Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 201510

Area Forecast Discussion
National Weather Service Pocatello ID
910 AM MDT Thu Jul 20 2017


Updating forecast for thunderstorms this afternoon into evening
and overnight. Models are not handling coverage of thunderstorms
well at all this morning. Furthermore, am seeing quite a bit of cu
across northeast Nevada that is streaming into the Magic Valley
and Snake Plain. Not sure if the cu will materialize into storms,
but believe a slight chance is warranted given trends for these



.PREV DISCUSSION... /issued 326 AM MDT Thu Jul 20 2017/

Today through next Thursday...A plume of monsoon moisture will
make its way into southeast ID today...resulting in isolated to
widely scattered tstms over the southern and eastern highlands
this aftn and eve. Isolated tstms may spill into the adjacent
Snake River Plain as well. By Fri...westerly flow aloft pushes the
monsoon moisture off to the east and south of ID. This will end
precip chances thru the weekend. The upper ridge builds back up
over the weekend...with the upper high centered over the Great
Basin. This keeps temps up and monsoon moisture out. The upper
high shifts to the 4 corners area on Mon as an upper trof enters
the Pac NW. This sets up more southerly flow aloft...and a
transport for monsoon moisture into ID. This increases the tstm
chances from Mon aftn thru the end of the period. Models have been
rather vague on timing...placement...and coverage. As a result...
will keep precip chances on the low side. Hedges

AVIATION...Monsoon moisture will flow back into southeast ID
today...with isold to widely sct tstms expected over the southern
and eastern highlands mainly this aftn and eve. Tstms may spill
into the Snake River Plain near KPIH and KIDA. Southwest winds are
also expected to pick up in the Snake River Plain this aftn.

FIRE WEATHER...Monsoon moisture slipping into the southeast corner
of the state this afternoon and evening, roughly Sublett to
Palisades and north to near Island Park will be favorable for
isolated dry thunderstorms. The second concern is a surface front
moving through Central and Northern Idaho today. Estimate the
front will pass Salmon about 1100 hours and Gilmore 1700-1800
hours. Forecast winds have been borderline Red Flag criteria for
several model runs, and this morning increased enough to favor
issuing a warning for Zone 476 below 6000 feet elevation and Zone
410. In Zone 410 the strongest winds gusting near or a little
above 30 mph will favor the Arco Desert and decrease east of
Roberts. A low pressure disturbance moving into British Columbia
and Alberta on Monday will bring dry westerly winds off the
Pacific across southern Idaho and push unstable air out of the
state. Some of that unstable air will be just across the border in
Nevada and Utah the next few days. Will look for that monsoon
moisture to work back into Idaho Monday through Wednesday.
Thunderstorms with wetting rains may be possible by next
Wednesday. RS


Red Flag Warning from 2 PM this afternoon to 9 PM MDT this
evening for IDZ410-476.


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