287
FXUS65 KGGW 102123
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
323 PM MDT Wed Sep 10 2025

.DISCUSSION...

KEY MESSAGES:

- Scattered or hit-and-miss showers and thunderstorms are
  possible over the next few days, a few of which may become
  marginally severe.

- A storm system from the Pacific will bring multiple rounds of
  accumulating rain showers and thunderstorms later this week and
  into the weekend.


WEATHER PATTERN OVERVIEW:

Most of the forecast attention is focused on the approaching low
pressure system from Oregon and Idaho. Overall impacts will be
marginally severe thunderstorms on Thursday and more accumulating
rainfall Friday night through Sunday.

Unfortunately, most of the model precip data show disagreement and
high uncertainty. I believe the automated NBM is broad-brushing
PoPs to high for areas too widespread to be helpful. Many
individual models are showing mixed periods of rainfall and dry
air all wrapping through this storm system. All of them at
different times and in different amounts. Thus, the high level of
uncertainty. I tried to make some manual adjustments to PoPs to
reflect this uncertainty, but it will soon be replaced with the
next automated NBM run.

The slow-moving storm system center will only be over eastern
Montana by this Sunday, still directing some form of unstable
conditions to bring hit-or-miss rain showers leading into the
beginning of next week.


FORECAST CONFIDENCE & DEVIATIONS:

Deviated from the NBM to increase winds on Day 1, and to tone down
PoPs through Day 3, until we see better model agreement.

Confidence is high only for decreased daily temperatures by
Friday/Saturday. Otherwise, confidence is less than average for
rainfall details i.e. timing, amounts, and placement.


&&

.AVIATION...

UPDATE: 2117Z, September 10th

FLIGHT CONDITIONS: VFR

PATTERN: Subtle short-wave disturbances ahead of a slowly-
approaching storm system will allow for hit-or-miss showers and
thunderstorms for NE MT TAF sites now through the next few days,
with possible more widespread rainfall through this weekend.

EQUIPMENT: Comms issues with the KSDY observation remain. AMD NOT
SKED will remain with the TAF there until transmission of obs
becomes more stable.

WINDS: Today from the SE around 15 to 18 kts and a few stronger
gusts. This evening, light and variable with a passing erratic
gust possible due to thunderstorms for KGDV and KSDY between 05Z
and 09Z. Tomorrow, from the E and SE around 5 kts.

&&

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

$$

weather.gov/glasgow