Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 181118

Area Forecast Discussion
National Weather Service Northern Indiana
459 AM EDT THU AUG 18 2016

Issued at 715 AM EDT Thu Aug 18 2016

Isolated to scattered thunderstorms are expected to develop by early
afternoon and continue into this evening. Highs will be in the low to
middle 80s.


.SHORT TERM...(Today and Tonight)
Issued at 459 AM EDT Thu Aug 18 2016

The challenges today and tonight include coverage of dense fog early
followed by chances and timing of storms today into tonight. Patchy
dense fog had formed overnight over far southern Lower Michigan into
far northern Indiana. The fog should lift out shortly after daybreak
with daytime heating and mixing.  A weak upper level system was
supporting some storms over Illinois early this morning. Deep layer
moisture flux was sufficient to sustain the storms, even in an
environment of stable mid level lapse rates around 5.5C/Km. Expect
storm development along a weak boundary late today across northeast
Illinois into northern Indiana in an area of weak convergence in a
theta e ridge. Scattered storms should continue tonight in this area.


.LONG TERM...(Friday through Wednesday)
Issued at 459 AM EDT Thu Aug 18 2016

A seasonally strong upper level trof will move into the Upper Great
Lakes Region this weekend. There is some support for marginally
severe storms given the upper level support and given precipitable
water values climbing to 2.0 inches. Although moisture will be
sufficient with modest shear, mid level lapse rates appear to be the
limiting factor for widespread severe storms. Will include this
mention in the Hazardous Weather Outlook Product. The best chance
for storms will be from Saturday afternoon into early Saturday
night. Much cooler air will spread across the area early next week
with highs around 75 Sunday and Monday.  Otherwise, kept a small
chance for storms Friday with a weak system.


.AVIATION...(For the 12Z TAFS through 12Z Friday Morning)
Issued at 715 AM EDT Thu Aug 18 2016

Small MCV had materialized out of convective cluster propagating ewd
through nrn IL. Xpc this cluster will persist ewd into nw IN before
diminishing but more importantly effectively seed new convective
development by 16-17Z given xpcd favorable downstream
destabilization through this morning. At least a bit better
confidence vs 06Z fcst to include a tempo group twd mid afternoon
but timing is still highly uncertain and likely too late. Otrws
prevailing conditions xpcd to be vfr w/a brief period of mvfr
potential in tsra as fog/low status burns off quickly to start.


.IWX Watches/Warnings/Advisories...


SHORT TERM...Skipper
LONG TERM...Skipper

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