940
FXUS65 KGGW 270652
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
1252 AM MDT Sun Sep 27 2026

.KEY MESSAGES...

- Possible showers and thunderstorms late tonight and early
  tomorrow morning along the North Dakota border and the
  Yellowstone Valley.

- Tuesday specifically will need to be monitored for fire weather
  concerns due to anticipated low RH and gusty winds.


&&

.DISCUSSION...

Synoptic Setup: Forecast begins with a ridge running from northern
Manitoba into Ontario and down the Mississippi Valley. It then
turns back west across the southern plains and into the high
pressure over the Desert SW. A broad trough over western half of
Canada has begun to break into two parts, with the eastern trough
running down the Canadian plains and into the Dakotas. The
western part begins roughly above British Columbia and moves
offshore the Pacific Northwest and Northern California.

Today through Monday: Surface high pressure will move through NE
Montana this morning, resulting in light winds. Winds will become
E-SE this afternoon as the high moves eastward. Zonal flow aloft
this morning will turn WSW this afternoon due to an approaching
shortwave. The wave will produce some rain showers and
thunderstorms, mainly late tonight and early Monday morning along
the North Dakota border and Yellowstone Valley. Look for somewhat
warmer temperatures on Monday as the system moves to the east.

Monday night into Wednesday: The western most trough will move
inland and dig into the Intermountain West and Four Corners
regions. In response, the northern section of the flow will build into
a ridge over Montana, keeping conditions mostly dry through
Wednesday. Tuesday specifically will need to be monitored for
fire weather concerns due to anticipated low RH and gusty winds
as the ridge begins to decay.

Wednesday night onwards: Flow aloft will attempt to become zonal
briefly. However, model ensembles begin to deviate on individual
waves within the flow. GFS runs indicate a brief ridge/trough
couplet, while EC members slowly orient flow more to the
northwest. Standard deviations amongst ensemble members suggest
that no particular run is favored, so confidence in these periods
is low. Expect changes in future iterations of the forecast from
this point onward.

FORECAST CONFIDENCE & DEVIATIONS:

- Low confidence in the western extent of rain and thunderstorm
  chances for late tonight and early Monday morning.

- Adjusted PoPs tonight at times to provide better hour-to-hour
  consistency. No other deviations from the NBM.


&&

.AVIATION...

LAST UPDATED: 0600Z

FLIGHT CAT RANGE: VFR

DISCUSSION: Skies will be clear early this morning ahead of
approaching mid and high clouds that will move into northeast
Montana this morning and afternoon. Skies will become BKN/OVC with
mid-level clouds this evening, remaining so overnight and into
Monday morning. Rain showers, few thunderstorms, and low VFR to
MVFR ceilings are likely late tonight and early Monday morning
around KSDY and KGDV.

SFC WIND: Light and variable, potentially W-NW at less than 10 kt
becoming light and variable this morning. Winds will become E-SE
at 5 to 10 kt by this afternoon.


&&

.GGW WATCHES/WARNINGS/ADVISORIES...

None.


&&

$$

weather.gov/glasgow