Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 261955

Area Forecast Discussion
National Weather Service Pocatello ID
155 PM MDT FRI AUG 26 2016

.DISCUSSION...A low pressure trough was progressing east through
Montana, Idaho and Wyoming today with some energy digging south
through Oregon toward the NRN Sierra`s which is expected to shear
east through the Great Basin tonight with little or no impact on
sensible weather. Further upstream, a second low pressure trough was
digging SE through the Northwest Territories and numerical models
have this wave turning east through Canada Saturday and Sunday. We
may see some wind Saturday afternoon and evening which may be of
some concern for local fires (see more on that in the Fire Weather
discussion). The flow becomes more southwesterly Sunday and weaker
heading into Monday as a ridge temporarily builds across the region
ahead of the next Pacific trough advancing into the Canadian and
Pacific NW coastal areas Monday afternoon. With the building ridge,
Sunday and Monday we should see daytime highs nosing back up into
the lower 90s in some areas. By Tuesday or Wednesday, depending on
which model you prefer (the GFS or ECMWF), a short-wave disturbance
ejects from the trough and lifts NE into and across North Idaho. The
passage of this system promises to bring the potential for increased
wind speeds and possibly isolated to scattered thunderstorm activity
across the region. The main upper trough settles further south to a
position off the Washington coast by Thursday afternoon resulting in
an increasing SW flow aloft across SE Idaho and the threat of breezy
winds and perhaps even a push of sub-tropical moisture north across
at least the eastern half of the forecast area. The trough remains a
major player Friday and Saturday as short-wave energy gradually
ejects from the trough across the NW states brining periods of
enhanced wind and the potential for shower and thunderstorm
activity. We will also see daytime temperatures cooling Thursday
into the weekend under the influence of this trough. Huston

.AVIATION...VFR conditions with light winds expected through
tonight.  Should have a wind increase Saturday afternoon at IDA and
PIH mainly with 10 to 20 knot winds expected with gusts in the 25
knot range.   The diurnal wind variation will continue Sunday with
again 10 to 15 knots at BYI...PIH and IDA but expect speeds to be
slightly less than Saturday.   Do not expect precipitation at any
TAF site.   Some smoke at IDA but do not expect continuous
visibility obstructions. GK

.FIRE WEATHER...Should have quiet conditions through Saturday
morning with mainly light winds and little convective activity. Only
isolated thunderstorm activity this evening expected in zone 411 and
along Wyoming border in zone 413.   Flow turns westerly Saturday and
do expect breezier conditions with 20 to 25 mph wind gusts expected
mainly in zone 410 as well as parts of zone 413 and 475 and 476. Not
expecting widespread Red flag conditions but potential for existing
fires to grow on the increased winds.   Some west to southwest winds
will continue Sunday but not expected to be as strong as Saturday
with again the brunt of the 20 plus mph wind gusts expected in zone
410.  A pretty strong south to southwest wind flow will set up next
week Tuesday through Thursday with potential wind issues daily. With
the southerly flow isolated thunderstorms possible next week as well
beginning Tuesday. GK

.PIH Watches/Warnings/Advisories...None.

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