309
FXUS65 KGGW 190452
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
1052 PM MDT MON MAY 18 2026
KEY MESSAGES
- THIS MORNING WILL BE COLD ACROSS NORTHEAST MONTANA, WITH
CHANCES FOR NEAR RECORD LOWS IF CLOUDS CLEAR OUT OVERNIGHT.
- WEDNESDAY AFTERNOON INTO THURSDAY MORNING LOOKS LIKE THE NEXT
CHANCE FOR SHOWERS AND PERHAPS AND FEW THUNDERSTORMS. MOST AREAS
THAT WOULD BE HIT LOOK TO HAVE LESS THAN A TENTH OF AN INCH.
- WARM WEATHER RETURNS BRIEFLY WEDNESDAY WITH 70S & 80S FOR HIGHS
EXPECTED FRIDAY ONWARD.
DISCUSSION
WEATHER PATTERN OVERVIEW:
FORECAST BEGINS WITH A LARGE COLD AIRMASS OVER THE HUDSON BAY. A
TROUGH RUNS WEST OUT OF IT AND DOWN THROUGH SOUTHERN CANADIAN
PRAIRIE PROVINCES AND EASTERN MONTANA, AND TERMINATES OVER
NORTHERN UTAH. AN EQUALLY AMPLIFIED RIDGE RUNS FROM NORTHERN
CALIFORNIA THE PCNW, ALBERTA, AND TERMINATES OVER THE NORTHWEST
TERRITORIES.
THIS MORNING THROUGH TONIGHT: CONDITIONS WILL START OFF COOL WITH
A GROUND FREEZE INITIALLY AS CLEAR SKIES HOVER OVER THE AREA. BY
THE LATE AFTERNOON A NEW ROUND OF MID TO UPPER CHINOOK ARCH CLOUDS
WILL MOVE IN FROM THE WEST ALONG WITH SLIGHTLY WARMER TEMPS UNDER
THE HIGHLY AMPLIFIED RIDGE.
WEDNESDAY INTO THURSDAY MORNING: RIDGE WILL EXIT THE AREA AS A
SHORTWAVE BEGINS TO DRIVE ITSELF DOWN IN NORTHWESTERN FLOW. AS THE
RIDGE BREAKS DOWN A LOW PRESSURE SURFACE TROUGH WILL FORM OVER
CENTRAL MONTANA MID DAY. BY THE LATE AFTERNOON AND EARLY EVENING
HOURS THIS WILL MOVE INTO EASTERN MONTANA ALONG A COLD FRONT WITH
RAIN SHOWERS AND PERHAPS A FEW THUNDERSTORMS. MOST STORMS SHOULD
EXIT OVERNIGHT WITH THE HEAT LEAVING RAIN SHOWERS TO LINGER INTO
THURSDAY MORNING. QPF TOTALS ARE IN FLUX CURRENTLY UNKNOWN BUT
GENERALLY A TENTH OF AN INCH OR LESS IS EXPECTED FOR THIS PASSAGE.
THURSDAY AFTERNOON INTO THE WEEKEND: CONDITIONS WILL CLEAR AND
WARM THROUGH THESE TIME PERIODS WITH MAYBE A WEAK SHOWER POSSIBLE
SATURDAY NIGHT WITH ENSEMBLE BREAKDOWN OCCURING ABOUT THIS POINT
FORWARD MAKING CONFIDENCE FROM SATURDAY ONWARD LOW.
FORECAST CONFIDENCE & DEVIATIONS:
CHANGES TO NBM WERE FOCUSED TO HOURLY POPS AROUND WEDNESDAY MID-
DAY TO THE EVENING. HOURLY NBM DATA WAS BEING DIRECT INTERPOLATED
IN THE LAST 5 HOURS. USED AND NPOP BLEND OF AVAILABLE CAMS TO TRY
TO QUICK BLEND IN A SLIGHTLY BETTER TREND.
GAH
AVIATION
LAST UPDATED: 0330Z
FLIGHT CAT RANGE: VFR.
DISCUSSION: OVERCAST CONDITIONS ACROSS THE EAST THIS EVENING ARE
EXPECTED TO EXIT THE AREA BY THE EARLY MORNING HOURS. A FEW
ISOLATED FOG POCKETS MAY BE POSSIBLE NORTHEAST OF KOLF AND KSDY AS
CLOUDS CLEAR BUT SHOULD NOT IMPACT THE MAIN TERMINALS DIRECTLY
TONIGHT. SUN-UP CONDITIONS SHOULD BE SKC BUT MID TO HIGH CLOUDS
WILL BEGIN APPROACHING THE AREA FROM THE WEST LATE TUESDAY
AFTERNOON EARLY EVENING.
WIND: LIGHT AND VARIABLE TONIGHT. BECOMING S TO SW AFTER SUN-UP
AND INCREASING TO 5 TO 15 KTS THROUGH TUESDAY. BACKING S TO SE
TUESDAY EVENING.
GAH
GGW WATCHES/WARNINGS/ADVISORIES
NONE.
WEATHER.GOV/GLASGOW
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