Sunrise 6:24 AM   Sunset 8:44 PM Moonrise 4:03 AM   Moonset 5:05 PM

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FXUS65 KPIH 052056 AFDPIH

Area Forecast Discussion National Weather Service Pocatello ID 256 PM MDT Sun May 5 2024

SHORT TERM
Tonight through Monday night.
Upper level low moves from southwest corner of state to southeast corner after midnight. Will see rain and snow showers continuing tonight and expect some precipitation to increase as wrap around moisture moves into the eastern areas after midnight and snow levels will likely drop to valley floors once again overnight into Monday morning. Winter weather advisories remain in effect in the eastern highlands and winter storm warning in the Bear River Range. Amounts generally 2 to 4 inches through Monday in the valley locations in the eastern mountains with much higher amounts at pass levels. Expect the potential of 1 to 2 inches of snow in the Snake River Plain overnight into Monday morning. There is less than a 20 percent chance more than that will fall. High probability of no impacts with the snow in the snake plain. Winds will increase in the southern hills, raft river region, Magic Valley and Snake River Plain on Monday and wind advisories have been issued starting Monday morning through Monday early evening.
Speed up to 30 mph and gusts up to 50 mph possible. Lows tonight mainly 20s mountains to mid 30s low elevations and highs in the upper 30s mountains to around 50 valleys on Monday. Lows in the 20s and 30s. Monday night and Tuesday morning.
GK

LONG TERM
Tuesday through next Sunday.
Unsettled and seasonably cool weather will continue into Tuesday as a H5 shortwave trough works through SRN Idaho. This will keep chances for snow going in addition to supporting strong winds as a cold front moves through the region. 30-40 kt 700 mb winds and an enhanced PGF will bring strong winds throughout the day on Tuesday around 20-40 mph with gusts up to 30-60 mph. The strongest winds will be favored around the Magic Valley and Lower Snake Plain region south into Utah and Nevada where locally stronger gusts around that 60-70 mph range will be possible. While additional snowfall amounts Tuesday will be around that T-2" range, locally higher totals will be possible along the Wyoming border region up to around 2-4".

As Tuesday's shortwave trough is absorbed into a much larger H5 low centered over the NRN Plains, isolated to scattered snow showers will continue further north and east as drier conditions return further west. Those precipitation will further decrease for Wednesday as the H5 low over the Plains splits, sending the bulk of its energy east as a secondary H5 low tracks SW over the Great Basin. This will be further aided by a well defined H5 ridge over the ERN Pacific with increased confidence on a Rex Block setting up late next week over the WRN CONUS. As a result, highs in the 30s/40s/50s midweek will increase to the 60s/70s as soon as Friday with the NBM 50th percentile high temperature forecast supporting the potential for some upper 70s and low 80s across our lowest elevations on Sunday. This would likely mean the warmest airmass in place over SRN Idaho that we have seen so far this year with normal highs for mid-May around the upper 50s to upper 60s.

This ridge feature over the West shows little signs of breaking down when taking a look at the EPS as the polar jet shifts further north/west leading to a broad SW/zonal flow over the western CONUS.
The GEFS in contrast takes more of a broad NW/zonal flow route which returns for early the following week leading to the EPS being the warmer model by around 10-15 degrees. This will ultimately come down to the strength and placement of the polar jet which will come into focus over the coming week but at this time, the NBM continues to follow more closely to the ECMWF. Stay tuned and enjoy the warmer weather on the way to round out next week! MacKay

AVIATION
For the 18Z TAFS through 18Z Monday.
Scattered rain/snow showers and isolated thunderstorms along the Wyoming border will continue through this evening as a dry slot shifts overhead. This will lead to more isolated precipitation chances ahead of a cold frontal passage Monday morning. This front will support an uptick in winds and areal coverage of precipitation with predominant snow favored as even colder air builds into the region. MVFR/IFR CIGS/VIS will be continue to be possible at times as bands of moderate to heavy snow move on station.

As a secondary trough begins to move through the PacNW on Monday, lingering instability behind the exiting cold front will support isolated to scattered thunderstorm development for Monday afternoon and evening. The HRRR model probability of thunder 12Z Monday to 12Z Tuesday shows a 40-60% chance at KBYI and KSUN with a 20-40% chance at KPIH, KIDA, and KDIJ. In addition to the strong synoptic winds tomorrow, primary hazards around stronger storms will center around heavy precipitation, small hail, and gusty outflows. MacKay

HYDROLOGY
Flooding has dropped to minor flood stage at the Portneuf River at Pocatello with rising levels back to moderate on Monday after all the precipitation and forecast to continue to be at moderate stage through next weekend. Peak is forecast to reach very near major flood stage on Tuesday. Minor flooding expected to continue for the Portneuf River at Topaz where the gauge remains just below flood stage and will rise above Monday and remain so for several days. Flood warnings also remain in effect for the Blackfoot River near Shelley at Wolverine Canyon with the river remaining at flood stage and also near Blackfoot where the river remains in flood stage. With more precipitation tonight and Monday, rivers will need to be monitored closely.
GK



PIH WATCHES/WARNINGS/ADVISORIES
Wind Advisory from 6 AM to 8 PM MDT Monday for IDZ051-052- 054>057.

Winter Weather Advisory until 6 AM MDT Monday for IDZ056-057.

Winter Storm Warning until 6 AM MDT Tuesday for IDZ060.

Winter Weather Advisory from 9 PM this evening to 6 AM MDT Tuesday for IDZ062>066.

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