367
FXUS65 KGGW 142009
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
209 PM MDT Fri Jun 14 2024

.DISCUSSION...

KEY MESSAGES:

- Showers and thunderstorms already popping up in far northeast
  Montana. Later tonight, highest severe risk will be south of
  the Missouri River.

- Another round of thunderstorms Saturday, with eastern zones
  seeing the greatest risk of a mixed severe hail/wind threat.

- Pattern change starting Sunday with well below average
  temperatures and more widespread rain by Monday.

WEATHER PATTERN OVERVIEW:

Warmest day of the year likely today with some locations
potentially seeing their first 90 deg reading of the summer. Upper
ridge begins moving east today with southwesterly flow moving into
the area. A few upper level disturbances along with some unstable
air moving into the region with a surface Low moving up from
Wyoming is already generating isolated thunderstorms in far
northeast Montana.

On Saturday 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 set off another round of
afternoon and evening thunderstorms. SPC has the eastern half of
our CWA in a slight risk for severe weather so this will have to
be monitored closely.

Highs Sunday behind the aforementioned front will be much cooler
than Saturday`s readings. 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. Weak ridging
begins building on Wednesday starting a warming trend with
temperatures heading back toward seasonal averages by the end of
the week.

FORECAST CONFIDENCE and DEVIATIONS:

Given this morning`s base reflectivities from GGW over the western
half of the CWA, I investigated the HREF members to determine
which one had a better grasp of this morning`s nuisance showers.
The best representation had been the 14 June 00Z initialization
of the NAM Nest. It nailed the convective strengthening of an
isolated thunderstorm near Daniels County. Though it is one model,
the NAM Nest has also hinted at convection developing near the
Prairie/Wibaux/Fallon County area and moving toward the south,
ahead of southeast MT`s main convective event this evening. This
individual storm has the possibility of producing a quick 50-60
mph gust. The 12Z initialization of the NAM Nest, doesn`t have
this northern storm in its guidance, but it is showing the
convection to the west of Billings already moving into the city,
which may modify the dynamics of any storm developing near Wibaux.

There is a moderate to high (60-90%) probability for a wetting
rain (0.10") across much of the region with the weekend system
with the highest chances in the northeast corner of the state.
Moderate probability (30-60%) of 0.25".

For the Monday/Wednesday AM system, QPF amounts are higher, with
a probability around 70-80% for at least 0.25", 50-60% for 0.50",
and 20-40% for 1". ** Update: the QPF dropped in areas along and
south of the Yellowstone River Valley. Otherwise, amounts came
down for the Monday-Wed AM range for most of northeast Montana by
about a 0.25 inches. **

-Bernhart/Enriquez


&&

.AVIATION...

LAST UPDATE: 2000Z

FLIGHT CAT RANGE: VFR

DISCUSSION: Thunderstorm over far northeast Montana continues
moving east, producing brief gusty outflows, reducing flight
categories down to MVFR.

WIND: SE at 15-25 kt for KGDV and KSDY. Otherwise, winds will
become light and variable overnight, outside of a
shower/thunderstorm.

-Bernhart/Enriquez


&&

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

$$

weather.gov/glasgow