Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 210617

Area Forecast Discussion
National Weather Service Northern Indiana
217 AM EDT Sun May 21 2017

Issued at 203 AM EDT Sun May 21 2017

A northward moving warm front will bring a few isolated showers
and thunderstorms to the area early this morning, with a better
chance of scattered showers and isolated thunderstorms toward
morning as a cold front approaches from the west. Conditions will
dry out from west to east this afternoon as the front pushes
across the area. Dry conditions are then expected tonight and
Monday before rain chances increase again for Monday night and
Tuesday. Temperatures will transition to below normal for
Wednesday and Thursday behind this system.


.SHORT TERM...(This Evening through Sunday)
Issued at 400 PM EDT Sat May 20 2017

Ardent warm air advection wing continues to lift northeast through
CWA. Modest MLCAPE reservoir on order of 1000 to 1500 j/kg with
surface based dewpoints into the lower 70s and 30 knots deep layer
shear quite sufficient for at least isolated to scattered deep
convection to develop upstream later this evening and nosing into at
least southern half CWA. Saving grace for non severe is putrid low
level lapse rates amid present cool post convection airmass over
CWA. This along with warm sectors disfavorable timing of low level
theta-e surge overall remain rather bullish with best severe
potential holding south of CWA this evening/early tonight, save
perhaps strong to near severe south of route 24 in Indiana. Rapid
north-northeast liftout of mid level cyclone with attendant cold
front sweeping eastward through CWA Sunday morning and into
northwest Ohio by 18 UTC Sun suggests insufficient time for strong
destabilization for little more than chance non-severe convection.


.LONG TERM...(Sunday Night through Saturday)
Issued at 400 PM EDT Sat May 20 2017

Hereafter...rapid dig of shortwave energy over Bitterroots through
base of mean layer trof to afford rapid plains cyclogenesis for
another round of shra/tsra chances on Tuesday followed by sig
cooler than normal Dy5/6 timeframe. Gradual thermal moderation
into next weekend expected with significant deep layer ridging
building into the Upper Great Lakes.


.AVIATION...(For the 06Z TAFS through 06Z Sunday Night)
Issued at 203 AM EDT Sun May 21 2017

Complex of showers and thunderstorms which formed in association
with strong low level theta-e advection and at the nose of upper
level speed max have progressed east-northeast of the terminals
early this morning. Additional isolated showers are developing to
the north of retreating warm frontal boundary with a few hit and
miss showers/storms possible through 09Z. A broken line of
showers/isolated storms has filled in along cool frontal across
northern/central Illinois, and additional precip may affect
terminals in the 09Z-12Z timeframe. Weak gradient ahead of the
front will also pose some fog risk, particularly at KSBN in the
pre-dawn hours this morning. Otherwise, IFR/MVFR conditions this
morning should give way to VFR cigs behind the front with some
west-southwest gusts into the 15 to 20 knot range possible this




LONG TERM...Murphy

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