FXUS65 KGGW 201855

AFDGGW



Area Forecast Discussion

National Weather Service Glasgow MT

1255 PM MDT Sun Sep 20 2026



.KEY MESSAGES...

- Precipitation is expected to end this evening, and the low

  pressure system will slowly move east by tomorrow afternoon.



- Above average temperatures beginning Tuesday as upper ridging

  builds in. A low pressure system is expected to move in by the

  weekend.







&&



.DISCUSSION...



A low pressure system over eastern Wyoming will continue to

maintain rain showers through about 9 PM tonight, and low cloud

cover from now through tomorrow morning is expected to remain in 

place. This system will eventually move far enough east for cloud

cover to begin breaking up tomorrow afternoon. A ridge is expected

to build in from Tuesday through Friday to bring temperatures up

to average and slightly above average. A shortwave trough will

move through on Wednesday to mostly affect the southeast part of

the area and bring rain showers. There is some uncertainty on the

timing of the next upper trough, but it appears more likely for 

this to occur on Saturday and Sunday.



FORECAST CONFIDENCE & DEVIATIONS:

The NBM typically likes to reduce PoPs quickly on the backside of

slow moving systems, so decided to manually add PoPs through 9 PM

tonight in the southeast. Increased winds through tomorrow

afternoon for the higher elevation locations across the area

(above 2500 feet). 



There is high confidence in rain showers ending late this 

evening, and a ridge building in by Tuesday.



There is high confidence on a shortwave trough moving through on

Wednesday in the southeast, but there is low confidence on

precipitation amounts.



There is moderate confidence on a low pressure system moving in by

Friday night.



&&



.AVIATION...

LAST UPDATED: 1830Z



FLIGHT CAT RANGE: A mix of MVFR, IFR, and LIFR through 18Z Monday,

and then mostly MVFR.



DISCUSSION: The surface low pressure system will continue to

influence the area. Precipitation will slowly come to an end, and

there is moderate to high confidence this precipitation will end

by 03Z. However, low ceilings will persist. There is moderate to

high (50 to 70 percent) confidence of scattered IFR and LIFR

ceilings occurring through 18Z. There is similar confidence that

these conditions will improve to MVFR after 18Z.

WIND: East southeast at 6 to 15 kts with gusts to 22 kts, 

becoming southeast after 18Z Monday.



&&



.GGW WATCHES/WARNINGS/ADVISORIES...

None.

&&



$$



weather.gov/glasgow