309
FXUS65 KGGW 162054
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
254 PM MDT Fri Aug 16 2024

.DISCUSSION...

KEY MESSAGES:

 - With an approaching short-wave disturbance from the west,
   multiple rounds of showers and thunderstorms are possible for
   differing portions of northeast Montana, now through Saturday.
   Some lightning, gusty winds, and brief heavy rain are
   possible.

 - A slight warming trend through this weekend will bring the
   return of widespread high temperatures back up to the mid 90s,
   especially on Sunday.


WEATHER PATTERN OVERVIEW:

A 500 hPa trough from the Gulf of Alaska will move south today,
parking itself off the Washington sate coastline, cutting off
from the jet stream, while a shortwave trough traverses the Great
Plains and parking itself in the ECONUS, setting up a large-scale
Omega Block pattern.

A shortwave trough downstream of the west coast low pressure
system, will move along the MT/Canada border today and tonight
flattening the ridge over eastern Montana and the Dakotas. This
will bring chances for showers and thunderstorms to NE Montana
mainly tonight when the wave passes through the area. Chances for
measurable rain tonight will be as high as 60-70 percent over
portions of Valley, Phillips, and Garfield Counties, but only
30-40 percent over the remainder of the region.

The upper ridge rebounds over Montana over the weekend with warmer
high temperatures mainly in the mid 90s from Sunday through
Wednesday. Weak disturbances moving through the ridge could bring
shower and thunderstorms at times for Monday and Tuesday.

FORECAST CONFIDENCE & DEVIATIONS:

Average to good confidence on the shower and thunderstorm chances
tonight. Low to average confidence on thunderstorm chances beyond
Saturday.

With respect to high temperatures from Sunday onward, the
probability of reaching 100F for max temperatures is highest for
locations in lower elevations of adjacent river valleys, though
these probabilities of exceedance do not go above a 25% chance. We
will have to carefully monitor the trends for the 500 hPa high
pressure and how much heights increase in subsequent model runs
and to see if we creep back up to the 100s.


&&

.AVIATION...

UPDATED: 2055Z, Friday afternoon, August 16th

FLIGHT CAT: Mainly VFR with occasional MVFR.

DISCUSSION: Tonight, as thunderstorms move through NE
MT, a few TAF sites may be directly impacted. Some lingering haze
from wildfires is possible over the next several days, but for
now the impact to visibility is expected to be minimal.

WINDS: Generally from the east at 10 to 15 mph this evening, then
variable and gusty near the stronger storms tonight. Tomorrow,
winds will be more from the SE around 10 to 12 mph.


&&

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

$$

weather.gov/glasgow