547
FXUS65 KMSO 050709
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
109 AM MDT Fri Jul 5 2024

.UPDATE...Forecast confidence and details in the upcoming
prolonged heat wave remains steady. Thus, no changes are
necessary to the previous discussion.

&&

.PREV DISCUSSION... /ISSUED 123 PM MDT Thu Jul 4 2024/

DISCUSSION...With some unsettled weather over the Midwest and a
massive ridge of high pressure over the eastern Pacific, the
Northern Rockies will stay under northwest flow aloft heading into
the weekend. The implications will be minor. Expect some
increasing northwest winds this evening. Temperatures will
gradually increase. A shortwave trough will bring some chances
(about 20%) for showers and thunderstorms to northwest Montana on
Saturday afternoon.

Impactful weather will start later in the weekend as the ridge of
high pressure over the eastern Pacific shifts eastward.
Confidence is high that a heatwave will affect the Northern
Rockies through next week. The middle of next week looks to be
the hottest period, with valleys in central Idaho hitting the
100-115 degree range and western Montana valleys reaching 90-105
degrees by next Wednesday (July 10th). Expect nighttime
temperatures to cool only into the 50s to 60s, which will make it
difficult for those without air conditioning or other means of
cooling down to find relief from the heat.

As upper level flow transitions back to the southwest later in
the week, embedded moisture will bring chances for afternoon
thunderstorms by about Thursday.

&&

.AVIATION...High pressure builds today across the Northern Rockies
and will remain in place for several days. With a lingering
northwesterly breeze, expect most terminals to see an afternoon
wind pick up between 05/2100Z and 06/0300Z.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...     Excessive Heat Watch from Tuesday afternoon through Friday
     evening for Kootenai/Cabinet Region...Lower Clark Fork
     Region.

ID...Excessive Heat Watch from Monday afternoon through Friday
     evening for Northern Clearwater Mountains...Southern
     Clearwater Mountains.

     Excessive Heat Warning from noon Tuesday to 11 PM PDT Friday for
     Orofino/Grangeville Region.

     Excessive Heat Warning from noon Monday to 11 PM PDT Friday for
     Lower Hells Canyon/Salmon River Region.

&&

$$