407
FXUS65 KGGW 160413
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
1013 PM MDT Sat Jun 15 2024

.DISCUSSION...

KEY MESSAGES:

- Pattern change starts today as a cold front brings showers and
  thunderstorms with eastern zones seeing the greatest risk of a
  mixed severe hail/wind threat.

- Cooler temperatures begin Sunday, with the coldest readings
  occurring on Monday and Tuesday.

- More widespread rain moves in during Monday and Tuesday.

- Warming trend later this week, but things remain unsettled with
  daily shower and thunderstorm chances.

WEATHER PATTERN OVERVIEW:

Today the first Pacific Northwest Trough will begin to settle
into the area driving a cold front ahead of it. This will not only
be the beginning of a pattern change to below average and wetter
conditions, but this front will be the focusing mechanism for another
round of afternoon and evening thunderstorms. SPC has the eastern
half of our CWA, roughly east of a line from Glentana to Winnett in
a slight risk for severe weather with large hail and damaging
winds the main threat. The supportive dynamics for any rotation
within a supercell looks to increase eastward, with the primary
focus of a tornadic concern in North Dakota. An isolated tornado
cannot be ruled out before crossing the North Dakota border late
this afternoon/evening.

Sunday will be cooler behind the front with a little break in the
action overall before a stronger Pacific trough moves in Monday
bringing widespread rain and even cooler temperatures at 10-20
degrees below mid June averages for both Monday and Tuesday.  A
warming trend begins Wednesday with temperatures warming close to
late June averages by the end of the week. Still unsettled with
afternoon showers and thunderstorms continuing to be a
possibility.

FORECAST CONFIDENCE and DEVIATIONS:

++ Discussion regarding this afternoon ++

This morning`s shower/thunderstorm activity has stabilized the
lower atmosphere across many places north of the Missouri River.
Since those showers have passed, ample sunshine has return for
most locations south of the Missouri. This will help recharge
southern zones with the sufficient instability to support stronger
updrafts, with sufficient shear to sustain upscale growth and
organized convection. At 20Z, a special upper air launch will give
us and the SPC a better idea of how the instability has evolved
since the return of sunshine, and consequently, whether the threat
for significant hail/severe winds remains as discussed from this
morning and/or increased/decreased.

++++
There is a moderate to high (50-90%) probability for a wetting
rain (0.10") across much of the region with today`s system with
the highest chances in the northeast corner of the state.
Low to moderate probability (25-60%) of 0.25". QPF`s have trended
downward some, especially in the southeastern zones.

For the Monday/Wednesday AM system, QPF amounts have trended
downward but are higher than today`s system, with a probability
around 70-80% for at least 0.25", 40-60% for 0.50", and 10-35%
for 1".

Confidence is lower Wednesday onward on shower and thunderstorm
chances and timing as models start diverging in that time period.

-Bernhart/Enriquez


&&

.AVIATION...

LAST UPDATE: 0410Z

FLIGHT CAT RANGE: VFR.

DISCUSSION: Rain showers will slowly exit into the early morning
hours. Where Gusting stops LLWS will become a threat through
roughly 11Z Sunday morning before exiting as well. Then expect
partly cloudy skies with mid level clouds through Sunday.

WIND: W at 10-20 through early morning. Increasing to 15-25 Gust
30 kts Sunday afternoon. Then veering NW in the evening and
decreasing to less than 10 kts before midnight.

GAH

&&

.GGW WATCHES/WARNINGS/ADVISORIES...
Lake Wind Advisory until 9 PM MDT Sunday for Central and
Southeast Phillips-Central and Southern Valley-Garfield-McCone-
Petroleum.

&&

$$

weather.gov/glasgow