Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 211032

Area Forecast Discussion
National Weather Service Northern Indiana
632 AM EDT Mon Aug 21 2017

Issued at 346 AM EDT Mon Aug 21 2017

Chances for showers and thunderstorms will exist over the next 24
to 36 hours, with the best chance bring tonight into Tuesday ahead
of a strong cold front. Cloud cover from overnight storms may
cause problems with those viewing the eclipse this afternoon.
Drier and cooler air will then filter in behind this system
midweek through next weekend.


.SHORT TERM...(Today and Tonight)
Issued at 346 AM EDT Mon Aug 21 2017

Remnant MCV and upper level trough as well as nose of theta e
ridge into the southwestern counties has allowed fairly vigorous
convection across far SW parts of the area. While most of the
storms have behaved, one cell over White county did see 65 DBz
briefly above the -20 C line, with a delayed report of hail just
over quarter size observed. Back edge of this area was finally
approaching the state line and should hopefully see a lull in
precip by 12Z before focus shifts to upstream in Iowa.

As noted, will have a brief dry period before remnants of
convection across Iowa begin to work towards the region. Exact
trajectory of any associated lift and lingering convection remains
in question with potential for extensive cirrus shield to keep
heating somewhat limited (as well as eclipse viewing). Am hopeful
that there will be some thinning of the clouds for viewers this
afternoon, but this same thinning could allow for fairly unstable
conditions with little overall capping. Marginal risk of severe
exists across the area and seems prudent at this juncture. Did not
make many changes to pops other than slightly slowed onset with
above noted concerns warranting a cautious approach.

Additional showers and storms are expected to develop on a cold
front back across Iowa and track east across the region overnight
into Tuesday. Have maintained likely pops in this period with
possible need to increase to categorical with focus of low level
jet into the area combined with deep moisture and some
instability. Severe weather could become a possibility tonight,
especially if convection can get organized to the west.


.LONG TERM...(Tuesday through Sunday)
Issued at 346 AM EDT Mon Aug 21 2017

Front will be clearing the area during the day on Tuesday.
Marginal risk for severe storms still in place, but thoughts are
main threat could exist further SE where outflow boundaries from
overnight convection may keep best focus.

Once the front is clear, not much left to write about as high
pressure takes control with dry and below normal conditions
through the remainder of the period.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday Morning)
Issued at 630 AM EDT Mon Aug 21 2017

Generally vfr across nrn IN attm though a couple clusters of shra/ts
continue to move across the area with embedded mvfr conditions. This
activity expected to shift east of the area early this morning.
Another mcv will likely move east from IA today and combined with
diurnal heating may cause sct ts to develop over nrn IN this
aftn. More widespread shra/ts expected to move through late
tonight and Tue morning as a cdfnt moves se across the area.
Generally expect vfr conditions to continue this taf period, but
will be mvfr or ifr in convection. For now, uncertainty in timing
convection high enough to just mention vcts in 12z tafs.




LONG TERM...Fisher

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