Sunrise 6:38 AM   Sunset 8:33 PM Moonrise 9:56 PM   Moonset 6:12 AM

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FXUS65 KPIH 250910 AFDPIH

Area Forecast Discussion National Weather Service Pocatello ID 310 AM MDT Thu Apr 25 2024

SHORT TERM
Today through Friday Night.
Early morning satellite imagery shows three separate H5 lows across the WRN CONUS and NE Pacific which are located across the Desert SW, WRN Canada, and off the PacNW coast respectively. A split H5 trough overhead with the two inland lows and a series of shortwave troughs continue to the main driver of precipitation and instability in our region with that third low off the coast expected to move onshore tonight into Friday. Isolated to scattered showers and thunderstorms today and tonight will increase in areal coverage for Friday as that PacNW low shifts SE into the Great Basin supporting wrap around bands of moisture heading into the weekend.

Taking a look at the convective environment for today, the HRRR ensemble SBCAPE shows around 200-500 J/kg and 20-30 kts of 0-6km shear with a focus on stronger shear across the Upper Snake Plain and ERN/SRN Highlands. This is where we can expect to see the potential for stronger storms due to a more favorable environment which is in line with the HRRR model probability of thunder showing a 60-80% chance for these aforementioned areas. Further west, those probabilities decrease west to east with a 10- 30% chance of thunder in the CNTRL Mountains/Magic Valley region.
Stronger storms today will be capable of producing wind gusts in excess of 30 mph, hail up to around nickel to quarter size, and brief moderate to heavy rain. Given the HRRR model probability of wind speeds greater than 35 mph remains less than 10% today, the primary hazards today will focus on small to perhaps some larger hail with more organized cells.

Winds aloft will also increase today with 700 mb winds around 20-35 kts supporting gusts around 25 to 40 mph across the Snake Plain and Magic Valley region. Winds for these areas will remain elevated heading into the weekend courtesy of continued breezy 700 mb winds. Highs today will be cooler than yesterday in the 50s/60s and will continue that trend into Friday returning back to the 40s/50s. As we end up getting a colder airmass in place for Friday and Saturday, accumulating snow is expected generally above 7000-8000 feet with an emphasis on highest totals in the CNTRL Mountains. This is especially the case in the Lost River, Lemhi, and Beaverhead Ranges where a 10-30% chance of greater than 12 inches of snow exists through Sunday morning across the highest elevations. MacKay

LONG TERM
Saturday through next Thursday.
Main impacts Saturday will be continuing showers and thunderstorms with most precipitation expected to be in the Snake River Plain and eastern mountains. Very high probability of over a tenth of an inch in those areas on Saturday with much lower chances of wetting rains further northwest in the central mountains. It will dry west to east Saturday night but showers and thunderstorms will continue mainly in the eastern mountains once again Sunday afternoon with lesser chances further west. It will be very cold Saturday with highs only in the 40s and 50s with widespread cloud cover and showers and thunderstorms limiting much rise. It will moderate to near normal Sunday with highs mainly in the 40s and 50s mountains and 50s to lower 60s in low elevations.
Temperatures will warm considerably next week with much lower chances of precipitation Monday through Thursday with only a slight chance of precipitation. Highs in low elevations will be well into the 70s by Wednesday and Thursday. With a fairly strong westerly zonal flow aloft expect breezy to windy conditions Monday through Thursday with the warmer temperatures. GK

AVIATION
For the 12Z TAFS through 12Z Friday.
Another short wave moving through eastern Idaho today will continue chances of showers and thunderstorms mainly this afternoon but will also see some activity this morning. Have a variety of vicinity showers and thunderstorms at all sites through the day. Ceilings will remain VFR and wind speeds at BYI, PIH, and IDA will rise to 10 to 15 knots sustained and 20 to 25 knot gusts later this morning and afternoon. DIJ is the best chance to see sustained showers today. Will continue to have showers and thunderstorms on Friday. GK

HYDROLOGY
Water levels remain elevated on the Portneuf River in Pocatello and Topaz where River Flood Warnings and River Flood Advisories remain in place respectively 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 gauge has also reached action stage and is 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 Thursday morning. MacKay

PIH WATCHES/WARNINGS/ADVISORIES
None.

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