798
FXUS65 KMSO 041826
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1226 PM MDT SAT JUL 4 2026
DISCUSSION
KEY MESSAGES:
- BREEZY AND WARM FOURTH OF JULY: CHOPPY CONDITIONS ON AREA
LAKES
- LOCALIZED HEAVY RAINFALL/GUSTY OUTFLOW WIND THREAT MONDAY AND
TUESDAY WITH SHOWERS AND STORMS.
THIS AFTERNOON AND SUNDAY: THIS AFTERNOON, A WEATHER SYSTEM
PASSING TO OUR NORTH THROUGH BRITISH COLUMBIA WILL FLATTEN THE
RIDGE OF HIGH PRESSURE OVERHEAD, LEADING TO STRONGER WESTERLY
WINDS. EXPECT SUSTAINED WINDS OF 10 TO 20 MPH WITH GUSTS REACHING
20 TO 25 MPH. THIS WILL CREATE CHOPPY CONDITIONS ON AREA LAKES, SO
RECREATIONAL BOATERS SHOULD EXERCISE CAUTION. FORTUNATELY, WINDS
WILL DIMINISH BY DUSK, LEAVING MOSTLY CLEAR SKIES AND CALM
CONDITIONS FOR EVENING FIREWORKS AND HOLIDAY FESTIVITIES.
ADDITIONALLY, A FEW WEAK SHOWERS MAY ATTEMPT TO DEVELOP OVER THE
MOUNTAINS BUT WILL STRUGGLE TO GROW OR PRODUCE ANY RAINFALL.
SUNDAY PROMISES WARM AND MOSTLY STABLE CONDITIONS FOR THE
MAJORITY OF THE NORTHERN ROCKIES. THE MAIN EXCEPTION WILL BE
ACROSS THE SOUTHERN PARTS OF OUR REGION (SPECIFICALLY SOUTHWEST
MONTANA AND LEMHI COUNTY, ID), WHERE MOISTURE SLOWLY MOVING
NORTHWARD WILL INTRODUCE ISOLATED AFTERNOON THUNDERSTORMS. WATCH
FOR GUSTY OUTFLOW WINDS OF 40 TO 45 MPH WITH ANY THUNDERSTORMS AS
FORECAST SOUNDING SHOW AN INVERTED-V PROFILE INDICATING VERY DRY
AIR IN THE LOWER LEVELS OF THE ATMOSPHERE.
MONDAY AND TUESDAY: THE MOST IMPACTFUL WEATHER OF THE WEEK
ARRIVES MONDAY INTO TUESDAY. WEATHER MODELS SHOW A STRONG SURGE OF
MOISTURE PUSHING INTO THE REGION, DRIVING ATMOSPHERIC MOISTURE
LEVELS WELL ABOVE NORMAL (PRECIPITABLE WATER NEAR TO JUST OVER 1
INCH) FOR EARLY JULY. AS AN ATMOSPHERIC DISTURBANCE MOVES THROUGH
THIS MOIST AIR DURING THE HOTTEST PART OF THE AFTERNOON, IT IS
EXPECTED TO TRIGGER ORGANIZED SHOWERS AND THUNDERSTORMS. BECAUSE
OF THESE HIGH MOISTURE LEVELS, ANY STORMS THAT DEVELOP WILL BE
CAPABLE OF PRODUCING HEAVY DOWNPOURS, CREATING LOCALIZED DEBRIS
FLOWS IN FLOOD PRONE AREAS. ADDITIONALLY, THERE IS A POTENTIAL FOR
A STRONG STORM OR TWO WITH GUSTY WINDS TO 50 MPH AND SMALL HAIL.
ONE FACTOR THAT COULD LIMIT THUNDERSTORM DEVELOPMENT IS THICK
MORNING CLOUD COVER, NOT EXPECTED AT THIS POINT BUT SOMETHING TO
WATCH FOR.
WEDNESDAY THROUGH LATE WEEK: ONCE TUESDAY'S SYSTEM CLEARS, THE
REMAINDER OF THE WEEK LOOKS WARM AND RELATIVELY UNEVENTFUL. WE
WILL RETURN TO A MORE TYPICAL SUMMER PATTERN, WITH NEAR-DAILY
CHANCES FOR ISOLATED, POP-UP AFTERNOON THUNDERSTORMS LARGELY
CONFINED TO THE MOUNTAINS OF SOUTHWEST MONTANA. BREEZY WESTERLY
WINDS WILL ALSO BE COMMON EACH AFTERNOON.
A TREND CONTINUES TOWARD A RIDGE OF HIGH PRESSURE OVER THE DESERT
SOUTHWEST EXPANDING NORTHWARD BY NEXT WEEKEND, BUT COMPUTER
MODELS DISAGREE ON EXACTLY WHERE THIS HIGH PRESSURE WILL SET UP
AND HOW STRONG TROUGHING TO THE WEST WILL BE. EVEN HOTTER
TEMPERATURES ARE FAVORED BY ENSEMBLE CLUSTERS IF THE RIDGING
ESTABLISHES NEARBY, MEANWHILE A MINORITY OF CLUSTERS SHOW
INCREASED MOISTURE AND DAILY THUNDERSTORMS COMING FROM THE
SOUTHWEST.
AVIATION
VFR CONDITIONS WILL PREVAIL ACROSS ALL NORTHERN ROCKIES
TERMINALS THROUGH THE WEEKEND. THE PRIMARY OPERATIONAL IMPACT
THIS AFTERNOON WILL BE AN INCREASE IN WESTERLY SURFACE WINDS AS A
WEATHER SYSTEM PASSING THROUGH BRITISH COLUMBIA FLATTENS THE
UPPER-LEVEL RIDGE. TERMINALS CAN EXPECT SUSTAINED WESTERLY WINDS
OF 10 TO 15 KNOTS WITH AFTERNOON GUSTS REACHING 20 KNOTS, WHICH
MAY GENERATE LOCALIZED MECHANICAL TURBULENCE FOR LIGHT AIRCRAFT
ALONG AND NEAR ELEVATED TERRAIN. THESE GUSTY WINDS WILL DECOUPLE
AND RAPIDLY DIMINISH BY DUSK, RESULTING IN LIGHT, TERRAIN-DRIVEN
WINDS AND MOSTLY CLEAR SKIES FOR THE OVERNIGHT HOURS. BREEZY
WESTERLY WINDS WILL ONCE AGAIN DEVELOP ON SUNDAY AFTERNOON.
A FEW WEAK SHOWERS MAY ATTEMPT TO DEVELOP ON THE TERRAIN THIS
AFTERNOON BUT WEAK INSTABILITY SHOULD LIMIT MUCH VERTICAL GROWTH.
THERE WILL BE A SLIGHT INCREASE IN MOISTURE AND INSTABILITY FOR
SUNDAY AFTERNOON LEADING TO ISOLATED SHOWERS AND ISOLATED
THUNDERSTORMS ACROSS LEMHI COUNTY AND SOUTHWEST MONTANA. INVERTED-V
SOUNDINGS INDICATE DRY LOW-LEVEL AIR AND GUSTY OUTFLOW WIND
POTENTIAL TO 40 KTS WITH STRONGER STORMS.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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