Hail and Damaging Winds in Montana, July 11, 2021

Area Forecast Discussion
National Weather Service Great Falls MT
145 PM MDT Sun Jul 11 2021

.SYNOPSIS...

Breezy warm and dry conditions will continue through the rest of
this afternoon with a few isolated thunderstorms possible over
southwest Montana as well as areas near the Canadian border.
Winds shift to northerly this evening with somewhat cooler and
less dry air moving into the region overnight. Another weather
disturbance will bring additional cooling along with a chance for
showers and thunderstorms Monday night and Tuesday. Warmer and
drier conditions return Wednesday into next weekend.

&&

.DISCUSSION...

Shortwave disturbance moving over the western US upper level
ridge will continue east across southern Alberta and Saskatchewan
tonight. Breezy winds have been somewhat slow to materialize this
afternoon, likely due the amount of smoke over the region, but
are still likely to develop through this afternoon as instability
increases some ahead of the upper level disturbance. Cumulus
cloud development is occurring across SW MT and may lead to a few
isolated mainly dry thunderstorms for areas south of Helena to
White Sulphur Springs. Further north, low level moisture increases
along and north of the Canadian border and this combined with the
upper level shortwave disturbance will lead to an isolated
thunderstorm or two tracking east mainly north of Hwy-2. Deeper
moisture in this area could lead to strong/severe thunderstorm
development which will be monitored for strong winds as well as
hail. Canadian frontal boundary moving south into the region late
this afternoon and evening could be boosted by outflow winds from
storms moving east near the Canadian border. Hoenisch

Monday through Tuesday...Not as hot of an air mass will be over
the region for Monday and Tuesday. Cloud cover and precipitation
will help keep temperatures closer to seasonal normals. Do expect
winds to be shifting through this period. There could be some
night time thunderstorms Monday night into Tuesday over North
Central MT. Overall precipitation looks minimal, but some
isolated heavier thunderstorms could produce a half inch of
precipitation.

Wednesday through Sunday...Another period of hot temperatures and
little to no precipitation is expected over the entire region, as
an upper level ridge rebuilds over the area. Widespread
afternoon temperatures ranging from 90 to 100 degrees are expected
through much of this period. The GFS is a bit more aggressive with
afternoon/evening thunderstorms, but again this seems to be the
most aggressive model for precipitation, thus the NBM of a bit
lower POPs looks on track at this time. Brusda

&&

.AVIATION...
1140 AM MDT Sun Jul 11 2021 (11/18Z TAF period)

Main concern today is wildfire smoke. Most terminals across
northcentral and southwestern Montana will see some of this smoke
reducing visibilities throughout the day today and into early this
evening. Right now kept any thunderstorms out of most terminals for
this afternoon/evening...as the storms look too isolated/low
probability to include right now. Surface winds will increase a bit
this afternoon. Mountains/passes will be obscured at times through
the period by smoke.

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

&&

.FIRE WEATHER...

Red Flag Warning continues through 9pm this evening. The most
critical hot, dry and breezy conditions will be across southern fire
districts through this evening with west winds gradually shifting to
northwest by late this afternoon. Winds shift to northerly this
evening as a Canadian frontal boundary moves through the region.
Thunderstorm activity and lightning will mainly be limited to areas
from the Little Belt/Castle mountains south with another area of
storms tracking east along the Highway-2 corridor. In addition to
lightning, gusty downdraft winds are a concern with any storms
and outflow from northern storms could move south through much of
north-central MT with the Canadian front this evening. Hoenisch

Looking ahead, for Monday and Tuesday, there will be a bit better
chance for a thunderstorm, along with some shifting surface
winds. Some storms will produce wetting rainfalls, but those
storms look to be fairly isolated at this time. Temperatures will
not be as hot Mon/Tue...which will help a bit...but hot temps/low
humidity return quickly starting on Wed and continue into next
weekend, with very low chances if at all for precipitation for
late next week. Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  51  91  56  83 /   0   0  20  30
CTB  48  85  53  80 /  10   0  30  30
HLN  57  94  60  89 /   0   0  10  20
BZN  50  92  54  88 /  10   0  10  20
WYS  41  86  43  83 /  20   0  10  20
DLN  50  91  53  88 /  10   0   0  10
HVR  53  89  59  83 /  20   0  10  30
LWT  52  85  57  80 /   0   0  10  40

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 9 PM MDT this evening Central and Eastern
Lewis and Clark National Forest Areas...Chouteau and Fergus
Counties...Deerlodge/Western Beaverhead National Forest...
Eastern Beaverhead National Forest...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...Lincoln Ranger District
of the Helena National Forest.

&&

http://www.weather.gov/greatfalls

Special Weather Statement
National Weather Service Great Falls MT
218 PM MDT Sun Jul 11 2021

MTZ009-010-112100-
Northern Rocky Mountain Front MT-Eastern Glacier MT-
218 PM MDT Sun Jul 11 2021

...A STRONG THUNDERSTORM MAY IMPACT NORTH CENTRAL GLACIER COUNTY
UNTIL 300 PM MDT...

At 215 PM MDT, Doppler radar was tracking a strong thunderstorm
along and north of the International Border, approximately 33 miles
north of North Browning, or 48 miles northwest of Cut Bank. Movement
was southeast at 30 mph. This storm may move southeast into north
central Glacier County.

HAZARD...Wind gusts of 50 to 55 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.

This storm will remain over mainly rural areas of north central
Glacier County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4900 11255 4881 11266 4899 11331
TIME...MOT...LOC 2015Z 289DEG 25KT 4904 11320

HART