Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 241735
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1135 AM MDT Mon Apr 24 2017

...Update to Aviation...

.UPDATE...

Partly cloudy skies prevail across the forecast area this morning.
A few areas of fog have yet to burn off, mainly over eastern
portions of the Hi-Line. Moderate to heavy snow also continues
over far southwest MT including the West Yellowstone area. A
stationary frontal boundary remains draped across central Montana.
Mostly sunny skies will lead to weak instability for the
afternoon. The forecast remains consistent with short-term
guidance, suggesting increasing coverage of afternoon/evening rain
and mountain snow showers, with isolated thunderstorms capable of
producing small hail. Have not made any updates to the inherited
forecast, but will continue to monitor for developing weather as
we move into afternoon. PN

&&

.AVIATION...
Updated 1735Z.

Upper level disturbance expected to impact Southwest and Central
Montana this afternoon and overnight. Periods of mountain
obscurations and widespread MVFR/VFR ceilings are expected with
possible IFR or lower ceilings at times. Isolated thunderstorms are
also possible until 03Z Tuesday. Lower elevation showers may mix
with or change to all snow showers from around 08Z to 18Z Tuesday.
mpj

&&

.PREV DISCUSSION...
/ISSUED 530 AM MDT Mon Apr 24 2017/

Today through Tuesday...Mostly cloudy skies and periods of
precipitation will prevail across the CWA as multiple shortwave
troughs move generally eastward over the region. The first primary
shortwave trough looks to impact Southwest MT this afternoon through
Tuesday morning, while the second primary disturbance should skirt
the international border and Hi-Line Tuesday afternoon. In general,
snow levels should fluctuate between approximately 5000 and 6000
feet MSL during the period. While most mountain passes should
receive minor snow accumulations, decided to issue a winter weather
advisory for Targhee Pass and West Yellowstone. Within the advisory,
slick and snow-covered roads are expected, especially overnight
tonight into early Tuesday morning. In addition, weak instability
and a minor cap will result in the possibility of isolated, brief
thunderstorms over Southwest and Central MT this afternoon
through early evening. Additional isolated thunderstorms are
possible for the western two-thirds of the CWA during the late
morning through afternoon hours of Tuesday. Lows will be near-
normal, while highs are expected to be about 5 to 10 degrees
cooler than normal for late April. Jaszka

Tuesday night through Monday...An unsettled weather pattern will
continue to reside over the region into early next week. The
precipitation is likely to become more widespread by late
Wednesday through Friday. Total precipitation amounts for later
this week are still expected to average between 0.30 and 0.60
inches for many areas, with some isolated higher amounts. The main
concern will be during the overnight hours as snow levels lower
to around 3500/4000 feet or so. Thus some snow is possible in the
bigger cities at lower elevations later in the week. At this time
most snow accumulations at lower elevations will be on grassy
areas, but a few inches of snow are likely in the mountains each
day. Afternoon temperatures will be below normal through the
entire period, with Thursday/Friday being the coolest days.
Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  54  33  50  33 /  30  40  60  40
CTB  51  32  47  32 /  60  70  80  40
HLN  54  36  55  36 /  40  40  50  40
BZN  51  34  52  32 /  50  60  50  50
WEY  40  28  43  26 /  70  70  50  40
DLN  49  35  52  33 /  50  70  50  20
HVR  56  33  47  32 /  30  30  60  40
LWT  52  31  43  31 /  40  50  60  50

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon MDT Tuesday Gallatin.

&&

$$

weather.gov/greatfalls


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