Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 181845

Area Forecast Discussion
National Weather Service Northern Indiana
245 PM 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...(This Evening through Friday night)
Issued at 243 PM EDT Thu Aug 18 2016

KIWX radar indicating scattered convection along the southern
portion of the CWA with a couple additional clusters moving up
into SW lower Michigan this afternoon. NVA moving into the NW CWA
in the wake of short wave energy combined with weak flow
environment should have this convection in a downward trend with
the loss of diurnal heating this evening and trend toward a dry
forecast. HIRES guidance in agreement on developing upstream
convective complex in vicinity of frontal wave over SE S. Dakota
and track E/SE toward the region after midnight. Various flavors
of the HRRR offering differing solutions on timing and track of
nocturnal complex but close enough to our CWA to warrant
introducing small chance POPs back into the NW CWA at 06Z. Friday
will be yet another day of weak flow in a humid and modestly
unstable airmass that will necessitate a continuation of low
chance POPs given potential for remnants of nocturnal convection
laying out boundary to support additional daytime development.
Humid conditions will keep overnight lows around 70 tonight and
Friday night with highs on Friday in the mid 80s.


.LONG TERM...(Saturday through Thursday) Issued at 243 PM EDT Thu
Aug 18 2016

Consistent signals in regards to long term period results in
little change to previous forecast for this cycle.

An amplified upper level trough will work across south central
Canada, north central CONUS on Saturday with fairly good agreement
in deterministic solutions of stronger lead short wave lifting
across the western Great Lakes late afternoon/early evening. A
narrow corridor of more substantial moisture (PWATS ~ 2 inches)
will rapidly advect northeast into the area Saturday afternoon).
Currently expecting that modest mid level lapse rates will limit
MLCAPES to the 1500-2000 J/kg range with modest increases in
primarily speed shear profiles through the day. Deep layer shear
profiles should increase into the 25 to 35 knot range in the
afternoon, combined with aforementioned instability may pose some
risk for a lower end severe threat with wind gusts as the likely
main threat. Other possible concern Saturday given PWAT axis and
increasing low level flow/weakening propagation vectors will be for
some localized heavier rain showers. Will need to monitor especially
areas across northwest portions of the forecast area that have
received the copious amounts of rain over the past several days.
Overall progression of main moisture axis and lead short wave may
tend to limit the heavy rain potential but will need to monitor this.
Will maintain high end likely PoPs from west to east across the area
Saturday afternoon/night.

Rain should taper late Saturday night into Sunday. Main upper level
trough axis should be progressing through the region Sunday which
gives some consideration of isolated shower PoPs, but will hold off
for now and keep things dry. Cooler and less humid conditions will
be the big story Sunday-Tuesday with moderation expected by mid week
as low level warm advection increases again. Highs by the end of the
period are expected to reach back into the lower 80s. Medium range
guidance continues to suggest active short wave pattern across
northern tier that may eventually push an elongated frontal zone
into the area by Day 7 with another chance of showers and storms.


.AVIATION...(For the 18Z TAFS through 18Z Friday Afternoon)
Issued at 120 PM EDT Thu Aug 18 2016

After over 3 hours of LIFR conditions at KFWA...finally back into
MVFR and expect to maintain remainder of the afternoon while over at
KSBN...subsidence in the wake of earlier convection is expected to
allow VFR to prevail will have no mention of thunder. KIWX radar
showing scattered storms west of KFWA which will require a VCTS
mention remainder of the afternoon and will amend if/when appears it
will be affecting the terminal. Concern again for fog development
overnight with ample low level moisture and weak flow. Will not go
down to LIFR but will keep MVFR/IFR for the early morning hours at
both sites.


.IWX Watches/Warnings/Advisories...


LONG TERM...Marsili

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