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000
FXUS65 KPIH 240835
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
235 AM MDT Wed Apr 24 2024

.SHORT TERM...Today through Thursday Night.
Early morning satellite imagery shows a split H5 trough in the NE
Pacific which is expected to shift east and move onshore over the
coming days as a transitory H5 high pressure ridge builds into
the Gulf of Alaska. This trough will lead to increasing
precipitation chances and slightly cooler temperatures over the
coming days with highs in the 60s/70s today and 50s/60s for
Thursday. During this time period, CNTRL and ERN Idaho will remain
situated in between a H5 low in WRN Canada and a secondary H5 low
in the SW CONUS with a series of shortwave troughs in between
these two lows allowing for moisture to build into our area.

While PWATs are only expected to reach around 0.50-0.80",
sufficient SBCAPE of 200-500 J/kg and 20-30 kts of 0-6 km shear
will allow for isolated to scattered thunderstorm development both
this afternoon and again for Thursday afternoon. Stronger storms
both days will be capable of producing outflow winds in excess of
40 mph, small hail, and brief moderate to heavy rain. Isolated
showers will continue to be possible in between these rounds of
storms as conditions remain predominantly dry, especially outside
the afternoon/evening hours.

Winds will remain light today outside of any thunderstorm
outflows courtesy of 700 mb winds staying less than 20 kts with
winds aloft increasing for Thursday as the H5 trough axis shifts
overhead. 700 mb winds around 20-35 kts will support gusty winds
with gusts to around 30 to 45 mph, strongest across the Magic
Valley and Snake River Plain region. As the aforementioned H5
split trough moves east over the Rockies Thursday night, a fast
approaching H5 low to the PacNW will move onshore with similar
timing supporting those elevated 700 mb winds continuing overnight
Thursday into Friday. Isolated to scattered precipitation chances
will then persist each day heading into the weekend. MacKay

.LONG TERM...Friday through next Wednesday.
Upper level trof will bring rain and snow Friday through Sunday.
Snow levels will be around 7 thousand feet. It will be cold Friday
through the weekend. Highs will be mainly in the 40s mountains
and 50s in low elevations. Lows will be in the 20s and 30s. Will
dry out a bit as flow aloft goes more zonal Monday into next
Wednesday. Weak short waves will keep the threat for showers going
but low chances and nothing more than isolated to scattered
coverage in the region. Will see a warming trend with highs in the
50s mountains and 60s valleys. Expect breezy to windy conditions
Sunday through Wednesday as strong westerly to southwesterly flow
aloft continues through the period. High elevation snow amounts
have a shot to go above 6 inches Friday through Saturday night
above 8 thousand feet and pass levels and peaks. Highest
precipitation amounts will be in the eastern mountains where a 50
percent chance of 0.5 inches liquid precipiation may fall. Main
impact in the long term will be precipitation early on Friday
through the weekend. GK

&&

.AVIATION...For the 12Z TAFS through 12Z Thursday.
A short wave and instability will produce showers and
thunderstorms this afternoon. For now have vicinity showers and
thunderstorms at all TAF sites today with the thunderstorms after
18Z. Winds will be light today outside of any thunderstorm
outflow. Will have mainly mid level ceilings but VFR conditions
will continue. 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
has also recently 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 early Wednesday morning. MacKay

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$