Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 200935
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
335 AM MDT Sun Aug 20 2017

.SHORT TERM...Today through Tuesday. Drier northwest flow aloft is
expected to keep monsoon moisture south of the ID/UT border
through Mon. Isolated tstms begin to creep across the border into
the southern highlands lat Tue. Cloud cover during the eclipse Mon
morn still a bit of a concern...but models still showing drier air
over the track which translated to less cloud cover. NAM BUFR data
show the potential for some high clouds near the WY border.

.LONG TERM...Wednesday through Sunday. The long stagnant upper low
over southern CA finally begins to open up on Wed...as a deeper
upper low approaches the southern BC coast. Increasing southwest
flow will open the path for the monsoon moisture...and raise the
chances for tstms Wed and Thu. The upper low moves east thru AB on
Fri...with a trof dragged thru ID. This will sweep the remaining
precip out of the area by Sat morn. Strong upper ridging builds
over the west thru the weekend...resulting in dry and warm
conditions. Hedges

&&

.AVIATION...Dry air with northwest flow aloft will result in
continued VFR conditions thru tonight. Hedges

&&

.FIRE WEATHER...Westerly flow is in place across the area bringing
breezy winds. Expect Haines Index to remain high today. Also, look
for relative humidity to remain critical today ranging from 7 to 14
percent across all valleys and 14 to 20 percent for mountains. Later
this afternoon into the evening a weak wave will move through the
Westerly flow increasing winds even more. Expect afternoon into
early evening wind gusts of around 30 mph in zones 410 and 425,
particularly for the Arco desert to include the northwest portion of
zone 410 and the northeast portion of zone 425.  The fire weather
watch for zones 410 and 425 has been upgraded to a red flag warning.
The southern portions of zones 422 and 476 as well as the northern
portion of zone 413 and all of zone 411 will see wind gusts of 20 to
25 mph. Winds will remain slightly elevated Monday as high pressure
starts to build into the area. Relative humidity will remain
critical mostly below 15 percent Monday and to a lesser extent on
Tuesday. Models are holding off showers and thunderstorm until
Wednesday when moisture starts to make its way into our southern
areas in southwest flow. The best shower and thunderstorm chances
look to be Thursday and Friday with an approaching system. This
system also elevates winds across the area on Thursday and Friday.
Wyatt

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 2 PM this afternoon to 9 PM MDT this
evening for IDZ410-425.

&&

$$


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