Severe Thunderstorm Warning 110, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
312 PM MDT Sat Aug 10 2019

.SYNOPSIS...
An upper level trof will approaches and moves through the region
this weekend. As a result, expect showers and thunderstorms to
move through the area this afternoon and evening and again on
Sunday. Some storms could be severe, with gusty winds, hail.
Additionally, the rainfall could be heavy at times, causing
isolated areas of flash flooding. The work week will begin with
drier condtions and breezy westerly winds for most areas.

&&

.DISCUSSION...

Remainder of this afternoon through Sunday...Showers and
thunderstorms are just beginning to develop this afternoon over
the southwest. This activity is forecast to increase as
conditions are favorable for the potential for some severe
thunderstorms, especially over southwest and central Montana,
although the far southern areas of Beaverhead, Madison and
Gallatin Counties may be a bit drier than areas further north. MU
cape values are roughly falling in the 1000 to 2000 J/kg range,
while mid level lapse rates range from 7 to 8 degrees C. Moisture
remains plentiful as well, with .75 to 1 inch PWATS across much
of southwestern Montana and areas to the north (highest values
over the north-central). These factors along with good effective
shear has lead to the issue of a severe thunderstorm watch for
portions of the area through 9 pm tonight, some of the stronger
storms may produce wind gusts in excess of 60 mph, hail up to lime
size, along with heavy rains. One limiting factor is a stubborn
deck of low stratus over the central and north-central portions of
the region. This may lower the severe weather threat for portions
of the north but heavy rain will still be possible. A flash flood
watch remains in effect for areas along the Rocky Mountain Front
and then for Lewis and Clark and Cascade Counties, including
Helena and Great Falls (please see our hydrology section). Shower
and thunder storm activity should diminish by midnight but
showers and a few storms will be possible during the overnight
hours. Expect similar conditions on Sunday, as the main upper
level trof moves through the region. However, the focus of severe
weather is expected to shift a bit to the north and east.
Afternoon temperatures are likely to be a few degrees below normal
for most areas today and Sunday due to precipitation and cloud
cover.

Monday through Friday...With a light westerly flow over the
region, expect a slow warming trend, with only a very small chance
for a passing storm from Monday through Wednesday. On Thursday,
the next upper level trof approaches the region, allowing for the
potential for another round of severe storms to move through the
region. Showers then linger into Friday and Saturday, along with
below normal temperatures. Brusda

&&

.AVIATION...
Updated 540 AM MDT Sat Aug 10 2019 (12Z TAFs)

Low ceilings with IFR conditions have developed over a good portion
of Central/North Central MT this morning. The low clouds will be
slow to burn off, possibly taking to mid day. Light rain showers
will affect the Helena area this morning. Otherwise expect
thunderstorms to become more numerous and widespread after 20z as
they move northeast through the region this afternoon/evening. Some
storms will be severe. Mountains/passes will be obscured for much of
the period because of distant smoke or thunderstorm activity. Brusda

&&

.FIRE WEATHER...
Periods of showers and thunderstorms will move through the region from
now through Sunday night. Most of the storms will be wet, but a
few storms could contain little rainfall or lightning could strike
away from the parent storm, resulting in new fire starts.
Slightly below normal temperatures are expected from today through
early next week, before a return to near normal temperatures is
expected for Tuesday and Wednesday.

Another round of storms is expected to move through the region
from late Thursday into Friday. Brusda/RCG

&&

.HYDROLOGY...
A flash flood watch remains in effect for areas along the Rocky
Mountain Front and portions of North Central MT from this
afternoon through late this evening. Some forecast models
continue to suggest that some areas may receive nearly 1 inch of
rainfall in less than 2 hours with the stronger storms this
afternoon and evening. This amount of rainfall could lead to
flooding problems in urban areas that have poor drainage, as well
as steep terrain and burn scar areas from this year or previous
years in areas that regrowth has not occurred. Brusda/RCG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  53  75  52  74 /  90  80  70  10
CTB  50  71  50  71 /  70  80  70  30
HLN  52  76  49  76 /  90  90  70   0
BZN  48  78  45  77 /  40  70  50   0
WEY  43  71  35  71 /  10  30  20   0
DLN  47  72  42  74 /  40  70  50   0
HVR  51  76  52  73 /  50  80  90  50
LWT  50  74  49  71 /  80  80  80  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until midnight MDT tonight Cascade...Central
and Southern Lewis and Clark...Northern Rocky Mountain Front...
Southern Rocky Mountain Front.

