Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 161040

Area Forecast Discussion
National Weather Service Great Falls MT
440 AM MDT Wed Aug 16 2017

...Updated Aviation Discussion...

A west to northwest flow aloft is developing over the region. As a
result, expect several days with little to no precipitation.
Afternoon temperatures will be on the warm side...with highs
generally in the mid to upper 80s.



Today through Friday...West to northwesterly flow aloft will
prevail over the region for the next few days. This, along with
very dry air across the region, will present fire weather issues
through the remainder of the week into the weekend. (See the fire
weather discussion for details.) A passing front tonight will result
in northwesterly winds Thursday over north-central MT along with
temperatures returning to near seasonal normals. Upper ridging
combined with increasing west-southwest winds and resultant
compressional warming will result in seasonably warm and very dry
conditions Friday. CC

Friday night through Tuesday night...Primary concerns in the long
term will be a wind shift and breezy conditions for the day on
Saturday. Otherwise, the remainder of the long term looks to be
fairly dry (with the exception of some diurnally forced
showers/storms) with near normal temperatures for August, as
zonal/near-zonal flow develops and remains the prominent upper
level feature over the Intermountain West and Northern Rockies.

A shortwave over the Intermountain West and Canadian Province of
British Columbia Friday evening will translate east through the
day on Saturday. At the surface, an area of low pressure will
develop and strengthen in lee of the Canadian Rockies in Alberta
during the evening hours on Friday, before quickly sliding
east/east northeast into the interior of Canada. The
aforementioned area of low pressure will drag a cold front across
North Central Montana during the morning hours on Saturday. This
front will bring a shift in wind direction from westerly (prior to
the frontal passage) to north-northwesterly (post frontal). In
addition to a shift in wind direction, breezy conditions are
expected with sustained winds of 10-15 mph and gusts approaching
25 mph. Following the cold front on Saturday, the remainder of the
long term currently looks "quiet". While a few showers/storms
can`t be ruled out over Southwest Montana during the evening hours
on Sunday, believe that any residual cloud cover should translate
east/dissipate for the viewing of the upcoming solar eclipse on
Monday. With that being said, mostly sunny to partly sunny skies
are currently anticipated for the day on Monday, with slight
chances for an afternoon shower/storm along the Idaho and Wyoming
borders. - Moldan


Updated 1040z.

VFR conditions will predominate with dry conditions expected through
the TAF period, with the possible of a narrow corridor between WYS
and EKS where an isolated thunderstorm may develop this afternoon or
early evening. West to southwest winds at HLN, GTF, CTB, AND HVR may
become occasionally gusty in the afternoon. A dry frontal passage
overnight tonight will result in increasing breezes out of the
northwest across the region. CC



A very active fire weather period is in store into the weekend.
Evening and overnight forecast model soundings and statistical
guidance for this afternoon and early evening suggests a more
localized critical fire weather threat with much lower humidity
values than initially expected today along a Helena to Great Falls
to Havre corridor this afternoon. A passing weather front tonight
will result in cooler (and near normal) temperatures for
Thursday, however the presence of sufficiently dry air and gusty
winds over our Lewistown-area fire districts will result in a
decent potential for reaching critical fire weather conditions
Thursday afternoon into the evening. Thus, a Fire Weather Watch
will be issued for Fire Weather Zones 113 and 115 for Thursday in
addition to the Red Flag Warnings for today for the more localized
threat for most zones.

Moderate downslope flow Friday into Saturday along with a dry
frontal passage will result in warm, windy, and very dry
conditions. Additional fire weather highlights are likely during
this time period as well. In addition, overnight humidity
recoveries will only be moderate in many areas with the breezy
conditions from tonight into the weekend. CC


GTF  87  53  84  51 /   0   0   0   0
CTB  82  51  81  49 /   0   0   0   0
HLN  86  54  85  52 /   0   0   0   0
BZN  83  49  83  49 /   0   0   0   0
WEY  72  38  74  37 /  10  10  10   0
DLN  82  48  82  47 /  10   0   0   0
HVR  88  54  85  52 /   0   0   0   0
LWT  85  52  81  51 /   0   0   0   0


Red Flag Warning from noon today to 9 PM MDT this evening
Central and Eastern Lewis and Clark National Forest Areas...
Chouteau and Fergus Counties...Eastern
Glacier/Toole/Central/Eastern Pondera/Liberty...Helena and
Townsend Ranger Districts of the Helena National Forest...Hill
and Blaine Counties...Lewis and Clark National Forest Rocky
Mountain District-Rocky Mountain Front.

Fire Weather Watch from Thursday afternoon through Thursday
evening Chouteau and Fergus Counties...Hill and Blaine Counties.


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