373
FXUS65 KGGW 301920
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
120 PM MDT Sun Jun 30 2024

.DISCUSSION...

KEY MESSAGES:

1) This evening, there are severe thunderstorms possible north of
HWY 2 and severe thunderstorms likely south of HWY 2.

2) Unsettled weather with frequent opportunities for
thunderstorms will continue the rest of the week.

WEATHER PATTERN OVERVIEW:
A strong shortwave trough will replace the currently benign
conditions. A strong cap is expected to erode along the high
terrain of central Montana late this afternoon, as moisture
advection will push dewpoints into the upper 50s to low 60s. Bulk
shear will mainly be above 40 knots, the low level jet will
eventually exceed 30 knots and MU CAPE values are expected to
exceed 800 J/kg. Max updraft helicity of 2 to 5 km of 30 to 70
meters squared per second squared are expected to occur between
01Z and 06Z, which is a proxy for the most likely time period of
severe hail. The highest values are centered on Garfield and
Petroleum county. These ingredients will aid in thunderstorm
development beginning around 5 PM and there is high (70 percent)
confidence for some of these storms to turn severe trekking
eastward. This activity is expected to continue through around
midnight before the storms weaken and/or move into North Dakota. A
cluster or line of storms producing severe wind is more favored
in this scenario, though a few cells containing severe hail are a
threat early on in the event.

Beyond this time period, shower and thunderstorm chances continue
throughout the week, which will help limit high temps from
reaching 90 degrees for most of the area. The strength of
thunderstorms and amount of beneficial rain in this period are in
question based on northwesterly flow continuing through the end
of the week.

FORECAST CONFIDENCE & DEVIATIONS:
There remains high (80 percent) confidence of thunderstorms
occurring this evening, with medium to high (50 to 60 percent)
confidence on severe wind and/or hail at any one location.

-Zanker/Stoinskers


&&

.AVIATION...

UPDATED: 2000Z

FLIGHT CAT: VFR through 02Z, then scattered IFR.

DISCUSSION: Mostly sunny skies, with scattered high clouds are
expected to transition into a line of thunderstorms moving through
TAF sites from 02Z to 09Z. Some of these may produce severe winds
(as high as 65 kts) and severe hail this evening, as well as
reduce visibility and ceilings down to brief IFR conditions.

WINDS: SE at 13 to 23 knots with gusts to 30 knots until 02Z
Monday, with intense gusty winds from thunderstorms after 00Z
Monday. Then west northwest at 5 to 10 kts at 15Z, increasing to
13 to 20 kts after 18Z.



&&

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

$$

weather.gov/glasgow