Severe thunderstorm watch is in effect until 9 pm MDT for the
following counties in central Montana - Fergus, Judith Basin,
Meagher, and Lewis and Clark...In southwest Montana - Beaverhead,
Broadwater, Gallatin, Jefferson, and Madison

&&

http://www.weather.gov/greatfalls

Special Weather Statement
National Weather Service Great Falls MT
313 PM MDT Sat Aug 10 2019

MTZ008-102200-
Beaverhead MT-
313 PM MDT Sat Aug 10 2019

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN BEAVERHEAD COUNTY
UNTIL 400 PM MDT...

At 313 PM MDT, Doppler radar was tracking a strong thunderstorm 11
miles east of Gibbonsville, or 30 miles north of Salmon, moving
northeast at 30 mph.

Half inch hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Wisdom.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 will relay your report to the National Weather Service
office in Great Falls.

&&

A Severe Thunderstorm Watch remains in effect until 900 PM MDT for
southwestern Montana.

LAT...LON 4584 11367 4588 11354 4594 11351 4580 11343
      4575 11336 4580 11335 4582 11328 4587 11322
      4588 11310 4584 11304 4543 11354 4555 11382
      4559 11380 4562 11384
TIME...MOT...LOC 2113Z 215DEG 27KT 4559 11369

Kredensor

Special Weather Statement
National Weather Service Great Falls MT
334 PM MDT Sat Aug 10 2019

MTZ008-102200-
Beaverhead-
334 PM MDT Sat Aug 10 2019

...A STRONG THUNDERSTORM WILL AFFECT NORTHWESTERN BEAVERHEAD
COUNTY...

At 333 PM MDT, a strong thunderstorm was located 10 miles east of
Wisdom, or 37 miles northwest of Dillon, moving northeast at 25 mph.

Winds in excess of 40 mph and penny size hail are possible with this
storm.

This storm will remain over mainly rural areas of northwestern
Beaverhead County east of Wisdom.

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.

A Severe Thunderstorm Watch remains in effect until 900 PM MDT for
southwestern Montana.

LAT...LON 4544 11323 4557 11341 4584 11309 4564 11282
TIME...MOT...LOC 2133Z 226DEG 22KT 4556 11324

Kredensor

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Special Weather Statement
National Weather Service Great Falls MT
501 PM MDT Sat Aug 10 2019

MTZ014-052-102345-
Jefferson MT-Central and Southern Lewis and Clark MT-
501 PM MDT Sat Aug 10 2019

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHERN LEWIS AND CLARK AND
NORTHWESTERN JEFFERSON COUNTIES UNTIL 545 PM MDT...

At 500 PM MDT, Doppler radar was tracking a strong thunderstorm over
Basin, or 9 miles northwest of Boulder, moving northeast at 25 mph.

Nickel size hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Helena, Basin, Montana City, Wickes, Rimini, Alhambra, Corbin, Spring
Meadow Lake State Park, Clancy and Jefferson City.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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 will relay your report to the National Weather Service
office in Great Falls.

&&

A Severe Thunderstorm Watch remains in effect until 900 PM MDT for
southwestern and west central Montana.

LAT...LON 4639 11240 4639 11236 4641 11232 4650 11231
      4668 11218 4650 11183 4619 11226 4630 11246
TIME...MOT...LOC 2300Z 217DEG 21KT 4630 11231

FMK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
543 PM MDT SAT AUG 10 2019

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

0535 PM     HAIL             5 W CLANCY              46.47N 112.09W
08/10/2019  E0.25 INCH       JEFFERSON          MT   TRAINED SPOTTER

            PEA SIZED HAIL AND HEAVY RAIN WITH NO WIND.

&&