Funnel Cloud in Montana, July 5, 2019

Area Forecast Discussion
National Weather Service Great Falls MT
507 PM MDT Fri Jul 5 2019

UPDATED AVIATION

.SYNOPSIS...

Unsettled conditions will continue through early next week,
with a chance for showers and thunderstorms each day through Tuesday.
Isolated severe thunderstorms are possible on Saturday across the
entire region, with an even better chance for severe
thunderstorms on Sunday over North Central and Central Montana.
Large hail and damaging winds will be the primary threats with any
severe thunderstorm on Saturday and Sunday, in addition to the
general thunderstorm threat for lightning, and locally heavy rain.

&&

.DISCUSSION...

Remainder of this afternoon through Sunday...A trough over the
Pacific Northwest will ensure a moist unstable southwesterly flow
through early next week. Showers and thunderstorm activity has
already developed today, mostly over mountain areas and over
Blaine and Fergus Counties. Thunderstorm threats for today will be
brief heavy rains, small hail, and gusty winds with the stronger
storms. Some of the storms are slow moving in Blaine and Fergus
Counties, so these areas will need to be watched for the potential
of localized flooding. Focus then turns to Saturday, as low level
southeasterly flow pumps moisture into the region from the Gulf of
Mexico. Increasing low level moisture and heating will aide in
marginal (Southwest Montana) to moderate (Central and North
Central Montana) instability during the afternoon/evening hours,
which combined with good wind shear could support a few severe
thunderstorms. While the entire region is currently under a
Marginal Risk for severe weather on Saturday, the area most at
risk for seeing a severe thunderstorm is over North Central
Montana, especially those areas in close proximity to the
surrounding mountains. The primary threat with any severe
thunderstorm will be large hail up to the size of quarters and
damaging wind gusts up to 60 mph. A low pressure trough extending
south over Western Canada into the Pacific Northwest of the United
States will keep Montana under an unstable southwest flow aloft on
Sunday with an inverted surface trough over Central Montana. The
moist Pacific air moving over this boundary will make for a good
set-up for potentially severe thunderstorms Sunday afternoon and
evening with moderate wind shear and instability. The most likely
thunderstorm threats will be heavy rains, large hail to the size
of golf balls, and gusty winds up to 70 mph.

Monday through Friday...

As the trough weakens and moves into Western Montana on Monday,
the surface trough will move southeast out of the area as a weak
Pacific cold front, which will bring cooler air and more northerly
surface winds. This will reduce the threat of severe storms, but
the more upslope flow will bring a much better chance for more
widespread rain showers, especially over Central and Southwest
Montana. A northwest flow aloft in the wake of the exiting trough
will keep a good chance for showers and a few thunderstorms into
Tuesday, as temperatures remain below normal. A high pressure
ridge will then move into Montana for the mid- to late-week
period, which will bring drier conditions with warmer than normal
temperatures. Thursday will likely be the warmest of these days,
with temperatures warming to between 5 and 10 degrees above
normal. Coulston

&&

.AVIATION...
Updated 507 PM MDT Fri Jul 5 2019 (00Z/Jul 6 TAF issuance)

Mainly VFR next 24-hours as southwesterly to westerly flow aloft and
embedded disturbances affect our area. Isolated showers and
thunderstorms, primarily found over and near the mountains, should
end by 06Z/Sat. Patchy fog may develop around daybreak Sat,
especially in north-central MT. Additional isolated to scattered
showers and thunderstorms are probable after 18Z/Sat. In addition, a
few severe thunderstorms are possible Saturday afternoon and
evening. Quarter-size hail and erratic surface wind gusts of 50 to
55 knots are the primary severe threats. Downpours are likely and
brief MVFR to IFR CIGS/VSBY are possible with any shower or storm
through the TAF period. Lastly, regional surface winds remain light
outside outflow (i.e. precipitation-cooled air emanating from any
shower or storm).
- Jaszka

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  50  82  54  80 /  10  20  30  60
CTB  47  79  50  74 /  20  20  40  60
HLN  52  83  53  82 /  10  20  30  70
BZN  49  82  50  82 /  10  20  20  40
WEY  35  77  42  78 /  10  20  20  30
DLN  47  78  49  77 /  10  30  20  50
HVR  53  82  55  83 /  20  20  20  50
LWT  48  76  51  80 /  20  20  20  50

&&

.TFX WATCHES/WARNINGS/ADVISORIES...

None.

&&

http://www.weather.gov/greatfalls

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
307 PM MDT FRI JUL 5 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0306 PM     HAIL             BASIN                   46.27N 112.27W
07/05/2019  E0.25 INCH       JEFFERSON          MT   TRAINED SPOTTER

            PEA SIZE HAIL REPORTED, LASTED ABOUT 10
            MINUTES, NOW EXPERIENCING INTENSE RAINFALL.

&&

TP

Special Weather Statement
National Weather Service Great Falls MT
353 PM MDT Fri Jul 5 2019

MTZ047-052230-
Blaine-
353 PM MDT Fri Jul 5 2019

...A STRONG THUNDERSTORM WILL AFFECT SOUTHEASTERN BLAINE COUNTY...

At 352 PM MDT, a strong thunderstorm was located 8 miles north of
Hays, or 13 miles north of Zortman, moving southwest at 30 mph.

Winds in excess of 30 mph and half inch hail are possible with this
storm.

Locations impacted include...
Hays and Lodge Pole.

If outdoors, consider seeking shelter inside a building.

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

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

To report severe weather, contact your nearest law enforcement
agency. They can relay your report to the National Weather Service
office in Great Falls.

LAT...LON 4797 10845 4799 10860 4792 10864 4792 10888
      4788 10889 4801 10915 4840 10847 4837 10840
TIME...MOT...LOC 2152Z 036DEG 28KT 4811 10863

TP

Special Weather Statement
National Weather Service Great Falls MT
715 PM MDT Fri Jul 5 2019

MTZ012-060130-
Cascade-
715 PM MDT Fri Jul 5 2019

...A STRONG THUNDERSTORM WILL AFFECT EAST CENTRAL CASCADE COUNTY...

At 715 PM MDT, a strong thunderstorm was located near Belt, or 19
miles southeast of Great Falls, moving north at 15 mph.

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

Locations impacted include...
Sluice Boxes State Park.

This includes the following highways...
 Highway 200 between mile markers 0 and 5.
 Highway 89 between mile markers 62 and 71.

If outdoors, consider seeking shelter inside a building.

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

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

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.

To report severe weather, contact your nearest law enforcement
agency. They can relay your report to the National Weather Service
office in Great Falls.

LAT...LON 4723 11113 4719 11095 4733 11078 4739 11113
TIME...MOT...LOC 0115Z 196DEG 14KT 4730 11100

TP