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000
FXUS65 KTFX 181805
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1205 PM MDT Thu Apr 18 2024

...AVIATION SECTION UPDATED...

.SYNOPSIS...

A lingering northwesterly flow aloft will keep temperatures up to
15 degrees below normal through Friday, with a chance of isolated
afternoon snow showers, mainly near and over the mountains. Weak
high pressure ridging will help warm temperatures back close to
normal through the weekend, but a Pacific disturbance will bring a
chance of showers back to the area for Sunday into Monday.
Continued warming is then expected into the middle of next week.

&&

.Update...

Morning update has been published, with the main adjustment being
to add isolated to scattered PoPs from this afternoon through
early this evening across most locations. Isolated to scattered
snow showers will develop this afternoon and persist through this
evening as lapse rates steepen amongst surface heating and very
cold air aloft being in place over the Northern Rockies. While
snow accumulations will be minimal across most locations given the
brevity of the showers, brief periods of reduced visibility to
below 1 mile are possible beneath the strongest showers. Where
snow showers are more persistent over the higher terrain of the
Continental Divide, mainly north of the MT Hwy 200 corridor and
south of the US Hwy 2 corridor, snowfall accumulations of 1-3"
will be possible through early this evening. Otherwise the
remainder of the forecast remains on track, with another cool and
breezy day expected across all of Southwest through North Central
Montana. - Moldan

&&

.AVIATION...
1205 PM MDT Thu Apr 18 2024 (18/18Z TAF Period)

A cold and moist northwesterly flow aloft will bring another round
of isolated to scattered snow showers this afternoon and evening.
Expect Low VFR/MVFR clouds during this time with some brief
degradations to IFR/LIFR with the heavier showers. This activity
diminishes after 19/03Z for most locations, but an H700 frontal
boundary may keep some light snow going into the overnight hours for
southwestern areas south of I90. Then another weak disturbance moves
into North-central MT Friday morning and brings a more persistent
MVFR/IFR stratus deck onto the plains. Northwesterly surface breezes
in northern areas will gust in the 25 to 30 kt range through this
evening. - RCG

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.PREV DISCUSSION...
/ISSUED 408 AM MDT Thu Apr 18 2024/

Today through Friday... An east-to-west oriented low pressure
trough along the Canadian Border will keep North Central,
Central, and Southwest Montana under a cool northwesterly flow
aloft through Friday. Temperatures should remain 10 to 15 degrees
below normal through the period, with widespread teens and 20s
for overnight lows likely causing a frost, if not a freeze, after
a stretch of highs in the 60s to lower 70s that ended just a few
days ago. The cyclonic nature of the northwesterly flow aloft
will likely combine with weak afternoon instability to cause a
few snow showers to form each day, especially over and near the
mountains. However, these showers are only expected to cause
minor measurable accumulation, if any at all. Surface high
pressure building south out of Canada will mostly cause lingering
breezy northwest winds to decrease and shift more northeasterly
tonight into Friday. However, that shift will likely cause winds
to become gusty through north-south oriented valleys of Southwest
Montana, including the Twin Bridges, Dillon, and Ennis areas.

Saturday through next Thursday... Weak high pressure ridging is
forecast to develop over the western United States for much of
this period Saturday through Monday, warming temperatures to near
seasonal averages. However, a low pressure trough off the Pacific
coast of North America is also forecast to eject a shortwave
trough over Montana Sunday into Monday, bringing at least a
chance of precipitation to much of the area. Right now, though,
probabilistic guidance is giving less than a 20 percent chance of
4 inches of snow accumulation in the mountains through this
period. Forecast models then indicate that the high pressure ridge
will start to amplify Tuesday into Wednesday, which should help
warm temperatures to around 10 degrees above normal through mid-
week. Mostly dry conditions are also expected on Tuesday, but the
low pressure trough is forecast to deepen off the Pacific coast
Wednesday into Thursday. This would shift the flow aloft more
southwesterly and unsettled, for an increasing chance of showers.
-Coulston

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  39  17  35  15 /  20  20  10  10
CTB  34  16  33  17 /  20  10  10  10
HLN  44  23  41  21 /  20  20  10   0
BZN  41  22  42  15 /  20  20  10   0
WYS  38   5  41   4 /  20  20  10  10
DLN  41  19  40  18 /  20  20  10   0
HVR  39  20  38  18 /  10  20  20  10
LWT  34  13  31  15 /  20  20  20  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

http://www.weather.gov/greatfalls