Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 251945

Area Forecast Discussion
National Weather Service Northern Indiana
345 PM EDT Sun Sep 25 2016

Issued at 341 PM EDT Sun Sep 25 2016

Rain showers will accompany a strong cold front tonight into
early Monday morning. An isolated thunderstorm with gusty winds
is possible mainly west of Interstate 69 this evening and early
tonight. Cooler and drier air will settle in on Monday and
Tuesday, with highs in the mid 60s to low 70s Monday and the 60s
on Tuesday. An upper level low will then bring renewed rain
chances Tuesday night into Wednesday.


.SHORT TERM...(This Evening through Monday)
Issued at 341 PM EDT Sun Sep 25 2016

The upper level trof across the Upper Midwest was becoming
negatively tilted this afternoon. A cold front associated with this
system was over extreme east Iowa and was moving east. Scattered
showers and thunderstorms had formed over the northern half of
Illinois. There is some risk for gusty winds in the 40-50 mph range
with DCAPE near 1000 J/Km per SPC mesoanalysis over areas west of
highway 31. Also, there is some support for isolated weak tornadoes
given favorable low level helicity, daytime heating with upstream
temperatures topping 90 degrees with dew points near 70, the
approach of the upper level trof. The 4Km NAM indicates 0-1Km shear
over 30 m/s with helicity approaching 300 m2/s2. However, it appears
the limiting tornadic factor will be relatively high LCLs around
1500 meters.

This system will trigger a round of showers and scattered storms as
the front moves east. Precipitable water values per BUFKIT will top
2.0 inches as an axis of moisture spreads northeast ahead of the
front. The precipitable values are near the climatological maximum
for this time of year.  The ongoing timing of the showers and storms
appears on track for tonight, so have made few changes. Showers
should end except possibly the far north as much cooler air spreads
into the area.


.LONG TERM...(Monday Night through Sunday)
Issued at 341 PM EDT Sun Sep 25 2016

Chilly air will spread south behind a cold front with temperatures
below normal during the middle of the week. An upper level low will
move into the area and bring a chance for showers especially from
Tuesday evening into Wednesday.  Very warm lake temperatures will
favor lake enhancement of showers as delta T values approach or
exceed 15C. The period Thursday through Sunday should be mainly dry
with temperatures recovering above normal into the mid 70s by


.AVIATION...(For the 18Z TAFS through 18Z Monday Afternoon)
Issued at 148 PM EDT Sun Sep 25 2016

Main focus still on cold front passage tonight with VFR until
then. Left in VCTS mention at KSBN due to slight chance for a
storm in the 00-04Z timeframe but low level moisture and
instability are fairly limited and coverage is expected to remain
low. Rain will cross the area overnight and expect at least MVFR
conditions along and behind front in CAA regime. Brief fuel
alternate, possibly IFR, conditions not out of the question but
not expected to persist given strong dry air advection and will
leave out any mention for now due to some lingering uncertainty
on exact timing. VFR will return by late Monday morning but
westerly winds will gust in the 20-25 kt range.




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

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