636
FXUS65 KGGW 282125
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
325 PM MDT Tue May 28 2024

.DISCUSSION...

KEY MESSAGES:

- Warm and dry conditions expected today.

- Strong and severe thunderstorms are expected Wednesday afternoon
  and evening, especially along the SPC slight risk area
  straddling our Montana/North Dakota border.

WEATHER PATTERN OVERVIEW:

The fast-moving ridge of high pressure today is already shifting
eastward across the region, pushed by an upper low pressure trough
approaching from Alberta. As the low continues eastward, a
surface low develops with an associated cold front. Overnight and
into Wednesday as the front moves east, the low level jet
strengthens, pulling moisture northward along the Montana/North
Dakota border. This will set up a favorable scenario for severe
thunderstorms, initially across the far eastern zones of eastern
Montana for Wednesday afternoon and evening, as noted by SPC with
a slight risk area.

As the upper trough sweeps across the Canadian prairies, cooler
temperatures along with some unstable air lingers over the region
for Thursday. Behind the trough, the flow aloft becomes generally
zonal, with occasional shortwave disturbances, for warmer and
drier conditions through the weekend.

CONFIDENCE & DEVIATIONS:

Confidence for severe weather on Wednesday afternoon continues to
increase, with CAPE in excess of 1500 J/kg, and moisture
advection on the strong low level southeast jet with winds in
excess of 30kt. Damaging winds and large hail will be the main
threats. HREF ensemble only giving a 10% probability for updraft
helicity in excess of 75 m2/s2 through 00z Thursday, but could see
higher probability in the early evening. With PW over 1"
indicated, heavy rain is also a possibility near the North Dakota
border.


&&

.AVIATION...

PATTERN: Ridge of high pressure today will be replaced by a trough
of low pressure on Wednesday, which will provide the focus for
strong to severe thunderstorm development through Wednesday
evening.

FLIGHT CATEGORIES: VFR through this TAF cycle, but the
introduction of strong to severe thunderstorms Wednesday afternoon
and evening may result in brief periods of IFR or worse for KSDY
and KGDV if a storm happens to pass directly overhead.

WINDS: Today through tonight, from the east and southeast at 10 to
15 kts. For Wednesday: ahead of the cold front, from the southeast
and south at 15 to 20 kts; then behind the cold front, from the
northwest at 20 to 25 kts. Gusty, erratic, severe wind gusts are
expected near the stronger storms.


&&

.GGW WATCHES/WARNINGS/ADVISORIES...
Lake Wind Advisory from 11 AM Wednesday to 9 PM MDT Thursday for
Central and Southeast Phillips-Central and Southern Valley-
Garfield-McCone-Petroleum.

&&

$$

weather.gov/glasgow