160  
FXUS66 KOTX 290720  
AFDOTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SPOKANE WA  
1220 AM PDT FRI AUG 29 2025  
   
KEY MESSAGES  
 
- SCATTERED SHOWERS WITH ISOLATED THUNDERSTORMS IN THE NORTHERN  
MOUNTAINS FRIDAY. THUNDERSTORMS WILL BE CAPABLE OF HEAVY  
RAINFALL.  
 
- WARMING UP INTO THE 90S NEXT WEEK, LOCALLY NEAR 100, WITH  
ELEVATED HEATRISK. RECORD WARM TEMPERATURES FOR SEPTEMBER  
POSSIBLE.  
 
 
   
SYNOPSIS  
 
THE THREAT FOR SHOWERS AND THUNDERSTORMS WILL SHIFT INTO THE  
NORTHERN MOUNTAINS TODAY. THUNDERSTORMS WILL BRING THE  
POTENTIAL FOR LIGHTNING AND BRIEF HEAVY RAINFALL. ISOLATED  
SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE NEAR THE CASCADE  
CREST OVER THE WEEKEND, OTHERWISE THE MAIN STORY WILL BE WARMING  
AND DRYING. HOT TEMPERATURES RETURN NEXT WEEK WITH HIGHS  
CLIMBING BACK INTO THE 90S TO NEAR 100 DEGREES.  
 
 
   
DISCUSSION  
 
FRIDAY THROUGH SUNDAY: THE PESKY UPPER LOW SPINNING OVER WESTERN WA  
ON THURSDAY WILL BEGIN TO DRIFT TO THE NORTH TODAY. IN CONCERT,  
THE AXIS OF RICH PRECIPITABLE WATER WILL ALSO DRIFT NORTHWARD  
AND THE THREAT FOR SHOWERS AND THUNDERSTORMS WILL MIGRATE INTO  
THE NORTHERN MOUNTAINS WHILE MIDLEVEL DRYING WORKS INTO SOUTHERN  
AND PORTIONS OF CENTRAL WA. HIGHEST THUNDERSTORM PROBABILITIES  
VIA THE HREF EXTEND FROM BONNERS FERRY TO REPUBLIC (40-60%) AND  
DROP OFF TOWARD 10-20% ON THE SOUTHERN PERIPHERY FROM COUER D  
ALENE TO THE METHOW VALLEY. CONVECTION WILL LARGELY BE DRIVEN BY  
SURFACE HEATING WITH WEAK LIFT ASSOCIATED WITH THE DRIFTING LOW  
OVER THE N CASCADES AND INTO THE OKANOGAN HIGHLANDS.  
 
BY THE WEEKEND, A DEEPER LOW WILL TAKE RESIDENCE ALONG THE WA COAST.  
THIS WILL ALLOW A RIDGE TO BEGIN BLOSSOMING OVER THE INLAND NW  
AND START OF A WARMING TREND. THE RIDGE AXIS WILL INITIALLY SET  
UP NEAR THE IDAHO/MONTANA BORDER. SOME MOISTURE AND WEAK  
DISTURBANCES RUNNING UP THE WESTERN FLANK OF THE RIDGE WILL KEEP  
A MENTION OF SHOWERS AND STORMS NEAR TO WEST OF THE CASCADE  
CREST THOUGH THE AIR MASS WILL BE CONSIDERABLY DRIER WITH LESS  
INSTABILITY LEADING TO A HIGHER THREAT FOR CLOUDS AND LIGHT  
SHOWERS VS WET THUNDERSTORMS. MEAN CAPES ARE FORECAST TO BE IN  
THE 300-600 J/KG RANGE WITH ACCOMPANYING SREF PROBABILITIES FOR  
LIGHTNING AROUND 10%. AS MENTIONED IN THE PREVIOUS AFD, THE  
RIDGE AND MIDLEVEL DRYING LOOKS TO BE THE MORE DOMINANT FEATURE  
FOR MUCH OF THE INLAND NW FOR THE UPCOMING WEEKEND.  
 
