976
FXUS65 KGGW 130630
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
1230 AM MDT Thu Aug 13 2026

.KEY MESSAGES...

- Scattered to occasional showers and a few isolated thunderstorms
  are expected to occur now through Friday night. Rain
  accumulations between two tenths of an inch up to about 1.4
  inches are expected in that period.

- Winds are expected to be gusting around 30 mph on Fort Peck Lake
  through noon today.

- Precipitation chances don`t completely go away this weekend and
  into early next week, but overall conditions will trend towards
  drier and warmer.




&&

.DISCUSSION...

WEATHER PATTERN OVERVIEW:
An upper trough over the Midwest and another one over the Pacific
northwest are expected to work in tandem (another word for
`together`) by combining into one trough starting tonight. This
trough is expected to bring significant rain to a good portion of
the area from now through Friday night. The latest ECMWF and GFS
ensembles are in fair agreement this trough will break up this
weekend. Fairly zonal flow is expected to occur early next week,
so there is uncertainty regarding precipitation chances since
shortwave troughs are challenging to predict in this flow pattern.
It is typical to only accurately predict shortwave troughs a few
days in advance.

For precipitation amounts through Friday night, the highest
amounts are expected in the eastern half of the area with a few
locations exceeding one inch. There is more uncertainty in the
western half of the County Warning Area, but there is still a
decent shot of reaching a quarter of an inch. A few spots in the
southeastern counties accumulated 0.5 inches to 1.34 inches with
the storms this evening, so it will be important to watch
potential flooding there if rain rapidly accumulates with any
future embedded thunderstorms.

A marginal risk of excessive rainfall is expected today and Friday.
There is a slight risk for excessive rain today. Will hold off on
any Flood Watches for now.

FORECAST CONFIDENCE & DEVIATIONS:
Increased the winds through noon today since observations were a
bit stronger than the base forecast.

There is high confidence in rainfall amounts in the east, with
low to moderate confidence in the west through Friday night.

There is moderate to high confidence in reaching gusts to 30 mph
on Fort Peck Lake in correspondence with the Lake Wind Advisory
in effect through noon today.

There is moderate confidence that any thunderstorms will remain
below severe limits from now through Friday night.

&&

.AVIATION...
LAST UPDATE: 0630Z.

FLIGHT CAT RANGE: VFR, scattered MVFR and IFR after 12Z this
morning.

DISCUSSION: Mid clouds will continue to increase as the upper
level low moves closer. There will off and on rain showers through
the period. There is high confidence (70 percent) of MVFR to IFR ceilings
occurring for KOLF and KGGW through 00Z Friday, and low confidence
for KSDY and KGDV. The highest likelihood for thunder is from 22Z
to 06Z Friday.

WIND: Mainly east northeast at 8 to 19 kts with gusts ranging from
18 to 28 knots.

&&

.GGW WATCHES/WARNINGS/ADVISORIES...
Lake Wind Advisory until noon MDT today for Central and
Southeast Phillips-Central and Southern Valley-Garfield-McCone-
Petroleum.

&&

$$

weather.gov/glasgow