Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 251042

Area Forecast Discussion
National Weather Service Missoula MT
442 AM MDT MON MAY 25 2015


A closed low pressure circulation from the northwest remains on-
track to impact the Northern Rockies with showers and
thunderstorms today through at least Thursday. The associated cold
front will sweep across the region from northwest to southeast,
with a line of thunderstorms concentrated along the frontal
boundary. Brief heavy rain, wind gusts to 40 mph, small hail, and
frequent lightning will be main weather hazards to be aware of
late this morning through this evening. Considering the track of
this low pressure system and southwesterly flow aloft today and
Tuesday, there is a very outside chance of thunderstorm
strengthening enough to produce hail that is one quarter inch in
diameter. Tuesday afternoon and evening will see a reprise of
showers and thunderstorms, however the best thunderstorm activity
will shift southward and eastward along the Continental Divide.
The precipitation chances begin to lessen, but not completely
dissipate on Wednesday and Thursday, as the low pressure slides
south and east of the region.

A weak ridge of high pressure will try to build over the region on
Friday, but several disturbances moving through Canada will allow
for showers and isolated thunderstorms to develop each afternoon
through the weekend. Models are in fairly good agreement with the
ridge breaking down and moving to the east on Monday. As the ridge
moves to our east, southwest flow will develop and provide a
favorable pattern for active thunderstorms next week.


.AVIATION...Showers and thunderstorms will eventually impact all
area terminals during the next 24 hours. KGPI will be the first
local terminal to be impacted with showers and thunderstorms,
beginning around 25/1600Z. KMSO, KBTM, and KSMN will be impacted
by showers and thunderstorms beginning 25/2000Z. Lightning,
temporarily lowered ceilings and visibility, very small hail, and
brief wind gusts over 25 knots are possible. All terminals will
see diminishing precipitation after 26/0300Z, however a slight
chance of additional showers will remain through the remainder of
the evening and overnight. Terrain will be obscured at times.



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