966
FXUS65 KMSO 050736
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
136 AM MDT SUN JUL 5 2026
DISCUSSION
KEY MESSAGES:
- GUSTY WINDS WITH THUNDERSTORMS THIS AFTERNOON IN LEMHI COUNTY
AND IN THE VICINITY OF BUTTE.
- LOCALIZED HEAVY RAINFALL/GUSTY OUTFLOW WIND THREAT MONDAY AND
TUESDAY WITH SHOWERS AND STORMS.
WARM AND MOSTLY STABLE CONDITIONS WILL PREVAIL ACROSS THE MAJORITY
OF THE REGION TODAY. HOWEVER, MOISTURE SLOWLY ADVANCING NORTHWARD
INTO SOUTHWEST MONTANA AND LEMHI COUNTY, IDAHO, WILL INTRODUCE
ISOLATED AFTERNOON THUNDERSTORMS. THERE IS A MARGINAL RISK FOR
THESE STORMS TO PRODUCE STRONG, GUSTY OUTFLOW WINDS OF 40 TO 50
MPH, PARTICULARLY IN LEMHI COUNTY AND AROUND THE BUTTE AREA, AS
RAIN FALLS THROUGH A VERY DRY LOWER ATMOSPHERE.
THE WEEK'S MOST IMPACTFUL WEATHER ARRIVES MONDAY INTO TUESDAY AS A
STRONG SURGE OF SUBTROPICAL MOISTURE PUSHES INTO THE REGION,
RAISING ATMOSPHERIC MOISTURE LEVELS WELL ABOVE NORMAL FOR EARLY
JULY. AS A WEATHER DISTURBANCE INTERACTS WITH THIS MOISTURE DURING
PEAK AFTERNOON HEATING ON MONDAY, ORGANIZED SHOWERS AND
THUNDERSTORMS ARE EXPECTED TO DEVELOP.
THESE STORMS WILL PRIMARILY TARGET NORTH-CENTRAL IDAHO AND
WEST-CENTRAL TO SOUTHWEST MONTANA DURING THE AFTERNOON AND
EVENING. THEY WILL CARRY MULTIPLE HAZARDS, INCLUDING LIGHTNING
CAPABLE OF IGNITING NEW WILDFIRES AND GUSTY WINDS REACHING 40 TO
50 MPH. ABUNDANT MOISTURE WILL ALSO FUEL HEAVY DOWNPOURS WITH
RAINFALL RATES OF 0.50 TO 0.75 INCHES PER HOUR, CREATING A RISK
FOR LOCALIZED DEBRIS FLOWS IN FLOOD-PRONE AREAS. FORECAST MODELS
SHOW THICK CLOUD COVER MOVING INTO THE REGION MONDAY MORNING,
WHICH COULD INHIBIT THE OVERALL STRENGTH OF CONVECTION. HOWEVER,
ATMOSPHERIC FORCING BY MONDAY AFTERNOON MAY BE ENOUGH TO OVERCOME
THIS.
BY WEDNESDAY AND CONTINUING THROUGH THE LATTER HALF OF THE WEEK, THE
REGION WILL TRANSITION BACK TO A TYPICAL SUMMER PATTERN FOLLOWING
THE DEPARTURE OF TUESDAY'S SYSTEM. CONDITIONS WILL REMAIN WARM
AND RELATIVELY QUIET, FEATURING BREEZY WESTERLY AFTERNOON WINDS
AND NEAR-DAILY CHANCES FOR ISOLATED, POP-UP THUNDERSTORMS LARGELY
CONFINED TO THE MOUNTAINS OF SOUTHWEST MONTANA.
LOOKING AHEAD TO NEXT WEEKEND AND INTO MID-JULY, FORECAST MODELS
INDICATE A STRONG RIDGE OF HIGH PRESSURE CURRENTLY OVER THE
DESERT SOUTHWEST WILL EXPAND NORTHWARD. WHILE THE EXACT PLACEMENT
OF THE HIGH PRESSURE REMAINS UNCERTAIN, THE PREVAILING TREND
STRONGLY FAVORS A SHIFT TOWARD WELL ABOVE NORMAL TEMPERATURES AND
GENERALLY DRIER CONDITIONS.
AS THIS PROLONGED HEAT BUILDS LATE IN THE WEEK AND THROUGH THE
WEEKEND, THE RISK FOR HEAT RELATED ILLNESSES WILL SIGNIFICANTLY
INCREASE. THIS WILL BE ESPECIALLY TRUE FOR VULNERABLE POPULATIONS
AND THOSE RECREATING OUTDOORS WITHOUT ADEQUATE HYDRATION AND
SHADE. ALTHOUGH A MINORITY OF FORECAST MODELS SUGGEST THIS HIGH-
PRESSURE SETUP COULD PERIODICALLY DRAW MOISTURE UP FROM THE
SOUTHWEST TO TRIGGER DAILY THUNDERSTORMS, ESCALATING EXTREME HEAT
WILL BE THE PRIMARY HAZARD TO MONITOR AS WE MOVE INTO THE SECOND
HALF OF THE MONTH.
AVIATION
PREDOMINANTLY VFR CONDITIONS WILL PREVAIL ACROSS THE
MAJORITY OF THE REGION TODAY UNDER STABLE ATMOSPHERIC CONDITIONS.
HOWEVER, ISOLATED AFTERNOON THUNDERSTORMS WILL IMPACT SOUTHERN
TERMINALS AS MOISTURE ADVANCES NORTHWARD. THE PRIMARY TERMINALS OF
CONCERN ARE KSMN AND KBTM, WITH THE MOST LIKELY TIMEFRAME FOR
CONVECTIVE ACTIVITY BETWEEN 05/2100Z AND 06/0100Z AT KSMN, AND
BETWEEN 05/2200Z AND 06/0200Z AT KBTM. HIGH-RESOLUTION MODEL
GUIDANCE INDICATES A ROUGHLY 30 PERCENT CHANCE OF ERRATIC OUTFLOW
WINDS GUSTING OVER 30 KNOTS IN THE VICINITY OF THESE STORMS,
DRIVEN BY RAIN FALLING THROUGH A VERY DRY LOWER ATMOSPHERE. NO
OTHER AIRFIELDS ARE EXPECTED TO EXPERIENCE THUNDERSTORM IMPACTS
TODAY, WITH DRY AND STABLE CONDITIONS MAINTAINING CLEAR FLIGHT
CATEGORIES ELSEWHERE ACROSS WESTERN MONTANA AND NORTH-CENTRAL
IDAHO.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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