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000
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 HREF
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 HREF 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 HREF 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.

&&

$$