Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 270946

Area Forecast Discussion
National Weather Service Great Falls MT
346 AM MDT Tue Sep 27 2016


Today through Thursday...Limited changes made to the short term
forecast. Models continue to show a flattening ridge across the
region for today. With quick cross barrier flow...some gusty winds
may develop by this afternoon. Winds will be short of High Wind
criteria, however, gusts could still exceed 30 mph across much of
North Central Montana, but gusts could exceed 40 mph closer to the
Rocky Mountain Front. This mainly downsloping air will also bring
dry and warm conditions for today. Some areas still look to be in
the low 80s with 70s elsewhere. An interesting surface feature
then looks to push across the region tonight through Wednesday
morning. A sfc high in Alberta will send a weak sfc cold front
south...and across the area tonight through Wednesday. Dewpoints
with this feature will be in the mid to upper 40s...with some mid
level moisture also available riding over the ridge. The main
question will this front and possible upslope
enhancements enough to overcome the dry downsloping air from the
daytime hours? Probability is low for any shower high enough to include slight chances for
isolated showers across the northern half of the CWA. Frontal
boundary stalls out across central portions on Wednesday
afternoon...and with warming and drying ends the
precipitation chances. Temperatures look to still be cooler on
Wednesday...with highs in the 60s and 70s. A developing upper
level low across the Pac NW then gives us sw flow for
Thursday...picking up some monsoonal type moisture from the desert
sw. Mildly unstable air will be found across the
region...however...much of it will be capped. Areas across the
west and sw will see cooler temps aloft...allowing for the cap to
break down...and chances for thunderstorms. Elsewhere will see
increasing clouds with highs slightly warmer in the 70s. Anglin

Thursday night through Tuesday...Quite a difference in solutions
for the medium range period tonight. Models continue to indicate
that the period will be dominated by an upper level low off the
British Columbia and Pacific Northwest coast. However, models
strongly differ on the strength, size and position of this feature
with the ECMWF developing a much broader trough that remains over
the western USA through the end of the forecast period.

Have not made major changes to the going forecast despite this new
development and the subsequent lower forecast confidence that it
represent. As before, a somewhat unstable airmass will fuel
scattered mountain showers and a few thunderstorms Thursday night
and Friday with an isolated storm or two possibly moving out over
the plains. Models have pushed back timing for the upper level
trough and associated front to move into the forecast area.
However,it still appears that this system will bring an increasing
chance for showers and thunderstorms this weekend with unsettled
conditions and cooler temperatures likely persisting through
Tuesday. mpj


Updated 0600Z.

Overall mainly VFR conditions expected through the forecast period.
Clear skies and light winds will be found across the region tonight
through Tuesday morning. Ridge of high pressure will break down
Tuesday afternoon...this will bring increased winds to the region.
Sites near the Rocky Mountain Front...such as KCTB...may see gusts
around 35 to 40 kts. This cross mountain flow could also bring some
turbulence across area mountain ranges. A weak cold front then
pushes south out of Canada Tuesday evening. This will bring a
noticeable wind shift from westerly to northerly direction...some
breezy winds at times...and perhaps near MVFR BKN deck. Anglin


GTF  82  47  68  48 /   0  20  20  10
CTB  78  42  62  42 /  10  20  10  10
HLN  81  44  74  47 /   0   0   0  10
BZN  79  46  77  49 /   0   0   0  10
WEY  71  34  73  40 /   0   0   0  10
DLN  78  43  75  45 /   0   0   0  10
HVR  82  46  69  48 /  10  20  10  10
LWT  80  45  70  50 /   0  10  10  10



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