Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 190628
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
228 AM EDT Tue Sep 19 2017

.UPDATE...
The LONG TERM Section has been updated below.

&&

.SYNOPSIS...
Issued at 226 PM EDT Mon Sep 18 2017

A diffuse frontal system will slowly dissipate across the area by
the middle of the week. High pressure is expected to build into the
area by later in the week, and on through the weekend.

&&

.NEAR TERM /Overnight/...
Issued at 1022 PM EDT Mon Sep 18 2017

Convection continues to gradually diminish in coverage across
central Indiana this evening. Additional convection however is
developing over central Illinois and moving east. A muggy feel to
the air tonight with 02Z temperatures mainly in the 70s and
dewpoints not far behind.

Attempted to add some detail to the current forecast with a
primary focus on convective coverage increasing over the area
after 06Z from the west as an upper level wave approaches the
region. This feature is aiding in the development of storms across
Illinois currently and considering the presence of a moist and
weakly unstable airmass across the forecast area...storms should
continue east into the forecast area during the predawn hours and
through daybreak Tuesday. Will increase pops through the
overnight as a result with highest values primarily in the 09-12Z
time period.

Patchy fog will again be a possibility late tonight...especially
in areas that received rain earlier today. Lows in the mid 60s
look reasonable.

Zone and grid updates out.

&&

.SHORT TERM /Tuesday through Thursday/...
Issued at 226 PM EDT Mon Sep 18 2017

Tonight`s mid level disturbance will be in the process of passing
off to the east by the midday hours Tuesday, so any lingering
activity should diminish during the morning hours. However, air mass
will be moderately unstable, along with little cap and a mid level
cool pool overhead. As a result, potential exists for additional
convection to develop later in the day Tuesday. Will keep PoPs going
through the day Tuesday.

Mid level cool pocket, along with little capping, will linger across
the area into Wednesday, but convective threat should be less than
what is expected on Tuesday as remnants of front wash out and
heights begin to build. By Thursday, air mass should be pretty well
capped. Will keep some small chance PoPs over mainly the eastern
zones Tuesday night and Wednesday, and cut them off after that.

Progged low level thicknesses suggest the GFS MOS highs for Tuesday
look a little on the cool side. Will nudge up the guidance a bit in
that period. The rest of the periods look reasonable at this time.

&&

.LONG TERM /Friday through Monday/...

Issued at 228 AM EDT Tue Sep 19 2017

ECMWF suggests dry weather with above normal temperatures through
this period. ECWMF shows strong ridging in place aloft across the
eastern half of the country. The strong ridge looks to keep
Indiana protected from passing dynamics...keeping them well
northwest of Indiana. Meanwhile at the surface strong subsidence
beneath the ridge results in surface High pressure across the
eastern Great Lakes that keep as dry Easterly flow across Indiana
through the weekend. thus have trended toward a dry forecast. With
little to no change in air mass...have trended highs at or above
the forecast builder blend as warm air reigns supreme under the
ridge.

&&

.AVIATION /Discussion for 190600Z TAF Issuance/...
Issued at 1133 PM EDT Mon Sep 18 2017

Restrictions possible within convection through the afternoon. More
widespread lower ceilings possible this morning as well.

convection has largely diminished over the forecast area as of late
evening...but more consolidated area of convection over central
Illinois associated with a weak upper wave which will drift east
across the region through midday Tuesday. Anticipate an increase in
convective coverage at all terminals after 07-08Z continuing through
the morning as the wave tracks through the Ohio Valley. With higher
confidence in impacts from rain and storms...will continue to carry
prevailing precipitation mention with a VCTS through mid morning.
Model soundings and RH progs are suggestive of renewed development
of lower stratus during the early morning hours as well...mixing out
by midday in most areas.

The upper wave will shift east of the terminals Tuesday afternoon
and while the airmass will remain unstable over the region...
convection should become increasingly isolated as deeper moisture
and forcing aloft move away to the east. Clouds will decrease
Tuesday evening as weak ridging builds in.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SYNOPSIS...JAS
NEAR TERM...Ryan
SHORT TERM...JAS
LONG TERM....Puma
AVIATION...Ryan



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