Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 250759

Area Forecast Discussion
National Weather Service Missoula MT
159 AM MDT Tue Jun 25 2024

.DISCUSSION...Warm and dry conditions continue through Wednesday
morning, then things become interesting. Currently, there is an
air mass of anomalous PWs over Arizona and southern California.
When we use the term PW or in this case anomalous PW, we are
talking about precipitable water, this is the amount of available
moisture for precipitation. This air mass will drift northward
tomorrow and into Wednesday morning. Expect high clouds during the
morning Wednesday and a couple high resolution models are
introducing warm frontal showers before noon, although a dry
surface may only allow for virga showers or sprinkles.

By the afternoon, mid-level instability increases across the
region and showers and thunderstorms develop. Looking at the
makeup of the atmosphere 2 things stand out, initially a dry
surface layer and then a deep saturated layer late afternoon.
Initial showers or storms will likely have gusty outflow winds
especially from southwest MT, Butte, through Lemhi County, ID.
Then as the atmosphere moistens up there is the potential for
heavy rainers. These storms should have good movement off to the
northeast so at this time isolated, brief but heavy showers is the
threat late afternoon.

Thursday as the low pressure moves north of our region, jet
dynamics along the base of the trough will allow for widespread
precipitation. Due to the convective nature of this system, exact
precipitation totals are difficult but the mountains have a 50%
chance of receiving 0.25 inch, while valleys especially north of
I-90 have a 10 to 20% chance.

Friday showers and thunderstorms continue along the Continental
Divide, while the rest of us enjoy a not as warm day with north
to northeasterly breezes.

Saturday a transient ridge will allow for a drier day, with
temperatures 70s and 80s in western Montana (mostly cloudy) and
upper 80s and 90s in north-central, ID (mostly sunny).

July 1st and 2nd, another system affects the region but details
are still lacking.


.AVIATION...The Northern Rockies air space will be under the
influence of a transient ridge today. Expect light breezes and VFR