWAVE TROUGH WILL SLOWLY MIGRATE
OVER THE ROCKIES BY THROUGH WEDNESDAY AND THEN OVER THE PLAINS
BY THURSDAY INTO FRIDAY. THE INLAND NORTHWEST WILL REMAIN UNDER
THE BACKSIDE OF THIS TROUGH TODAY WITH A CONDITIONALLY UNSTABLE
AIR MASS. LINGERING SHOWERS OVER EXTREME EASTERN WASHINGTON INTO
THE IDAHO PANHANDLE EARLY THIS MORNING WILL WANE WITH
DECREASING INSTABILITY AT MID LEVELS. HOWEVER, DIURNAL HEATING
WILL DESTABILIZE THE LOWER LEVELS OF THE ATMOSPHERE FOR THE
AFTERNOON. THERE WILL BE A LACK OF INSTABILITY OVER THE
COLUMBIA BASIN TODAY, WHICH SHOULD RESULT IN MUCH OF THE SHOWERS
AND THUNDERSTORM ACTIVITY CONFINED TO MAINLY THE HIGHER TERRAIN
TODAY. INSTABILITY PARAMETERS WILL BE MUCH LESS COMPARED TO
SUNDAY WITH UPPER LEVELS TRENDING WARMER. MUCH LESS LIKELY TO
SEE AS MUCH SMALL HAIL LIKE WE'VE SEEN WITH THIS STORMS, BUT
SOME IS EXPECTED WITH SLIGHTLY STRONGER THUNDERSTORMS OVER THE
MOUNTAINS. CONVECTION WILL ALSO BE CAPABLE OF WIND GUSTS UP TO
AROUND 20-25 MPH AND INFREQUENT CLOUD TO GROUND LIGHTNING
STRIKES. BEST POTENTIAL FOR THUNDERSTORMS TODAY WILL BE OVER
NORTHEAST WASHINGTON INTO THE NORTHERN PANHANDLE WITH 20-25%
CHANCE OF OCCURRING. CONVECTION IS EXPECTED TO WANE MORE QUICKLY
INTO THE EVENING HOURS COMPARED TO SUNDAY.
WE THEN SEE A DRYING TREND INTO MID WEEK AS A RIDGE OF HIGHER
PRESSURE IN THE EASTERN PACIFIC NUDES EAST INTO THE NORTHWEST.
THERE IS A SHORTWAVE DISTURBANCE THAT PUSHES ACROSS BC ON
TUESDAY AND DOES BRING A 20-30 PERCENT CHANCE FOR SHOWERS ACROSS
THE FAR NORTHERN MOUNTAINS CLOSER TO THE CANADIAN BORDER, AND
THIS POTENTIAL COULD LINGER INTO WEDNESDAY FOR NORTH IDAHO AS
THE SHORTWAVE PUSHES ACROSS FAIRLY SLOWLY. THERE IS A 15% CHANCE
THAT PLACES LIKE LAUIER, NORTHPORT, METALLINE FALLS, PORTHILL,
AND EASTPORT MAY ALSO SEE A PASSING THUNDERSTORM. TEMPERATURES
WARM UP ABOVE NORMAL BY WEDNESDAY WITH OUR HIGHS BACK INTO THE
70S. THE RISK FOR MORNING FROST WILL DECREASE AS WELL AS
TEMPERATURES SEE A SLOW WARM INTO THE WEEKEND.
SATURDAY THROUGH SUNDAY: MODEL ENSEMBLES REMAIN IN PRETTY GOOD
AGREEMENT WITH A SHORTWAVE TROUGH OF LOWER PRESSURE TO FLATTEN
THE RIDGE. THERE IS UNCERTAINTY WITH HOW DEEP THIS SHORTWAVE
WILL BE. ABOUT 80 PERCENT OF THE ENSEMBLE MEMBERS SHOW THIS
DISTURBANCE TO BE FAIRLY WEAK WITH MINIMAL COOLING OF JUST A FEW
DEGREES SATURDAY INTO SUNDAY. WESTERLY WINDS WILL SEE AN
INCREASE. STRONGER WIND GUSTS OF UP TO AROUND 30 MPH WILL BE
ACROSS THE CASCADES AND INTO THE WESTERN BASIN AND UP TO AROUND
20-25 MPH POTENTIALLY INTO PLACES LIKE SPOKANE AND THE PALOUSE.
