Special Weather Statement, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
1155 PM MDT Mon Jul 5 2021

...Updated aviation discussion...

.UPDATE...

Main adjustments to the forecast for the remainder of the evening
through tonight into Tuesday morning were to mostly remove mention
of storms in the southwest and to increase coverage / strengthen
wording of thunderstorms expected along the Hi-Line overnight into
the morning. Activity over the southwest has mostly diminished for
the night. However, a disturbance moving along the Canadian border
is on track to move east-southeast on the Hi-Line into Tuesday
morning. A storm in far southwest Alberta has been strengthening
over the last hour or so and is showing signs of bowing on the
radar, indicating that damaging winds are possible. Therefore, as
it starts to approach the border, have increased storm mention to
numerous along the Hi-Line overnight and added mention of damaging
winds and small hail, and there is a widespread chance for 0.10 to
0.25 inches of rainfall (some higher amounts possible along the
border). We will be monitoring these storms for potentially severe
thunderstorms, but there have been no signs of severe storms so
far in Canada, and there is much uncertainty regarding whether
they will become severe. The disturbance should start to exit the
area to the east in the morning.

&&

.SYNOPSIS...
A few isolated thunderstorms will be possible through tonight
over the area, while drier and warmer temperatures move into the
area for Tuesday. On Wednesday, there will be another chance for
thunderstorms for most areas. By late in the week, widespread
temperatures in the 90s along with mostly dry conditions are
expected to redevelop.

&&

.AVIATION...
1155 PM MDT Mon Jul 5 2021 (06/06Z TAF period)

VFR conditions are expected to continue at most TAF sites over the
next 24 hours. The exception to this is KHVR, as a cluster of strong
thunderstorms along the Hi-Line continue to progress eastward. As of
midnight MDT, the strongest of these storms was NE of Shelby, moving
due east. On its current trajectory, expect this storm to be near
KHVR between 1:30 and 2:00 AM MDT.

Looking to later today, a few additional thunderstorms may be
possible along the Hi-Line this afternoon, but otherwise VFR
conditions will continue through the day. Ludwig

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

&&

.FIRE WEATHER...
A few storms will affect the region tonight, but drier and warmer
conditions develop on Tuesday. For Wednesday, expect a chance for
storms in most areas. By Thursday, windy west winds are forecast
to develop. Thus there is the potential for fire highlights on
Wednesday and Thursday, with Thursday looking like the more
likely day at this time. Looking ahead, it remains very warm/hot
over the weekend, along with mostly dry conditions. Brusda

&&

.PREV DISCUSSION...
/ISSUED 605 PM MDT Mon Jul 5 2021/
Tonight through Wednesday...Expect a few thunderstorms over
Southwest MT this evening, why a stronger upper level disturbance
will moves across the Hi-line area overnight. There is a marginal
risk for severe storms tonight for areas north of Great Falls,
with the potential for any severe storms likely occurring during
the overnight hours. On Tuesday, it turns drier and warmer ahead
of the next upper level disturbance. That disturbance will move
through the region on Wednesday, resulting in isolated storms for
most areas. Again, an isolated severe storm is possible on
Wednesday.

Thursday through Monday...Drier air returns to the region by late
in the week and into the weekend, as shortwave ridging develops
over the region. The chances for storms will start to increase by
next Monday, as the next upper level trof approaches the area.
Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  54  90  54  92 /  10   0   0  20
CTB  52  84  53  85 /  70  10   0  20
HLN  58  96  60  96 /  10   0   0  20
BZN  52  94  53  96 /  10   0   0  20
WYS  40  84  42  86 /  20   0   0  10
DLN  52  91  53  93 /  20   0   0  20
HVR  59  86  56  93 /  80  60  10  10
LWT  56  86  55  92 /  10  30   0  20

&&

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

http://www.weather.gov/greatfalls

Special Weather Statement
National Weather Service Great Falls MT
1242 AM MDT Tue Jul 6 2021

MTZ013-060715-
Chouteau MT-
1242 AM MDT Tue Jul 6 2021

...SPECIAL WEATHER STATEMENT...

At 1241 AM MDT, Doppler radar was tracking a strong thunderstorm over
Fort Benton, moving east at 20 mph.

