491 FXUS65 KPIH 030326 AFDPIH Area Forecast Discussion National Weather Service Pocatello ID Issued by National Weather Service Boise ID 826 PM MST Tue Feb 2 2021 .DISCUSSION...Cold front and showers making steady eastward progress across southern Idaho this evening. At 800 PM MST the leading edge of showers was in Camas and Jerome Counties. Expect brief wind gusts 30 to 40 mph and a wind shift to southwest or west as the cold front passes just before the showers begin. The front and showers will reach the eastern Magic Valley by 900 PM and Pocatello around 1 AM. Showers will start as rain in the Magic Valley but change to snow shortly after midnight. Otherwise all snow is expected with light accumulations overnight in the Upper Snake Plain but several inches in the mountains. Precipitation should last 4 to 6 hours followed by partial clearing, breezy, and colder weather Thursday. LC && .AVIATION...VFR becoming MVFR and locally IFR as cold front and showers approach from the west, reaching KBYI 04Z and KPIH 09Z, then continuing east. Mountains becoming obscured. Showers will be initially rain at KBYI but will change to snow behind the cold front. Elsewhere only snow. Surface winds SW 15-25 kt becoming WSW 20-30 kt behind the front and during showers, then decreasing to 15-25 kt. LC && .PREV DISCUSSION... SHORT TERM...Tonight through Thursday night...Upper trough has been slow to move inland. Precipitation has started to move into the Central Mountains per area web cams. Frontal boundary still west of the state but precipitation starting to fill in ahead of the front per radar imagery. Aside from the slightly lower start, trough and precipitation progression appears to remain on track. Snow continues to target higher elevations primarily Central Mountains and Eastern Highlands. Warm southerly flow has induced very warm temperatures in lower elevations, especially along and south of I-86. Precip shifts into the Snake Plain and eastern highlands around/after midnight, and temperatures may be warm enough to the south for precipitation to at least start as rain. NAM soundings support burst of moderate snow along the front as it passes through Pocatello. Given the strong warming this afternoon, may be more difficult to lower temperatures enough to accumulate any meaningful snow in the Pocatello region before sunrise, but character should shift to all snow with frontal passage. Surface winds increase behind the front and will be quite breezy, but blowing snow may be minimized if the temperatures can stay warm enough. Upper trough shifts through during the afternoon. This may not be well picked up with the short term ensembles yet, and will be feature to watch over the next forecast cycle or two. Otherwise will likely see additional light snow showers continue over higher elevations into late Wednesday. Cool northwest flow is in place for Wednesday night into late Thursday. Reinforcing shortwave arrives from the northwest Thursday night, producing upslope snows in portions of the central mountains and most of the eastern and southern highlands into Friday. DMH LONG TERM...Friday through next Tuesday. The long term portion of the forecast will be characterized by persistent northwest flow, at least through Monday or so, as central and eastern Idaho will remain in between a ridge of high pressure across the eastern Pacific and a strengthening polar vortex near the Great Lakes and northern Great Plains. A disturbance embedded in the flow will pass through the region on Friday. Snow showers will be ongoing by daybreak Friday morning across the eastern highlands/WY border region and also across the central Idaho mountains. The western edge of the snow shower activity is a bit uncertain and will straddle the I-15 corridor, so it is possible that snow showers activity could extend west to the Pocatello to Idaho Falls corridor during the day Friday. Snow shower activity should peak in coverage and intensity midday, then gradually wind down through Friday night. A second, weaker disturbance will briefly re-invigorate snow shower activity over the same locations late Friday through Saturday. A few inches of snow are expected across the eastern highlands during this period. From Saturday night through much of Monday, lingering moisture within the NW flow pattern will promote a continuation of occasional light snow showers over the same areas. WPC clusters generally indicate decent confidence in this pattern, with lesser likelihood for the ridge to take hold over the western U.S., as some earlier solutions were suggesting. One interesting trend to watch is there is a slight nod toward a trend indicating the southwest portion of the cold air associated with the above-mentioned polar vortex could reach farther west into Montana and Wyoming. This scenario could bring arctic air as far west as the Continental Divide, along with the potential for much colder temperatures than currently forecast across portions of east Idaho (particularly near the Montana border) from Sunday into early next week. This is something that will bear watching, but at this point the going forecast reflects the most likely scenario as it stands currently. The forecast becomes less certain at the end of the forecast period as it appears the upper pattern will begin to break down and evolve. AD && .PIH WATCHES/WARNINGS/ADVISORIES... None. && $$