147
FXUS65 KGGW 030821
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
221 AM MDT Fri May 3 2024

.DISCUSSION...
KEY MESSAGES:

- Night-time temperatures will drop below freezing in many areas
  tonight.

- Unusually warm conditions are expected on Sunday.

- Another round of rain is expected starting Sunday night through
  at least Thursday. Ranges are looking on track to be around a
  inch and a half to 2 inches for many locations with moderate
  confidence(50-70%).


WEATHER PATTERN OVERVIEW:
Synoptic Setup: Forecast begins with a trough running down from
Saskatchewan through eastern Montana and Wyoming. A closed low
sits off the coast of the Pacific Northwest with a ridge formed up
between these two features from Nevada through the Pacific
Northwest and into British Columbia.

Today through Tonight: Local trough will exit for the Dakotas
taking the surface low along with it. This will pull the showers
remaining across the area this morning towards the east and
northeast with the final showers clearing or dissipating around
Noon. Clearing should begin to filter in behind the showers
during the late afternoon and early evening. By around Midnight
enough clouds will exit to drop off temps to near freezing or
lower as cold air continues to filter in.

Saturday through Sunday: Expect a warming trend of 10 to 15
degrees each day as the ridge to the west moves into the region.
The ridge looks like it is going to tap into Desert Southwest air
which will make it unusually warm for the region by Sunday with
70s and perhaps brief 80s for highs. Meanwhile, the closed low
from the PCNW will ram itself onshore and push into the
Intermountain west while stretching into a very amplified trough
in response to the ridge.

Sunday night through Monday night: A southern flow interface will
setup between the extremely warm temps of the exiting ridge and
the incoming trough over the Intermountain West. This will start
pulling gulf moisture into the Great Plains potentially all the
way up toward eastern Montana. The intense cool down will generate
a closed low over south central Montana with enough lift energy
to not only generate rain showers but also thunderstorms across
the region through these periods.

There is a small chance (5-20%) that some of these thunderstorms
could become severe, but with overnight convection being the main
periods of interest there will be no insolation and severe weather
will likely not occur. Will need to monitor SKEW-Ts in these
periods as they get within CAM model ranges for further scrutiny.

Tuesday through Thursday night: Closed low will migrate
northeastward and start to cut off from the warm air. However,
this just means that most of the convective elements will become
mainly stratiform. Main problem here onward is that positioning of
the low is in question with a range for its center position from
South Dakota all the way up to southern Saskatchewan. The low
looks to generate a trowal in most models which will bring a heavy
amount of rain to areas directly under or behind it. The majority
of the ensembles place this over eastern Montana which could
easily generate 1 to 2 inches to the area it hits. This feature
has remained consistent over the last 48 hours raising confidence
to moderate(50-70%).

Friday onward: A new ridge looks to move into the area which will
raise temps and dry conditions out. GAH


&&

.AVIATION...

LAST UPDATED: 0730Z

FLIGHT CAT RANGE: VFR - LIFR

DISCUSSION: Low clouds, rain, and snow showers will linger
through the morning at KGGW, KOLF and KSDY with some clearing of
precip around 18Z. With temperatures hovering around freezing and
wintry mixed showers across the area, ICING aircraft surfaces may
become a problem that could hold on till about 18Z when the
showers clear.

Ceilings will be the main controlling factor through the cycle at
the Terminals with MVFR ceilings being pretty universal till
about 00-02Z this evening. IFR or worse will have an impact at
KSDY and briefly KOLF around 10-19Z this morning. VFR should
return to all the terminals this evening around 00-02Z.

WIND: NW at 10 to 20 kts from this morning through today. Calming
to 5 to 10 kts this evening through tonight.

GAH


&&

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


&&

$$

weather.gov/glasgow