606
FXUS65 KMSO 120847
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
247 AM MDT WED AUG 12 2026
DISCUSSION
KEY MESSAGES:
* STRONG, SUDDEN NORTHEAST WIND SHIFT THIS EVENING ACROSS
NORTHWEST MONTANA, INCLUDING FLATHEAD LAKE.
* THUNDERSTORMS CAPABLE OF 50+ MPH WIND GUSTS ACROSS SOUTHWEST
MONTANA AND EXTREME NORTHWEST MONTANA, LATE-AFTERNOON AND
EVENING.
FIRE WEATHER, AIR QUALITY, AND NORTHEAST WIND TODAY/TONIGHT:
SMOKE HAS ONCE AGAIN POOLED INTO VALLEY AREAS THIS MORNING AS
SHARP INVERSIONS HAVE DEVELOPED OVERNIGHT UNDER CLEAR SKIES. GOES
SATELLITE IMAGERY SHOWS MONSOON MOISTURE BEGINNING TO STREAM INTO
MID-UPPER LEVELS OF THE ATMOSPHERE AS SOUTH-SOUTHWEST FLOW HAS
DEVELOPED ALOFT. WARM AND DRY CONDITIONS ARE EXPECTED IN LOWER
PORTIONS OF THE ATMOSPHERE THROUGH THIS AFTERNOON, WITH LATE
AFTERNOON GUSTY WINDS LEADING TO ELEVATED FIRE WEATHER CONCERNS,
ESPECIALLY ACROSS SOUTHWEST MONTANA. THE AFTERNOON WINDS MAY
PROVIDE LOCALIZED TEMPORARY RELIEF FROM HIGHLY CONCENTRATED
WILDFIRE SMOKE. CONFIDENCE HAS INCREASED FOR A STRONG AND SUDDEN
NORTHEAST WIND SHIFT THIS EVENING ACROSS NORTHWEST MONTANA, WITH
GUSTS OF 30-40 MPH ACROSS THE FLATHEAD VALLEY, FLATHEAD LAKE, AND
WESTERN FOOTHILLS OF THE MISSION MOUNTAINS. A LAKE WIND ADVISORY
HAS BEEN ISSUED AS THIS WIND SHIFT WILL BRING HAZARDOUS
CONDITIONS FOR THOSE WITH PLANS ON OUTDOOR LAKES THIS EVENING.
THUNDERSTORMS RETURN:
MONSOON MOISTURE WILL CONTINUE TO STREAM INTO THE REGION, OPENING
THE DOOR FOR HIGH BASED SHOWERS AND THUNDERSTORMS BY MID-AFTERNOON
THROUGH THE EVENING. WARM AND DRY SUB-CLOUD LAYERS WILL PROMOTE MAINLY
DRY THUNDERSTORMS CAPABLE OF 40+ MPH WIND GUSTS OVER SOUTHWEST
MONTANA AND ACROSS EXTREME NORTHWEST MONTANA. LITTLE APPRECIABLE
RAINFALL IS EXPECTED WITH THE WEDNESDAY STORMS, HOWEVER MOISTURE
WILL BECOME MUCH MORE AVAILABLE FOR SUBSEQUENT DAYS THROUGH THE
WEEKEND. IN FACT, A MARGINAL RISK OF EXCESSIVE RAINFALL ARRIVES AS
SOON AS THURSDAY, WITH RECENT AND ONGOING WILDFIRES HAVING THE
HIGHEST RISK OF RUNOFF AND FLOOD IMPACTS. THE PRESENCE OF WILDFIRE
SMOKE WILL BE A BIT OF WILD CARD IN THE EFFICIENCY OF
THUNDERSTORM DEVELOPMENT.
BIGGER PATTERN CHANGE TO COME?
LONG RANGE MODEL ENSEMBLES SUGGEST THAT A LOW PRESSURE TROUGH WILL
PERSIST OFF COASTAL WESTERN US NEXT WEEK. MOST PATTERN SOLUTIONS
FEATURE EITHER SOUTHWEST FLOW ALOFT OR A RIDGE OF HIGH PRESSURE OVER
THE NORTHERN ROCKIES. EITHER WAY, THE MOISTURE FROM TROPICAL STORMS
IN THE PACIFIC OCEAN WILL PLAY A FACTOR IN WHETHER TEMPERATURES
RETURN TO SUMMERTIME WARMTH OR NOT. WILDFIRE SMOKE IS STILL A BIG
QUESTION MARK NEXT WEEK. OVERALL, THE PATTERN WILL BE MOVING AWAY
FROM ELEVATED TO CRITICAL FIRE WEATHER CONCERNS (HOT, DRY, WINDY
PATTERN) THAT WE'VE HAD CONSISTENTLY FOR MANY DAYS.
AVIATION
WILDFIRE SMOKE WILL CONTINUE TO LIMIT VISIBILITY
ACROSS THE NORTHERN ROCKIES AIR SPACE DURING THE NEXT 24 HOURS.
THESE VISIBILITY REDUCTIONS WILL BE FOCUSED DURING THE MORNING
HOURS, FROM MISSOULA INTO THE BITTERROOT VALLEY AND ALONG THE
DIVIDE IN SOUTHWEST MONTANA. SHOWER AND THUNDERSTORM ACTIVITY WILL
DEVELOP ACROSS THE HIGHER TERRAIN IN LEMHI COUNTY INTO SOUTHWEST
MONTANA AND FAR NORTHWEST MONTANA BY EARLY AFTERNOON. LIGHTNING
CHANCES INCREASE (30% PROBABILITY) FOR KGPI AND KBTM AFTER
12/2100Z AS WELL. ANOTHER WEATHER IMPACT DURING THIS TIME WILL BE
SURFACE WIND SHIFTING TO NORTHEAST FROM NORTH TO SOUTH ACROSS
WESTERN MONTANA THIS EVENING INTO THURSDAY MORNING. 30-40 KNOT
WINDS WILL EXIST OVER THE TERRAIN ALONG THE PORTION OF THE
CONTINENTAL DIVIDE JUST EAST OF KGPI, WITH LESSER WIND SPEEDS
FURTHER SOUTH.
MSO WATCHES/WARNINGS/ADVISORIES
MT...LAKE WIND ADVISORY FROM 6 PM THIS EVENING TO MIDNIGHT MDT
TONIGHT FOR FLATHEAD/MISSION VALLEYS.
ID...NONE.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page