352
FXUS65 KGGW 190822
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
222 AM MDT Sat Sep 19 2026

.KEY MESSAGES...
 - Issued Flood Watch for today through Sunday for Petroleum,
   Garfield, Prairie, Dawson and Wibaux Counties. Heavy rain is
   likely south of MT 200 from Winnett to Glendive as well as
   south of I-94 through Wibaux. Embedded thunderstorms are
   possible and can cause local heavier rainfall.

- Little or no rain is expected north of the Missouri River today
  through Sunday with a sharp gradient in forecast rainfall totals
  between the Missouri River and MT 200.


&&

.DISCUSSION...

SYNOPTIC SETUP:

A low pressure system over Idaho this morning will track east
across southern Montana and northern Wyoming tonight and Sunday.
This system is cutoff by a northern stream shallow ridge in the
Canadian Prairies which is leading to dry air cutting off the
northern extent of the precipitation north of the Missouri River.
Latest WPC, EC and CMC ensembles forecast QPF shows a sharp
gradient along the Missouri River with little or no precipitation
north of the Missouri River and over an inch south of MT 200 and
MT 200S through Winnett, Jordan, and Glendive and south of I-94
between Glendive and Wibaux. Across these southern locations,
heavier bands of showers and embedded thunderstorms that remain
persistent enough may produce minor flooding of small streams,
open fields, and poor drainage locations such as low lying areas.
A Flood Watch has been issued for Petroleum, Garfield, Prairie,
Dawson and Wibaux Counties today through Sunday.

At this time, confidence has increased in that heavy rain is
likely south and little or no rain is expected north. However, exact
precipitation totals through Sunday remains below average in the
sharp gradient between the Missouri River and MT 200. The
probability of one inch of rain is 60 to 80 percent south of MT
200 and drops quickly to less than 10 percent to the north.

Confidence is greater to the south of the CWA closer to the storm
track. The WPC now has a Moderate Risk for Excessive Rainfall
just south of the CWA for Day 1 with a Slight Risk South of MT
200.

The storm system looks to exit Sunday into Monday with ensembles
showing the northern stream ridge having a bit more influence over
conditions. As a result look for a warm up in temperatures and
drier weather into early next week.

FORECAST CONFIDENCE & DEVIATIONS:

Confidence is high that there will be heavy rain in most areas
south of MT 200 and little or no rain north of the Missouri River.
Confidence is low in rainfall totals in between due to the sharp
gradient between the Missouri River and MT 200. Minor tweaks to
pops at times today through Sunday with no other changes to NBM.



&&

.AVIATION...
LAST UPDATED: 0800Z

FLIGHT CAT RANGE: VFR north, VFR early becoming MVFR/IFR this
morning south.

DISCUSSION:

Showers and isolated thunder look to increase in coverage mainly
south of the Missouri River this morning. This will lead to
reductions in ceilings and visibility. KGDV will have frequent
showers with isolated thunderstorms today and tonight. KSDY will
have showers at times today and tonight while KOLF and KGGW will
see only isolated showers from the system to the south.

SFC Wind: NE at 5 to 15 knots this morning becoming east to NE 10
to 15 knots this afternoon and tonight.


&&

.GGW WATCHES/WARNINGS/ADVISORIES...
Flood Watch from 6 AM MDT this morning through Sunday afternoon
for Dawson-Garfield-Petroleum-Prairie-Wibaux.

&&

$$

weather.gov/glasgow