Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 230948

Area Forecast Discussion
National Weather Service Missoula MT
348 AM MDT Wed Jul 23 2014

...A few severe thunderstorms this afternoon and evening...
...Strong cold front tonight bringing gusty winds and cooler
temperatures for Thursday...

.DISCUSSION...Showers and thunderstorms will continue to pass
through Idaho and western Montana this morning as a vigorous
short wave passes. Clouds are clearing behind the shortwave and
this clearing is forecast to also take place from mid to late
morning through north central Idaho and western Montana. The
clearing later this morning and early afternoon will allow
temperatures to warm today which in turn will add to unstable
conditions this afternoon.

The well advertised low pressure system is on track to move into
Washington through today and its presence will enhance
thunderstorm potential. The Storm Prediction Center has a slight
risk area for severe thunderstorms from a line near Grangeville
to Lost Trail Pass to Butte and north to the Canadian border,
meaning this is the area with best chances for thunderstorms that
could become strong with hail the size of quarters and damaging
gusty winds. This area has been fairly consistent for the past few
days so confidence is highest for thunderstorms north of the
aforementioned line through this afternoon and evening. There will
also be high amounts of available atmospheric moisture expected
that will lead to a few storms with heavy rain and a risk of flash
flooding on recent burn scars as well as the Going-To-The-Sun-Road
in Glacier National Park.

The main low pressure system and cold front will push into western
Idaho and northwest Montana late this evening bringing gusty
winds that will continue through Thursday. These winds will be
sustained around 20 mph with gusts 30 mph or higher. Conditions on
area lakes are likely to be choppy through Thursday. Higher
elevations, particularly in Glacier NP, will see wind gusts of 60
mph during Thursday as well. Temperatures are going to drop
dramatically with the cold front with high temperatures dropping
20 degrees from today. Snow levels will also drop to around 7000

There is some question on how chilly low temperatures will be on
Friday morning due to the potential for light wind to maintain. At
this time there is enough support for a cool forecast so
temperatures were not changed.

High pressure with warming temperatures are on tap for the weekend
and into next week.

Very low shower chances have been re-introduced to the extended
forecast for southern locations with monsoon moisture forecast to
work northward.


.AVIATION...A broad area of showers and embedded thunderstorms is
moving through the region this morning in response to a shortwave
trough. The shortwave will continue through the region and move off
to the northeast during this morning. High resolution model
guidance agree that showers and thunderstorms will mostly vacate
north central Idaho and western Montana by around 23/1500z,
thereafter, skies will clear. Temperatures will warm and
destabilize the atmosphere during the afternoon. Storms will
initiate around 23/2100z in north central Idaho and western Montana
and intensify as they move to the northeast. The Storm Prediction
Center has most of the region in a slight risk area for severe
thunderstorms this afternoon. At this time the best concentration
of strong thunderstorms will be around KMSO northward through
KGPI. The main threat will be large hail the size of quarters and
gusty, damaging wind. Heavy rain will also reduce visibilities
under stronger cores. In the long list of potential aviation
impacts will be gusty winds along a strong cold front that will
pass late this evening and overnight.




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