Wildfire in Idaho, August 26, 2017

Area Forecast Discussion
National Weather Service Pocatello ID
158 PM MDT Sat Aug 26 2017

.DISCUSSION...High confidence in the expectation that a strong
ridge of high pressure will continue to strengthen across the
Great Basin through early next week, resulting in a gradual
warming trend across SE Idaho. High temperatures are expected to
approach record values well into the 90s for the Snake Plain by
Monday. By Tuesday, a strong Gulf of Alaska low is projected to
force a disturbance eastward across the PacNW, causing the
northern portion of the ridge to temporarily flatten -- resulting
in a slight cooldown (albeit with temperatures still remaining
above climatological averages) Tuesday-Thursday. This feature is
at the same time forecast to interact with a wave wafting
northeast through the Great Basin. As a result, isolated
Thunderstorms were from the Sawtooths southward to the UT/NV
border for Monday afternoon/evening, with the support of high-
resolution forecast guidance. Shower and thunderstorm chances are
then forecast to overspread all of Southeast Idaho by Tuesday,
continuing into Wednesday. Shower and thunderstorm chances will be
favored over high terrain areas, the Central Mountains eastward
along the Montana border region in particular, with less coverage
over the Snake Plain. Any shower or storm will have the potential
to produce gusty winds with the expectation for dry near-surface
conditions. The wave and associated moisture is forecast to exit
into Wyoming by Thursday while the Great Basin ridge
simultaneously builds back into our area. This will result in a
renewed run at near-record high temperatures for the end of the
week and into next weekend. AD/Huston

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.AVIATION...High pressure will continue to bring widespread VFR
conditions today as well as tomorrow. Wyatt

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.FIRE WEATHER...A high pressure ridge will continue to build over
Southeast Idaho today into Sunday. There are slightly breezy winds
over the area this afternoon in weak northwest flow. Current water
vapor imagery shows a band of dry air moving across our southwest
areas as well as the Snake River plain. On Sunday, drier air will
impact most of our area bringing critical humidities, below 15
percent, in most areas outside of our extreme northeast area by
Island park.

By Monday the high pressure ridge will move over our eastern areas
allowing moisture to move across our western areas bringing
afternoon into early evening, mostly dry, isolated thunderstorms.
With continued moisture moving into the area,  thunderstorms become
more widely scattered over Southeast Idaho Tuesday and Wednesday.
Models show a weak system off the Pacific pushing moisture and
instability east and south of our area by late Thursday. Wyatt

&&

.AIR STAGNATION...Areas of smokey air and poor air quality remain
in the forecast across the Central Mountains and the Air Quality
alert will remain in effect for the foreseeable future. No additional
showers or thunderstorms are expected over the area until next
week. Additional areas of smoke are possible in the Upper Snake
Plain resulting from the Deer Park Wildfire, however the variable
nature of the wind direction makes the smoke forecast tough. NP/RS

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
None.
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