688
FXUS65 KMSO 292000
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
200 PM MDT Sun Jun 29 2025

.DISCUSSION...

KEY MESSAGES:

- Moderate risk of heat impacts for valley areas with warming
  trend under high pressure through Wednesday.

- Thunderstorms return Tuesday south of I-90, with gusty outflow
  winds.

- Strong thunderstorms Wednesday, with risk for isolated severe
  thunderstorms, capable of damaging winds, hail, and heavy rain.

A warming trend remains on track across the Northern Rockies
through Wednesday. Moderate heat impacts are expected by Monday
and Tuesday, with valley temperatures climbing into the low to
mid-90s in Montana and eclipse the century mark in the lower
elevations of Idaho and Clearwater Counties, where a heat
advisory remains in effect.

The initial push of monsoon moisture will arrive late Monday
afternoon and evening, with cumulus expected to initiate across
Lemhi County and southwest Montana. HighRes models suggest
isolated high-based showers will develop Monday evening along the
divide, with little to any precipitation reaching the ground.
These virga type showers will be capable of producing gusty
erratic winds. Forecast PoPs may need to be increased by
subsequent shifts if this trend continues overnight in future
model runs.

Moisture increases further in south-southwest flow Tuesday
afternoon, with high-based thunderstorms forming south of I-90.
Warm, dry sub-cloud layers will fuel gusty outflow winds, with
isolated gusts as high as 50 mph.

Southwesterly flow deepens on Wednesday as a disturbance pushes
eastward across the Pacific Northwest. Model guidance has been
consistent showing atmospheric moisture climbing 125-150% above
normal, fueling modest instability. The approaching disturbance
will provide plenty of lift for widespread convective initiation
across much of the Northern Rockies, with instability and shear
indices supporting strong to isolated severe thunderstorms. Early
looks at vertical profiles suggest the strongest outflow winds
will focus across west-central and southwest Montana, with north-
central Idaho and northwest Montana seeing a greater risk for
heavy downpours and hail.

As discussed previously, the consensus of the models indicate
that the Northern Rockies will remain under southwesterly to
westerly flow through the remainder of the work week into the
holiday weekend. This pattern will be conducive to
afternoon/evening showers and thunderstorms along with
temperatures remaining 5 to 10 degrees above seasonal averages.

&&

.AVIATION...Satellite imagery shows shallow cumulus clouds across
northwest Montana this afternoon, where yesterday`s shower
activity provided sufficient moisture to the boundary layer.
Otherwise, skies remain clear and this will remain the trend
through the evening under high pressure. VFR conditions will
continue into Monday, with cumulus forming across Lemhi County and
Southwest Montana by mid-afternoon.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...Heat Advisory from noon Monday to 9 PM PDT Tuesday for Lower
     Hells Canyon/Salmon River Region...Orofino/Grangeville
     Region.

&&

$$