744
FXUS65 KGGW 270246
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
846 PM MDT Wed Jun 26 2024

.DISCUSSION...
Going forecast appears to have things well in hand. I did tweak
pops up a bit for tonight NW of Glasgow.

Also looked into Flood Watch potential for eastern Roosevelt and
Sheridan counties as there seems to be a low chance for a quick
inch of rainfall with the late-day thunderstorms. But felt later
shifts would have a better handle on this. TFJ

Previous Discussion...
KEY MESSAGES:

1) Severe thunderstorms are increasingly likely on Thursday
beginning late morning over central Montana and tracking east into
the Dakotas during the evening hours.

2) Breezy conditions are likely on Friday behind the cold front,
with Lake Wind criteria expected.

3) Cooler temperatures are also expected Friday and Saturday with
chances for showers and thunderstorms on Friday.

WEATHER PATTERN OVERVIEW:

Surface low pressure looks to develop over central Montana
tonight as existing ridge axis moves east turning the flow aloft
to the SW which will allow for a chance of showers and
thunderstorms. An upper low moves in from the west on Thursday.
The surface low will shift east across eastern Montana during the
day on Thursday along with a surface cold front. SE winds ahead
of the cold front will bring dew points into the 60s east of
Glasgow and Jordan on Thursday and approaching 70 near Sidney.
The mean surface based CAPE over eastern portions of the CWA looks
to reach 2000 J/KG or better by Thursday afternoon and evening
while forecast soundings show 40-50 kts of 0-6 km shear present.
This will all set the stage for the return of active severe
weather across NE Montana.

Latest HREF maximum updraft helicity shows storms reaching SW
zones around 10am and spilling into the area during the late
morning hours. Meanwhile, storm coverage looks to increase along
the MT/ND border during the late afternoon and evening hours.
Initial supercells may congeal into line segments during the
evening as storms shift into the Dakotas. All hazards are favored
including up to 2 inch diameter hail, wind gusts to 75 mph, an
isolated tornado, and locally heavy rainfall. The SPC has eastern
portions of the CWA under an enhanced risk for severe storms. Fast
progression of the storms to the east should limit the flooding
threat, but conditions will continue to be monitored.

The upper trough will push into eastern Montana on Friday with
additional lingering general thunderstorms along with gusty west
winds (sustained 20, gust 30), and cooler temperatures. These
conditions may be sufficient for the Lake Wind Advisory issuance
at some future point.

Upper ridging will guide warm and dry weather on Saturday before
more ensembles hint at more active weather early next week.

FORECAST CONFIDENCE & DEVIATIONS:

The forecast was trended toward the NBM but edits were made to
include severe wording into the weather grids and heavy rainfall.

Confidence is high that there will be thunderstorms on Thursday.
Confidence is low on rainfall amounts as there will be widely
varying precipitation depending on exactly where storms track;
ranging from a trace to upwards of an inch. Forecast soundings
show precipitable water values exceeding an inch as WPC has the
area under a Marginal risk for excessive rainfall. Widespread
hydrology concerns are not expected as the storms will move fairly
steadily eastward, but locally heavy rainfall may result in some
of the storms.


&&

.AVIATION...
Mainly VFR conditions are expected tonight but MVFR/IFR
conditions may result between 18Z and 02Z Thursday as strong to
severe thunderstorms track from west to east across NE Montana.
Expect low ceilings and visibilities if a storm tracks directly
over a station. Some of the storms may produce large hail, gusty
and shifting winds, and heavy rainfall.


&&

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

$$

weather.gov/glasgow