Special Weather Statement, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
114 PM MDT Thu Jun 10 2021

.SYNOPSIS...

Scattered showers and thunderstorms this afternoon will move
away to the east overnight. Temperatures remain cool on Friday
before a significant warming trend begins this weekend. Expect
widespread 90s at least next Monday and Tuesday.

&&

.DISCUSSION...

A potent upper level trough and its attendant surface front is
crossing the Continental Divide this afternoon. Observations
reveal a line of showers and thunderstorms developing over
Southwest Montana. This activity will continue to spread further
east through the evening as the trough lifts from Southwest toward
Northeast. A cool and stable airmass remains in place over North-
central Montana. Only scattered light rain showers would be
expected here until the front passes through and increasing
westerly downslope winds develop. Isolated stronger thunderstorms
are possible further east, where stability and shear profiles are
more favorable for possibly severe convection. The main concern
from any severe thunderstorms (eastern Fergus and Blaine counties)
will be gusty winds and large hail. The passing cold front will
lower snow levels to around 6000 feet, so some light snow
accumulation may be possible where precipitation lingers
overnight. Furthermore, frost is likely tonight for some of the
higher elevation Southwest valleys. Skies clear out on Friday to
start the beginning of a warming trend. PN

Saturday through next Thursday...A broad ridge of high pressure
builds across the area this weekend into at least early next week,
bringing dry conditions and significant warming. Widespread 80s
are expected by Sunday, with a few 90s possible. The peak of the
next heat wave looks to occur Monday and Tuesday Tuesday, with
afternoon temperatures in the 90s for much of the CWA, and a few
100s can't be ruled out. There is fairly good agreement that on
Wednesday a Pacific cool front will move through the region,
resulting in increased winds developing. Between the anticipated
dry nature of this front and the antecedent hot and dry weather,
fire weather concerns would be on the rise. This 'cool' front may
bring some relief from the heat for Wednesday and next Thursday,
but the degree of any cool-off remains uncertain as there is
disagreement among the deterministic models and increasing spread
in ensemble probabilities. -Kredensor

&&

.AVIATION...
1130 AM MDT Thursday Jun 10 2021 (10/18Z TAF period)

Low stratus remains over KHVR/KLWT producing IFR/MVFR conditions.
These clouds are expected to thin and mix out through late
afternoon. A cold front advancing across the Continental Divide is
helping to generate a line of thundershowers. Expect increasing
coverage of thunderstorms, likely impacting KHLN/KBZN/KEKS/KWYS
(southwest Montana terminals) around 00-03Z. Skies gradually clear
overnight, with prevailing VFR conditions on Friday.

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  40  70  45  78 /  30   0   0   0
CTB  39  66  41  70 /  30   0   0   0
HLN  40  73  48  82 /  40   0   0   0
BZN  35  71  43  83 /  70   0   0   0
WYS  27  61  33  75 /  70   0   0   0
DLN  32  67  43  80 /  50   0   0   0
HVR  44  72  46  80 /  30   0   0   0
LWT  39  69  44  79 /  50   0   0   0

&&

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

http://www.weather.gov/greatfalls

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1013 AM MDT THU JUN 10 2021

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

0720 PM     HAIL             HAYS                    47.99N 108.69W
06/09/2021  E2.50 INCH       BLAINE             MT   PUBLIC

            PUBLIC REPORT FROM HAYS, MT THAT THERE WAS
            PING PONG TO TENNIS BALL SIZE HAIL WHEN THE
            FIRST SYSTEM MOVED THROUGH.

&&

TP

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1017 AM MDT THU JUN 10 2021

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

1159 PM     HEAVY RAIN       3 S LEWISTOWN           47.03N 109.42W
06/09/2021  M0.45 INCH       FERGUS             MT   TRAINED SPOTTER

            0.45 INCHES RAIN IN AN EVENING THUNDERSTORM.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1028 AM MDT THU JUN 10 2021

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

1005 PM     HAIL             HAYS                    47.99N 108.70W
06/09/2021  E1.00 INCH       BLAINE             MT   PUBLIC

            QUARTER SIZE HAIL REPORTED DURING THE SECOND
            SYSTEM TO PASS OVER HAYS, MT.

&&

TP

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1031 AM MDT THU JUN 10 2021

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

1055 PM     HAIL             HAYS                    47.99N 108.70W
06/09/2021  E1.50 INCH       BLAINE             MT   PUBLIC

            QUARTER TO PING PONG BALL SIZED HAIL
            REPORTED IN HAYS, MT WITH THE THIRD SYSTEM
            THAT TRACKED THROUGH THE AREA, GUSTY WINDS
            THAT SHOOK THE TRUCK, ESTIMATED 50 MPH
            GUSTS.

&&

TP

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