461 FXUS65 KPIH 260920 AFDPIH Area Forecast Discussion National Weather Service Pocatello ID 320 AM MDT Fri Apr 26 2024 .SHORT TERM...Today through Saturday Night. Early morning satellite imagery shows a H5 low off the PacNW Coast which is expected to track SE throughout the day today into the Great Basin before ultimately shifting onto the Great Plains this weekend. This system will be the driver of precipitation and instability overhead in addition to a return to seasonably cool temperatures, supporting isolated to scattered showers and thunderstorms regionwide through Saturday night. With this, we will see predominant valley rain and a mix of rain/high elevation snow in the mountains. Best chances for accumulating snow will remain above 8000 feet across the higher summits of the CNTRL Mountains, especially in the Lost River, Lemhi, and Beaverhead Ranges where a 10-30% chance of 12 inches of snow or more exists above 9000 feet. The latest QPF/rainfall forecast through Saturday night remains in line with previous forecasts showing 0.25-0.75" of rain in the valleys outside the Magic Valley and WRN CNTRL Mountains where amounts should remain less than 0.25". Heading up into the mountains, those totals should be closer to 0.50-1.50" dependent on elevation. With respect to the convective environment over the next couple of days, the HREF model shows ensemble SBCAPE around 200-400 J/kg for both Friday and Saturday but does show the highest 0-6km shear we have seen so far this week today around 20-40 kts. That shear profile will support stronger storms today with weaker storms tomorrow as the 0-6km shear decreases for Saturday aided by the exit of a H5 low over the CNTRL Rockies. Stronger storms today will be capable of wind gusts in excess of 30 mph, hail up to nickel size, and moderate to heavy rain. As seen with storms yesterday, accumulating small hail may lead to hazardous travel conditions at times with more organized storms. In addition to precipitation chances, this H5 low passing to our south with aid in elevated winds out of the west around the Magic Valley and out of the north across the Upper Snake River Plain supporting gusts to around 30-45 mph. Winds elsewhere will remain lighter, generally seeing gusts less than 25 mph outside of any convection. Highs both today and Saturday will be in the 50s to low 60s with overnight lows above freezing each night outside of some our colder, high elevation mountain basins. MacKay .LONG TERM...Sunday through next Friday. Will remain fairly active with breezy to windy conditions through the period as flow goes more zonal. Will have lingering showers Sunday mainly in the eastern mountains behind exiting system and another upper trof will move through Monday with more widespread showers and thunderstorms. Operational models diverge greatly after the system Monday with the blend going with some drying Tuesday and Wednesday with mainly mountain showers and then more widespread scattered showers on Friday. Highs will be in the 40s mountains and 50s to near 60 valleys on Sunday through Tuesday which is slightly below normal to near normal. It will be above normal then Wednesday through Friday with low elevations near or into the low 70s with Thursday the warmest day with the low 70s widespread in the Snake Plain and eastern Magic Valley. With the system Monday will have widespread wind speeds sustained in the 20 to 25 mph range especially in the Snake Plain with gusts 30 to 40 mph. GK && .AVIATION...For the 12Z TAFS through 12Z Saturday. Little will change today as will have showers and thunderstorms once again but coverage will isoalted to scattered in the morning and have vicinity most locations. Showers will likely become more widespread overnight and may include predominant conditions especially at DIJ. May see occasional MVFR ceilings there in heavier showers but for the most part will remain VFR at all sites. Expect 10 to 15 knot sustained winds at BYI,PIH, and IDA today with gusts 20 to 25 knots. GK && .HYDROLOGY... Water levels remain elevated on the Portneuf River from Pocatello to Chesterfield Reservoir where River Flood Warnings remain in effect until further notice. Minor to moderate flooding is expected or ongoing in these areas with both locations forecast to crest this weekend before dropping slightly heading into early next week. Further north and west along the Snake River, water managers have increased releases from upstream reservoirs leading to high flows in excess of 10,000 cfs downstream from Palisades to Milner. The Snake River near Heise and Snake River at Lorenzo gauges have also reached action stage and are forecast to be at that stage until further notice due to releases from Palisades. Willow Creek below Tex Creek above Ririe Reservoir and the Blackfoot River above Blackfoot Reservoir both also continue to be in action stage since Monday with no major impacts seen elsewhere in our CWA as of Friday morning. MacKay && .PIH WATCHES/WARNINGS/ADVISORIES... None. && $$ |