594
FXUS65 KGGW 132058
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
258 PM MDT SUN SEP 13 2026
KEY MESSAGES
- LIKELY SCATTERED RAIN SHOWERS AND EMBEDDED THUNDERSTORMS
BEGINNING AROUND MIDNIGHT AND LASTING THROUGH TOMORROW EVENING.
- WINDS WILL REACH LAKE WIND ADVISORY CRITERIA TODAY AND TOMORROW.
WAVE HEIGHTS WILL HAVE THE POTENTIAL TO REACH 4 TO 5 FT
TOMORROW AFTERNOON.
- SLIGHT CHANCES FOR RAIN SHOWERS ARE POSSIBLE TUESDAY NIGHT INTO
WEDNESDAY MORNING. CONFIDENCE IN RAIN AMOUNTS IS LOW.
DISCUSSION
SYNOPTIC SETUP:
A WEAK RIDGE IS OVER THE WESTERN GREAT PLAINS AND A CLOSED UPPER-
LEVEL LOW HAS MOVED OVER THE PACIFIC NORTHWEST. THE INTERACTION
OF THESE TWO SYSTEMS HAS PRODUCED SW FLOW ALOFT OVER MONTANA,
TRANSPORTING PACIFIC MOISTURE INTO THE REGION.
TODAY THROUGH TOMORROW:
WHILE THE STABILITY IN THE UPPER ATMOSPHERE WILL KEEP CONDITIONS
DRY INTO EARLY THIS EVENING, THE AFOREMENTIONED PNW LOW WILL
WEAKEN AND DIG OVER MONTANA TONIGHT. THIS WILL LIKELY PRODUCE
SCATTERED RAIN SHOWERS AND EMBEDDED THUNDERSTORMS BEGINNING AROUND
MIDNIGHT AND LASTING THROUGH TOMORROW AFTERNOON. A COLD FRONT
ASSOCIATED WITH THE TROUGH WILL LIKELY PASS BETWEEN MIDNIGHT AND
6AM, PRODUCING PRECIPITATION TOTALS BETWEEN 0.01" AND 0.50".
ADDITIONALLY, VORTICITY-INDUDCED INSTABILITY ASSOCIATED WITH THE
BACKSIDE OF THE LOW MAY RESULT IN RAIN SHOWERS LASTING INTO EARLY
MONDAY EVENING ACROSS NORTHERN PORTIONS OF THE CWA. CONFIDENCE IN
PRECIPITATION AMOUNTS ASSOCIATED WITH LATER AFTERNOON AND EVENING
SHOWERS IS LOW, BUT EXPECT HIGHER TOTALS NORTH OF A LINE DRAWN
BETWEEN MALTA AND TERRY.
WINDS WILL VEER AND BECOME WESTERLY BEHIND THE FRONT MONDAY
MORNING AND BE COMPARABLE IN STRENGTH TO WINDS EXPERIENCED TODAY.
WINDS WILL REACH LAKE WIND ADVISORY CRITERIA TOMORROW. WAVE
HEIGHTS WILL HAVE THE POTENTIAL TO REACH 4 TO 5 FT TOMORROW
AFTERNOON.
TUESDAY ONWARD:
THE TROUGH WILL FULLY EXIT THE REGION BY TUESDAY MORNING, LEAVING
ZONAL FLOW IN ITS WAKE. SLIGHT CHANCES FOR RAIN SHOWERS ARE
POSSIBLE TUESDAY NIGHT INTO WEDNESDAY MORNING DUE TO A SWATH OF
PACIFIC MOISTURE MOVING THROUGHOUT THE FLOW. CONFIDENCE IN RAIN
AMOUNTS IS LOW, BUT BEST CHANCES WILL BE ACROSS NORTHERN PORTIONS
OF THE CWA. RAIN CHANCES FULLY DIMINISH BY WEDNESDAY AFTERNOON AS
SKIES CLEAR AND TEMPERATURES WARM UNDER A DEVELOPING RIDGE OVER
THE CENTRAL US. ALTHOUGH, A WEAK TROUGH HAS EMBEDDED ITSELF
BETWEEN US AND THE RIDGE IN A SIGNIFICANT PORTION OF THE
ENSEMBLES, WHICH COULD POTENTIALLY PRODUCE RAIN AND INCREASING
CLOUD COVERAGE FRIDAY NIGHT.
FORECAST CONFIDENCE & DEVIATIONS:
THERE IS HIGH CONFIDENCE IN SUSTAINED WINDS AT OR ABOVE 20 MPH ON
TODAY AND TOMORROW ACROSS FORT PECK LAKE.
THERE IS MODERATE CONFIDENCE IN THE TIMING OF SCATTERED SHOWERS
AND THUNDERSTORMS ON TONIGHT INTO MONDAY (THEY COULD BEGIN
EARLIER OR LATER), BUT THERE HIGH CONFIDENCE IN THEM LASTING INTO
THE EVENINGS HOURS.
THERE IS LOW CONFIDENCE IN THE FORECAST BEYOND THURSDAY.
DON
AVIATION
LAST UPDATED: 2100Z
FLIGHT CAT RANGE: VFR
DISCUSSION: MID-LEVEL CLOUDS WILL SLOWLY DROP IN HEIGHT THIS
EVENING AND THROUGH TONIGHT AS A DISTURBANCE AND ASSOCIATED FRONT
APPROACHES. THIS DISTURBANCE WILL BRING SCATTERED RAIN SHOWERS
AND THUNDERSTORMS TO TERMINALS TOMORROW MORNING.
SFC WIND: SE AND INCREASING TO 10 TO 20 GUST 30 KTS THIS
AFTERNOON AND EVENING. WINDS WILL VEER RAPIDLY TO W TO NW AFTER
AFTER THE PASSAGE OF A COLD FRONT AROUND MIDNIGHT.
DON
GGW WATCHES/WARNINGS/ADVISORIES
LAKE WIND ADVISORY UNTIL MIDNIGHT MDT MONDAY NIGHT FOR CENTRAL
AND SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY-GARFIELD-
MCCONE-PETROLEUM.
WEATHER.GOV/GLASGOW
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