Special Weather Statement, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
530 PM MDT Tue Jun 22 2021

Updated Aviation Section

.SYNOPSIS...
A few showers and thunderstorms will affect Southwest MT tonight,
while a better chance for showers, thunderstorms, and cooler air
moves into North Central MT for Thursday and Friday. It turns
dry and warm over the weekend, with hot temperatures expected
across the region by early next week.

&&

.DISCUSSION...
Tonight through Wednesday...Main concern tonight is the upper
level disturbance moving towards Southwest MT. Isolated
thunderstorms are expected this evening/overnight...with the most
likely area south of I-90. Lightning/gusty winds will be the main
threat. The chance for showers/thunderstorms shifts northward on
Wednesday, but still generally remain isolated/spotty. Confidence
in good rainfall amounts looks low at this time, with most areas
receiving less than 0.10 inches, but a heavier shower can't be
ruled out. Afternoon temperatures will not be quite as hot
tomorrow in most areas.

Thursday and Friday...A cool front will move southward through the
region on Thursday. The best chance for rainfall with this front
will be over North Central MT. Overall, rainfall amounts look
light at this time, generally less than 0.10 inches, but some
isolated higher amounts are possible. The main impact will be a
wind shift to the north, along with cooler air to move into the
region for Thursday/Friday...especially over the northern portions
of the region. Over Southwest MT, the cool front will have less of
an impact in terms of precipitation and temperatures...as
afternoon readings will not be as hot behind the front, yet above
normal temperatures will continue.

Saturday through Tuesday...Expect dry conditions to develop over
the weekend and continue into early next week, as a strong upper
level ridge of high pressure develops over the region. Above
normal temperatures are expected this weekend, transitioning to
hot temperatures for the first half of next week. Afternoon
temperatures are likely to exceed 100 degrees in many areas by
Tuesday. Some forecast models are showing temperatures near 105
degrees, which could approach all-time record highs in some areas.
The only change to the NBM was to blend the NBM with the warmer
GFS/EC models for Tuesday afternoon high temperatures. Heat
advisory/warnings might be needed for portions of the region for
this event. Brusda

&&

.AVIATION...
530 PM MDT Tue Jun 22 2021 (23/00Z TAF period)

Mostly clear skies over Northcentral Montana with a few higher
clouds lingering around through the period.  The main concern this
evening is thunderstorm potential over Southwest MT, mostly south of
I-90 this evening. Any storms should be brief/isolated, with the
main threat being wind gusts/lightning. Some storms will continue
overnight in the Southwest, and the storms should gradually diminish
as they move northward into Central MT. Overall, VFR conditions are
expected across the region through the period.

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.FIRE WEATHER...
Main concern tonight is thunderstorm potential, mainly over the
southern portions of Zone 118. The thunderstorm potential shifts
north on Wednesday to North Central MT, but remains isolated. On
Thursday, a cool front will move southward through the region,
resulting in a wind shift to the north, and a chance for
precipitation, mostly over North Central MT. Overall, rainfall
amounts will be spotty over the next 3 days, and most areas will
receive less than 0.10 inches.

Looking ahead, it is dry over the weekend, along with warm
temperatures. Then confidence is increasing for hot temperatures
and dry conditions starting Monday and continuing into the Middle
portion of next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  57  83  53  74 /   0  20  10  20
CTB  58  78  51  68 /   0  20  20  50
HLN  62  89  57  84 /  10  10   0  20
BZN  54  88  51  84 /  20  20  10  20
WYS  44  80  44  74 /  30  20  20  40
DLN  54  85  51  83 /  40  10  10  20
HVR  61  85  55  74 /   0  10  30  30
LWT  57  83  53  76 /   0  20  10  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.

&&

http://www.weather.gov/greatfalls