691
FXUS65 KMSO 210725
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
125 AM MDT Fri Jun 21 2024

.DISCUSSION...A weak disturbance and mid level moisture in
westerly flow will bring a few sprinkles this morning. There may
even be a predawn rumble of thunder from Clearwater County into northwest
Montana with a few lightning strikes already observed in the
Idaho Panhandle early this morning. Instability increases by early
afternoon (CAPE values near 500 J/kg), leading to scattered
showers and few thunderstorms, mostly for northwest Montana and
along the Divide, diminishing around sunset. Given the deep dry
layer from the surface to near 11,000 msl, any thunderstorms will
be capable of gusty outflow winds.

A weak ridge of high pressure briefly builds over the Northern
Rockies this weekend, that will allow for afternoon temperatures
to run around 15 degrees above normal. High temperatures will
reach into the mid/upper 80s in western Montana valleys, and
mid/upper 90s lower elevations of north-central Idaho. As the
ridge breaks down on Sunday afternoon, gusty westerly winds are
expected. Probabilities have increased to 40-60% for gusts over 30
mph in the valleys of western Montana and Lemhi County. Those
planning activities on area lakes should prepare for choppy
conditions. Daytime temperatures cool several degrees and breezy
afternoon winds continue Monday, rain chances remain near zero.

Ensemble clusters (about 80%) continue to trend toward ridging
Tuesday and Wednesday of next week. As a result, high temperatures
have also trended warmer, once again around 15 degrees above
normal. Also, expect breezy westerly winds with gusts of 20-30
mph each afternoon.

Nearly 100% of ensemble clusters support a trough knocking down
the ridge late next week (27th-29th). Details are somewhat scarce
but a general consensus points toward daytime temperatures
returning to seasonable levels with an increase in precipitation
chances. Interesting to note, the probability of widespread,
significant rains (> 0.50") has increased to 15-25% across the
Northern Rockies but much will depend on how far south the trough
digs. The more realistic expectation at this point is for
scattered showers and thunderstorms to bring spotty rain
accumulations.


&&

.AVIATION...A weak disturbance and mid level moisture in westerly
flow will bring a few sprinkles this morning. There may even be a
predawn rumble of thunder from Clearwater County into northwest
Montana with a few lightning strikes already observed in the Idaho
Panhandle early this morning. Instability increases by early
afternoon (CAPE values near 500 J/kg), leading to scattered
showers and few thunderstorms, mostly for northwest Montana and
along the Divide, diminishing around sunset. Of the terminal
sites, KGPI has the best opportunity at a shower or storm in the
vicinity after 20Z.

Aside from gusty outflow winds near thunderstorms, deep mixing
will allow for afternoon gusts of 15-20 kts at terminal sites with
gusts diminishing quickly around sunset. VFR conditions continue
on Saturday with dry conditions.


&&

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

$$