Hail in Idaho, July 13, 2021

Area Forecast Discussion
National Weather Service Pocatello ID
134 PM MDT Tue Jul 13 2021

.SHORT TERM...Tonight through Thursday night. Water vapor imagery
this afternoon shows a dry upper trough extending from NW MT into
central Idaho. Winds this afternoon are a bit gusty, and should
continue to be so through this evening. Winds are strong enough to
warrant a Lake Wind Advisory for American Falls Reservoir. This
could be enough to trigger some modest thunderstorms over the Island
Park area this evening. Those storms should subside after sunset and
the passage of the upper trough, while surface winds begin to turn
down-valley overnight tonight. Lighter winds are in the forecast
tomorrow along with some cooler temperatures. As we head into
Thursday, models start picking up a weak shortwave coming in with
just enough moisture to trigger some isolated thunderstorms--mainly
across the Central Mountains and the Southeastern Highlands.
Hinsberger

.LONG TERM...Friday through next Tuesday. The models continue to
show a low pressure system anchoring in off the Canadian coast
Friday with the downstream ridge axis briefly shifting into WRN
Wyoming as an ejecting short-wave disturbance lifts NE through
Washington resulting in a slightly enhanced wind flow across the
CNTRL mountains and Snake Plain Friday afternoon. The low gradually
retrogrades westward and merges with a second incoming Pacific
disturbance further off the NW coast Saturday into Sunday with
amplification occurring Monday. This will allow and encourage the
ridge to expand westward across SE Idaho and intensify once again
resulting in hotter temperatures and possible Heat
Warnings/Advisories for portions of the Eastern Magic Valley, Snake
Plain, and southern mountains Sunday through Tuesday. The models are
also advertising monsoon moisture rotating north around the
periphery of the high into CNTRL Idaho Monday and/or Tuesday. Huston
&&

.AVIATION...A short-wave trough was shifting east through WRN
Montana early this afternoon. Convective allowing models suggest
that we could see an extension of thunderstorm activity southward
into DIJ through early this evening. Otherwise breezy WSW winds will
transport smoke from upstream fires into the region with partial VIS
restrictions possible in some areas (BYI and SUN). Winds decouple
after sunset with mostly VFR conditions outside of areas with smoke.
Huston
&&

.FIRE WEATHER...A weak, dry upper trough is working its way through
the Central Mountains this afternoon. This is the basis of our Red
Flag Warning this afternoon/evening for zones 410, 413, 425, and
427. The southern half of zone 422 will see some marginal
windspeeds, but also a persistent Haines of 6--so that zone is also
included in our current Red Flag Warning. The trough will move off
to the east tonight. Coverage of Haines 6 decreases overnight and
expands again tomorrow. Lighter winds are expected across the region
tomorrow as the weather regime remains hot and dry. Thursday gets a
little more interesting with the addition of some isolated
thunderstorms over the Central Mountains and Southeastern Highlands.
Coupled with a Haines of 6, we could see another round of critical
fire weather conditions on Thursday. Hot and dry weather remains in
the forecast through the weekend, but there are some signs we'll see
some moisture from the Southwest Monsoon make its way into the
region by next Tuesday. Hinsberger
&&

.AIR STAGNATION...
The accumulation of smoke from distant fires in NE California, SRN
Oregon, and SE Washington as well as fires in the CNTRL Idaho
mountains may produce moderate to unhealthy air quality conditions
across portions of SE Idaho as the flow aloft continues to advect
smoke from these fires east into our area. Huston
&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning continues until 10 PM MDT this evening for IDZ410-
413-422-425-427.

Lake Wind Advisory continues until 9 PM MDT this evening for IDZ054.
&&