715
FXUS65 KPIH 051421
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
821 AM MDT Sun May 5 2024

.UPDATE...
Snow has moved into the Eastern Magic Valley and Lower Snake River
Plain and updating for that.
GK

&&

.PREV DISCUSSION... /issued 302 AM MDT Sun May 5 2024/

SHORT TERM...Today and Monday
Hopefully you were able to get out and enjoy the sunshine and warmth
on Saturday because there won`t be any of that for awhile. A potent
storm system has already begun to impact the region this morning and
these impacts will be felt throughout the days ahead. Early morning
satellite imagery shows a potent low in place across south-central
Oregon and the center of this feature will move along the 42nd
parallel over the next 24-36 hours. Winds remain gusty ahead of a
frontal boundary and a Wind Advisory will expire at 4AM across the
South Hills this morning. The temperature gradient along the
aforementioned boundary is quite apparent with temps in the 60s at
PIH and IDA with Boise and Twin Falls sitting in the 40s. Rain will
continue to overspread the region with snow expected above 5500 to
6000 feet. Winter Weather Advisories continue for a handful of
mountain zones across the region with a Winter Storm Warning in
place across the Bear River Range. As we get into late tonight and
into Monday morning, expecting snow levels to drop even further
to the valley floors of the Snake Plain. Could see some very light
snow accumulations here. As far as temperatures are concerned
today, they will run 15-25 degrees colder than Saturday. Highs
will generally be in the 40s this afternoon with clouds, rain/snow
and wind. Not a pleasant day by any means. Monday looks very
similar to Sunday with continued clouds, rain and wind. McKaughan

LONG TERM...Tue through Sat
Tue appears once again rainy and snowy, but by Tue night the
precipitation threat starts to life from southwest to northeast.
By late night Wed the threat is nearly gone. After this time,
there is limited showery activity limited to afternoon and early
evening hours in the eastern highlands for every afternoon through
the period. But it`s all slight chance, and actual locations will
be hit or miss. On Tue/Tue night/Wed, the upper level trough and
associated cold front is still driving through all of eastern
Idaho, which triggers the instability for thunderstorms and
continued very windy conditions in the eastern Magic Valley and
southern hills, with windy conditions elsewhere.

By Thu, the upper level low has shown a retrograde motion to south
of the forecast area and a high building to the north in a Rex block
pattern. At the beginning the airflow is northerly and cold with
freeze conditions possible in the Agricultural areas for Tue night,
and possible Wed night. Strong sunshine will modify temperatures
strongly, with a return to near to above normal temperatures on Thu
night/Fri. Windy conditions at least appear to continue, but it has
upper level support with easterly airflow, so it may be very
localized.

The clusters are fairly similar in timing and only slight
variations in the depth of this low. And there is high confidence in
the return of warming high pressure, though varying degrees of
northerly airflow that would bring the cold air and freezing
conditions. The winds are confidently expected to be in the 90th
percentile range for both Tue and Wed afternoon. Welcome to a
tempestuous mid-Spring. Messick

AVIATION...
Expecting conditions to continue to deteriorate around the region
over the next few hours. MVFR conditions likely to prevail
through much of the period with occasional IFR possible. Winds,
rain and snow will impact all eastern Idaho terminals. Breezy
SW winds expected throughout the day at KPIH, KIDA and KBYI. Winds
will be a touch lighter at KSUN and KDIJ but still occasionally
breezy. McKaughan

HYDROLOGY...
Flooding has dropped to minor flood stage at the Portneuf River
at Pocatello with rising levels back to moderate on Sunday 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 continues for the Portneuf River at Topaz where
the gauge remains above flood stage and will remain so for several
days with only a slight rise expected late this weekend into
early next week. 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 the potential for significant
precipitation Sunday and Monday, rivers will need to be monitored
closely. GK

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM MDT Monday for IDZ056-057.

Winter Storm Warning from noon today to 6 AM MDT Tuesday for
IDZ060.

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

&&

$$