819
FXUS65 KMSO 171841
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1241 PM MDT Sat Aug 17 2024

.DISCUSSION...High pressure remains over the region today,
bringing generally sunny skies, light winds and warm temperatures
to the region. Cloud cover will increase tonight into Sunday as a
wave of mid level monsoonal moisture advects northwards into
western Montana and north central Idaho. Forecast models have
begun to show potential for some light showers and isolated
thunderstorms associated with this wave as it moves through
northwest Montana early Sunday morning, thus the probability of
precipitation has been increased for these areas. In addition,
with high pressure generally off to the east and low pressure to
our west, a north east to easterly gradient will develop tonight.
It doesn`t look overly strong, but will be enough to help limit
any fog development for Sunday morning.

Monsoonal moisture will continue to be drawn northwards into the
Northern Rockies region Sunday into Monday. Afternoon and evening
showers and thunderstorms are anticipated both days, primarily
across western Montana, though a few storms could form in the
higher terrain of north central Idaho near the Bitterroot Divide.
The main threats with storms will be gusty outflow winds of 40 to
50 mph, lightning, small hail and brief heavy rain.

For Tuesday and Wednesday next week, forecast models show the
upper level flow becoming more southwesterly as a persistent area
of low pressure develops off the west coast of Washington and high
pressure shifts slightly east of the Four Corners area. While
afternoon and evening thunderstorms will be possible in this
pattern, the region largely appears to get cut off from monsoonal
moisture surges, and thus convection looks to be more isolated and
focused across southwest Montana. Near normal temperatures and
breezy conditions can be expected area wide.

There is still significant spread in the forecast models with how
the low pressure system in the Pacific Northwest will eject
inland mid to late next week. Differences exist both in the
timing of this occurring as well as how it occurs (weaker open
wave vs a more significant closed low type feature). Most
solutions lean towards cooler temperatures, but the amount of
precipitation (and timing of when precipitation may occur) is
very much in flux.

&&

.AVIATION...High pressure will bring mostly sunny skies through
this evening across western Montana and north central Idaho.
Local/regional fires in Idaho will likely send another plume of
elevated smoke into central Idaho and Northwest Montana, which
may result in locally lowered visibility. A wave of mid level
monsoonal moisture will move into the region late tonight into
Sunday morning, bringing an increase in cloud cover for the mid
levels. A few showers and possibly even a thunderstorm are being
shown by high resolution models across northwest Montana late
tonight between 18/0600z and 18/1200z. Also of note, a northeast
to east gradient is expected late tonight into early Sunday, which
could produce some breezes up to 10 to 15kts for exposed
locations, including KGPI and KMSO.

&&

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

$$