Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 110913

Area Forecast Discussion
National Weather Service Pocatello ID
313 AM MDT Fri Aug 11 2017

.SHORT TERM...Today through Monday. Monsoon moisture continues to
linger over southeast ID today...but is becoming more limited.
Isolated to widely scattered showers and isolated tstms are
expected during the late afternoon and evening hours mainly over
the mtns thru Sunday. The pattern changes Sun night as an upper
trof moving thru the Pac NW pushes the upper ridge out of the
Great Basin. Models show a frontal boundary strengthening over the
central mtns generating a band of heavier precip Sun night and have increased precip chances and QPF. Precip is being
supported by upward forcing from ageostrophic flow associated with
an upper jet core. As the front progresses southeast...the jet
core moves out of the area and the precip diminishes. Precip over
the rest of the area becomes more isolated on Mon with some
orographic enhancement over the southern and eastern highlands.
Temps will be a few degrees cooler on Mon.

.LONG TERM...Tuesday through Friday. Drier westerly flow in the
wake of the upper trof will result in little if any precip and
more seasonal temps for the rest of the week.



.AVIATION...Isolated tstms possible again this aftn/eve over the
mtns. KSUN and KDIJ may see impacts such as gusty outflow winds.
VFR conditions expected for the most part...with ocnl MVFR vis due
to smoke. Hedges


.FIRE WEATHER...Upper low that had been positioned off of the
Northern California coast has transitioned to an open wave and is
located over Oregon. Meanwhile, vigorous disturbances embedded in
persistent Northwest flow over Montana with SE Idaho situated in
between these features. The net effect will be a repeat of isolated
afternoon and evening showers and thunderstorms once again today and
Saturday. One difference is that mid-level winds are beginning to
increase, and these stronger winds may be transported to the surface
via shower and thunderstorm outflow winds. Otherwise, a warming and
drying trend will commence through Saturday. Sunday, a Pacific
trough approaches via Washington and Oregon. Winds will increase
ahead of this trough, first over the mid and upper slopes across the
Central Mountain region of the Salmon-Challis NF. Above thermal
belts, winds should be persistent both Saturday night and Sunday
night with limited RH recovery. On Sunday, breezy winds are expected
to develop across all of SE Idaho, with critically low min RH values
across the Arco desert. This will bring elevated fire weather
conditions -- possibly borderline critical fire weather conditions.
On Monday, a cold front is forecast to swing across SE Idaho.
Forecast models are now generating a swath of wetting rains in
association with the front, developing across the Salmon-Challis NF
Monday morning and sweeping eastward through the day across at least
the northern Snake Plain. Models are not advertising this to be a
dry frontal passage at this time, however breezy winds are possible
with the front, so this will bear watching for critical fire weather
potential as well. AD/Hedges



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