Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 252039

Area Forecast Discussion
National Weather Service Missoula MT
239 PM MDT MON MAY 25 2015

.DISCUSSION...Widespread cellular thunderstorms are being
observed across central Idaho and western Montana this afternoon.
Storms will continue to develop through this evening, with
lightning and small (pea-sized) hail being the main threats. Brief
rainfall and gusty winds may also accompany many of the
thunderstorms that occur. People with outdoor plans should be
prepared for rapidly changing conditions.

This will be the trend for Tuesday afternoon and evening as well,
as this could be an equally-unstable day where thunderstorm
development is favorable. Central Idaho, namely those in Idaho
county and adjacent locations, could see the brunt of thunderstorm
activity. That being said, the entirety of the Northern Rockies
will be under the threat of small hail, lightning, and heavy
downpours. As before, anyone with outdoor plans should plan
accordingly for quickly changing, inclement conditions.

The upper-level low responsible for this week`s round of
precipitation will slow down as it moves across the northern
Rockies, allowing for a continued threat of showers/thunderstorms
Wednesday and Thursday (though not as strong due to gradual weakening
of the low). Wednesday looks to be the coolest day of the week as
the low will reside directly over central Idaho at that time. A
warming trend will begin from that point on.

Looking ahead to next weekend, forecast models are continuing to
show a trend towards weak ridging across the western US. The ridge
will not be strong enough to suppress afternoon
shower/thunderstorm activity, but will bring warmer temps to the
area. Some valleys of central Idaho could approach 90 degrees,
with 80s in western Montana valleys. In fact, current guidance
suggests some of the warmest temperatures yet this year.


.AVIATION...Scattered thunderstorms with periodic lightning, small
hail, and brief but heavy rainfall will be possible at all
aviation terminals through roughly 26/0400Z, with lingering
rainfall thereafter. Another round of similar convective activity
is likely Tuesday afternoon as well, between 26/1800Z and
27/0300Z for all terminals.



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