Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 211742

Area Forecast Discussion
National Weather Service Great Falls MT
1142 AM MDT SUN AUG 21 2016


.UPDATE...The Fire Weather Watch for portions of the Rocky Mtn
Front have been upgraded to a Red Flag Warning for Monday
aftn/eve. Confidence is high on the forecast for very low
humidity and gusty winds tomorrow.



VFR conditions prevail through the period. Water vapor imagery
reveals dry air across the region. Expect generally clear skies
today and tonight. Areas of high clouds will begin to spread
across the Rocky Mountains Monday morning. Breezy west- southwest
winds will develop over north-central Montana this afternoon but
then taper this evening. Stronger winds are expected Monday
morning with gusts up to 40kt at KCTB, and up to 30kt at


/ISSUED 930 AM MDT SUN AUG 21 2016/

Today through Tuesday...Overall mainly dry and warm conditions
are expected for today...with elevated fire danger returning. Flat
ridging will change the flow to more westerly breezes. With this
warm and very dry air will settle in across the region. Mainly dry
condtions and clear skies are expected for today...except across
far sw portions. Here a brief window of 500+ J/Kg instability may
be just enough to provide some afternoon thunderstorms. These
storms will be very high based...and mostly dry thunderstorms.
Gusty winds and occasional lightning will be the main threats.
Most areas will see low RH values and some increasing westerly
winds this afternoon. Elevated fire danger is expected across most
areas. See the Fire Weather Discussion for more details. Any
thunderstorms that can develop will diminish early this evening.
Large upper level low and its associated cold front look to impact
the area in separate stages for Sunday night through Monday.
Trough from the upper low swings across the region Sunday night
into Monday morning. This tight gradient will bring strong
westerly flow over 50 knots across the mountains. With the frontal
boundary lagging...stable air will cause the quick moving flow to
likely form a mountain wave and downslope across the Rocky
Mountain Front. Strong winds will likely be found through the
morning hours Monday. The peak of these winds now looks to be in
the mid to late morning hours as a strong jet streak over 90 kts
moves overhead. A mainly dry cold front then moves across the area
Monday afternoon and evening. Surprisingly this front may slightly
lower the winds as it provides less of a gradient...and not as
much stable air for the mountain wave to break. Either way...most
areas should expect winds gusting 25 to 40 knots on Monday...with
the mountains areas seeing winds near 50 knots. This feature also
has a lot of dry air associated with it. Only far northwestern and
southwestern portions will see chances for precip on Monday. All
areas will see another day of elevated fire danger with the
combination of dry and windy conditions. Areas that have critical
fuels could see extreme fire danger...prompting the issuance of a
Fire Weather Watch for Monday. Again see the Fire Weather
Discussion below for details. Upper low hangs near the Canadian
and MT border Monday night into Tuesday. This tight gradient will
allow for breezy winds to continue. Moisture wrapping around this
low could bring a slight chance of a few isolated to scattered
showers...mainly across the northern half of the CWA. Temperatures
will return into the 90s today...but with Monday`s cold
front...temperatures will fall back to near normal levels in the
low 80s on Monday...and below normal levels in the 70s on Tuesday.

Tuesday night through Sunday...Medium range models start off
the forecast period with an upper level low over southern
Saskatchewan and northerly flow aloft over Montana. This feature
moves slowly eastward and weakens into a broad trough across central
and eastern Canada with north/northwest flow aloft persisting over
Montana through at least Thursday. Temperatures during this period
will remain below seasonal averages and isolated to scattered shower
and thunderstorm activity can be anticipated. Unfortunately, models
continue to show diverging solutions by Thursday night and remain in
disagreement throughout next weekend. Despite their disparate
solutions, it appears likely that temperatures will rebound back
toward seasonal averages on Saturday. Additionally, both models
remain relatively dry across Montana with each suggesting that
shower activity will remain north of the Canadian border or over the
Pacific Northwest. mpj


GTF  90  53  81  49 /   0   0   0   0
CTB  87  52  72  49 /   0   0  10  20
HLN  89  55  82  51 /   0   0   0   0
BZN  90  48  86  44 /   0   0  10   0
WEY  79  40  76  38 /   0   0  10  10
DLN  86  47  82  42 /   0   0   0   0
HVR  91  53  83  51 /   0   0   0  10
LWT  86  53  83  49 /   0   0  10  10


Red Flag Warning from noon to 8 PM MDT Monday for MTZ114-116-118.

Red Flag Warning from noon to 9 PM MDT Monday for MTZ110-111.


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