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.
&&

$$