Special Weather Statement, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
357 AM MDT SAT JUN 11 2016

.DISCUSSION...

Today through Monday...An upper level trough remains over British
Columbia and the Pacific Northwest this morning with an unstable
southwest flow aloft over Montana. Models significantly weaken
this feature as it moves slowly eastward through the weekend.
Isolated/scattered showers and thunderstorms will continue today
through this evening across the forecast area with much cooler
high temperatures expected this afternoon. Models and SPC are
indicating that the risk for strong to severe thunderstorms will
shift eastward today, affecting mainly northeast Montana. However,
do not believe that I can rule out an isolated strong storm or two
in Blaine and Fergus Counties this afternoon/evening. Slightly
warmer, breezy and mostly dry conditions will prevail on Sunday as
the weakening upper trough moves away from the region and Montana
is left beneath a brisk westerly flow aloft. Temperatures continue
to warm on Monday as another short wave trough approaches the
state with isolated/scattered showers and thunderstorms developing
over southwest Montana and tracking northeastward during the
afternoon. mpj

MONDAY NIGHT THROUGH SATURDAY...Medium range forecast models agree
on moving a low pressure center out of the Gulf of Alaska and south
along the Pacific Coast through Friday. This will deepen the upper
trough there through the period and shift the relatively dry
southwest flow aloft to an increasingly moist and unstable southerly
flow. As a result, there will be a fairly consistent chance for
showers and thunderstorms over the forecast area Tuesday through
Thursday, along with near normal temperatures. However, the models
differ somewhat for the Friday through Saturday period. The ECMWF
(European) and GEM (Canadian) models keep this flow aloft in place,
continuing the unsettled weather, while the GFS starts to build the
central CONUS high pressure ridge west into the state and keeps the
forecast area dry. Have therefore decided to keep a slight chance of
showers/thunderstorms through Saturday, but kept the chance below
climatological normals. Model consensus also hints at temperatures
warming back above normal to end the week, so have stayed with that
trend.  Coulston

&&

.AVIATION...
UPDATED 0540Z.

Conditions will generally remain VFR through this period, unless
otherwise stated. Thunderstorm activity has decreased significantly
across North Central and Southwest Montana this evening. However,
scattered showers will persist through around 14Z across much of the
area north of a KDLN to KLWT line under a moist and unsettled
southwest flow aloft. A few thunderstorms are possible, but they
will likely not impact the terminals directly. Some of the heavier
showers may cause occasional lowering of ceilings to MVFR/high IFR
levels. Gusty westerly winds will then develop in the wake of the
passing cold front, hindering shower/storm development across much
of North Central Montana on Saturday, but areas closer to the
trailing portion of the front (KHLN KBZN KLWT) may still see some
thunderstorm activity between 20Z and 02Z and lingering showers
after 02Z.  Coulston

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  64  42  71  45 /  30  20  10   0
CTB  62  40  67  43 /  30  10   0   0
HLN  63  44  73  47 /  40  30  10   0
BZN  68  42  71  44 /  40  40  10  10
WEY  62  36  61  39 /  40  30  10  20
DLN  66  40  70  42 /  50  40  10  10
HVR  64  44  72  45 /  30  30   0   0
LWT  63  43  70  46 /  40  50  10  10

&&

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

weather.gov/greatfalls

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
452 AM MDT SAT JUN 11 2016

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

0450 AM     HAIL             5 SW GREAT FALLS        47.46N 111.38W
06/11/2016  M1.00 INCH       CASCADE            MT   OFFICIAL NWS OBS

            QUARTER SIZE HAIL FELL AT THE WFO GREAT FALLS OFFICE

&&

MARTIN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
505 AM MDT SAT JUN 11 2016

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

0452 AM     HAIL             GREAT FALLS             47.50N 111.29W
06/11/2016  M1.00 INCH       CASCADE            MT   PUBLIC

&&

MARTIN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
507 AM MDT SAT JUN 11 2016

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

0455 AM     HAIL             GREAT FALLS             47.50N 111.29W
06/11/2016  M1.50 INCH       CASCADE            MT   TRAINED SPOTTER

&&

MARTIN

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREAT FALLS MT
532 AM MDT SAT JUN 11 2016

MTZ012-014-048-049-111200-
CENTRAL AND SOUTHERN LEWIS AND CLARK MT-
SOUTHERN ROCKY MOUNTAIN FRONT MT-CASCADE MT-EASTERN TETON MT-
532 AM MDT SAT JUN 11 2016

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN CASCADE...
SOUTHEASTERN TETON AND CENTRAL LEWIS AND CLARK COUNTIES UNTIL 600 AM
MDT...

AT 531 AM MDT...DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM 11
MILES SOUTHWEST OF FORT  SHAW...OR 12 MILES NORTHWEST OF CASCADE...
MOVING NORTHEAST AT 60 MPH.

NICKEL SIZE HAIL AND WINDS IN EXCESS OF 30 MPH WILL BE POSSIBLE WITH
THIS STORM.

LOCATIONS IMPACTED INCLUDE...
POWER...FORT SHAW...FORT  SHAW...SIMMS...VAUGHN...SUN RIVER AND FIRST
PEOPLES BUFFALO JUMP STATE PARK.

LAT...LON 4724 11192 4735 11211 4781 11165 4759 11129
TIME...MOT...LOC 1131Z 223DEG 51KT 4737 11193

MARTIN