Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 210810

Area Forecast Discussion
National Weather Service Indianapolis IN
410 AM EDT Mon Oct 21 2019

The Aviation Section has been updated below.


Issued at 235 AM EDT Mon Oct 21 2019

A cold front is expected to move through the area this afternoon
and evening. In the wake of this front, high pressure is expected
to build in for the middle parts of the week. Another front may
affect the area around Thursday and Friday.


.NEAR TERM /Today/...
Issued at 235 AM EDT Mon Oct 21 2019

Short term model data suggest an area of rain and thunderstorms
currently over Missouri and Iowa will be approaching the western
border zones by sunrise. This area of precipitation should expand
rapidly northeast across the area later this morning, aided by a
55-60 kt low level jet. Shower activity may tend to diminish in
coverage by early afternoon, as the low level jet weakens and
shifts off to the east. Additional activity may develop along and
ahead of cold front, which is expected to move into the western
zones by the mid to late afternoon hours.

Will concentrate the highest PoPs today from the mid morning hours
through the midday hours, coinciding with the best lift. Lapse
rates, and resultant instability, continues to look poor today,
although deep layer shear will be strong. Potential exists for
high winds to mix down with any deep convection that may develop,
especially from the late morning hours until about sunset.

Low level thicknesses suggest the GFS MOS highs for today look
reasonable, so won`t stray far from them.


.SHORT TERM /Tonight through Wednesday Night/...
Issued at 235 AM EDT Mon Oct 21 2019

Model data suggest cold front may be about half way through the
forecast area by sunset, and should pass off to the east around
220500Z. Will hold onto some PoPs along and ahead of the front

The rest of the short term looks dry at this time, as the surface
low lifts towards north of the Great Lakes by Tuesday, and high
pressure slides into the Tennessee Valley. There looks to be quite
a bit of cold advection cloud that may wrap around the departing
surface low into the area on Tuesday. A weak wave may pass
through the Great Lakes by Wednesday night, but models indicate
any precipitation threat from this wave should remain north of the
local area.

Progged low level thicknesses suggest the GFS MOS temperature
guidance may be a little on the warm side, especially from tonight
through Tuesday night. Will nudge the guidance numbers down a bit
in those periods.


.LONG TERM /Thursday through Sunday/...

Issued at 308 AM EDT Mon Oct 21 2019

The long term pattern begins with a trough extending
southwestward from an upper low over James Bay. GFS moves this
trough progressively across the country then through the rest of
the week and weekend. The ECMWF, though, produces a cutoff low
over the southwest U.S. for the end of the week and then slowly
kicks it out northeast during the weekend. Both solutions bring
cooler air in for the end of the week and into the weekend, with
differences being on just how cold temperatures will get, and both
show warming for Saturday night and Sunday. There is some
agreement on a front setting up across the area Thursday night
into Friday with chances for precipitation, but amounts vary by
quite a bit. Will keep the highest PoPs confined to Thursday night
when there is better agreement on rain potential, but should see
some small PoPs for parts of the area on most days due to the
differences in timing of shortwaves out of those aforementioned
troughs. Thus low confidence on precip but increasing confidence
on below normal temperatures Friday and Saturday.


.AVIATION /Discussion for the 21/09Z TAF Issuance/...
Issued at 410 AM EDT Mon Oct 21 2019

Updated current conditions. Previous discussion follows...

Good confidence in VFR conditions through 14z. Showers will be
overspreading the area from southwest to northeast 12z-15z and good
confidence that flying conditions will then deteriorate to MVFR or
worse after 14z. Would not rule out a thunderstorm, but chances too
low to mention.

Good confidence conditions will improve back to VFR after 21z as the
rain moves out.

Winds will start off southeast around 6 knots and then increase to
greater than 10 knots after 12z. Low level wind shear is possible
through 15z as a 40 plus knot low level jet moves in from the

After that, winds will mix down with gusts 20 to 30 knots or more.
Wind direction will shift to the south and then southwest after 21z
as the strong cold front moves in from the west.




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