447
FXUS65 KGGW 200702
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
102 AM MDT WED MAY 20 2026
KEY MESSAGES
- A FRONTAL PASSAGE WILL BRING SCATTERED SHOWERS AND THUNDERSTORMS
THIS AFTERNOON AND EVENING. AN ISOLATED STORM OR TWO MAY BE ON
THE STRONGER SIDE WITH WIND GUSTS TO 60 MPH.
- A SECOND ROUND OF SHOWERS AND ISOLATED THUNDERSTORMS WILL BE
POSSIBLE NEAR THE ND BORDER THURSDAY AFTERNOON.
- WARMER TEMPERATURES ARE EXPECTED BEGINNING FRIDAY WITH 80S FOR
HIGHS BEGINNING SUNDAY ONWARD.
DISCUSSION
WEATHER PATTERN OVERVIEW:
FORECAST BEGINS WITH NORTHWEST FLOW RUNNING FROM BRITISH COLUMBIA
THROUGH EASTERN MONTANA AND TO THE CENTRAL US PLAINS. A SERIES OF
RIDGE TROUGH COUPLETS ARE EMBEDDED WITHIN THIS FLOW PATTERN.
TODAY INTO TONIGHT: THE FIRST UPPER TROUGH IN NW FLOW MOVES INTO
THE AREA THIS MORNING. THIS SYSTEM WILL BRING A COLD FRONT ACROSS
EASTERN MONTANA THIS AFTERNOON AND EVENING WITH RAIN SHOWERS AND
ISOLATED TO SCATTERED THUNDERSTORMS. SPC'S HREF SHOWS SOME
ISOLATED CELLS WITHIN THIS FRONTAL PASSAGE PRODUCING WIND GUSTS UP
TO 60 MPH WHICH WILL NEED TO BE MONITORED. THE PASSAGE ITSELF
LOOKS LIKE IT WILL BE A 6 HOUR TREK ACROSS THE AREA STARTING
AROUND NOON AND EXITING AROUND 6 TO 7 PM. PRECIP WILL BE VERY HIT-
AND-MISS WITH MOST AREAS RECEIVING NOTHING BUT A FEW LOCATION
GETTING 1 TO 2 TENTHS OF AN INCH MAX.
THURSDAY: THE SURFACE TROUGH THAT MOVES INTO THE REGION DURING
THE PREVIOUS AFTERNOONS KIND OF STALLS OUT AT THE ND BORDER AND
WILL BECOME A FOCAL POINT FROM THE MORNING TO AFTERNOON HOURS FOR
ADDITIONAL SHOWERS AND ISOLATED THUNDERSTORMS. THESE DO NOT LOOK
SEVERE YET AT THIS TIME.
THURSDAY NIGHT INTO SUNDAY: CONDITIONS WILL CLEAR AND WARM
THROUGH THESE TIME PERIODS WITH MAYBE A WEAK SHOWER POSSIBLE
SATURDAY NIGHT.
SUNDAY NIGHT ONWARD: SYNOPTIC ENSEMBLES ARE STARTING TO FIRM UP
ON A RIDGE MOVING INTO THE REGION AND THEN CLOSING UP INTO A HIGH
PRESSURE SYSTEM FOR A SHORT TIME MONDAY AND TUESDAY WITH VERY
WARM TEMPERATURES. BUTTING UP AGAINST THIS WILL BE A DEEPLY
AMPLIFIED TROUGH ACROSS THE PACIFIC NORTHWEST. THESE TWO FEATURES
WILL PLAY CHICKEN FOR AWHILE WITH A CHANCE AT THE HIGH/RIDGE OVER
EASTERN MONTANA TO BREAK DOWN AND SOUTHERN FLOW WITH STRONG
THUNDERSTORMS TO TAKE OVER TUESDAY TO THURSDAY AFTERNOON. IF THE
RIDGE STAYS PUT, WE'LL BE DRY AND HOT. IF IT MOVES FORWARD THEN WE
BECOME WET QUICKLY WITH POSSIBLE SEVERE WX DEPENDING ON TIMING.
FORECAST CONFIDENCE & DEVIATIONS:
CHANGES TO NBM WERE FOCUSED TO HOURLY POPS IN THE LATE AFTERNOON
AND EVENING ALONG WITH DURING THE DAY ON WEDNESDAY. HOURLY NBM
DATA HAD A DEFINITIVE 6 HOUR BIAS THAT WAS THROWING NATURAL HOURLY
TRENDS OFF. USED AND NPOP BLEND OF AVAILABLE CAMS AND SHRINK
STRETCHED UP POPS A FEW PERCENT AFTERWARD TO TRY TO QUICK BLEND
IN A SLIGHTLY BETTER TREND. ALSO DID THIS FOR WIND AND WIND GUST
TO BETTER CAPTURE THE TIMING OF THE FRONTAL PASSAGE THAT WAS
WASHED OUT BY NBM.
CONFIDENCE IN TIMING ANY SHOWERS AND THUNDERSTORMS TODAY IS HIGH.
CONFIDENCE IN SEVERE WINDS GUSTS FROM CELLS EMBEDDED IN THE
SYSTEM WEDNESDAY IS LOW.
AVIATION
LAST UPDATED: 0345Z
FLIGHT CAT RANGE: VFR.
DISCUSSION: EXPECT VFR AND MID TO HIGH CLOUDS ACROSS THE REGION
THROUGH THE NIGHT AND EARLY MORNING WEDNESDAY. SHOWERS AND
THUNDERSTORMS WILL MOVE THROUGH THE AREA LATE MORNING TO EARLY
AFTERNOON AND TAKE ABOUT A 6 HOUR TREK ACROSS THE REGION. THERE IS
A OUTSIDE CHANCE (5-20%) FOR ONE OR TWO CELLS TO BECOME SEVERE
WITH WIND GUSTS UP TO 50KTS, BUT THE CHANCE AT ANY GIVEN TERMINAL
IS TOO LOW TO PLACE IN THE TAFS DIRECTLY TILL THEY ARE CLEAR ON
RADAR THIS COMING AFTERNOON. STORMS SHOULD EXIT ALL TERMINALS BY
ABOUT 02Z BEFORE CLEARING OUT FOR MOST OF THE NIGHT WITH ONLY AND
ISOLATED SHOWERS POSSIBLE FROM THEN ON.
LLWS: THERE IS A SMALL CHANCE(10-30%) FOR SOME LOW LEVEL WIND
SHEAR AT KGDV AND KSDY BETWEEN 06Z AND 12Z THIS MORNING.
WIND: S TO SW AT 10 TO 15 KTS THROUGH MID MORNING. VEERING W IN
THE LATE MORNING. BRIEFLY INCREASING TO 15-25 KTS WITH THE FRONTAL
PASSAGE THIS AFTERNOON. BECOMING LIGHT AND VARIABLE WEDNESDAY
EVENING.
GAH
GGW WATCHES/WARNINGS/ADVISORIES
NONE.
WEATHER.GOV/GLASGOW
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