WINDS WOULD PICK UP SATURDAY AFTERNOON, BUT COULD ALSO REMAIN
FAIRLY BREEZY INTO SUNDAY AS WELL. MODELS CONTINUE TO DIVERGE
AS WE HEAD INTO THE BEGINNING OF NEXT WEEK. OUTLIERS SUCH AS THE
00Z OPERATIONAL ECMWF AND CANADIAN INDICATE A DEEP TROUGH TO
DIG IN INTO BC AND POTENTIALLY AS FAR SOUTH AS THE PACIFIC
NORTHWEST. THIS SCENARIO WOULD REPRESENT MORE COOLING AND A
BETTER POTENTIAL FOR SHOWERS THAN WHAT IS IN THE FORECAST. THE
NBM SUGGESTS A MORE ZONAL FLOW PATTERN WITH THE POTENTIAL FOR
PROGRESSIVE WEAKER WAVES THAT COULD BRING LIGHT SHOWER ACTIVITY
BUT NOTHING LOOKING ALL THAT SUBSTANTIAL. AFTER OUR WARM UP LATE
IN THE WEEK, TEMPERATURES LOOK TO COOL NEAR NORMAL FOR SUNDAY
INTO THE BEGINNING OF NEXT WEEK. /SVH
AVIATION
12Z TAFS: A MOIST BOUNDARY LAYER IS IN PLACE EARLY THIS MORNING
ACROSS FAR EASTERN WASHINGTON AND NORTH IDAHO. NIGHTTIME
MICROPHYSICS SATELLITE IMAGERY REVEALS A STRATUS DECK BETWEEN
4.5K-7KFT FROM SANDPOINT TO PULLMAN AND PATCHY SHALLOW FOG
FROM DEER PARK TO THE SPOKANE METRO AREA. GIVEN THE STRATUS DECK
ACROSS NORTH IDAHO, CONFIDENCE IS LOWER FOR FOG DEVELOPMENT AT
KCOE. FOG AT KGEG/KSFF MAY BRING IFR/MVFR CONDITIONS THROUGH
16-17Z. CONVECTIVE SHOWERS WITH ISOLATED THUNDERSTORMS ARE
EXPECTED 18Z-04Z PRIMARILY OVER THE MOUNTAINS OF NORTHEAST
WASHINGTON INTO THE IDAHO PANHANDLE.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
CONFIDENCE IS LOW FOR VISIBILITY RESTRICTIONS AND IFR CONDITIONS
WITH RADIATIONAL FOG AT KGEG/KSFF THIS MORNING. LOW CONFIDENCE
FOR STRATUS TO BRING MVFR CONDITIONS TO KCOE AND KPUW.
-----------------------
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 66 41 69 44 72 45 / 10 10 0 0 0 0
COEUR D'ALENE 64 41 67 44 70 45 / 20 20 10 0 0 0
PULLMAN 62 39 65 42 68 43 / 10 0 0 0 0 0
LEWISTON 67 43 71 46 73 48 / 10 0 0 0 0 0
COLVILLE 69 36 71 40 75 41 / 20 30 10 10 0 0
SANDPOINT 62 40 66 43 68 43 / 30 30 10 10 0 0
KELLOGG 61 39 66 43 68 43 / 20 20 10 0 10 10
MOSES LAKE 73 42 75 46 78 49 / 0 0 0 0 0 0
WENATCHEE 72 48 74 51 77 54 / 10 0 0 0 0 0
OMAK 73 43 75 48 78 51 / 10 10 10 0 0 0
OTX WATCHES/WARNINGS/ADVISORIES
WA...FROST ADVISORY UNTIL 7 AM PDT THIS MORNING FOR NORTHEAST
MOUNTAINS-OKANOGAN HIGHLANDS-SPOKANE AREA-WASHINGTON
PALOUSE.
ID...FROST ADVISORY UNTIL 7 AM PDT THIS MORNING FOR CENTRAL
PANHANDLE MOUNTAINS-COEUR D'ALENE AREA-IDAHO PALOUSE-
NORTHERN PANHANDLE.
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