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Area forecast discussion
National Weather Service Pocatello Idaho
258 am MDT Mon Sep 25 2017

Short term...today and tonight. The low over Wyoming continues to
weaken and move away from US. Lingering showers on the back side
of the storm will remain along near the Wyoming line especially
this morning. Light amounts with minimal impact on our side of the
border. We haven't seen much of it so far, but some fog is still
possible across the southeast corner and also north toward the
Swan Valley through mid morning. The frost advisory remains in
place for the upper plain as temperatures are dropping into the
low/mid 30s in many areas. Clouds will keep increasing from the
northwest as moisture spills over the top of a ridge building
in from the west. Very light snow is possible on higher peaks and
ridges tonight across the central mountains. Anything falling
will not amount to nothing more than a dusting if that.
Temperatures remain 10-15 degrees below normal with highs
approaching 60 across the lower plain, Magic Valley and around
Challis. Keyes

Long term...Tuesday through next Monday. A temporary Rex block
pattern (high pressure over US and a closed low to our south)
through Thursday. This brings dry weather along with temperatures
finally returning to around normal. By Friday, another storm
moving in from the Pacific breaks the down the ridge. This helps
to "kick" out the low to our south, with the question of how close
to southeast Idaho will it pass and possible produce some light
precipitation. At the moment, the consensus is that it will stay
farther east. Saturday looks showery and breezy as the Pacific
storm sweeps across the state. At the moment, we didn't go too
high with the chance of rain and snow but if trends continue
expect the numbers to go up in the coming days. The forecast for
Sunday and beyond is a bit more muddled. The main versions of the
GFS and European model (ecmwf) show a stronger area of high pressure building over
the west. On the other hand, model consensus and the ensembles
have a storm moving toward Idaho. We do have a very low chance of
showers for the central mountains and along the Montana border by
Monday based on that. Temperatures drop off a skosh because of
this as well, but if we end up with the ridge overhead expect
warmer temperatures to stay with US. Keyes




&&

Aviation...upper level low is taking a bit longer than previous
thinking to clear, so will delay the scattering out for a few more
hours. There is some clearing in the afternoon, but a second weak
trough re-inforces the closed low that is departing Wyoming,
allowing for some increased cloudiness, but no precipitation is
expected at any of the terminals from the shortwave, just mid-level
ceilings. Light wind will continue with some up valley component during
the afternoon. Messick

&&

Fire weather...upper level low is slow to leave, but shower
activity today is limited to portions of the Idaho-Wyoming 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
Idaho-Montana border in the Salmon-Challis nf. By Tue afternoon this will
also trigger some light precipitation along the Idaho-Wyoming 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 Idaho-Wyoming border. Messick

&&

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