916
FXUS65 KGGW 061930
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
130 PM MDT SUN SEP 6 2026
KEY MESSAGES
- SHOWER AND THUNDERSTORM CHANCES AT TIMES TODAY WITH SOME
BECOMING STRONG TO SEVERE. HAZARDS INCLUDE LARGE HAIL, STRONG
ERRATIC WINDS, AND BRIEF TORRENTIAL RAINFALL.
- WIDESPREAD RAIN IS EXPECTED TONIGHT THROUGH MONDAY NIGHT AS THE
UPPER LOW MOVES THROUGH MONTANA.
- STRONG WEST WINDS DEVELOP MONDAY AFTERNOON AND CONTINUE THROUGH
TUESDAY NIGHT.
- COOLER START AND END TO THE WEEK, WITH A BRIEF WARM UP AROUND
MID WEEK.
DISCUSSION
WEATHER PATTERN OVERVIEW:
MONTANA WILL BE IN SW FLOW ALOFT TODAY WITH UPPER LOW OVER THE
PACIFIC NW AND UPPER RIDGE TO THE EAST. A HUMID AIRMASS WILL
COMBINE WITH THE MOIST SW FLOW ALOFT TODAY TO CREATE AN UNSTABLE
ATMOSPHERE WHICH WILL ALLOW FOR CHANCES FOR SHOWERS AND
THUNDERSTORMS AT TIMES. A FEW STORMS COULD BECOME SEVERE WITH
LARGE HAIL AND DAMAGING WINDS. PWATS MEASURING NEAR THE DAILY MAX,
AND WELL ABOVE THE 90TH PERCENTILE, PROVIDE STRONGER STORMS AMPLE
MOISTURE FOR HIGH RAINFALL RATES. HREF GUIDANCE SUGGESTS 1HR QPF
GREATER THAN 0.25", AND A 3HR QPF MAXIMUM OF GREATER THAN 4".
WHILE MEETING THIS IS UNLIKELY, STORMS WILL BE ABLE TO PRODUCE
TORRENTIAL RAINFALL. ANY STORM THAT STALLS OR MOVES SLOWLY MAY
LEAD TO LOCALIZED FLOODING. NAM FORECAST SOUNDINGS SUGGEST VERY
HIGH MUCAPE AND STRONG DEEP LAYER SHEAR AFTER 3Z. GIVEN THE
ISOLATED UPDRAFT HELICITY TRACKS DURING THE SAME WINDOW VALUES
BETWEEN 150-300 M^2/S^2 SUPPORTS AN ISOLATED SUPERCELL OR TWO.
THE UPPER LOW MOVES INTO MONTANA ON MONDAY AS THE SURFACE LOW
MOVES NORTH INTO SASKATCHEWAN. RAIN IS EXPECTED TO CONTINUE MOST
OF THE TIME IN THE NORTH WHILE THE MODELS DIFFER ON HOW MUCH THE
DRY SLOT WILL LIMIT RAIN IN THE SOUTH. THE UPPER LOW MOVES TO
SASKATCHEWAN AND MANITOBA TOMORROW NIGHT AND BECOMES STACKED WITH
THE SURFACE LOW. GUSTY WEST WINDS WILL DEVELOP DURING THE DAY ON
TOMORROW AND CONTINUE THROUGH TUESDAY WITH GUSTS TO 40 TO 50 MPH
POSSIBLE. WRAP AROUND RAIN IS LIKELY MONDAY NIGHT AND TUESDAY OVER
THE NW HALF OF THE FORECAST AREA WHILE THE SE WILL BE DRY MOST OF
THE TIME.
RAINFALL TOTALS 1 TO 2 INCHES ARE LIKELY IN THE NW BETWEEN TONIGHT
AND TUESDAY WHILE SOME AREAS IN THE SE COULD END UP WITH LESS THAN
A TENTH OF AN INCH.
THE SYSTEM EXITS THE REGION TUESDAY NIGHT AND WEDNESDAY AND
THURSDAY ARE EXPECTED TO BE DRY.
FORECAST CONFIDENCE & DEVIATIONS:
UPPED DAY 1-2 POPS TO FURTHER COLLABORATION. DID NOT TOUCH WINDS
OR WIND GUSTS, BUT GIVEN HOW OFTEN WE SURPASS NBM WINDS DURING
STRONG LOWS AND 60KT 700MB WINDS, THAT WILL NEED TO BE A
CONVERSATION WITH NEIGHBORS SOON.
AVIATION
LAST UPDATED: 1830Z
FLIGHT CAT RANGE: VFR, DIMINISHING MVFR CIGS. MVFR IN ANY STRONG
STORMS TONIGHT.
DISCUSSION: LOW LEVEL CLOUDS CAUSING MVFR/IFR CIGS CONTINUE TO
LIFT AND CLEAR, BUT RETURN AND AGAIN AFTER 12Z MONDAY. WIDESPREAD
RAIN WITH SCATTERED THUNDERSTORMS WILL DEVELOP LATE TONIGHT AND
CONTINUE ON MONDAY.
WINDS: NORTH TO NORTHEAST AT 5 - 15 KNOTS TODAY BECOMING EAST TO
NE TONIGHT. WINDS BEGIN TO SHIFT AFTER 14Z FOLLOWING A SURFACE
LOW. STRONG WEST WINDS 20 - 25 KTS BEGIN IN THE AFTERNOON TOMORROW
AND LAST THROUGH TUESDAY NIGHT.
GGW WATCHES/WARNINGS/ADVISORIES
NONE.
WEATHER.GOV/GLASGOW
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