Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 202002

Area Forecast Discussion
National Weather Service Northern Indiana
402 PM EDT Sat May 20 2017

Issued at 402 PM EDT Sat May 20 2017

A cold front will move east through the region as low pressure
lifts northeast through the Upper Great Lakes. Showers and some
thunderstorms are expected ahead of this system overnight into
Sunday morning. Another frontal system will approach and bring
chances for rainfall again on Tuesday, followed by below normal
temperatures Wednesday and Thursday.


.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 18Z TAFS through 18Z Sunday Afternoon)
Issued at 122 PM EDT Sat May 20 2017

Deepening low pressure system moves north from the Plains allowing
a warm front to slowly move north and a cold front to slide east
across the area during the forecast period. The big question will
be how far north the warm front gets, which would indicate the
strength of any thunderstorms that come across the area. 925mb
warm front is slowly moving north with elevated thunder around the
area and the sfc front seems to lag behind so the stronger storms
will hold off until later this afternoon. After drying out some
early in the overnight, VFR conditions drop back into MVFR by 12z
Sun with renewed moisture from the cold front moving through.
During the early overnight, LLWS may also need to be considered
for a brief time.





LONG TERM...Murphy

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