228
FXUS65 KGGW 180414 AAA
AFDGGW

Area Forecast Discussion...UPDATED
National Weather Service Glasgow MT
1014 PM MDT Mon Jun 17 2024

.DISCUSSION...

KEY MESSAGES:
- Cool temperatures with widespread rain expected tonight and
  Tuesday.

- Gusty Winds across Fort Peck Lack will persist through Tuesday.

- Warm temperatures starting on Wednesday with frequent chances
  for showers and thunderstorm chances between Wednesday and
  Saturday, especially Friday evening.

WEATHER PATTERN OVERVIEW:

There will be an upper trough/low moving into western Montana
today while a surface low develops over Wyoming. SW flow aloft
ahead of the trough will bring deep moisture into the forecast
area today which will allow widespread rain showers to develop by
sometime this afternoon with embedded thunderstorms. To the
northeast of the surface low today, an inverted surface trough
along the Yellowstone River will bring somewhat warmer and
more unstable airmass with a marginal risk of severe
thunderstorms. At the same time precipitable water rises to 1.0
to 1.25 inches this afternoon and evening in the east. WPC has a
marginal risk for excessive rain today and tonight and the best
chance for excessive rain would come in any embedded thunderstorms
that develop.

The upper low moves through central Montana tonight and eastern
Montana on Tuesday which will keep the rain going most of the time
until the low moves to the northeast Tuesday night. At this point,
there is a 60-80 percent chance of a half inch of rain and a 20-40
percent chance of an inch of rain today and Tuesday from this
event.

Montana spends the remainder of the week in an unstable WSW to SW
flow aloft which will bring warmer temperatures and frequent
chances for showers and thunderstorms. With the closer proximity
to the upper trough Friday Night, chances for precipitation are
expected to be higher. With warmer temperatures, some of these
thunderstorms could be severe.

FORECAST CONFIDENCE and DEVIATIONS:

For the system today through to Tuesday night, QPF amounts varied
slightly from the previous forecast, with a probability around
70-100% for at least 0.25", 60-80% for 0.50", and 20-40% for 1".

From Wednesday onward confidence is moderate on a gradual warming
trend, but low on precipitation chances. Models agree on a broad
western US and Canada trough with a WSW to SW flow aloft over
Montana but disagree on the timing of waves within the flow aloft.


&&

.AVIATION...

LAST UPDATE: 0410Z, Monday night, June 17th

FLIGHT CAT RANGE: Mainly MVFR this evening, becoming IFR tonight.

DISCUSSION: Cloud bases will lower to IFR levels overnight.
Periodic rain is expected through Tuesday for most locations.

WIND: From the northeast and north overnight tonight at around 15
kts. Tuesday from the north and northwest at 5 to 10 kts.

---BMickelson


&&

.GGW WATCHES/WARNINGS/ADVISORIES...
Lake Wind Advisory until 4 PM MDT Tuesday for Central and
Southeast Phillips-Central and Southern Valley-Garfield-McCone-
Petroleum.

&&

$$

weather.gov/glasgow