Special Weather Statement, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
1119 AM MDT Tue Jul 11 2017

UPDATED AVIATION

.UPDATE...
Going forecast seems to be in decent shape so far. Much of the
shower activity today should focus on the Alberta/Montana border
and points north. One last day before heat returns tomorrow.

/Issued by WFO Glasgow, Montana

&&

.SYNOPSIS...

Several upper-level disturbances will move through the region
through today. As a result, expect scattered showers and
thunderstorms to develop during this time, mainly during the
daylight hours. High temperatures will cool a few degrees through
today, before another significant heat wave develops by late next
week.

 &&

.AVIATION...
Updated 1719Z

Mainly VFR expected next 24-hours. A weak weather disturbance will
move E'ward over MT this afternoon and evening. Thus, a few showers
and thunderstorms are possible, especially along the Hi-Line and
over/near the mountains of Central and SW MT through about 06Z/Wed.
Surface wind gusts of 30-50 knots and brief MVFR CIGS may accompany
any shower or storm. Clearing skies are expected after 06Z/Wed as
high pressure ridging aloft builds-in from the west.
Jaszka

&&

.PREV DISCUSSION...
/ISSUED 443 AM MDT Tue Jul 11 2017/

Today through Wednesday...Shortwave trough will move across Montana
and Saskatchewan today on nearly zonal flow aloft. The system will
bring cooler temperatures and some temporary relief from the heat.
With atmosphere remaining unstable, there will be a chance of
showers and thunderstorms, mainly along the Canadian border.

The wave moves to the east this evening with mainly dry weather
prevailing.

Upper ridge will build back into Montana on Wednesday with warmer
temperatures. Look for mostly clear skies with mainly dry
weather.

Wed night through Tue...Upper-level ridge continues to build into
Montana along with most of the Western U.S. on Thursday and Friday.
Expect a return to hot and dry weather conditions.

The upper ridge only strengthens through the end of the week and
persists right on through at least the first part of the weekend.
During this time forecast highs will be in the 90s and low 100s
each day with little, if any measurable rainfall.

00Z/Tue models continue to differ some on evolution of the pattern
late in the weekend and early next week. The 00Z ECMWF has the ridge
axis sliding east of the forecast area into the Dakotas, with upper-
level southwest flow aloft on the backside of the ridge, while a
surface cold front approaches the forecast area. The GFS keeps the
ridge parked over the western U.S. right on through the period,
though does introduce some flattening late in the weekend and early
next week, keeping Montana on the northern periphery and becoming
influenced more by embedded shortwaves in the flow which could
generate chances for showers and thunderstorms. The bottom line is
that a return to hot and dry conditions is in the cards for the
second half of this week and into the weekend, but some uncertainty
exists late in the weekend and early next week due to increasing
model solution differences.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  81  53  87  56 /  10   0   0   0
CTB  76  50  83  52 /  20  10   0   0
HLN  84  56  88  58 /  10   0   0   0
BZN  82  51  85  52 /  10  10   0   0
WEY  74  41  76  42 /  20  20  10  10
DLN  80  51  82  53 /  10   0   0   0
HVR  79  54  88  58 /  30  10  10  10
LWT  79  52  82  57 /  10  10  10  20

&&

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

weather.gov/greatfalls

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1015 AM MDT TUE JUL 11 2017

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

0313 PM     HAIL             3 S BOZEMAN             45.63N 111.04W
07/10/2017  M0.75 INCH       GALLATIN           MT   BROADCAST MEDIA

            PENNY-SIZE HAIL. REPORT RELAYED BY KBZK.

&&

KJ

Special Weather Statement
National Weather Service Great Falls MT
221 PM MDT TUE JUL 11 2017

MTZ011-047-112100-
Hill MT-Blaine MT-
221 PM MDT TUE JUL 11 2017

...SIGNIFICANT WEATHER ADVISORY FOR WEST CENTRAL BLAINE AND EAST
CENTRAL HILL COUNTIES UNTIL 300 PM MDT...

At 219 PM MDT, Doppler radar was tracking a strong thunderstorm near
Havre, moving southeast at 20 mph.

Dime size hail and winds in excess of 30 mph will be possible with
this storm. This storm will impact mainly rural areas south of
Highway 2.

Locations impacted include...
Havre.

LAT...LON 4848 10982 4858 10972 4845 10930 4829 10943
TIME...MOT...LOC 2019Z 298DEG 19KT 4850 10970

KLG