618
FXUS65 KGGW 171836
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
1236 PM MDT SUN MAY 17 2026
KEY MESSAGES
- AREAS OF RAIN LASTING THROUGH MONDAY EVENING. OVERNIGHT
TEMPERATURES TONIGHT AND MONDAY HAVE A DECENT CHANCE OF BEING
EXPECTED TO BE AT OR NEAR FREEZING, COLDEST ON MONDAY NIGHT.
- A LAKE WIND ADVISORY IS IN EFFECT THROUGH MIDNIGHT TONIGHT.
- ALTHOUGH THE TROUGH WILL WEAKEN A BIT EARLY THIS WEEK, WAVES OF
ENERGY WILL BRING A FEW ISOLATED THUNDERSTORMS ON TUESDAY AND
WEDNESDAY TO VARIOUS PARTS OF THE AREA.
DISCUSSION
WEATHER PATTERN OVERVIEW:
A STRONG UPPER TROUGH WILL KEEP COOL CONDITIONS THROUGH MONDAY
NIGHT BEFORE THE TROUGH WEAKENS A BIT AND TEMPERATURES CLIMB
CLOSER TO NORMAL BY WEDNESDAY. RAIN SHOWERS ARE MOSTLY WEST OF
A LINE FROM SCOBEY TO CIRCLE CURRENTLY, AND THE UPPER TROUGH WILL
HELP BRING SCATTERED RAIN SHOWERS TO THE WHOLE AREA THROUGH MONDAY
EVENING BEFORE CLEARING TO THE EAST. ALTHOUGH MOST LOCATIONS ARE
EXPECTED TO ACCUMULATE LESS THAN FIVE HUNDREDTHS DURING THIS TIME,
A FEW ISOLATED LOCATIONS MAY SEE UP TO TWO TENTHS OF AN INCH OF
RAIN. THERE IS A BRIEF PERIOD WITH 10 TO 15 PERCENT CHANCE FOR
THUNDER THIS AFTERNOON. WINDY CONDITIONS ON FORT PECK LAKE WILL
EVENTUALLY COME DOWN A BIT AFTER MIDNIGHT TONIGHT.
TONIGHT AND TOMORROW NIGHT THERE IS POTENTIAL FOR MULTIPLE
LOCATIONS TO DROP BELOW FREEZING. HOWEVER, THE THICK AND LOW CLOUD
COVER WILL BE OVERHEAD, WHICH KEEPS TEMPERATURES FROM DROPPING.
MONDAY NIGHT HAS THE BEST CHANCE OF DROPPING BELOW FREEZING SINCE
CLOUD COVER IS EXPECTED TO BE SOMEWHAT SCATTERED THAT NIGHT. WITH
THESE COOLER TEMPERATURES, MAKE SURE TO PROTECT SENSITIVE
VEGETATION.
THE UPPER TROUGH WILL CONTINUE TO REMAIN OVER THE AREA AFTER
TUESDAY, ALTHOUGH A BIT WEAKER THAN THIS WEEKEND. THIS WILL LIKELY
ALLOW SHORTWAVE TROUGHS TO SNEAK THROUGH THE OVERALL FLOW,
BRINGING SOME ISOLATED THUNDERSTORM ACTION TO THE AREA. THERE ARE
500 MILLIBAR TEMPERATURES EXPECTED TO BE AROUND -20 TO -25
CELSIUS, WHICH OFTEN LINES UP WITH AT LEAST ISOLATED CONVECTION.
THE BEST CHANCE FOR GENERAL THUNDERSTORMS IS IN THE WESTERN HALF
OF THE AREA ON TUESDAY AFTERNOON, ESPECIALLY WITH CAPE VALUES UP
TO AROUND 200 J/KG AND LAPSE RATES AROUND 9 TO 10 CELSIUS DEGREES
PER KILOMETER. CURRENT MODEL PLUMES SUGGEST WEAK INSTABILITY IN
THE ~300 J/KG MLCAPE RANGE DURING WEDNESDAY AFTERNOON, BUT LOW
FORECAST RH MAY SUGGEST IT AS A WIND EVENT.
FORECAST CONFIDENCE & DEVIATIONS:
THE ONLY DEVIATION WAS THE POP GRID ON TUESDAY AFTERNOON FOR
ISOLATED THUNDERSTORM OPPORTUNITIES.
THERE IS HIGH CONFIDENCE OF RAIN SHOWERS OCCURRING IN VARIOUS
PARTS OF THE AREA THROUGH MONDAY EVENING AND LOW CLOUDS STAYING
OVER THE AREA THROUGH AT LEAST TOMORROW EVENING.
THERE IS HIGH CONFIDENCE THE LAKE WIND ADVISORY WILL BE CANCELED
AT MIDNIGHT. THERE IS LOW TO MODERATE CONFIDENCE OF TEMPERATURES
DROPPING BELOW FREEZING TONIGHT AND TOMORROW NIGHT.
THERE IS MODERATE TO HIGH CONFIDENCE OF ISOLATED THUNDERSTORMS
OCCURRING ON TUESDAY AND WEDNESDAY IN A PORTION OF THE AREA, WITH
LOW CONFIDENCE FROM THURSDAY GOING FORWARD.
AVIATION
LAST UPDATED: 1830Z
FLIGHT CAT RANGE: MVFR, IFR AFTER 00Z.
DISCUSSION: LOW OVERCAST SKIES WITH MODERATE CONFIDENCE IN
SCATTERED RAIN SHOWERS OCCURRING THROUGH TOMORROW AFTERNOON. THERE
IS HIGH CONFIDENCE OF CEILINGS AS LOW 1000 FEET, AND MODERATE
CONFIDENCE IN CEILINGS DROPPING AS LOW AS 500 FEET FROM 00Z
TONIGHT THROUGH 18Z MONDAY. THE CHANCE OF SEEING A WEAK
THUNDERSTORM THIS AFTERNOON IS 10 TO 15 PERCENT, SO WE OPTED TO
LEAVE IT OUT OF TAFS.
WINDS: FOR KSDY, SOUTHEAST AT 5 TO 10 KNOTS BECOMING NORTHWEST AT
10 TO 20 KNOTS AFTER 21Z, BECOMING NORTH AT 10 TO 18 KNOTS AFTER
12Z MONDAY. FOR ALL OTHER SITES, NORTHWEST AT 12 TO 25 KNOTS WITH
GUST TO 34 KNOTS, DECREASING TO 8 TO 16 KNOTS AFTER 02Z, BECOMING
NORTH AFTER 12Z.
GGW WATCHES/WARNINGS/ADVISORIES
LAKE WIND ADVISORY UNTIL MIDNIGHT MDT TONIGHT FOR CENTRAL AND
SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY-GARFIELD-MCCONE-
PETROLEUM.
WEATHER.GOV/GLASGOW
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page