Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 242107

Area Forecast Discussion
National Weather Service Great Falls MT
307 PM MDT TUE MAY 24 2016

Area of low pressure over
southwest corner of Saskatchewan and extending into north central MT
will remain nearly stationary tonight. Long streamer of Pacific
moisture cutting diagonally across the state from the Big Hole
Valley to the MT/ND border and wrapping around the low`s circulation
center is providing plenty of moisture for widespread mostly cloudy
skies.  As of 2:30 pm radar/satellite imagery indicates scattered
showers developing in several locations across central/southwest MT
as the atmosphere destabilizes with afternoon heating. Expect the
coverage of showers and some small, isolated, short-lived
thunderstorms to increase through late aftn, but then gradually
dissipate this eve.  Only light (less than 0.1 inch) rainfall is
forecast for most locations, though a few spots along the Rocky Mtn
Front may receive a bit more (up to 0.2 inch). Quiet conditions
expected overnight with just a few lingering showers over the
foothills and higher terrain of southwest MT.  Little change in
conditions are predicted for Wed/Thur.  Forecast models have the
Canadian low drifting down to the Hiline tomorrow and then head
eastward to the Dakotas by Thurs aftn.  Additional moisture will be
pulled into our area as the low shifts its position, bringing
another round of showers and isolated thunderstorms both Wed and
Thur aftn/eve.  Given the marginal convective energy and wind shear
associated with the low, no strong thunderstorms are expected,
though a few may produce brief, moderate downpours and a little bit
of small hail. Temps holding steady next few days, with highs in the
upper 50s to mid 60s.

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.


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.


GTF  39  64  44  64 /  20  20  30  40
CTB  37  65  42  64 /  20  20  30  40
HLN  42  64  45  66 /  20  40  30  40
BZN  38  62  40  65 /  20  50  30  40
WEY  34  50  33  54 /  40  60  40  60
DLN  38  59  39  63 /  30  60  40  40
HVR  41  65  43  68 /  10  20  20  30
LWT  39  61  42  63 /  20  50  30  40



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