Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 270330

Area Forecast Discussion
National Weather Service Great Falls MT
930 PM MDT Wed Apr 26 2017


Only update this evening was to better focus mention of more
widespread showers over the Chouteau/Judith Basin/Fergus County
areas this evening to better reflect current conditions. A few
lightning strikes are also lingering across this area, but the
storms are showing signs of weakening. Brief heavy rain will be
the main threat from any lingering storms.

Otherwise, the current forecast appears on track. Scattered light
showers will linger overnight across much of the area. Snow
showers will likely cause slushy mountain pass accumulation into
Thursday morning over the Rocky Mountain Front, Little Belt
Mountains, and in the mountains of far Southwest Montana, so have
left the Winter Weather Advisories for those mountain areas as is.


Updated 0001Z.

Another in a train of shortwaves is moving through at this time,
almost like a broken record, with scattered showers and isolated
TSRA. The heaviest SHRA/TSRA may produce a brief period of MVFR
CIGS/VIS as well as some small hail. The hail may accumulate up
to an inch for any terminal impacted by the stronger TSRA. There
may be a lull in precip overnight across central MT, but a
developing moist, NW flow aloft will likely lead to another round
of showers on Thursday. At any terminal, a rain/snow mix or
transition to all snow cannot be ruled out overnight into early
Thursday morning if temperatures cool enough. In general, most
sites will see gradually lowering CIGS overnight into Thursday
with MVFR or lower conditions and mtn obscurations. Martin


/ISSUED 601 PM MDT Wed Apr 26 2017/

Tonight through Friday...Upper level pattern through the rest of
the work week features a nearly stationary low centered over
southern SK/AB while a strong and moist Pacific Jet dives east-
southeastward into the Great Basin with shortwave disturbances to
its north pivoting by to the south of the Canadian low. Diffluent
flow aloft and incoming shortwave energy from the west will lead
to increasing convective shower development through the remainder
of this afternoon over much of the forecast area with a few
thunderstorms also possible, primarily over central/SW MT, where
brief heavy rainfall and small hail (potentially in large
quantities) will be the main threats. Mid level shortwave and
surface trough shift east across the region overnight, continuing
a good chance for showers across the forecast area. Gradual
cooling aloft will lead to lowering snow levels with accumulating
snow down to 4500 ft in the north and 5500 feet in the south after
midnight tonight. Models consistently produce enhanced
precipitation accumulation across northern portions of the Rocky
Mtn Front, the little Belt Mtns and Gallatin/Madison ranges
tonight, with general accumulation at pass levels in these areas
of around 2-4 inches likely and localized higher amounts across
the higher peaks. Since this occurs during the overnight period,
some slushy accumulation is possible on roadways including Marias
Pass, Raynolds Pass and Kings Hill tonight through early Thursday
and A Winter Wx Advisory has been issued to highlight this.
Additional shortwave energy pivots SE into the region late
Thursday through Friday as an upper level trough is carved out to
the north of the jet streak diving into the 4-corners region.
Showers will be likely across much of the region Thursday
afternoon through Friday with somewhat greater coverage over north
central MT as flow aloft becomes northerly, favoring enhanced
precipitation again over the Little Belts and along the Rocky Mtn
Front. Snow levels will lower further Thursday and Friday with
some potential for minor snow accumulations at lower elevations
during the Thursday night and early Friday morning period.

Thursday Night through Next Wednesday...Somewhat drier weather is
expected Saturday as upper ridging builds eastward into the CWA.
However, unsettled weather looks to become more widespread again
Sunday through Tuesday of next week as a series of shortwave
troughs break-down the aforementioned ridging. Thereafter,
Wednesday looks to be primarily dry and warmer as another upper
ridge builds-in from the west. Near-normal lows are expected
during the period, while highs should remain below-normal through
next week Tuesday. By next Wednesday, highs should be closer to


GTF  36  46  30  47 /  40  50  50  50
CTB  33  43  30  48 /  50  80  60  40
HLN  35  47  33  51 /  30  40  40  50
BZN  33  45  29  47 /  50  50  30  40
WEY  27  35  19  38 /  80  80  50  30
DLN  31  43  27  47 /  50  50  30  40
HVR  37  48  31  52 /  50  70  50  30
LWT  34  44  29  43 /  50  70  60  50


Winter Weather Advisory until noon MDT Thursday For the Little
Belt Mountains in Central Montana, including Kings Hill Pass in
Cascade...Judith Basin...Meagher.

Winter Weather Advisory until noon MDT Thursday above 6000 feet
for Gallatin...Madison.

Winter Weather Advisory until noon MDT Thursday above 5000 feet
for Northern Rocky Mountain Front.


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