398
FXUS65 KMSO 152020
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
220 PM MDT WED JUL 15 2026
DISCUSSION
KEY MESSAGES:
- THUNDERSTORMS ARE IN THE FORECAST THROUGH THE WEEK FOR MUCH OF
WESTERN MONTANA AND PORTIONS OF CENTRAL IDAHO.
- STRONG TO POTENTIALLY SEVERE THUNDERSTORMS MAY OCCUR IN
PORTIONS OF WESTERN MONTANA ON THURSDAY AFTERNOON AND EVENING;
MAIN THREATS BEING STRONG WINDS, HAIL AND VERY HEAVY RAIN
- ABOVE NORMAL TEMPERATURES OCCURRING INTO NEXT WEEK
WESTERN MONTANA AND NORTH CENTRAL IDAHO REMAIN SANDWICHED BETWEEN
STRONG HIGH PRESSURE TO THE EAST AND A LOW PRESSURE SYSTEM OFF THE
BRITISH COLUMBIA COAST, PLACING THE REGION UNDER SOUTHWEST FLOW
ALOFT. SURGES OF MOISTURE FROM THE NORTH AMERICAN MONSOON WILL
MAINTAIN ABNORMALLY HIGH ATMOSPHERIC MOISTURE CONTENT THROUGH THE
REST OF THE WORK WEEK, BRINGING A DAILY CHANCE OF SHOWERS AND
THUNDERSTORMS. ABOVE NORMAL TEMPERATURES WILL ALSO REMAIN ACROSS
THE REGION INTO THE WEEKEND.
THURSDAY AFTERNOON AND EVENING IS STANDING OUT AS A PERIOD OF
POTENTIALLY MORE WIDESPREAD STRONG TO SEVERE THUNDERSTORMS ACROSS
THE ENTIRE REGION. AS THE LOW PRESSURE SYSTEM MENTIONED EARLIER
SAGS SOUTHWARDS SLIGHTLY, IT WILL WEAKEN THE RIDGE OF HIGH
PRESSURE OVER THE REGION ENOUGH TO INCREASE INSTABILITY. A WAVE
OF ENERGY MOVING THROUGH THE FLOW WILL COUPLE WITH THE ABOVE
NORMAL MOISTURE TO CREATE CONDITIONS FAVORABLE FOR STRONG WINDS,
HAIL AND VERY HEAVY RAINFALL. THE ONE LIMITING FACTOR TO STORM
STRENGTH MAY BE THE POTENTIAL FOR CLOUD COVER TO DAMPEN THE
AMOUNTS OF HEATING (AND THUS INSTABILITY) TOMORROW AFTERNOON.
CURRENT MODELS SHOW CLEAR SKIES FOR MUCH OF TOMORROW MORNING,
HOWEVER, THEY CURRENTLY SEEM TO BE UNDERESTIMATING THE AMOUNT OF
MOISTURE OVER THE REGION AND THUS MAY NOT BE FULLY REPRESENTING
THE POTENTIAL FOR CLOUD COVER. THAT WILL BE ONE THING WE WILL BE
MONITORING CLOSELY AS WE APPROACH THURSDAY MORNING.
THE STORM PREDICTION CENTER HAS PLACED LOCATIONS FROM MISSOULA
SOUTH AND EAST TO BUTTE UNDER A SLIGHT RISK (15 PERCENT CHANCE) OF
SEVERE WIND GUSTS OVER 58 MPH AND HAIL OF 1 INCH DIAMETER OR
GREATER. THOUGH NOT CURRENTLY REFLECTED IN THE FORECAST, RECENT
HIGH RESOLUTION MODELS ARE BEGINNING TO SHOW ANOTHER AREA OF
POTENTIALLY SEVERE STORMS DEVELOPING IN THE IDAHO PANHANDLE INTO
FAR NORTHWEST MONTANA. THERE ARE ALSO HINTS THAT THIS AREA
(NORTHWEST MONTANA) MAY SEE THE STRONGEST THUNDERSTORM POTENTIAL
LATE THURSDAY EVENING INTO EARLY FRIDAY MORNING. BEYOND THE
THREATS OF WIND, LIGHTNING AND HAIL, STORMS MAY BE CAPABLE OF
RAINFALL RATES OF HALF AN INCH PER HOUR OR MORE. RECENT BURN SCARS
AND FLOOD PRONE AREAS COULD BE IN DANGER OF ROCK/DEBRIS FLOWS IF
THEY TAKE A DIRECT HIT FROM STORMS.
SIMILAR CONDITIONS WILL BE IN PLACE FRIDAY AFTERNOON AND EVENING,
THOUGH ATMOSPHERIC FORCING MAY NOT BE QUITE AS FAVORABLE.
NEVERTHELESS, THE POTENTIAL FOR ANOTHER ROUND OF STRONG TO SEVERE
STORMS CONTINUES.
ON SATURDAY, THE PACIFIC LOW PRESSURE SYSTEM MOVES NORTH OF OUR
REGION AND THE FLOW FLATTENS TO A DRIER, WESTERLY FLOW WITH
DECREASED INSTABILITY. THE CHANCES OF AFTERNOON SHOWERS AND
THUNDERSTORMS MAY BE CONFINED TO SOUTHWEST MT. ADDITIONALLY, AS
THE GRADIENT BETWEEN LOW PRESSURE IN CANADA AND HIGH PRESSURE
RIDGE IN THE DESERT SOUTHWEST INCREASES, EXPECT A BREEZY
AFTERNOON.
AVIATION
VFR CONDITIONS EXPECTED ACROSS THE REGION UNDER A
RIDGE OF HIGH PRESSURE THROUGH 16/18Z. THEN TOMORROW AFTERNOON
THUNDERSTORMS WILL INITIATE OFF THE TERRAIN AND POTENTIALLY AFFECT
ALL AREA TERMINALS. KSMN, KHRF, AND KBTM WILL BE THE FIRST TO BE
AFFECTED BY THUNDERSTORMS NOT LONG AFTER THEY INITIATE. TERMINAL
KMSO WILL MORE LIKELY BE AFFECTED AFTER 16/23Z, AND TERMINAL KGPI
WILL LIKELY HAVE AN EVEN LATER START WITH THE POTENTIAL FOR STORMS
LASTING THROUGH THE NIGHT AND PAST 17/06Z. THERE IS A 5% CHANCE OF
WIND GUSTS OF 60KTS OR MORE AND HAIL FROM SEVERE THUNDERSTORMS
AFFECTING KGPI, KMSO, KHRF, AND KBTM TOMORROW.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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