textproduct: Boise

LONG TERM...Friday through Tuesday

The high pressure center will continue to track northward towards British Columbia through the weekend, keeping the Western US in a vise grip of stable conditions. Temperatures will continue to stay similar to the last week, with slight cooling each day dependent on low cloud cover and fog through the weekend. Mountain valleys will continue to be very cold overnight, with lows expected to be in the teens to single digits each night.

Relief from the stagnant conditions looks to come late next Tuesday into Wednesday with an upper level trough bringing chances of precipitation and increased mixing. Ensemble members of the ECMWF/GFS show varying degrees of precipitation and timing of the next system, but there is generally good agreement in the breakdown of the ridge by the end of next week.

AVIATION

VFR. Patchy fog/low stratus developing by 12Z and mixing out by late morning, mainly in sheltered mountain- valleys and lower basins. MVFR-LIFR and mountain obscuration in fog/low stratus. Surface winds: variable up to 8 kt. Winds aloft at 10kft MSL: NW 10-25 kt.

KBOI...Primarily VFR with fog in the vicinity. Brief LIFR/VLIFR is possible in fog that creeps toward the terminal, but confidence is very low with the latest forecast (10% chance). Clearing after Tue/16Z. Surface winds: light and variable.

AIR STAGNATION

High pressure will keep a persistent inversion in place across the region. Surface winds will remain light less than 10 mph with very low mixing heights (between 1000-2000 ft AGL). This will keep patchy fog, cool temperatures, and trapped pollutants in these sheltered valleys due to limited mixing. The Air Stagnation Advisory remains in effect for all valley zones in southeast Oregon and southwest Idaho through Monday 5 AM.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Air Stagnation Advisory until 5 AM MST Monday IDZ011>014-016-028-033. OR...Air Stagnation Advisory until 5 AM MST /4 AM PST/ Monday ORZ061>064.