Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 251945

Area Forecast Discussion
National Weather Service Pocatello ID
145 PM MDT Mon Sep 25 2017

.SHORT TERM...Tonight through Thursday. The latest satellite imagery
was showing the Wyoming low lifting NE of the region early this
afternoon with no remaining impacts across the ERN highlands.
Meanwhile, a weak disturbance was digging SE through the Rockies
with attending light radar returns noted upstream near Missoula.
Numerical models show this wave continuing its SEWRD trek tonight
resulting in a slight chance of light snow showers over the NE
mountains late tonight and Tuesday. A ridge of high pressure builds
along the NW coast Wednesday for dry and warmer conditions
throughout the region. By Thursday, the GFS and NAM show a closed
low circulation ejecting from the Lower Colorado River Basin across
Utah. The GFS is a bit slower while taking the track a little
further north and west of the NAM and consequently clips the Bear
Lake area generating a weak threat of light rain showers. The GFS
falls on the NW most envelope of the most recent model runs and thus
has been given very little weight in the forecast for this model
cycle. We will continue to watch how it evolves with time and adjust
appropriately. Daytime temperatures warm to climatological norms
Wednesday and Thursday with overnight lows mostly running above 34
to 35 degrees in the Snake River Plain and thus have held off on any
Frost Advisories for now. But hey, if you want to milk a few more
weeks out of the garden, you may want to consider covering it just
in case. Huston

.LONG TERM...Thursday night through Monday. Models starting to agree
on a cold frontal passage on Saturday. Expect continued mild and
mainly dry conditions on Friday with the possibility of some showers
in the southeast corner. Expect increased chances for showers
Saturday with the cold frontal passage. Temperatures should cool off
significantly behind the front on Sunday and Monday with about a 10
degree drop from Saturday`s highs. Windy conditions will be possible
ahead of and behind the front on Saturday and Sunday as well. GK

.AVIATION...Expect mainly mid level clouds tonight through Tuesday
with winds expected to stay under 10 knots. Stratus has finally
lifted at Driggs and expect it to stay VFR as well. GK

.FIRE WEATHER...Upper level low is slow to leave, but shower
activity today is limited to portions of the ID-WY border. Another
weak shortwave moves into the closed low, keeping cloud cover with
mild temperatures under the cloud cover again tonight. However,
there is limited precipitation from this weak trough, mostly on the
ID-MT border in the Salmon-Challis NF. By Tue afternoon this will
also trigger some light precipitation along the ID-WY border again,
but again most locations will receive zero. In fact, the trough does
little to prevent a warming and drying for Tue. High pressure
returns for Wed with temperatures up strongly and humidity down
strongly underneath partly sunny to mostly sunny skies. The next
threat of rain is on Sat, when the high gives way to a weak and
splitting trough that brings a minor threat of rain and high
elevation snow (perhaps 7000 ft or higher elevation). This will
clear out by Sun night with a return to warming and drying in
central Idaho by Sun afternoon, by Mon at the ID-WY border. Messick


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