409
FXUS65 KMSO 121837
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
1237 PM MDT FRI JUN 12 2026
DISCUSSION
KEY MESSAGES:
- A COLD FRONT WILL MOVE NORTH TO SOUTH THROUGH THIS EVENING,
BRINGING SCATTERED THUNDERSTORMS, LOCALIZED HEAVY RAIN, AND
WIND GUSTS UP TO 40 MPH.
- HIGH PRESSURE THIS WEEKEND INTO EARLY NEXT WEEK BRINGING
WARMING TREND, WITH 80S FOR WESTERN MONTANA AND MID-UPPER 90S
FOR CENTRAL IDAHO.
- WEST-NORTHWEST FLOW PATTERN BY MIDDLE OF NEXT WEEK, OPENING THE
DOOR FOR PERIODIC DISTURBANCES, SHOWERS, AND THUNDERSTORMS.
SHOWERS AND THUNDERSTORMS HAVE DEVELOPED ACROSS LINCOLN AND
FLATHEAD COUNTY EARLY THIS AFTERNOON, WITH SATELLITE IMAGERY
POINTING TOWARDS CONVECTION INITIATE NORTH OF THE I-90 CORRIDOR
WITHIN THE NEXT FEW HOURS. A POTENT SHORTWAVE AND SURFACE COLD
FRONT REMAIN ON TRACK TO MOVE SOUTHWARD FROM CANADA THROUGH THIS
EVENING. HIGH-RESOLUTION MODELS ARE IN GOOD AGREEMENT FOR SHOWERS
AND THUNDERSTORMS TO PROGRESS SOUTHWARD THROUGH THIS EVENING,
ARRIVING ALONG THE INTERSTATE 90 CORRIDOR BETWEEN 5:00 PM AND
8:00 PM LOCAL TIME.
SHOWERS AND THUNDERSTORMS WILL STRUGGLE TO ORGANIZE AS VERTICAL
PROFILES SUGGEST LIMITED MOISTURE AND WIND SHEAR. THE LACK OF
SHEAR SUGGESTS PULSE CONVECTION, WHICH RADAR IMAGERY HAS POINTED
TOWARDS THUS FAR. GIVEN THIS, THUNDERSTORM CORES WILL PRIMARILY
BRING LOCAL HEAVY RAIN AND GUSTY OUTFLOW WIND CONCERNS. THE
HEAVIER RAIN RATES WILL FOCUS ACROSS NORTHWEST MONTANA AND OVER
THE HIGHER TERRAIN, WITH RAINFALL RATES OF 0.30 TO 0.50 INCHES
PER HOUR. HIGH RESOLUTION MODELS SUGGEST ERRATIC MICROBURST
OUTFLOW UP TO 40 MPH, MOVING NORTH TO SOUTH AS CONVECTION
DEVELOPS ALONG THE COLD FRONT. THOSE WITH OUTDOOR RECREATION PLANS
ON AREAS LAKE SHOULD MONITOR CONDITIONS CLOSELY, ESPECIALLY ON
FLATHEAD LAKE. CONVECTIVE DEVELOPMENT WILL DECREASE RAPIDLY AS THE
FRONT CROSSES SOUTH OF THE I-90 CORRIDOR AND THE SUN SETS,
KEEPING NORTH- CENTRAL IDAHO AND SOUTHWEST MONTANA LARGELY DRY.
COOL, BREEZY NORTHERLY FLOW ESTABLISHES BEHIND THE FRONT ON
SATURDAY.
MODEL ENSEMBLES ARE IN STRONG AGREEMENT (90% CONFIDENCE IN CLUSTER
ANALYSIS) FOR HIGH PRESSURE TO BUILD AND SHIFT INLAND ALONG THE
PACIFIC NORTHWEST COAST THIS WEEKEND. THIS LEAVES THE NORTHERN
ROCKIES POSITIONED UNDER WEST-NORTHWEST FLOW ALOFT WITH STRONG
SUBSIDENCE AND WARMING TO OUR WEST. VALLEY TEMPERATURES WILL
CLIMB INTO THE UPPER-70S AND 80S ACROSS WESTERN MONTANA. EXTREME
LOW ELEVATION RIVER VALLEYS OF CENTRAL IDAHO WILL PUSH INTO THE
MID-TO-UPPER 90S BY TUESDAY.
FORECAST UNCERTAINTY BEGINS TO INCREASE BY THE MIDDLE OF NEXT
WEEK. MODEL CLUSTER ANALYSIS POINTS TOWARDS DIFFERENCES WITH THE
UPPER LEVEL RIDGE AND TROUGH AXIS WEST AND EAST OF THE NORTHERN
ROCKIES. OVERALL, ENSEMBLE MEANS PLACE THE NORTHERN ROCKIES
WITHIN WEST-NORTHWEST FLOW ALOFT BETWEEN THE RIDGE AXIS TO THE
WEST AND TROUGH AXIS TO THE EAST. HISTORICALLY, OUR AREA IS
SUSCEPTIBLE TO DISTURBANCES DROPPING SOUTHEASTWARD FROM CANADA,
OPENING THE DOOR FOR SHOWER AND THUNDERSTORM ACTIVITY. MODEL
CLUSTERS HAVE DIFFERENT IDEAS ON THE AMOUNT OF MOISTURE,
INSTABILITY, AND FORCING WITHIN THESE DISTURBANCES. THE CURRENT
OFFICIAL FORECAST HAS SHOWERS AND THUNDERSTORMS ALONG THE DIVIDE
AND IN NORTHWEST MONTANA, WITH OTHER AREAS REMAINING MOSTLY DRY.
AROUND 20% OF MODEL ENSEMBLE CLUSTERS BRING SHOWERS AND
THUNDERSTORMS INTO WESTERN MONTANA AND NORTH-CENTRAL IDAHO BY
WEDNESDAY THROUGH FRIDAY. THOSE WITH OUTDOOR PLANS BY THE MIDDLE
TO END OF NEXT WEEK SHOULD MONITOR THE FORECAST CLOSELY.
AVIATION
A COLD FRONT IS DIVING SOUTH OUT OF CANADA THIS
AFTERNOON. FRONTAL PASSAGE IS CAUSING SCATTERED THUNDERSTORMS
CAPABLE OF LOCALIZED MVFR VISIBILITY/CEILINGS IN EMBEDDED HEAVY
DOWNPOURS, SMALL HAIL, AND ERRATIC OUTFLOW WIND GUSTS AS HIGH AS
40 KNOTS. POST-FRONTAL NORTHERLY WINDS WILL REMAIN GUSTY BEFORE
STABILIZING LATE OVERNIGHT.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
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