Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 241950

Area Forecast Discussion
National Weather Service Pocatello ID
150 AM MDT Fri Mar 24 2017

.SHORT TERM...Tonight through Sunday night. Early afternoon
satellite imagery was showing a Pacific storm system advancing
through the NW coast. Numerical models show the associated
precipitation spreading into the CNTRL mountains later this
afternoon and then the remainder of SE Idaho overnight with upwards
of 3 to 8 inches of new snowfall expected across the CNTRL mountains
above 7000 feet MSL by noon Saturday and mostly rain below 6000
feet. The main band of precipitation works east into the Wyoming
border Saturday morning followed by widespread convection favoring
the mountains Saturday afternoon as the upper trough axis passes
through the region. Clearing skies follow late Saturday night with
the leading edge of a second Pacific storm system advancing into the
CNTRL mountains and ERN Magic Valley Sunday evening and then the
remainder of SE Idaho Sunday night through Monday. The models appear
to maintain the idea of a split trough working through the Nrn
Rockies and Great Basin Monday (more on that below) and thus there
may not be as much precipitation accompanying this second storm as
we end up seeing in tonight`s system. Daytime temperatures should
cool toward climatological norms by Sunday/Monday. Huston

.LONG TERM...Monday through Friday. Fairly active long term pattern
with two systems affecting southeast Idaho.  The first will continue
rain and snow showers on Monday with snow levels generally around 6
thousand feet with that system. Locations above that level may see
some accumulation.   Both the European and GFS models drive through
a strong cold front Thursday with another batch of precipitation.
Both are dropping snow levels to near valley floor level Thursday
night but at this point so far out will not overplay as models could
change several more times with this system in the next 6 days.
Temperatures are forecast to be very near seasonal normal for late
March. GK

.AVIATION...Pacific system is expected to bring rain showers to all
sites starting late this afternoon in SUN and overspreading the
remaining TAF sites overnight tonight.  MVFR conditions are possible
mainly at SUN...IDA and DIJ. Do not have at BYI and PIH sites but
could also occur there overnight. Showers should taper off Saturday.
10 to 20 knot winds likely at BYI...PIH and IDA this afternoon and
early evening and again Saturday afternoon. GK

.Hydrology...An Areal Flood Watch will be extended through the
weekend as two Pacific storm systems (tonight/Saturday and Sunday
night/Monday) are expected to push through the region bringing lower
elevation rain and higher mountain snow. Cooler temperatures should
help to mitigate snowmelt while the addition of lower valley rain
may just offset the benefits of the cooler temps. The Portneuf River
at Pocatello is expected to peak near Moderate Flood stage over the
weekend and slowly recede early next week but remain above flood
stage for the foreseeable future. The Bear River is expected to
benefit from the cooler temperatures this weekend, peaking today and
then slowly dropping below flood stage sometime tonight and then
below bankfull sometime Sunday evening. Numerous flood advisories
will likely continue across the region through the weekend due to
the anticipated rainfall. Huston

Flood Watch until noon MDT Saturday for IDZ017>019-022>025-031-032.


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