Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 220151

Area Forecast Discussion
National Weather Service Pocatello ID
751 PM MDT Sun May 21 2017

.UPDATE...Have already made a couple quick edits this evening.
First was to add isolated convection to northern portions of
Eastern Magic Valley where single thunderstorm cell developed with
indications of up to half inch hail. That cell has largely
dissipated along with convection in Bear Lake region, and do not
expect further development for the remainder of tonight. Other
update this evening was to cancel Lake Wind Advisory with winds
below thresholds necessary for chop near American Falls Dam. No
other updates are anticipated this evening. DMH


.PREV DISCUSSION... /issued 206 PM MDT Sun May 21 2017/

SHORT TERM...Sunday night through Wednesday. A trough embedded in
northerly winds aloft is slowly moving south and out of the state
this afternoon. A few showers and isolated thunderstorms have
developed over the Caribou Highlands, by evening this should be
just the Bear Lake area and that should end by 9 pm this evening.
On Monday there will be a chance of showers in the Upper snake
Highlands south to about Palisades Reservoir from a disturbance
sliding along the Divide. High pressure ridge moves inland and
over this area Monday night through Wednesday morning for mostly
clear skies and warmer temperatures. Models today are in much
better agreement with a low pressure system tracking through
Alberta/Saskatchewan Wednesday afternoon and trailing a cold front
into Southeast Idaho. Wednesday should be a windy day across the
area and potentially a wind advisory could be issued. Models are
also consistent with rather dry air behind the front, and most
showers and thunderstorms focused over the South Central and
Caribou Highlands during the afternoon and evening. This is
faster timing than previous forecasts had. RS

LONG TERM...Thursday through Sunday. Following the passage of a
cold front Thursday, winds are expected to be elevated from the west
or southwest in the southern Snake Plain and southern Highlands
throughout the day. Shifting wind directions are expected the
northern half of the Snake Plain and upper Highlands. Temperatures
will be 10 degrees or so cooler compared to Wednesday. This trend
will persist into Friday with very slight and gradual warm-up
possible over the weekend. Cloud cover and anticipated additional
precip will assist in determining if these temperatures will
increase further or not. As these computer models are quickly
changing our weather forecast, almost run-to-run, especially in this
long term forecast our confidence in the precip and temperature
forecast is not very high. New short wave disturbances are
indicated in forecast models Friday and over the weekend, which
would bring widespread showers and thunderstorms across Idaho,
Wyoming and Montana. Sunday is looking to be the driest day at
this time. NP/RS

AVIATION...MVFR ceilings are working their way out of KBYI with
visible imagery trending clearer. All sites are expected to remain
VFR through the period. Snake Plain will see a modest northeast wind
this afternoon becoming light and variable this evening. Very
isolated showers are indicated in mesoscale models, but are not
expected to show up at the terminals. Hinsberger



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