Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 101025

Area Forecast Discussion
National Weather Service Pocatello ID
425 AM MDT Tue Oct 10 2017

A ridge of high pressure remains in control of our weather this
morning. The ridge axis is actually already to our east and
departing, but all model guidance across the board allows the
nearby ridge to maintain control through tonight, signaling a
continuation of high forecast confidence in dry weather, mostly
sunny skies, and breezy conditions across the Snake Plain and
southern Highlands. High temps today will run about 5-10 degrees
higher than Mon. Another beautiful fall day across SE Idaho.

A wave of low pressure will graze SE Idaho Wed, the first of two
systems this week. Models continue to show good agreement on the
evolution of this system, keeping most associated precip north of
our forecast area, but brushing the Central Mntns and Upper Snake
Highlands with some isolated to scattered rain/snow showers over
the course of the day. Once again, only very minor adjustments
were made to the ongoing forecast, and our confidence this point
is moderate to high. No major impacts are expected with this
system, with QPF less than 0.10 inches and snow accumulations of
less than 2 inches above about 6,000 to 6,500 feet. The majority
of SE Idaho is still looking dry with this system.

Forecast confidence is slow to grow for our next low pressure
system and cold front forecast for Fri-Sat. GFS/ECMWF/Canadian
are actually in decent agreement early this morning with precip
beginning Fri morning, peaking Fri evening, and a frontal passage
Sat morning with precip ending W to E during the day, BUT this is
after some notable differences and run-to-run changes over the
last 24 hours. So, we are not yet fully investing in the current,
albeit good-looking model consensus just yet. The trend toward a
more progressive system that began yesterday morning continues,
however, and this morning`s forecast update again pushed start and
end times of the precip up by at least several hours. Bottom
line: confidence is slowly increasing that this system will bring
to precip to the entire region, with Fri afternoon/night most
favorable at this time. PoPs have been nudged up into the 30-60%
range during this period. As we began mentioning yesterday, the
current temp/snow level forecast suggests there is the potential
for snow accumulations to occur with this system, especially for
the higher terrain with some impacts possible. Stay tuned.

At this early vantage point, a period of dry weather appears to be
on tap for next Sun through Tues, with some degree of ridging
expected to overspread the region. - KSmith/GK


We will have continued VFR conditions today with only mid and
high level clouds expected at all the TAF sites. Southerly winds
are expected to increase at PIH and IDA this afternoon into the
10-20 knot sustained range. The approaching cold front will keep
strong winds in play Wednesday with again 15 to 25 knot sustained
winds at BYI, PIH and IDA from the west to southwest. - GK


Flow aloft will turn southwesterly today with low level winds
beginning to increase from the south, and the winds will be the
main issue the next two days. A cold front will move through Idaho
on Wednesday and the strongest winds will be Wednesday. We will
have mild temperatures today and Wednesday with much colder
conditions expected Thursday behind the front. The most
precipitation with the system will be to the north in zones 475
and 476. Snow levels will drop from about 7,000 feet on Wednesday
to about 5,000 feet on Thursday. - GK




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