Severe Thunderstorm Warning 97, NWS Great Falls, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1155 AM MDT Mon Aug 5 2013

AVIATION SECTION UPDATED

.UPDATE...
Made minor updates to forecast this morning. Adjusted POPs to
include isolated showers/thunderstorms across portions of
southwest and central Montana associated with a jet core moving
into the area from the west. Have also adjusted thunderstorm
wording to include gusty winds across southwest Montana this
afternoon/evening. Wind shear at the 0-6 km level increases to
the 40-50 kt range during that time, allowing for the potential
for some of those winds to partially translate down to the
surface. Am keeping the mention of gusty winds/small hail/heavy
rain for thunderstorms across north central/central Montana.
Precipitable water values range from 0.75 to 1.00 inches there and
instability mostly ranges from 400 to 800 J/kg, but 0-6 km wind
shear is much less than in the areas farther south. Therefore,
with less upper level support, hail will likely not become large.
However, with the potential for the brief heavy rain over the
still moist areas along the Hi-Line, will be alerting decision-
makers to this potential. Otherwise, temperatures and winds seem
to be trending similarly to the going forecast.  Coulston

&&

.AVIATION...
UPDATED 1755Z.
An upper-level trough and accompanying plume of Pacific moisture
will move along the US/Can border today, sparking scattered
thunderstorms across central and southwest MT this afternoon/
evening. A weak surface cold front from this system is currently
near KCTB and should only make slow southward progress through 00Z.
There is potential for isolated stronger storms near/along the
front, mainly vcnty KCTB/KHVR, but could come as far south as KGTF
by late aftn. Main threat would be gusty outflow winds and brief
heavy rainfall. Expect VFR conditions for the most part, though
brief MVFR is possible near any stronger storms. Convective activity
will dissipate this evening with gradually decreasing cloud cover.
Waranauskas

&&

.PREV DISCUSSION...
/ISSUED 545 AM MDT Mon Aug 5 2013/
Today through Wednesday...An upper trough extended from central
Alberta to southern B.C. early this morning. This trough will
move into northwest Montana this afternoon then continue moving
southeast overnight. The trough combined with an unstable airmass
will lead to scattered thunderstorms this afternoon into this
evening. There should be enough instability and wind shear and
lift and moisture for a few of the thunderstorms to have strong
gusty winds, small hail, and brief heavy rain over the central and
northern forecast zones. Tuesday and Wednesday expect quieter
weather as an upper ridge develops over the Pacific Northwest. For
Tuesday a stable layer aloft should generally prevent any
thunderstorms from forming. The exception will be over
northcentral Montana where the airmass will still be unstable. A
weaker stable layer aloft Wednesday could lead to a little more
coverage of thunderstorms in the north. Blank

Wednesday night through Monday...A slightly unstable summer like
weather pattern will continue to reside over the region for the
second half of the work week and into next weekend. Again tonight
both the GFS/EC models differ in the exact timing/placement with
the upper level disturbances moving through the region. Thus
isolated thunderstorms look possible most days from Thursday
through Monday. However...there looks to be just enough model
support to try and keep the lower elevations drier from Wednesday
night through Thursday night...thus pops have been lowered just a
touch for many lower elevation locations. Otherwise...isolated to
scattered thunderstorms are expected across the region later this
week...through the weekend...and into early next week. In terms of
temperatures...summer like temperatures will continue through the
period...with afternoon highs near normal most days. The only
change was to lower the afternoon highs a touch for next
weekend...especially in southwest MT...as the latest forecast
models indicate afternoon highs in southwest MT should now
generally be in the upper 80s rather than near or just above 90
degrees. Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  83  50  79  51 /  30  40  10  10
CTB  75  48  77  50 /  50  30  10  10
HLN  87  55  84  54 /  20  30  10  10
BZN  86  48  82  47 /  20  20  10  10
WEY  79  37  76  34 /  20  10   0   0
DLN  84  48  82  47 /  20  20  10  10
HVR  81  53  78  51 /  30  40  20  20
LWT  81  49  75  48 /  30  40  10  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

SHORT TERM...BLANK/COULSTON
LONG TERM...BRUSDA
AVIATION...BRUSDA

weather.gov/greatfalls

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREAT FALLS MT
416 AM MDT MON AUG 5 2013

MTZ009>014-044>051-054-061030-
NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER-HILL-CASCADE-
CHOUTEAU-CENTRAL AND SOUTHERN LEWIS AND CLARK-TOOLE-LIBERTY-
EASTERN PONDERA-BLAINE-SOUTHERN ROCKY MOUNTAIN FRONT-
EASTERN TETON-JUDITH BASIN-FERGUS-MEAGHER-
416 AM MDT MON AUG 5 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL
MONTANA...NORTH CENTRAL MONTANA AND SOUTHWEST MONTANA.

.DAY ONE...TODAY AND TONIGHT

SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED ACROSS MUCH OF
NORTH CENTRAL AND CENTRAL MONTANA THIS AFTERNOON AND EVENING. A
FEW OF THE THUNDERSTORMS WILL HAVE BRIEF HEAVY RAINFALL...GUSTY
WINDS TO 40 MPH AND SMALL HAIL.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

MTZ008-015-052-053-055-061030-
BEAVERHEAD-MADISON-JEFFERSON-BROADWATER-GALLATIN-
416 AM MDT MON AUG 5 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST
MONTANA.

.DAY ONE...TODAY AND TONIGHT

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREAT FALLS MT
117 PM MDT MON AUG 5 2013

MTZ010-044-046-052000-
EASTERN GLACIER MT-EASTERN PONDERA MT-TOOLE MT-
117 PM MDT MON AUG 5 2013

...SIGNIFICANT WEATHER ADVISORY FOR EASTERN PONDERA...EASTERN GLACIER
AND SOUTHERN TOOLE COUNTIES UNTIL 200 PM MDT...

AT 116 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM 8 MILES SOUTH OF CUT BANK...MOVING SOUTHEAST AT
25 MPH.

HAIL UP TO THE SIZE OF PENNIES AND WIND GUSTS UP TO 40 MPH ARE
EXPECTED WITH THIS STORM...ALONG WITH HEAVY RAIN AND FREQUENT
DANGEROUS LIGHTNING.

* LOCATIONS IMPACTED INCLUDE...
   ETHRIDGE...
   SHELBY...
   LEDGER...
   DEVON...

LAT...LON 4868 11127 4839 11127 4806 11164 4846 11252
      4873 11254
TIME...MOT...LOC 1917Z 294DEG 43KT 4853 11226

HOENISCH