808
FXUS65 KGGW 202029
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
229 PM MDT Mon May 20 2024

.DISCUSSION...

KEY MESSAGES:

1) Isolated showers and thunderstorms will continue during the
afternoon and evening hours today and to a lesser degree on
Tuesday.

2) A more widespread chance for showers and thunderstorms will
begin late Wednesday through Friday. Unsettled weather will remain
likely at times into the upcoming weekend.

WEATHER PATTERN OVERVIEW:

An upper trough will prevail across the western CONUS this week
with occasional shortwaves helping produce enough lift and
instability for daily shower and thunderstorm chances.

A more organized low pressure system will track through the
northern Rockies for the second half of this week with a more
widespread opportunity for wetting rains from showers and
thunderstorms. This unsettled weather pattern looks to linger into
the upcoming weekend. There currently exists about a
Upper trof will be over the western states through the end of the
week. As shortwave push through the base of the trof, occasional
showers and thunderstorms are expected.

The greatest probability for rain will be Wednesday through
Friday as a lower pressure pushes through the northern Rockies and
into the northern plains. The NBM 72 hour probability of 0.50
inches or more of QPF ending Saturday morning ranges from 40 to 50
percent along and south of HIghway 2 and between 30 and 40 percent
to the north.

CONFIDENCE LEVEL and POTENTIAL DEVIATIONS FROM BASE FORECAST:

Confidence is high that a wetter weather pattern is set to unfold
for the second half of this week with ensembles showing strong
consensus for a broad trough pattern and low pressure system
pushing through the region. Confidence is lower on exact
precipitation amounts and precise location given the convective
nature of expected precipitation, but in general, expecting
greater QPF to the southwest and lesser to the northeast.

For now, have decided to remain close to the base forecast given
that the NBM lines up with consensus view of a cool but wet
pattern unfolding and the above average confidence. As the event
works its way into the short term and human detail gains greater
input value, some deviations become increasingly likely to better
capture mesoscale details and placement of precipitation.


&&

.AVIATION...
VFR conditions will continue through tonight. Isolated showers and
thunderstorms will remain a possibility, especially near KGGW
through 06Z. Winds will be northwest tonight at 5 to 9 kts, at
times light and variable.

&&

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

$$

weather.gov/glasgow