Severe Thunderstorm Warning 7, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
938 AM MDT Fri Jun 14 2019

.UPDATE...

Overnight convection has ended or moved away to the east as of
mid-morning. Attention now turns to the north, as we monitor a
cold front crossing into North-central Montana. The convective
outlook has been raised to a marginal risk for severe
thunderstorms due to steepening mid-level lapse rates associated
with the amplifying upstream trough. However, the cold front may
be advancing faster than earlier forecast. If it continues to
advance, it will preclude to some extent the surface heating
needed to produce stronger storms. However, elevated
thunderstorms forming over the cooler airmass remain possible,
producing locally heavy rain and small hail in a few storms. The
ensemble of available convection allowing models provide a strong
consensus for storms developing around noon and spreading
south/east along the HiLine. Overall forecast remains in good
shape for today, but with low confidence in terms of the potential
for strong to severe thunderstorms. The forecast was updated to
better match observed trends, but with no significant changes. PN

&&

.SYNOPSIS...

A cold front will advance south from Canada today, producing another
round of showers and thunderstorms this afternoon. The chance for
showers and thunderstorms will continue into the weekend, especially
in mountain areas, as temperatures cool closer to seasonal averages.
a general unsettled pattern is expected to continue into next
week.

&&

.AVIATION...
Updated 600 AM MDT Fri Jun 14 2019 (12Z/14 TAFs)

There will be a few isolated showers and thunderstorms this morning
but in a few places but the more impactful activity is expected to
develop after 18Z. Most of this will be northeast of a Great Falls
to Lewistown line. Mostly VFR conditions are expected but showers
and storms could produce brief MVFR conditions at times. Showers and
storms are expected to diminish this evening. Northwesterly breezes
are also expected, mostly for the north-central terminals. rcg

&&

.PREV DISCUSSION...
/ISSUED 557 AM MDT Fri Jun 14 2019/

A line of showers and thunderstorms developed overnight north of
the Great Falls area due to a combination of lift provided by a
Canadian cold front, outflows from collapsing thunderstorms, and
decent mid-level lapse rates. Some of these storms were on the
strong side but this line of precipitation has since diminished to
an area of lighter showers and thundershowers as it moves eastward
into Blaine and northern Fergus County. A mid-level shortwave
trough will dive southeastward from British Columbia and Alberta
today, which will work with a relatively moisture rich environment
to produce another round of showers and thunderstorms by early
afternoon. The Storm Prediction Center has included a portion of
our CWA in a marginal risk area for severe Thunderstorms. This
area roughly extends north and east of a Cut Bank to Lewistown
line. There may be a few storms that approach severe limits (60
mph wind gusts, hail to the size of 1" in diameter) this afternoon
but not expecting a widespread event. Thunderstorm threats for
today will be localized brief heavy rains, small hail, and gusty
winds. Breezy northwesterly winds will develop this afternoon,
especially for North-central locations and temperatures will
trend around five to ten degrees cooler for many northern
locations. Showers and thunderstorms should diminish and move off
to the east this evening as the supporting upper level trough
exits the region. rcg

Saturday through next Friday...

An upper level ridge is still forecast to temporarily rebuild along
the Pacific NW coast and shift inland this weekend, maintaining a
northwest flow aloft with weak embedded disturbances tracking SE
across the Northern Rockies and MT. Showers and a few thunderstorms
are possible each afternoon and evening, especially in/near the
mountains but with little support for organized storm development,
main threat will be isolated locally heavy rain with slow storm
movement or storms anchored to higher terrain. On Monday of next
week, a shortwave is expected to approach from the west and yield a
better chance for showers and thunderstorms for Monday afternoon and
evening, especially southwest of a Cut Bank to Lewistown line. some
storms could be on the strong side, with the primary threats being
brief heavy rains, small hail, and gusty winds. By mid-week, models
and ensembles support the idea of strong ridge amplification well
off the west coast and a deepening trough downstream across the
Rockies/N-central US. This signals, a shift to cooler and wetter
conditions by Wednesday or Thursday of next week, although some
details still need to be worked out in regards to timing and
specific impacts. One feature that does seem apparent, is an
unseasonably strong (120+ kt) upper level jet expected to move with
the developing trough along with a fairly packed height field which
combined with afternoon mixing could result in breezy to windy
conditions and possibly lead to some more organized thunderstorm
activity. Hoenisch/rcg

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  77  51  73  51 /  50  40  20  10
CTB  69  47  70  46 /  80  40  30  20
HLN  82  51  78  51 /  10  10  20  10
BZN  79  46  78  47 /  30  20  10  10
WEY  70  38  70  38 /  40  40  20  20
DLN  76  46  76  48 /  10  10   0   0
HVR  76  50  75  49 /  60  40  10  10
LWT  75  47  69  47 /  60  50  30  20

&&

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

http://www.weather.gov/greatfalls

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
147 PM MDT FRI JUN 14 2019

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

0133 PM     HAIL             VALIER                  48.31N 112.25W
06/14/2019  E1.75 INCH       PONDERA            MT   LAW ENFORCEMENT

            PONDERA COUNTY SHERIFF RELAYED A PUBLIC
            REPORT OF GOLF BALL SIZE HAIL BREAKING
            WINDOWS ON NORTH FACING SIDE OF A HOME IN
            VALIER.

&&

PN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
203 PM MDT FRI JUN 14 2019

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

0140 PM     HAIL             5 SSE VALIER            48.23N 112.23W
06/14/2019  E1.75 INCH       PONDERA            MT   TRAINED SPOTTER

&&

SAC

Special Weather Statement
National Weather Service Great Falls MT
209 PM MDT Fri Jun 14 2019

MTZ013-142045-
Chouteau-
209 PM MDT Fri Jun 14 2019

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

At 208 PM MDT, a strong thunderstorm was located 11 miles southeast
of Fort Benton, moving east at 40 mph.

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

Locations impacted include...
Geraldine, Shonkin and Square Butte.

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.

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 4747 11004 4746 11007 4761 11068 4779 11061
      4771 10995
TIME...MOT...LOC 2008Z 285DEG 34KT 4768 11053

Coulston