Severe Thunderstorm Warning 102, NWS Great Falls, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
259 PM MDT Mon Aug 5 2013

.DISCUSSION...

This afternoon through Wednesday...Scattered thunderstorms have
developed this afternoon across north central and southwest
Montana ahead of a shortwave trough moving southeast out of
Alberta. A weak cold front has also moved south into north central
Montana, providing a focus for thunderstorm development. Moderate
to strong wind shear with moderate to high precipitable water has
caused many of the storms across north central Montana to become
strong with small hail, brief heavy rainfall, and gusty winds. A
few of these storms have even become severe with large hail. The
convective activity extends north only into far southern Alberta,
so am expecting the activity to generally decrease after 6 pm MDT,
with the threat for small hail, heavy rain, and gusty winds
continuing into the early evening hours. The primary additional
threat will be the potential for localized flooding from the brief
heavy rainfall. Will continue to monitor this situation for
possible flood highlights. Thunderstorms will likely diminish
before midnight as the shortwave trough moves into the area
overnight. An upper level ridge of high pressure will then begin
to build back into the area for Tuesday through Wednesday, for a
more anticyclonic northwesterly flow aloft. A few weak
disturbances will move through this flow through the period, for
at least a slight chance of showers/thunderstorms across north
central Montana, mainly during the afternoon/evening hours. The
airmass should remain dry enough to prevent storm development
across southwest Montana. Temperatures will remain about 5 degrees
below seasonal averages through Tuesday, but the rebuilding ridge
will help warm temperatures closer to normal into Wednesday.
Coulston

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

&&

.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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  51  80  54  85 /  40  10  10  10
CTB  48  77  53  79 /  30  10  10  20
HLN  55  84  57  87 /  40  10  10  10
BZN  49  82  49  85 /  20  10  10  10
WEY  33  76  36  78 /  10  10   0  10
DLN  48  82  49  84 /  20  10  10  10
HVR  53  78  54  80 /  40  20  10  30
LWT  50  75  51  81 /  50  20  10  20

&&

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

SHORT TERM...COULSTON
LONG TERM...BRUSDA
AVIATION...WARANAUSKAS

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.

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