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000
FXUS65 KGGW 140826
AFDGGW

Area Forecast Discussion
National Weather Service Glasgow MT
226 AM MDT Sun Apr 14 2024

.DISCUSSION...

KEY MESSAGES:
- Large temperatures shift downward after Monday night with the
  passage of a cold front.

- Winds worthy of Lake Wind Advisory could last from Tuesday
  morning to Thursday evening.

- Chances for precip behind the frontal passage will last through
  Thursday morning but are not expected to contain much in the
  way of wetting rains/snow.

MORNING DISCUSSION:
Synoptic Setup: A ridge currently runs north through the western
half of the CONUS cresting around Montana. To the west a closed
low has set up off the central California coast. To the north
semi-zonal flow runs from southern Saskatchewan back west to just
off the coast of British COlumbia. The coldest air in the northern
hemisphere lies off the coast of the Alaskan North slope with a
trough dropping south into Alaska and modifying warmer over the
Gulf of Alaska.

Today into tonight: Ridge crest will grow across the area today
allowing 850 mb temperature to rise to nearly 20*C. This will lead
to warmer than average temps from the models as surface layer
mixes out in the afternoon. Therefore, have replaced NBM MaxTs
with a 50/50 blend of NBM/NBM90 especially in the southwest and
readjusted edges to match up better with neighbors. Afternoon
showers and perhaps an isolated thunderstorm may develop over the
the central Montana mountains from the extra heat. Moving into
tonight there is a 10-30% chance that a shower over the central
Montana mountains could jump onto the backside of the ridge axis
as it passes through the area and move out over the Plains. Though
these should die quickly in the evening hours if they do exit
their main form of orographic lift. Meanwhile, a surface trough
will set up off the front range to the west and weak trough over
the Gulf of Alaska will pick up steam move onshore and roll into
Canadian Rockies as a large disturbance.

Monday to Monday night: Surface trough will become the focus for
new showers and thunderstorms through the day. As the late
afternoon hits, 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
in down the front range behind it. This will enhance lift and
some weak thunderstorms and rain shower development into the
evening hours.

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. As it currently stand almost all
12 hour periods are looking to have a Lake Wind Advisory out with
a nearly 80% chance for it to go out tomorrow for the Tuesday
event. Though there is some question as to how far into the future
to run it.

Thursday night onward: large trough begins over the north central
CONUS and central Canada. But, an equally large ridge develops
over the North American west coast. This will lead to drier and
warmer temps from here onward. Surprisingly, while 500mb height
deviations accelerated from 20 to nearly 70 dm Monday through
Tuesday with the frontal passage, they then hold steady or back
off to 60 dm through the end of the forecast allowing these
periods to have 60-90% confidence in the warming and drying trend.
GAH


&&

.AVIATION...

LAST UPDATED: 0700Z

FLIGHT CAT RANGE: VFR

DISCUSSION: Expect dry conditions with FEW to SCT mid to high
clouds through the afternoon. During the evening hours there is a
10% chance that an isolated showers may be able to pass by KGGW
before dying before midnight

SFC WIND: Light and variable through the morning. Becoming east
and increasing to 10 to 15 kts this afternoon through tonight.

GAH


&&

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


&&

$$

weather.gov/glasgow