877
FXUS65 KGGW 271859
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
1259 PM MDT SUN SEP 27 2026
KEY MESSAGES
- HIGHS WILL REMAIN THE 60S AND 70S THROUGH THE END OF THE COMING
WORK WEEK.
- ISOLATED RAIN SHOWERS ARE EXPECTED ACROSS THE AREA TONIGHT INTO
MONDAY MORNING. ONLY REPORTABLE TOTALS ANTICIPATED MAY BE A FEW
HUNDREDTHS ON THE SE SIDE OF THE YELLOWSTONE VALLEY.
- THE FIRST MAJOR FROST OF THE SEASON WILL LIKELY BE THURSDAY
MORNING ALONG RIVER BOTTOMS BEHIND A COLD FRONTAL PASSAGE.
- TUESDAY AFTERNOON IS BEING MONITORED FOR POTENTIAL FIRE WX
CONCERNS IN THE NORTHEAST.
DISCUSSION
SYNOPTIC SETUP: FORECAST BEGINS WITH HOT HIGH PRESSURE OVER THE
FOUR CORNERS PUSHING INTO WYOMING. A BROAD TROUGH OVER THE WESTERN
TWO-THIRDS OF CANADA HAS BROKEN INTO TWO PARTS WITH THE EASTERN
TROUGH RUNNING FROM NORTHERN MANITOBA INTO ONTARIO AND THE
MISSISSIPPI RIVER VALLEY. THE WESTERN PART BEGINS OVER ROUGHLY
SOUTHERN BRITISH COLUMBIA AND MOVES SOUTH ALONG THE SHORE OF THE
PACIFIC NORTHWEST TO NORTHERN CALIFORNIA. IN BETWEEN THESE TWO
AIRMASSES, ZONAL TO SW FLOW HAS SET UP OVER MONTANA AND THE
INTERMOUNTAIN WEST.
TODAY THROUGH MONDAY: SURFACE HIGH PRESSURE HAS MOVED INTO THE
DAKOTAS THIS AFTERNOON FOR LIGHT SE TO E WINDS. ZONAL FLOW ALOFT
WILL GAIN A MORE SW TILT WITH AND APPROACHING SHORTWAVE
DISTURBANCE TONIGHT INTO MONDAY. THE WAVE WILL BRING ISOLATED
SHOWERS LATE TONIGHT INTO EARLY MONDAY MORNING TO NORTHEAST
MONTANA WITH POSSIBLY A FEW REPORTABLE HUNDREDTHS ON THE SE SIDE
OF THE YELLOWSTONE VALLEY. LOOK FOR SOMEWHAT WARMER TEMPERATURES
ON MONDAY AS THE SYSTEM MOVES TO THE EAST.
MONDAY NIGHT INTO WEDNESDAY: THE WESTERN MOST TROUGH WILL MOVE
INLAND AND DIG INTO THE INTERMOUNTAIN WEST AND FOUR CORNERS. IN
RESPONSE THE NORTHERN SECTION OF THE FLOW WILL BUILD UP INTO A
RIDGE OVER MONTANA THAT WILL KEEP CONDITIONS MOSTLY DRY THROUGH
THESE PERIODS. TUESDAY SPECIFICALLY WILL NEED TO MONITORED FOR
FIRE WEATHER CONCERNS DUE TO LOW RH AND GUSTY WINDS AS THE RIDGE
BEGINS TO BREAK DOWN.
WEDNESDAY NIGHT ONWARDS: A COLD FRONT ARRIVING WEDNESDAY INTO
WEDNESDAY NIGHT WILL ALLOW TEMPS TO GET COOL ENOUGH TO POSSIBLY
CAUSE FROST ON RIVER BOTTOMS. PEOPLE WITH OUTSIDE PLANTS THAT ARE
STILL ALIVE MAY WISH TO BRING THEM IN BEFORE. ENSEMBLE AGREEMENT
FROM HERE ONWARD HAS IMPROVED RAISING CONFIDENCE SLIGHTLY
COMPARED TO YESTERDAY. A RIDGE IN THE FLOW NOW LOOKS TO MOVE IN
FRIDAY AND RAISE TEMPS BRIEFLY BEFORE A TROUGH FOLLOWS ON SWIFTLY
THAT NIGHT. THE MAIN MODELS NOW APPEAR TO LOSE SYNC AROUND
SATURDAY NIGHT.
FORECAST CONFIDENCE & DEVIATIONS:
DEVIATION TO NBM INCLUDE HOURLY POPS FOR TONIGHT. MAIN NBM WAS NOT
CAPTURING OUTPUT FROM CAM SUCH AS THE NAMNEST, ARW, AND HRRR FOR
ISOLATED RAIN SHOWERS ACROSS THE WEST AND GOT A PARTIALLY BLENDED
UPDATE FROM THOSE MEMBERS.
LOW TO MODERATE CONFIDENCE ON CHANCES FOR SHOWERS LATE TONIGHT
AND EARLY MONDAY MORNING.
LOW CONFIDENCE IN FIREWX TUESDAY AFTERNOON.
MODERATE CONFIDENCE IN PARTIAL FROST THURSDAY MORNING.
AVIATION
LAST UPDATED: 1730Z
FLIGHT CAT RANGE: VFR - MVFR
DISCUSSION: EXPECT VARYING AMOUNTS OF MID AND HIGH CLOUDS MOVING
INTO NORTHEAST MONTANA THROUGH THIS AFTERNOON. SKIES WILL BECOME
BKN TO OVC MID-LEVEL EARLY THIS EVENING AND REMAIN THAT WAY
OVERNIGHT INTO MONDAY MORNING. RAIN SHOWERS WITH MVFR CLOUDS ARE
LIKELY MONDAY MORNING AROUND KSDY AND KGDV FROM ROUGHLY 12 TO
21Z.
SFC WIND: LIGHT AND VARIABLE AT 10 KTS THIS MORNING BECOMING E TO
SE AT 5 TO 10 KTS THIS AFTERNOON AND TONIGHT. THEN, REVERTING BACK
TO LIGHT AND VARIABLE MONDAY AFTERNOON ADN EVENING.
GAH
GGW WATCHES/WARNINGS/ADVISORIES
NONE.
WEATHER.GOV/GLASGOW
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