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000
FXUS65 KGGW 150906
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
306 AM MDT Mon Apr 15 2024

.DISCUSSION...

KEY MESSAGES:
- Gusty winds and low RH worthy of a Fire Weather Watch arrive by
  Tuesday afternoon and linger into Wednesday...see details in
  fire discussion.

- Strong winds are expected to last into Thursday Evening and
  generate concerns for a hard chop on Fort Peck and other area
  lakes through that time.

- Isolated afternoon and evening thunderstorms may be possible
  today south of the Missouri but do not look severe and will
  likely produce little if any rain.

MORNING DISCUSSION:
Synoptic Setup: A ridge currently runs north through the central
third of the CONUS and then curves back west, cresting around
Montana. To the west a closed low is moving across southern
British Columbia. To the north the coldest air in the northern
hemisphere lies within a trough over the Northwest Territories and
quickly dropping into the Canadian Plains.

Today to tonight: Surface trough over central Montana will become
the focus for new showers and thunderstorms through the day. As
the late afternoon hits, the disturbance over the Canadian Rockies
will exit the front range and form a low over southern Alberta
and latch onto the surface trough and begin dragging it slowly
across eastern Montana. This trough will begin to morph into a
cold front as arctic air filters down the Canadian front range
behind it. This will enhance lift for some weak thunderstorms and
rain shower development into the evening hours, especially south
of the Missouri River. Wetting rain are not expected with this
passage. With maximum top out CAPE in the HREF no higher than 750
J/kg and almost no shear, chances for any cell to hit severe is
less than 10%.

Tuesday through Thursday: Cold Air Advection behind the frontal
passage will slowly drag temperatures down through these periods
as well as keep Wind Gusts high. This wind will be strong enough
to provide for rough chop on areas lakes and a Lake Wind Advisory
was issued for it running Tuesday morning to Thursday evening.
There will be some lulls in the overnight hours but each day the
CAA will pick the wind again quickly. The Initial passage of the
Cold front will also be dry enough that when the low RH is
combined with the raised gusts has made the southwest fire weather
zones worthy of a Fire Weather Watch for Tuesday afternoon. Will
be keeping an eye on this for the need for a future Red Flag.

Thursday night onward: large trough begins over the north central
CONUS and central Canada. But, an equally large ridge develops
over the west coast of North America. This will lead to drier and
warmer temps from here onward as the ridge presses east. Standard
deviation of 500 mb decameter heights has improved from ~60 dm to
~40 dm through the weekend allowing confidence near the end of
the forecast to improve to moderate.

GAH



&&

.AVIATION...

LAST UPDATED: 0845Z

FLIGHT CAT RANGE: VFR

LLWS: Low level wind shear will be a possibility this morning
through roughly 14Z for KSDY and KGDV. This threat should go away
quickly after sunrise.

DISCUSSION: Expect generally dry conditions with SCT mid to high
clouds through the morning. During the afternoon hours showers
and weak thunderstorms will begin impacting the terminals around
22Z. Strongest chances reach up to about 40% from 01 to 04Z at
KGDV this evening. Will probably handle these with Prob30s.

SFC WIND: East at 5 to 15kts through today. Becoming Light and
variable this evening before a cold frontal passage. After the
passage Tuesday morning, Northwest at 15 to 25 Gust 30 kts into
Tuesday.

GAH



&&

.GGW WATCHES/WARNINGS/ADVISORIES...
Lake Wind Advisory from 3 AM Tuesday to 9 PM MDT Thursday for
Central and Southeast Phillips-Central and Southern Valley-
Garfield-McCone-Petroleum.

Fire Weather Watch from Tuesday morning through Tuesday evening
for Southern Petroleum and Southern Garfield Counties-The Little
Rockies-The Lower Missouri River Breaks including the Charles M
Russell National Wildlife Refuge.

&&

$$

weather.gov/glasgow