900
FXUS65 KGGW 170057
AFDGGW

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

.DISCUSSION...
Did an upstate this evening to try to refine the timing of
showers/thundertorms better through Saturday morning. Rest of
forecast looked good. TFJ

Previous 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: 0055Z, Friday evening, August 16th

FLIGHT CAT: Mainly VFR with occasional MVFR.

DISCUSSION: scattered showers/thunderstorms will move in mainly
after midnight and linger Saturday morning. Look for possible gusty/erratic
winds in the vicinity of them.

Haze will linger a bit tonight but should be mainly clear Saturday.

WINDS: Generally from the east at 5 to 15 kts tonight, stronger
and erratic near thunderstorms. Then will be more from the SE
around 10 to 12 kts Saturday. TFJ

&&

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

&&

$$

weather.gov/glasgow