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000
FXUS65 KPIH 110808
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
208 AM MDT Thu Apr 11 2024

.SHORT TERM...Today and Friday
High pressure remain in control once again today with no weather
impacts expected today. Aside from a few high clouds from time to
time, skies will be mostly clear. Temperatures will warm into the
60s for much of the lower elevations today and we may flirt with 70
in parts of the Magic Valley. Still expecting mid to upper 50s
across the high country this afternoon. Winds will be just a touch
breezier in the afternoon but still generally 10-15 knots throughout
the region. As we move into Friday, temperatures will continue to
warm with lower 70s likely across many of the lower valleys with low
to mid 60s elsewhere. Clouds and winds will likely be on the
increase however as a weak shortwave and some moisture will push
into the region from the west. The warmer temps could allow for
enough instability in the afternoon and evening hours to support
some potential for thunderstorms, especially in the central
mountains and to the west of the forecast area. Things would likely
be scattered in nature but nevertheless is something to watch over
the next 24-36 hours. McKaughan

.LONG TERM...Sat through Wed
Extended period clusters appear very similar until Tue, with a
closed low keeping to the south of the forecast area and fairly
far away so that precipitation should not amount to much, and
neither should the wind. However northerly airflow on the north
side of the low should bring in cold air and end the warm pattern
before the start of this period (Fri). As the southern Great Basin
low moves into the central Rockies, a Canadian low, moving more
slowly than the southern low, is able to move southward on Mon and
bring not only more cold air but some wind and precipitation as
it dives southward and directly over the northern Great Basin and
northern Rockies. This is were there is more divergence in the
solution, with about 20 percent of the solutions in the clusters
going for more of a glancing blow as the low, more an open wave,
translates farther east before reaching southern Idaho. Will there
be a Wed departure of this low? That appears not likely with
again about 20 percent of the solutions moving this upper level
low fast enough to end the precipitation. The majority solution is
for this low to linger even into next Thu. So look for much
colder temperatures with the temporary end to southerly flow on
Mon night. Temperatures are expected to drop to near climatic
normals over the weekend, then on Tue drop 15 to 20 deg F compared
to Mon, remaining cold and somewhat wet for the end of the
period. Messick


&&

.AVIATION...
VFR conditions will prevail through the period with light winds and
mostly clear skies. SW winds this afternoon could be a touch
breezier than yesterday but still only in the 10-15 kt range at
the highest. McKaughan

&&

.HYDROLOGY...
As has been discussed for several days now, the Portneuf River
continues to be our only river of concern for flooding at this
early stage of our spring flood season, with very warm temps
averaging 15 degrees above normal by Fri and Sat supporting
increasing snowmelt, especially at mid-elevations in the basin.
Our latest collaborated forecast with the Northwest River Forecast
Center continues to bring the river back into minor flood stage
in the Pocatello area by early Friday morning, and then to
moderate flood stage by early Sunday morning. This potential crest
above moderate flood stage has PERHAPS trended SLIGHTLY higher in
the forecast over the past 48 hours...increasing from about 10.0
feet to about 10.3 feet...but otherwise no significant changes or
trends are noted, and resultant impacts should be approximately
the same with lowland flooding along the river, flooding into
Sacajawea Park and other trailheads in western Pocatello, and
significant flooding of agricultural land in the Blackrock area
and also down in Inkom near the confluence of the Portneuf River
and Marsh Creek. A FLOOD WARNING remains in effect until further
notice. A bit further upriver near Lava Hot Springs, the forecast
for the Portneuf River at Topaz continues to carry bankfull
conditions (action stage) with the river perhaps getting close to
that minor flood threshold. REMEMBER... despite recent warm air
temps...the water in all of our rivers, creeks, and streams
largely originates from melting mountain snow and is dangerously
cold this time of year. Be especially careful to keep children
away from the water. - KSmith

&&

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

$$