Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 220609

Area Forecast Discussion
National Weather Service Indianapolis IN
209 AM EDT Tue Aug 22 2017

The SYNOPSIS...NEAR TERM and SHORT TERM Sections have been updated below.


Issued at 210 AM EDT Tue Aug 22 2017

A cold front is forecast to cross Indiana today. By Wednesday high
pressure will extend across central parts of both the USA and Canada.
This high pressure system is expected to be very long lasting. It
should control Hoosier weather through Monday.


.NEAR TERM (Today)...

Issued at 210 AM EDT Tue Aug 22 2017

Thunderstorms are likely. Otherwise this is a low confidence

All models have thunderstorms occurring as a front passes today,
but they differ in the details. The HRRR in particular has several
waves of storms.

An all-day rain is unlikely. Whether it will be raining at any
given time is uncertain. Severe weather is not probable today, but it
is possible depending on when storms form and how well organized
they get. These issues should gradually be resolved as the HRRR

For temperatures, consensus should work as well as anything.
However errors could be as much as 5 degrees depending on exactly
when rain occurs.


.SHORT TERM (Tonight through Thursday night)...

Issued at 210 AM EDT Tue Aug 22 2017

The models have come into good agreement. There is high confidence
precipitation should be shortly after 8 pm, with dry weather for the
rest of the period.

There is also agreement skies should be mostly clear, except for
partly cloudy conditions under a secondary system Thursday.

As with other parameters, guidance is close on temperatures.
Consensus should be accurate to within 2-3 degrees.


.LONG TERM /Thursday Night through Monday/...
Issued at 240 PM EDT Mon Aug 21 2017

Dry and pleasant weather through the weekend as the Great Lakes
and Ohio Valley reside under a broad upper trough and strong high
pressure at the surface. Dry flow from the north then east will
maintain highs ranging from the mid 70s to lower 80s through
much of the period. Nights will have a distinct autumn feel with
temperatures dropping as low as the lower 50s...maybe even upper
40s...Thursday and Friday night in some spots.

Heights aloft will recover with the upper trough shifting off to
the east by late weekend. The region will remain under the
influence of a surface ridge...but low level flow will transition
to southerly on the back side of the high...enabling Gulf moisture
to be drawn north into the region. Potential for a few showers and
storms by Monday and have introduced low pops.


.AVIATION (Discussion for 220600Z TAFs)...

Issued at 1222 AM EDT Tue Aug 22 2017

VFR through the period with winds at or below 10 knots veering from
south to southwest then west with frontal passage in the afternoon.

Scattered showers in central Illinois and moving east may affect
KIND, KLAF and KHUF early in the period.

More likely precipitation timing is ahead of the cold front which
would be 221100Z-1200z in KLAF and KHUF, then KIND around 221300Z
and KBMG before 1400Z. Cloud bases with thunderstorms should be
relatively high at 4000 feet to 6000 feet, but brief lower
conditions could occur.

Despite high humidity, relatively dry ground of recent weeks and
winds remaining up above 5 knots should prevent any fog from forming
at daybreak.




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