237
FXUS65 KGGW 282019
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
219 PM MDT Sun Apr 28 2024

.DISCUSSION...

KEY MESSAGES:

1) For the 24-hour period ending at 6 AM Tuesday, there is a
70-90% chance of a wetting rain (at least 0.1 in) for most of
northeast Montana. The chance for at least 0.25 in and 0.5 inches
of rainfall for the same period maxes out around 50-70% and
20-40% chance, respectively.

2) Winds pick up on Tuesday elevating fire weather concerns
particularly for any areas that stay mostly dry, with gusts as
high as 50 mph possible.

3) For the rest of the week, mostly dry and slightly cooler than
normal conditions prevail.

WEATHER PATTERN OVERVIEW:

An upper level trough and cold front moves in across the area by
Monday night, bringing chances for precipitation through at least Tuesday,
as described probabilistically above.

From Tuesday, a shortwave ridge aloft builds and moves across
southeast MT, resulting in surface high pressure moving areas of
precipitation generally north of MT Hwy 200. As the high pressure
builds to the south, a tight pressure gradient develops from
northwest MT into eastern Montana. This increases winds speeds,
mainly south of the Missouri River, with a medium to high chance
for at least 40 mph gusts, but low chance (<20%) for gusts in
excess of 55 mph. Given this, not issuing any wind headlines at
this time. Chances for precipitation shift north thanks to this
surface high pressure influence from the south. The chances for at
least 0.25 inches for the period from Tuesday through Wednesday
range from 30 to 50% for areas north of the Hi-Line.

Discussion regarding fire weather headlines on Tuesday is
provided in the fire weather section below. From Thursday, the
trough fills and moves into the Great Plains, placing the region
in northwest flow aloft, resulting in chances for daily afternoon
showers.

CONFIDENCE AND POTENTIAL DEVIATIONS FROM BASE FORECAST:

The NBM has tended to underestimate the last few wind events
across the region, so trended winds slightly higher than the
deterministic for Tuesday following the cold frontal passage. This
will dictate headline decisions.

-Enriquez/Zanker

&&

.AVIATION...

LAST UPDATED: 2000Z

FLIGHT CAT RANGE: VFR

DISCUSSION: Look for scattered mid-level clouds and a lack of
gusty winds, lending to dry and quiet flying conditions through
Monday afternoon.

&&

.FIRE WEATHER...

A cold frontal passage Monday night brings medium to high (50-80%)
confidence for a wetting rain for most areas outside of zone 122.
Gusty west winds of up to around 50 mph behind it with rapid
clearing and a sharp drop in humidity values present near
critical fire weather conditions Tuesday, primarily south of the
Missouri River. However, the extent of antecedent wetting rain
Monday night will be monitored to determine how rapidly the fuels
and air can dry out. Thus, with wetting rains unlikely across much
of zone 122 there is enough confidence for a Fire Weather Watch
there from 11am to 8pm on Tuesday. This is also the area with the
most below normal departure for precipitation within the last
month. Afterward, winds and RH recover enough under a slightly
cooler than normal pattern to minimize fire weather concerns at
this time for the rest of the week.


&&

.GGW WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Tuesday morning through Tuesday evening
for Dawson/McCone/Prairie/Richland/Wibaux Counties.

&&

$$

weather.gov/glasgow