132
FXUS65 KGGW 210637
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
1237 AM MDT Mon Sep 21 2026

.KEY MESSAGES...

- Low clouds presenting as patchy fog may drop visibility to 2
  miles in localized areas of higher terrain until noon today,
  especially along HWY 200, 200S, and 253.

- Above average temperatures beginning Tuesday as upper riding
  builds. Highs peak near the end of the work week.


&&

.DISCUSSION...

- Synoptic Setup:

A low pressure system over eastern Wyoming will continue keep low
clouds from now through tomorrow morning. A similar set up to
yesterday is likely, with low clouds presenting as patchy fog.
Visibility drops to 2 miles in localized areas of higher terrain
until noon today, especially along HWY 200, 200S, and 253.

A ridge is expected to build in Tuesday through Friday bringing
southwesterly upper level flow and warmer temperatures. By midweek
a shortwave trough will move through the region, remaining mostly
affecting the southeast part of the area, bringing rain showers
and possibly a thunderstorm or two.

Thursday and Friday will see widespread 80 degree afternoon
temperatures. Highest temperatures of the week trend warmer on
Thursday now, suggesting a quicker exit. Towards the end of the
week an upper level trough deepening over the PNW and pushing east
over the Rockies will push temperatures down closer to normal as
well as the next likely chance for a more widespread precipitation.
Depending on the strength of the low, wind speeds behind the cold
front will need to be monitored.

FORECAST CONFIDENCE & DEVIATIONS:
Minor tweaks to cloud base and visibility grids within the first 6
hours. No changes to NBM otherwise.

Winds on Friday night through Saturday will need to be monitored,
as we both think NBM/GFS/ECMWF are washing higher speeds out.
Strong frontogenesis from sinking air on the cold side of the low
is trending stronger, meaning this event will need to be watched
for wind headlines.

&&

.AVIATION...
LAST UPDATED: 0530Z

FLIGHT CAT RANGE: LIFR/IFR - VFR

DISCUSSION: MVFR/IFR ceilings will persist through the morning,
beginning to improve starting 18Z. Ceilings over KGDV will
fluctuate between IFR and at or near airport shutdown at times.
KSDY looks to maintain VFR ceilings, but may approach MVFR
conditions.

WIND: East southeast at 5 to 10 kts becoming southeast at 10 to
15 kts after 15Z.


&&

.GGW WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

weather.gov/glasgow