Area Forecast Discussion
Issued by NWS Pocatello, ID
Issued by NWS Pocatello, ID
677 FXUS65 KPIH 171944 AFDPIH Area Forecast Discussion National Weather Service Pocatello ID 144 PM MDT Tue Sep 17 2024 .DISCUSSION... An upper low in place over the region is bringing waves of showers/storms throughout eastern Idaho this afternoon. Widespread clouds and precip have kept temperatures in 40s and 50s throughout the area and the cooler than normal temperatures look to stick around through the forecast period, although they will slowly moderate over the days ahead. Today will be the coolest and wettest day though as the low continues to pivot overhead on its way to Montana by tomorrow morning. PoPs will slowly diminish from SW to NE over the next 24 hours or as the low departs to the east. That being said, most of the precipitation will be today but we could see a few additional hundredths across the upper Snake and up towards Island Park during the first part of the day Wednesday. A second low will move into the Pacific NW tomorrow and traverse through the Great Basin throughout the remainder of the work week. As has been the case for the past few days, looks as if the bulk of the moisture will stay to our south. In fact, models have continued to trend drier and we`ve seen the PoPs for Thu and Fri get trimmed back for most spots although we could still squeeze out an isolated shower or two. The cooler air will be reinforced though with the upper flow aloft remaining predominantly out of the north. Temperatures will slowly moderate into the weekend but will remain on the cooler side of normal. Later this weekend and into next week, there remains disagreement amongst model ensembles on the upper level pattern over the region but clusters are slowly trending towards more of a ridge solution. This would keep us on the warmer side and dry but for now, will maintain NBM blend since things certainly aren`t set in stone just yet. If the trends hold, I`d imagine forecast temps creeping up a few degrees from their current values. Something to keep an eye on over the days ahead. McKaughan && .AVIATION...For the 18Z TAFS through 18Z Wednesday A mix of VFR/MVFR conditions are expected this afternoon through Wednesday morning as a wet Pacific system shifts directly overhead. Scattered to widespread showers and thunderstorms will continue to shift NE into tonight, bringing progressively drier conditions in from the SW through the overnight hours. Where there are some clearer skies and drier conditions building in, low stratus and fog will be possible and will allow for further MVFR/IFR CIGS/VIS at times, particularly Wednesday morning. Isolated to scattered showers and thunderstorms will continue for Wednesday with best chances around KIDA, KSUN, and KDIJ. MacKay && .FIRE WEATHER... A wet Pacific low pressure system working directly overhead today will support continued scattered to widespread showers and thunderstorms with wetting rains expected 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. 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. Flash flooding potential will exist on burn scars given locally heavier rain from more organized showers and thunderstorms. Precipitation will trend more isolated to scattered starting Wednesday and shift northeast before becoming much more isolated in nature starting Thursday through the weekend. As a generally weak unsettled pattern persists over our region, a secondary Pacific low will moves onshore to California and tracks east across the Great Basin. Given this southerly track in comparison to our system earlier in the week, little to no 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 each day, 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. Our next chances for precipitation will depend on this ridge feature and how it responds to several H5 troughs that look to move onshore for next week starting midweek. MacKay && .PIH WATCHES/WARNINGS/ADVISORIES... None. && $$