Sunrise 5:51 AM   Sunset 9:16 PM Moonrise 3:20 PM   Moonset 2:57 AM

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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.

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