HAZARD...Winds in excess of 30 mph, torrential rainfall, and pea
         size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Fort Benton.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4769 11075 4786 11079 4795 11031 4768 11026
TIME...MOT...LOC 0641Z 262DEG 19KT 4779 11067

PN

Special Weather Statement
National Weather Service Great Falls MT
115 AM MDT Tue Jul 6 2021

MTZ011-013-044-045-060815-
Chouteau MT-Liberty MT-Hill MT-Toole MT-
115 AM MDT Tue Jul 6 2021

...SPECIAL WEATHER STATEMENT...

At 114 AM MDT, Doppler radar was tracking a strong thunderstorm 14
miles south of Chester, moving east at 45 mph.

HAZARD...Winds in excess of 30 mph, heavy rain, and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Chester, Big Sandy, Azure, Inverness, St. Pierre, Gildford, Joplin,
Sangrey, Boneau, Box Elder, Agency, Hingham, Rudyard, Rocky Boy,
Tiber Dam, Laredo, Kenilworth and Virgelle.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4821 11134 4879 11097 4845 10968 4795 10995
TIME...MOT...LOC 0714Z 282DEG 37KT 4831 11087

PN

Special Weather Statement
National Weather Service Great Falls MT
118 AM MDT Tue Jul 6 2021

MTZ013-060745-
Chouteau MT-
118 AM MDT Tue Jul 6 2021

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL CHOUTEAU COUNTY UNTIL 145
AM MDT...

At 117 AM MDT, Doppler radar was tracking a strong thunderstorm 11
miles northwest of Geraldine, or 13 miles east of Fort Benton, moving
east at 20 mph.

HAZARD...Winds in excess of 40 mph and penny size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4765 11054 4783 11055 4789 11001 4762 11001
TIME...MOT...LOC 0717Z 269DEG 18KT 4776 11038

PN

Special Weather Statement
National Weather Service Great Falls MT
144 AM MDT Tue Jul 6 2021

MTZ013-047-051-060830-
Chouteau MT-Fergus MT-Blaine MT-
144 AM MDT Tue Jul 6 2021

...SPECIAL WEATHER STATEMENT...

At 144 AM MDT, Doppler radar was tracking a strong thunderstorm 10
miles north of Geraldine, or 20 miles east of Fort Benton, moving
east at 20 mph.

HAZARD...Winds in excess of 30 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4768 11049 4782 11051 4789 10947 4762 10947
TIME...MOT...LOC 0744Z 270DEG 19KT 4776 11023

PN

Special Weather Statement
National Weather Service Great Falls MT
216 AM MDT Tue Jul 6 2021

MTZ011-061045-
Hill-
Including the cities of Havre, Rocky Boy, and Rudyard
216 AM MDT Tue Jul 6 2021

Widespread moderate to heavy rainfall is occurring across Hill
County early Tuesday morning. The rain has developed as an area of
thunderstorms merged into an organized convective weather system.
Lightning is ongoing as well, and small hail is possible at times.
Rainfall amounts of one-half to two inches are possible through
5am Tuesday. Do not attempt to drive through flooded roadways.
Access to unpaved rural roads may be difficult in some areas
Tuesday morning.

Special Weather Statement
National Weather Service Great Falls MT
222 AM MDT Tue Jul 6 2021

MTZ013-060900-
Chouteau-
222 AM MDT Tue Jul 6 2021

...A STRONG THUNDERSTORM WILL AFFECT CHOUTEAU COUNTY...

At 221 AM MDT, a strong thunderstorm was located 15 miles northeast
of Fort Benton, moving east at 60 mph.

Winds in excess of 30 mph and pea size hail are possible with this
storm.

Locations impacted include...
Big Sandy, Boneau, St. Pierre, Parker School, Loma and Virgelle.

This includes Highway 87 between mile markers 44 and 89.

Torrential rainfall is also occurring with this storm, and may cause
localized flooding. Do not drive your vehicle through flooded
roadways.

LAT...LON 4822 10984 4822 10973 4813 10973 4813 10953
      4780 10954 4787 11091 4831 11008 4830 10985
TIME...MOT...LOC 0821Z 272DEG 50KT 4796 11039

PN