Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 170848

Area Forecast Discussion
National Weather Service Northern Indiana
448 AM EDT Thu Aug 17 2017

Issued at 444 AM EDT Thu Aug 17 2017

Chances for showers and thunderstorms will continue today. There
is a chance for isolated strong to severe thunderstorms later this
afternoon into the evening, especially east of Route 31.
Highs today will be in the lower to middle 80s. Cooler and drier
air will filter in behind this system tonight into Friday. Highs
Friday will be in the middle 70s to around 80. This will followed
by low rain chances on Saturday as an upper level disturbance
tracks through the region.


.SHORT TERM...(Today and Tonight)
Issued at 442 AM EDT Thu Aug 17 2017

Continued conditional severe potential today in association with
strong shortwave trof over western Upper Great Lakes lifting
northeast into Ontario today. Strengthening southwesterly deep layer
flow in advance of attendant cold frontal boundary to bring marked
increase in deep layer shear to about 40 kts along with moderate
instability by afternoon, especially along/east of Route 31. MLCAPE
to increase to around 1000-1500 j/kg with effective low level tap of
lwr/mid 70s surface dewpoints now into Lower Ohio Valley. Primarily
wind risk in short lived bowing segments though low end tornadic
risk in 0-1km 200 m2/s2 helical flow, especially should near surface
flow back in advance of linear convection and/or should discreet
modality develop.


.LONG TERM...(Friday through Wednesday)
Issued at 442 AM EDT Thu Aug 17 2017

Little substantive changes from prior forecast. Secondary wave races
across northern CONUS and digs underneath downstream trof undergoing
filling over northern Great Lakes/eastern Ontario for low chances
convection on Saturday. And another period of decent potential
convection on Dy6 with frontal boundary approach. Feature associated
with initially high belted energy through Canada to sag southeastward
into Upper Great Lakes. Suspect with progressive build of western to
central CONUS ridge in latter part of week to help shunt moisture
south of CWA with temperatures trending seasonably cool.


.AVIATION...(For the 06Z TAFS through 06Z Thursday Night)
Issued at 130 AM EDT Thu Aug 17 2017

Increased lift and moisture was allowing isolated showers and
possible thunderstorms to develop. While both sites may see a
brief shower or 2, coverage and impacts warrants no more than the
inherited shower mention with vcts. Hi res models show more
expanded development with next wave and precipitation back across
SW Illinois. Will keep TAFs rather simple for now with amendments
possible as evolution becomes clearer. Precipitation on the actual
front still looking questionable later this afternoon before
drier air arrives Thursday night.


IN...Beach Hazards Statement from this afternoon through Friday
     afternoon for INZ003.

MI...Beach Hazards Statement from this evening through Friday
     afternoon for MIZ077.

LM...Small Craft Advisory from 6 PM this evening to 5 PM EDT Friday
     for LMZ043-046.



LONG TERM...Murphy

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