Flash Flood Warning 19, NWS Pocatello, ID

Area Forecast Discussion
National Weather Service Pocatello ID
111 PM MDT Tue May 30 2023

.SHORT TERM...Tonight and Wednesday. Showers and thunderstorms
will continue to impact central and eastern Idaho. While showers
and thunderstorms are forecast through this evening almost
everywhere, the main focus will be along the southern and eastern
benches across the Snake Plain and Magic Valley and into the
central mountains and eastern highlands. This is where the
"higher" risk for heavier rainfall, although given slow storm
movement and quite a bit of moisture in the atmosphere...heavy
rainfall and the associated risk of additional flooding is
possible. Gusty winds over 40mph are still possible with storms
across the Snake Plain, Magic Valley and South Hills into this
evening. Overnight, a few showers are forecast across the central
mountains with a couple of lightning strikes possible. For
Wednesday, the daily repeat of showers and storms is there. There
is a chance everywhere, but the focus again is from the
southern/eastern benches north and west into the central
mountains. The "higher risk" of heavier rainfall shifts to the
central mountains, Magic Valley and South Hills. As with today
though, the risk of flooding is there due to slow storm movement.
The threat of winds over 40mph, with gusts over 50mph possible,
exists across similar areas as today. Any storm both days may
also produce small hail.  Keyes

.LONG TERM...Thursday through next Tuesday.
An area of low pressure working through the Four Corners region
Thursday will continue to work E/NE as a secondary area of low
pressure moving onshore to Oregon is absorbed into a broad 500 mb
upper level trough situated directly over the Rocky Mountains. PWATs
will remain around 140 to 180 percent of normal each day through
next Tuesday keeping our active, unsettled weather pattern going
with slow moving thunderstorms capable of producing heavy rainfall
rates. Ensemble and deterministic models support this solution well
with long-range models all in relatively close agreement. High
temperatures Friday and Saturday will be the coolest during the
period in the 60s to mid 70s as a ridge of high pressure developing
over the Pacific NW and portions of WRN/NRN Idaho ushers in warmer
temperatures even as moisture works over the west over the
Continental Divide into ERN Idaho. Afternoon highs Tuesday will be
feeling much warmer in the 70s to mid 80s with little change each
day to showers and thunderstorms that will peak in coverage and
intensity each afternoon and evening becoming increasingly isolated
after sunset through the overnight and early morning hours. MacKay

&&

.AVIATION...Our active weather pattern continues across ERN Idaho for Tuesday
with another round of scattered afternoon thunderstorms beginning to
develop late this morning that will increase in coverage and
intensity later today. HREF probabilities show a 70 to 90 percent
chance of thunderstorms for all terminals with wind gusts up to 45
kts, small hail, and heavy rain expected with stronger thunderstorms
that develop. Predominant VFR conditions are expected outside of
showers and thunderstorms with storms capable of MVFR/IFR VIS/CIGS
as they move on station. Thunderstorms starting in the mountains
will work out onto the Snake Plain this afternoon and evening as a
more organized line of convection pushes north after sunset with
mostly dry conditions returning overnight outside of some isolated
mountain showers. Much of the same is expected for Wednesday with
thunderstorms again developing late in the morning and continuing
into the afternoon and evening hours. HREF probabilities Wednesday
show a 50 to 70 percent chance of thunderstorms at KPIH, KIDA, and
KDIJ and a 60 to 80 percent chance at KBYI and KSUN. MacKay

&&

.FIRE WEATHER...A slow moving low pressure system will work through
southern California and into the southern Great Basin through this
week. Scattered showers and thunderstorms are likely through much of
the week. Locally heavy rain and gusty winds are likely near
thunderstorms.

13

&&

.HYDROLOGY...We are dropping the FLOOD ADVISORY for Bear Lake
County as more widespread flooding, other than the Bear River
itself, has subsided. We have also dropped all of the warnings and
the one watch EXCEPT for the Big Wood at Hailey due to dropping
levels and bigger impacts not expected at the moment. Otherwise,
portions of central and eastern Idaho are under a MARGINAL RISK
for excessive rainfall through Saturday. Any heavy rainfall on top
of already swollen/flooding rivers and streams will cause rapid
rises, even if they are short-lived.  Keyes

&&

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