Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 222338

Area Forecast Discussion
National Weather Service Great Falls MT
538 PM MDT Tue Aug 22 2017

Aviation Section Updated

With an upper level ridge of high pressure over the region, it
will be dry with mostly clear skies tonight through Wednesday
morning. On Wednesday afternoon, a weak upper level disturbance
will produce a few isolated thunderstorms over Southwest MT. The
storms will become a bit more widespread on Thursday as a stronger
upper level disturbance moves through the region. Afternoon
temperatures will be very warm on Wednesday, then cool a bit for
Thursday and Friday.


Tonight through Thursday...Quiet and dry conditions will prevail
over the region through Wednesday morning. On Wednesday afternoon,
an upper level disturbance will move into Southwest MT and along
the western divide. A few isolated storms will be possible late
in the day/early Wed evening along the divide, and mainly south of
a Dillon to Big Sky line. Otherwise, it will be very warm across
the region. On Thursday, the upper level ridge moves east as a few
upper level disturbances move into the region. This will be the
best chance for any rainfall over the next week or so. Most areas
will see rainfall less than 0.10 inches, but a few isolated higher
amounts are possible. The best chances for storms will be over
Southwest MT where the airmass will be slightly more unstable.
Temperatures will be slightly cooler on Thu because of cloud
cover/chances for precip. Brusda

Thursday Night through Tuesday...The aforementioned upper trough
will begin to pull away from the area late Thursday night through
Friday morning, which will allow for areas of scattered showers and
thunderstorms to exit to the east through the night with drier air
to follow. Thereafter, high pressure aloft builds-in from the south
and west. Accordingly, the potential and coverage of showers and
thunderstorms should dwindle as Friday elapses. Drier weather is
then expected during the upcoming weekend through next week Tuesday
as the aforementioned high pressure ridge aloft continues building
over the area. Temperature-wise, near-normal lows are expected
throughout the period. Behind the aforementioned cold front, Friday
will feature highs mainly in the 70`s to near 80 degrees, which will
be several degrees below-normal for many places. The building high
pressure ridge should then yield near-normal to slightly above-
normal highs this weekend through Tuesday of next week, with many
locations experiencing readings in the 85 to 90 degree range.


Updated 2338Z.

VFR conditions are expected through Wednesday at
KCTB/KHVR/KGTF/KLWT. VFR conditions are likely through Wednesday at
KHLN/KEKS/KBZN, but a brief period of MVFR VIS cannot be ruled out
late tonight or early Wednesday morning due to smoke continuing to
advect in from fires to the west. As for the overall weather
pattern, an upper level ridge will move over the area tonight, then
begin to push east late tomorrow. Moisture pushing north out of the
Great Basin may bring a gradual increase in clouds across far SW MT
with a TSRA possible as well. For now, though, TSRA look to hold off
beyond the current TAF cycle at KEKS/KBZN. MARTIN


A fire weather watch has been issued for Wednesday for portions of
the region for Wednesday for low humidity and winds. Wind speeds
might not reach impact criteria over zones 117 and 118 and this
will be evaluated more tonight. Thunderstorms are possible on
Thursday, but look too isolated right now for any highlights.
After some slightly cooler temperatures on Friday, it then turns
mostly dry and warm again over the weekend and early next week.


GTF  87  52  92  57 /   0   0   0   0
CTB  85  48  89  52 /   0   0   0  10
HLN  84  53  91  56 /   0   0   0  10
BZN  84  46  88  49 /   0   0   0   0
WEY  79  31  76  35 /   0   0  10  10
DLN  82  49  84  50 /   0   0   0  10
HVR  89  51  93  54 /   0   0   0   0
LWT  90  54  89  55 /   0   0   0  10


Fire Weather Watch from Wednesday afternoon through Wednesday
evening Central and Eastern Lewis and Clark National Forest
Areas...Helena and Townsend Ranger Districts of the Helena
National Forest.

Fire Weather Watch from Wednesday afternoon through Wednesday
evening Eastern Glacier/Toole/Central/Eastern Pondera/Liberty...
Lewis and Clark National Forest Rocky Mountain District-Rocky
Mountain Front.


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