textproduct: Boise

LONG TERM

The progressive pattern remains through the long term, with multiple looks at precipitation from active upper- level troughing. A closed upper-level low will continue its march from California into the Great Basin Wednesday, with another upper-level low swinging around it off the California coast. These individual closed lows look to combine into broader upper-level troughing late Wednesday, placing the western CONUS under longwave troughing. This feature will slowly move east into the Four Corners region by Friday. This pattern will keep precipitation chances through the midweek, with models disagreeing heavily on magnitude. By Friday, brief upper- level shortwave ridging will move quickly over the area, before another storm system moves into the Pacific Northwest late Friday into Saturday. Forecast confidence is low with nearly all aspects of these systems, except the general pattern as clusters have been supporting this solution for a few days/runs. Confidence in the extent of cold air to support winter precip, precip coverage, precip amount, etc. should increase in the coming days.

AVIATION

VFR. MVFR-IFR conditions to develop Sun morning across E OR and Central ID from lowering ceilings and precipitation. Snow levels 6-7 kft MSL. Precipitation coverage increases Sun afternoon/evening following cold front, bringing MVFR- IFR conditions to lower elevations. Mtns obscured in precipitation/low ceilings. Surface winds: variable under 10 kt, becoming SW-SE 5-15 kt Sun afternoon, with gusts 25-35 kt in SE OR. Winds aloft at 10kft MSL: W-SW 25-40 kt. LLWS concerns Sun evening.

KBOI...VFR. Slight chance (5-15%) of MVFR in rain/lowering ceilings Sun evening. Surface winds: SE 5-10 kt Sun morning, increasing to SE 7-12 kt Sun afternoon, becoming W-NW 10-15 kt Sun evening. LLWS concerns Sun evening.

LONG TERM...Wednesday through Sunday

We plan to end the Air Stagnation Advisory at 10 AM MST this morning, as winds and mixing heights increase ahead of an approaching Pacific cold front. Stronger winds along the front and widespread rain late Sunday will fully scour and/or cleanse any lingering stagnant air left in the valleys.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Air Stagnation Advisory until 10 AM MST this morning IDZ012-014-016-033. OR...Air Stagnation Advisory until 10 AM MST /9 AM PST/ this morning ORZ064.