Area Forecast Discussion
Issued by NWS Pocatello, ID
Issued by NWS Pocatello, ID
000 FXUS65 KPIH 162012 AFDPIH Area Forecast Discussion National Weather Service Pocatello ID 212 PM MDT Mon Sep 16 2024 .DISCUSSION... Afternoon satellite imagery shows a potent upper low moving across northern Nevada this afternoon. Out ahead of this feature, satellite imagery shows mostly cloudy to cloudy skies across much of eastern Idaho. This will be the last warm day we see for the next week. Expecting scattered showers and thunderstorms this afternoon with some storms capable of producing gusty winds to around 50 mph. Precip will trend more towards widespread showers and isolated thunderstorms overnight and into the day tomorrow as the low settles over the region. Temps will be noticeably cooler tomorrow with valley locations struggling to get above 60 with most areas expected only to top out in the 50s tomorrow. Storm total QPF amounts through Wed AM are expected to reach 0.15 to 0.40 inches in lower elevations like the Snake Plain and Raft River area, and 0.50 to 1.00 inches across many of our mountain ranges...which should damper ongoing wildfire activity. The first low moves to the northeast on Wednesday while a second low shifts into the Great Basin and takes a few days to travel slowly east towards the Four Corners by the weekend. Looks like the bulk of the moisture will be to our south with this second low. We do carry low end PoPs (20-30%) for southern and eastern parts of the forecast area though as we could squeeze out just a little bit of precipitation. The low will help to keep things on the cooler side of normal through the remainder of the work week. Once we get into the weekend, and early next week, not much confidence in the upper level pattern in place over the region. Operational GFS/ECMWF continue to trend warmer and drier but ensemble clusters still show some potential for a trough to move over the region. Until we see better agreement, it`s hard to have too much confidence in the weekend forecast. NBM has trended slightly warmer over the last 24 hours, but not much. Current forecast still relies on the NBM given all the uncertainty, a blend of solutions appears to be the best bet but things could change warmer or cooler depending on which scenario wins out. McKaughan && .AVIATION...For the 18Z TAFS through 18Z Tuesday. Predominant VFR conditions will continue for Monday as wet Pacific low pressure system continues to build in overhead. This will lead to an uptick in showers and thunderstorms regionwide this afternoon and evening of which will continue overnight and throughout the day on Tuesday. The HREF model probability of thunder from 21Z Monday through 12Z Tuesday shows a 60-70% chance at all terminals with a 60- 80% chance 12Z Tuesday through 12Z Wednesday. Stronger thunderstorms both today and tomorrow will support heavy rain and wind gusts to around 30-45 kts, bringing brief MVFR potential as convection moves on station. As this system works directly overhead on Tuesday, look for lower CIGS as shower and thunderstorm chances persist. MacKay && .FIRE WEATHER... A wet Pacific low pressure system remains on track to shift NE through the Great Basin tonight before becoming directly overhead for Tuesday. Scattered to widespread showers and thunderstorms are expected starting later today of which will continue overnight tonight and throughout the day on Tuesday, supporting wetting rains regionwide. Cooler temperatures will accompany this system with highs across our lower elevations in the 50s/60s and 30s/40s in the higher terrain, bringing accumulating mountain snow generally above 8500-9000 feet. Both today and tomorrow, stronger more organized showers and thunderstorms will be capable of producing wind gusts to 40-60 mph, heavy rain, and small hail. As this system departs NE into Montana Tuesday night into Wednesday, best precipitation chances will also shift NE as drier conditions build in from the SW. Isolated precipitation chances will then continue starting Thursday through the weekend as a secondary Pacific low moves onshore to California and tracks east across the Great Basin. Given this southerly track in comparison to our system earlier in the week, less precipitation is expected but it will keep temperatures seasonably cool courtesy of zonal/NW flow with sufficient lift and moisture to at least support isolated showers and storms, primarily in the mountains. Starting late this week into the weekend, a ridge of high pressure remains favored to build into the NE Pacific which will allow for a shift in the H5 jet, turning the bulk of moisture north as warmer and drier conditions prevail. Will see exactly how model guidance evolves this week as there has been some back-and- forth with a wetter and drier solution, but our latest forecast will favor the drier and warmer side of things to round out this week into next week. MacKay && .PIH WATCHES/WARNINGS/ADVISORIES... None. && $$