584
FXUS65 KMSO 181814
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
1214 PM MDT Sat May 18 2024

.DISCUSSION...Breezy winds have developed due to a tightening
pressure gradient ahead of an approaching trough and low-pressure
center. Although winds are not expected to be as strong as
yesterday, most of the region has a high chance (80-90%) of wind
gusts exceeding 25 mph this afternoon, according to the NBM. High-
resolution model guidance indicates modest instability north of
I-90 this afternoon, leading to showers with a 20% chance of
lightning.

Ensemble and deterministic models agree that the trough will move
into north-central Idaho and western Montana tonight. Showers
associated with this system are forecast to spread into north-
central Idaho overnight. These showers will expand eastward Sunday
morning, with most areas experiencing showers and isolated
thunderstorms by Sunday afternoon. As the trough moves further
south on Monday, central Idaho and western Montana will have
continued below-average high temperatures and another round of
showers and isolated thunderstorms by Monday afternoon. During
this period, snow levels are expected to drop to around 5,000
feet, with light accumulations mainly occurring above around
6,000 feet.

Model clusters and ensemble mean guidance show good agreement for
the Northern Rockies to be between weather systems on Tuesday,
indicating near-normal temperatures and isolated afternoon
showers.

The forecast for Wednesday to Friday (22nd-24th) is trending
wetter, dominated by a broad trough. Eighty percent of model
clusters maintain a closed low weather pattern with cool
temperatures and widespread precipitation. However, there are
still timing and strength differences regarding the potential low-
pressure system, making it difficult to pinpoint specific details.


&&

.AVIATION...All TAF sites across central Idaho and western
Montana have an 80-90% chance of wind gusts reaching at least 22
knots through this evening. This applies to areas in between and
in the high terrain as well. Forecast soundings indicate modest
instability, suggesting showers and isolated thunderstorms will
linger into the evening north of I-90.

The next trough and low-pressure center is on track to move into
the region tonight. This will bring increasing shower coverage
expanding from west to east, lowering cloud cover. Obscured
terrain is expected to become common during Sunday morning.


&&

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

$$