Area Forecast Discussion

KEY MESSAGES

- Not nearly as cold tonight into Monday but a few spots will approach the freezing mark.

- Significant Warming Trend: A major warm-up begins today with high pressure amplifying, returning temperatures to the 70s in lower valleys for the next few days

- Mid-Week Active Pattern: A broad Pacific system is progged to move inland late Tuesday into Wednesday, bringing cooler temperatures and increased precipitation chances to Eastern Idaho.

DISCUSSION

Issued at 115 PM MDT Sun Apr 19 2026

Satellite imagery shows upper low deepening off Pacific coast - will be the expected player by midweek across East Idaho. In the meantime, warming trend already in progress under influence of strengthening ridge with daytime highs rising into the 60s today, then into the 70s for Monday and Tuesday. Overnight lows continue to rise as well. Temperatures across northern portions of the Upper Snake Plain may drop to just above freezing tonight, but will forego any additional headlines in light of recent lows, and the potential for lows to approach freezing again later in the week.

Focus shifts to the incoming system for mid week. Gusty southerly winds develop Tuesday ahead of the low pushing inland, and the deep southerly flow will help temperatures reach the highest of the week. There is some potential to see showers and a potential thunderstorm develop across the Sawtooths and along the Wyoming border Tuesday afternoon, but confidence is low. Increasing chances for showers arrive after midnight Tuesday night, and increase drastically along with isolated to scattered thunderstorms Wednesday. Cold front passage Wednesday brings temperatures back into the 50s, and strong winds remain possible through portions of the Snake Plain.

Unsettled conditions persist into the weekend with continued cool temperatures, a potential return to sub-freezing conditions in portions of the Snake Plain, and snow levels lowering to 4500-5500 ft by the weekend. There are still quite a bit of differences in how the ensembles and clusters want to handle the system as it ejects into south-central Canada, leaving multiple shortwave features rotating around it through Idaho. Timing and depth of these systems will influence the details in the forecast moving forward.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1102 AM MDT Sun Apr 19 2026

Another period of VFR conditions on the way with some increase in higher clouds expected.

PIH WATCHES / WARNINGS / ADVISORIES

None.