Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 190932
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
332 AM MDT Sat Aug 19 2017

.SHORT TERM...Today through Monday. Models continue to show a
transition from zonal flow today...to a broad upper trof over the
Pac NW by Sun. The only real change is dropping tstm chances thru
Mon to only isolated activity early Mon morn over the southern
highlands. Both NAM and GFS keeping the bulk of the mid level
subtropical moisture just to the south of the total eclipse path
over far eastern ID Mon morn. Mid level moisture with the northern
stream flow is just north of the path. The drier...and less cloudy
area is very narrow. The NAM seems to be the most confident. The
rest of the path across the central mtns and upper Snake River
Plain looks better.

.LONG TERM...Tuesday through Saturday. Upper ridging builds up
again by mid week...while the weak upper low stays anchored over
the southern CA coast. Not seeing the monsoon moisture returning
until Wed...with isolated tstms late afternoon and evening. On
Thu...a deep upper low is expected to move into southern BC.
Increasing southwest flow will raise precip chances by Thu
afternoon...and even more Thu eve as a cold front moves thru ID.
Precip diminishes to isolated mtn tstms on Fri...then nothing by
Sat as drier air takes over. Hedges

&&

.AVIATION...VFR conditions again today and tonight as dry air
remains in place. Breezy SW winds expected this aftn and eve in
the Snake River Plain. Hedges

&&

.FIRE WEATHER...Westerly flow is in place across the area. The first
of two waves will move through the area today.  Expect strong wind
gusts of 25 mph in valleys and 30 to 35 mph across ridgetops across
the Central mountains and Arco desert. Relative humidity will remain
low, if not slightly lower than yesterday, ranging from 8 to 18
percent for the area. A Red Flag warning is in effect today from
noon until 9 pm mdt for east Idaho fire weather zones 422, 475, and
476. Winds in all other zones, though elevated, are slightly below
critical values. Haines Index will remain high today and Sunday.
Relative humidity remains low Sunday with only slight increases
early in the week before rising more significantly later in the
week. Sunday the second and weaker wave will move through bringing
near critical winds to southern portions of zones 422 and 476 as
well the Arco desert to include the northeast portion of zone 425
and northwest portion of zone 410. Sunday expect weak southwest flow
allowing moisture to creep into our southern areas. Expect mostly
mountain afternoon isolated showers and thunderstorms Monday and
Tuesday mainly across our Southern areas. Models now show more
significant moisture in stronger southwest flow Wednesday through
the end of the week. Wyatt

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon today to 9 PM MDT this evening for
IDZ422-475-476.

&&

$$



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