MONDAY THROUGH FRIDAY: THE DEEP LOW RESIDING OFF THE WA COAST  
WILL RETREAT INTO THE GULF OF AK AND A STRONG RIDGE OF HIGH  
PRESSURE WILL AMPLIFY OVER THE NORTHWEST. RESIDENTS OF THE  
INLAND NW NEED TO PREPARE FOR A MULTI-DAY HEAT WAVE WITH  
TEMPERATURES SURGING INTO THE 90S TO LOWER 100S. THIS COMES WITH  
HIGH CONFIDENCE GIVEN STRONG SUPPORT FROM THE ENTIRE 100 MEMBER  
ENSEMBLE OUTPUT. THE PEAK OF THE HEATWAVE SPANS FROM MONDAY  
THROUGH WEDNESDAY BUT WOULD NOT BE SURPRISED IF THURSDAY AND  
FRIDAY COME IN WARMER IN FUTURE MODEL RUNS GIVEN THE STRENGTH OF  
THIS RIDGE AND ONLY INDICATE 1-4 DEGREES OF COOLING COMPARED TO  
WEDNESDAY. NUMEROUS DETERMINISTIC MODELS FORECAST 500MB HEIGHTS  
IN EXCESS OF 5900 METERS. LOOKING BACK AT HISTORICAL DATA FOR  
500MB HEIGHTS AT THE SPOKANE BALLOON DATA, THE MAXIMUM HEIGHT OF  
5996 METERS WAS ACHIEVED ON SEP 4, IN 1988 AND TWO OTHER OF THE  
TOP TEN READINGS CAME IN EARLY SEPTEMBER. SO RIDGES IN  
SEPTEMBER ARE NOT UNCOMMON BUT HEIGHTS IN EXCESS OF 5900 METERS  
ARE AND THE NAEFS ENSEMBLE SITUATIONAL TABLE INDICATES THE  
FORECAST HEIGHTS OF 5900 METERS HAVE A RETURN INTERVAL OF EVERY  
5 TO 10 YEARS IN EARLY SEPTEMBER. /SB  
 
 
   
AVIATION  
 
06Z TAFS: THE AREA OF LOW PRESSURE RESPONSIBLE FOR SHOWERS AND  
THUNDERSTORMS NEAR THE CASCADES ON THURSDAY WILL DRIFT NORTHWARD  
ON FRIDAY SHIFTING THE THREAT FOR CONVECTION INTO THE NORTHERN  
MOUNTAINS. BONNERS FERRY, COLVILLE, REPUBLIC, AND OMAK HAVE A  
30-50% CHANCE FOR LIGHTNING WHILE COUER D ALENE, DAVENPORT, AND  
WINTHROP VARY FROM 10-20%. CONFIDENCE FOR ACTIVITY TO IMPACT THE  
TAF SITES IS LOW. MODEST DRYING IN THE MIDLEVELS WILL REDUCE THE  
THREAT FOR POINTS FURTHER SOUTH. THUNDERSTORMS WILL BE CAPABLE  
OF TORRENTIAL RAINFALL AND SCATTERED LIGHTNING.  
 
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: HIGH CONFIDENCE  
IN VFR CONDITIONS AT MOST TAF SITES. LOW CONFIDENCE FOR  
THUNDERSTORMS IMPACTING AIRPORT TERMINALS WITH OMAK, COLVILLE,  
AND BONNERS FERRY CONTAINING THE HIGHEST POTENTIAL. /SB  
 
-----------------------  
 
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:/WEATHER.GOV/OTX/AVNDASHBOARD  
 
 
   
PRELIMINARY POINT TEMPS/POPS  
 
SPOKANE 89 59 93 62 97 63 / 0 0 0 0 0 0  
COEUR D'ALENE 88 59 92 62 96 63 / 10 10 0 0 0 0  
PULLMAN 87 54 92 59 94 58 / 0 0 0 0 0 0  
LEWISTON 94 65 97 66 100 67 / 0 0 0 0 0 0  
COLVILLE 89 49 92 51 94 52 / 20 10 0 0 0 0  
SANDPOINT 84 53 90 55 93 57 / 30 20 0 0 0 0  
KELLOGG 84 61 90 64 94 65 / 20 10 0 0 0 0  
MOSES LAKE 92 58 94 64 97 63 / 0 0 0 0 10 10  
WENATCHEE 92 67 94 71 96 71 / 0 0 0 10 10 10  
OMAK 92 63 94 66 97 66 / 10 10 0 0 0 10  
 
 
   
OTX WATCHES/WARNINGS/ADVISORIES  
 
WA...NONE.  
ID...AIR QUALITY ALERT UNTIL 10 AM PDT TUESDAY FOR LEWIS AND  
SOUTHERN NEZ PERCE COUNTIES-LEWISTON AREA.  
 
 
 
 
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