Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 212123
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
323 PM MDT Mon Jul 21 2014

...Strong thunderstorms possible Tuesday and Wednesday...

...Much cooler with low snow levels on Thursday...

.DISCUSSION...

Showers and thunderstorms will linger into this evening along a
line from around Salmon Idaho to Butte Montana. These storms are
expected to remain weak with limited instability in the area.

The first in a series of impulses is forecast to slide northward
through Central Idaho Tuesday morning, bringing a round of showers
and thunderstorms from that area northward into Western MT into
the early afternoon. By the afternoon hours, more widespread
coverage of storms is expected as instability increases with
daytime heating. The main threat at this time appears to be brief
heavy rain, although gusty winds and small hail cannot be ruled
out.

Wednesday...An unseasonably strong upper level low approaching
the region will bring numerous thunderstorms to north central
Idaho and western Montana. Models have been consistently showing a
shortwave moving through the area early Wednesday morning. A brief
break may be possible mid morning on Wednesday before another
stronger wave moves in the afternoon. Thunderstorms will be more
widespread in the afternoon with some severe storms possible. At
this point the best instability looks to be across western
Montana. The main threats with the thunderstorms Wednesday
afternoon will be damaging winds and hail. Thunderstorms will be
moving fairly quickly but brief intense rain could also create
isolated areas of flash flooding with the recent burn scars of
particular concern.

Wednesday evening through Thursday...A powerful cold front is
expected to pass through late Wednesday evening and overnight.
This will cause wind speeds to increase with wind gusts up to 30
mph for valleys and area lakes. High elevation passes in northwest
Montana such as Logan pass could see wind gusts of 60 mph on
Thursday. Snow levels could lower to the peaks in Glacier NP
vicinity where a few flakes are possible. High temperatures will
also be well below normal, especially in northwest Montana where
highs are forecast to be in the 40s to 50s in the terrain and 60s
in the valleys.

Drier weather and a warming trend is expected from Friday into
next weekend as a ridge builds over the Northern Rockies.
Temperatures look to rebound to above normal, with lower-elevation
valleys seeing 90s for highs. Moisture may begin to work its way
northward to Northern ID and Western MT and bring a return of
afternoon/evening thunderstorms.

&&

.AVIATION...
A few weak showers/thunderstorms will linger into the evening
hours over SW Montana and N Central ID, possibly affecting KBTM
and KSMN vicinity. A disturbance moving northward through the area
overnight will bring another chance of showers/thunder to Western
MT and Central ID by mid-morning Tuesday, mostly to KMSO and KGPI,
then impacting all terminals by the afternoon.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$

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