140 FXUS65 KPIH 100843 AFDPIH Area Forecast Discussion National Weather Service Pocatello ID 243 AM MDT Wed Oct 10 2018 .DISCUSSION...An upper low is spinning across southern Idaho/northern Utah this morning. The surface cold front is well into southern Utah, however a TROWAL signature can be seen in the mid-level theta-e field across southeast Idaho. The TROWAL becomes less prominent later this morning, and precipitation should taper off significantly as the low continues eastward. Focus this afternoon will shift to the Central Mountains where an shortwave drops into the upper trough over the Northern Rockies. Additional high elevation snowfall will total around 4 to 6 inches above 7000 ft. Snowfall will extend eastward to the Island Park area, which will see an additional 3 to 5 inches of snow through tomorrow morning. The upper trough will deepen over the California coast and form a closed circulation by Friday, while ridging tries to establish itself over the PAC NW. A couple shortwaves will drop in from the northwest east of the upper ridge: one on Saturday, and another Monday night. These should only clip the extreme eastern parts of our forecast area. Temperatures will drop significantly, especially Sunday and Monday mornings, with overnight lows dropping into the 20s, and will likely be a hard freeze for the Burley area and Zone 55. Hinsberger && .AVIATION... Aviation concerns will persist through the period as an area of Low Pressure currently located over northern Utah slowly exits the region, and a trailing disturbance swings southeastward crosses SE Idaho from this evening thorugh the overnight hours. One certainty with today's TAF forecast is that extensive Stratus will be found across the region. There is low confidence on details such as precise ceiling height and subsequent categories for all TAF sites. Currently, IFR Stratus exists across much of the Magic Valley, and this should impact BYI through much of the morning hours, quite likely extending into the early afternoon. Conditions have improved at KSUN, however model cross sections indicate that stratus will re- develop with the generation of up-valley flow, and will follow model trends that indicate the presence of this feature from around 17Z- 03Z or so, with the expectation that the development of typical down- valley flow by late evening should scour the remnants of stratus out of the valley. Cannot rule out SHSN at KSUN either, generally in the 18-00Z timeframe, which could certainly bring degraded CIG and VIS. For PIH, CIG has held steady in the MVFR cat, but anticipate some of the Eastern Magic Valley IFR Stratus may advect into PIH around 12Z. DIJ has escaped much of the impactful clouds, and expect this to continue into early afternoon, when high-resolution models indicate the development of SHSN in the area. It will be difficult to pin down the exact location and timing of this activity, so will hint at the potential for deteriorating conditions. Do know that any heavier SHSN activity will have the potential to bring brief IFR conditions. Expect mainly IFR CIG at IDA today with low-end chance of Stratus from farther south working into the airspace. Finally, model cross-sections strongly hint at the re-development of Stratus across the Snake Plain tonight, mainly after 06Z, with high- end chance for MVFR with some potential for IFR CIGs in this regime. IDA and PIH are most favored to experience this, but cannot completely rule out the possibility at BYI and DIJ. Models insist this Stratus will linger through Thu morning before conditions gradually improve. AD/Hinsberger && .FIRE WEATHER...Widespread wetting Rains have fallen across the area in the last 24 hours, with Pocatello, Stanley, Challis and Burley all setting record Rainfall amounts for Oct 9. Rainfall amounts have approached 1" from American Falls to Burley. Expect Rain Showers and Snow Showers above 5,000 feet elevation to persist thorugh the morning for areas mainly along/south of I-86, with the most activity in the Bear Lake region. This activity will wind down this Afternoon. Additional Snow Shower activity expected this Afternoon and early Evening across the Salmon-Challis NF eastward across the Montana border region, Upper Snake Plain and Targhee NF in/around Pine Creek and Palisades. Drying conditions forecast to take hold for Friday, although min RH forecast to remain well above critical values. Strong cold front forecast to drop south across the region on Saturday. Breezy W/SW winds expected ahead of the front Friday night, with breezy to occasionally windy North winds behind the front on Saturday, with gusts 25-30 mph possible. Light Showers are possible along/behind the front as well Saturday Afternoon and Evening. Cold Temperatures will settle in behind the front for Sunday and Monday. A ridge of High Pressure is then forecast to build across the Pacific Northwest next week, bringing warming Temperatures back to near to above climatological averages by midweek with no Precipitation in sight for the remainder of the week. AD/Hinsberger && .PIH WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 10 AM MDT this morning for IDZ060>063-067. && $$