Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 241739

Area Forecast Discussion
National Weather Service Great Falls MT
1140 AM MDT TUE MAY 24 2016


Widespread mostly cloudy to overcast skies across our region this
morning with some light rain over Liberty/Hill/Blaine counties.
Current satellite imagery/webcams show an arc of reduced clouds
from Glacier NP southeast to Great Falls and over to Lewistown,
but expect some of that will fill back in this afternoon as
scattered showers and isolated thunderstorms develop. Going
forecast in good shape with just a few minor adjustments on precip
probabilities along southern portions of the Continental Divide
through early aftn.


Upper level low centered over SW Saskatchewan will move little today
and tonight, continuing to circulate moisture into the region from
the NW. Low clouds with CIGS 2000-4000ft will impact local TAF sites
through this aftn.  Showers be widely scattered today with an
increase in coverage during the afternoon as the airmass
destabilizes.  There is also a chance for a few thunderstorms,
mainly south/west of a line from KCTB to KLWT, but probability too
low at primary airfields to include in latest TAFs. Showers will
dissipate this evening with VFR ceilings tonight. Surface winds will
remain generally light at 10kts or less.


Today through Thursday...An unsettled weather pattern will reside
over the region through this period, as a cut-off upper level low
pressure system continues to spin over southern Saskatchewan. With
the upper level low just `wobbling` over the same area for the
next few days, scattered light showers will continue to rotate
around this upper level low, and the scattered showers will
affect much of the region from today through Thursday. There will
be breaks in the precipitation, but confidence is low when the
breaks of the precipitation will occur. Thus at least a small
chance for scattered showers is in place for most areas, most
periods. There will be just enough instability, that there will be
a chance for a passing thunderstorm, mainly during the
afternoon/early evening hours today through Thursday. Afternoon
temperatures will continue to be below normal through Thursday,
but a slow/gradual warming trend is still expected. Additionally,
wind speeds should generally be on the light side across the
entire region for the next few days.

In terms of snow, scattered light snow showers will affect the
Rocky Mountain Front, Kings Hill, and Big Sky areas through the
period. Snow levels this morning will be near 6000 feet, but
will gradually rise to above 7000 feet by Wednesday morning, then
generally remain above 7000 feet Wed afternoon thru Thursday.
Overall total snow accumulations will be low, generally in the 1
to 3 inch range today through Wednesday, with the best
accumulating snowfall above 7000 feet. Brusda

Thursday Night through Tuesday...Weakening upper level low that
has been meandering about the Canadian Prairies lifts out to the NE
Thursday night while a new upper level low dropping south through BC
moves into the Pacific NW Friday and gradually shifts east into the
Northern Rockies this weekend through early next week. Diffluent
southerly flow aloft ahead of the low moving into the Pacific NW and
initial pieces of shortwave energy rotating around the low will
bring increasing moisture and instability to the region Friday with
showers and thunderstorms likely by late in the day. Additional
energy ejecting out of the low across western MT Saturday and Sunday
will maintain high chances for precipitation through the weekend
with temperatures cooling some and instability decreasing, though
some thunderstorms during the afternoon/evening periods will remain
possible. Models diverge with some with details of the eventual
evolution of the upper low/trough by early next week but continue to
maintain general troughing over the Northern Rockies and MT for a
chance of showers on Monday and Tuesday with temperatures moderating
some. Hoenisch


GTF  58  40  64  44 /  20  20  20  30
CTB  57  37  65  42 /  20  20  20  30
HLN  59  42  64  45 /  40  20  40  30
BZN  58  38  62  41 /  40  20  50  30
WEY  52  34  50  34 /  40  40  60  40
DLN  56  38  59  39 /  50  30  60  40
HVR  59  41  66  43 /  30  10  20  20
LWT  56  39  62  42 /  30  20  50  20



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