Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 260230
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
830 PM MDT Thu Apr 25 2019

.UPDATE...Quick update this evening mainly to adjust for
precipitation chances the remainder of the evening. Convection
remained south of the Utah border, so decreased threat of showers
and thunderstorms prior to midnight. Convection in northern
NV/southwest OR expected to reach the western edge of the forecast
area between 06-09Z. Have left forecast unchanged for the rest of
the night. Winds still expected to be the main concern in post
frontal environment under influence of strong downward mixing. DMH

&&

.PREV DISCUSSION... /issued 129 PM MDT Thu Apr 25 2019/

SHORT TERM...Tonight through Sunday. Early afternoon satellite
imagery was showing a broad shallow ridge across the region with
isolated convective buildups noted across Nevada. Numerical models
continue to suggest that isolated convective buildups will nose
northward into the south-central highlands late this afternoon and
early this evening and thus have maintained a slight chance mention
of showers in that region this evening. The models also continue to
drive a strong Pacific trough and associated cold front through the
region Friday resulting in very strong winds throughout the Snake
River Plain and South-central Highlands Friday afternoon and
numerous showers and scattered thunderstorms advancing through the
region with the front into the eastern mountains. We anticipate that
High Wind Warning criteria will be met with the frontal passage
Friday with winds gradually settling into Advisory levels within a
couple of hours after the frontal passage. We have continued the
Watch for now and will allow the mid-shift a chance to make the
final call. Temperatures will cool behind the front which should
help alleviate some of the melting on area rivers by Monday (see
more in the Hydrologic discussion below). By Saturday afternoon
gusty winds will return to the Snake River Plain as a low pressure
system slowly drops south out of Canada into the northern Rockies
and then shears east into the Dakotas Sunday. We may see some shower
activity associated with the exiting low up along the divide but
nothing as dramatic as previous model runs were showing earlier in
the week. Temperatures will run at or above normal through Saturday
but then drop below normal Sunday as cooler temps settle into the
region from the north. Huston

LONG TERM...Sunday night through Thursday. Much cooler temperatures
are expected Monday as a mostly dry cold front drops through the
area on Sunday. Expect rain/snow Tuesday into Wednesday morning as
an upper level low drops over the area. Snow levels will be around
5000 to 5500 feet near the Montana line and around 7000 to 8000 feet
along the Utah line. Expect brief dry conditions on Wednesday with
cooler temperatures before models show another system starting to
move through later on Thursday. Temperatures Monday morning will
likely be at or below freezing for most locations including the
Snake River plain. Eastern Magic valley will be near freezing to
around the mid thirties. Temperatures will range from 5 to 15
degrees below normal through the period. Wyatt

AVIATION...Expect high pressure to gradually break down with
increasing clouds. Expect mostly vicinity showers by this evening
and continue into tomorrow morning with a frontal boundary moving
through. Winds will start increasing by mid to late tomorrow morning
with the strongest winds expected tomorrow afternoon. Wyatt

HYDROLOGY...Above normal temperatures will continue through
Saturday with a modest precipitation event expected Friday as a
front pushes east through the region. The models are now holding the
second storm system north of the region Sunday while a third system
digs further south into the region sometime Tuesday for our next
rain event. As a result, river levels will continue to run high at
least through Saturday with improving conditions anticipated Sunday
into Monday as a result of the cooler temperatures. A Flood Warning
continues for the Portneuf River at Pocatello and the Big Wood River
at Hailey (although flooding has now been delayed a day at Hailey).
Numerous other gauges continued to run near bankful including the
Blackfoot River near Henry (where a Flood Advisory continues),
Antelope Creek near Darlington, Willow Ck above Ririe Res (where a
Flood Advisory has been issued), the Snake River downstream of
Palisades Res near Heise, at Lorenzo, near Menan (where a Flood
Advisory has been issued), and at Blackfoot all due to elevated
releases out of Palisades Reservoir. The most recent forecast
hydrographs were advertising near flood conditions Sunday afternoon
on the Henry`s Fork near Rexburg. Huston

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from Friday afternoon through Friday evening for
IDZ051>057.

&&

$$



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