textproduct: Boise

DISCUSSION

Updated lower PoP today through this evening to better align with latest radar and satellite imagery, and QPF. Added a slight (10-15%) chance of afternoon/ evening thunderstorms in southern Harney and Malheur Counties, similar to latest SPC forecast. The main pcpn (rain below 7000 feet) will fall tonight through Monday morning as a Pacific upper low comes inland across northern California and Nevada. After sunny, mild wx Tuesday, a cold front Wednesday morning will begin a change to showery, colder wx with rapidly lowering snow level.

AVIATION

Showers increase from the S to N today. Moderate precip rates possible this afternoon coincide with a 10% chance of lightning in SE OR and near the ID/NV border. With snow levels at 7-8 kft MSL, surface precip at TAF sites will be rain. Ceilings trend towards MVFR this evening, and tonight through tomorrow morning may drop to IFR. Surface winds: Variable up to 12 kt, localized gusts up to 20 kt near strong showers. Winds aloft at 10 kft MSL: SW 5-20 kt.

KBOI...Low VFR and overcast, as light rain picks up this afternoon and remains through tomorrow ceilings drop to MVFR. Brief moderate rainfall possible in stronger showers this afternoon. Winds remain light and variable.

PREV DISCUSSION

SHORT TERM...Today through Tuesday night...A weak system off the CA coast will slowly track inland with scattered showers (30-50% chance) this afternoon and a 10-15% chance of thunderstorms across eastern OR. Snow levels range from 7000-8500ft with this system. Minimal snow accumulations expected over the mountains. Showers and thunderstorms Sunday and Monday afternoon have the potential to produce gusty outflow winds up to 30-40 mph. Scattered showers continue into Monday afternoon as the system slowly tracks across NV/UT and into WY. Conditions dry out by Monday night. Upper level ridging returns on Tuesday ahead of the next system. Temperatures Tuesday will be the warmest of the period, with low to mid 60s possible across the Snake Basin, or around 10 degrees above normal. Surface winds shift to the southeast and become breezy ahead of an approaching trough.

LONG TERM...Wednesday through Sunday...Widespread precipitation is expected come Wednesday, as an upper level trough and its associated cold front crosses our area from west to east. Snow levels Wednesday morning will start out at 5.5-6.5 kft MSL, before lowering to 3.5-4.5 kft following the frontal passage. Precipitation chances will remain elevated across higher terrain Thursday and beyond, with orographic lift being the main driver in the moist northwesterly flow. High pressure building in over the North Pacific and into our area will support a warming trend beyond Thursday. Uncertainty in regard to precipitation chances increase next weekend. As high pressure continues to build in the Pacific, and a low closes off near the Baja Peninsula, the question becomes where our area will be situated in relation to the low and the jet stream aloft. Latest deterministic guidance is favoring the ridge extending east over our area, keeping the main storm track north. Precipitation trends in ensembles are beginning to reflect this, with the GFS ensemble backing off on precip (outside of the west central Idaho mountains) over the last two runs. The Euro ensemble is still holding on, but in the latest run is trending downward in regard to QPF. For now, am maintaining elevated precipitation chances area-wide come Sunday afternoon.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None. OR...None.