832
FXUS65 KGGW 150759
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
159 AM MDT Sun Sep 15 2024

.DISCUSSION...

KEY MESSAGES:

1) Warm temperatures will continue through Tuesday.

2) Showers and thunderstorms chances start on Monday.

3) Cooler temperatures move in Tuesday night with widespread rain
that continues through Wednesday night.


WEATHER PATTERN OVERVIEW:

Eastern Montana will be in a shortwave ridge in SW flow aloft
today which will bring warm and dry weather.

Meanwhile, ensembles continue to show the Pacific trough
deepening across the west with divergent upper flow over Montana
by Monday. Given 1000 to 2000 J/KG CAPE with 20-30 kts of shear
and precipitable water values around an inch or slightly higher across
the CWA, expect support the chance for multicellular
thunderstorms Monday afternoon and evening. An isolated strong
storm is possible with gusty winds and small hail given the
instability present, but with modest shear unable to sustain the
updrafts, do not expect widespread severe weather concerns at this
time. The trough moves east on Tuesday and brings and upper low
across Montana Tuesday night and Wednesday with cool and wet
weather over the region. The NBM 48 hour probability of 1 inch of
rain is now 60 to 70 percent across Phillips County between
Tuesday and Wednesday night and drop quickly south and east of
there. Closer to the MT/ND Border, probability of an inch of rain
is only around 10 percent while the probability of 0.25 inch of
rain is 40 to 60 percent. Dry slotting is expected at times along
the MT/ND border which will result in lower rainfall amounts.

While the upper low moves north Wednesday night, varying degrees
of upper trough remains over the area into next weekend with
chances of showers at times.

 FORECAST CONFIDENCE & DEVIATIONS:

High confidence exists on warm and dry weather today.

Medium confidence exists on thunderstorms Monday given the modest
setup.

Confidence for rain is high west and low to medium east for
Tuesday and Wednesday with decent support for cooler and wetter
weather unfolding. Consensus continues to show for widespread rain
in the west but there remains uncertainties in the coverage and
amount of precipitation due to dry slotting at times, especially
for eastern areas. Have opted to keep the forecast in line with
NBM overall for now, which handles the big picture well.


&&

.AVIATION...
Last Updated: 0800Z

Discussion: VFR conditions will continue today and tonight. High
clouds will be over parts of the area this morning before
clearing this afternoon. More high clouds will move into the area
tonight.

Winds: Variable early 10 knots or less become SE 5 to 10 knots
this afternoon east to NE 5 to 15 knots tonight.

&&

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

$$

weather.gov/glasgow