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Area forecast discussion
National Weather Service Indianapolis in
751 PM EDT sun Sep 22 2019

the aviation section has been updated below.


issued at 338 PM EDT sun Sep 22 2019

A cold front will swing across central Indiana tonight bringing the
threat for showers and thunderstorms. Cooler and drier air will
expand into the region on Monday with comfortable conditions through
midweek. Scattered rain chances will return Wednesday and Wednesday
night before dry weather resumes. Summer is back late week into the
weekend with well above normal temperatures.


Near term /tonight/...
issued at 338 PM EDT sun Sep 22 2019

The rest of the night will focus on the approach and passage of
the cold front to the west as the ridging breaks down and the
upper low currently over the northern plains tracks into the Great
Lakes by daybreak Monday. Ample bl shear should enable convection
to maintain into the forecast area tonight but as instability
wanes...showers and storms are likely to become more scattered as
the night progresses. Stronger upper level forcing will remain
focused north of the area and the deeper moisture axis is narrow
and a bit disjointed. Ultimately...that will likely trend towards
a disorganized multicellular convective Mode overnight with
localized heavy rainfall and gusty winds with stronger cells. A
few lucky locales that get under heavier cells will Cash in with
nice rainfall amounts but unfortunately for our parched
area...amounts less than 0.50 inches will be the norm and not the
exception. Rain will shift to the southeast half of the forecast
area by 12z as the front shifts east.

Temps...cooler airmass behind the front will be delayed until Monday
with lows remaining up in the 60s across the forecast area. May see
temps slip into the lower 60s prior to daybreak in the northern
Wabash valley. A model blend will work well.


Short term /Monday through Wednesday/...
issued at 338 PM EDT sun Sep 22 2019

Forecast challenges focus on cooler and drier weather for much of
the short term with a potential for rain and storms Wednesday ahead
of a weak front.

The front will shift east of the region Monday morning with the long
awaited cooler and drier airmass making its arrival as coincidence
would have it on the first official day of astronomical fall. A
combination of strong Canadian high pressure and a suppression of
upper level heights well south of the Ohio Valley will produce a
seasonable first half of the week to the region.

A few lingering showers in eastern counties will continue through
mid morning before a much drier airmass takes hold. Model soundings
show deep subsidence building down through the column with any
stratocu gradually diminishing as the day progresses. This will set
the stage for two fantastic days Monday and Tuesday with abundant
sunshine by day...clear skies at night and pleasant conditions.
Could see some winds gust near 20mph at times both afternoons as

By Wednesday...low pressure will track from the upper Midwest into
Ontario with a trailing cold front approaching the region from the
northwest. With the surface low lifting away from the region...mid
and upper level forcing will remain well north of central Indiana
and a limited source of moisture with the Gulf of Mexico largely cut
off. The front also is likely to run out of gas as it runs into the
ridge to the south by Wednesday night. Will carry a low chance pops
for isolated to scattered rain and storms...but not overly impressed
with precipitation potential at this point in time with this system.

Temps...nice taste of fall albeit brief coming for Monday and
Tuesday. Prefer the warmer mavmos guidance for highs throughout the
short term with a model blend for overnight lows. Highs in the mid
70s for Monday and Tuesday will rise back up to around 80 on
Wednesday. Lows will fall back into the low and mid 50s for Monday
night before recovering back into the upper 50s to near 60 Tuesday


Long term /Wednesday night through Sunday/...
issued at 310 PM EDT sun Sep 22 2019

Models in agreement that a cold front will move across central
Indiana Wednesday night in response to a deep trough moving across
the northern Great Lakes. This lends good confidence in at least
scattered thunderstorms over the area Wednesday night. After that,
surface high pressure should provide dry weather through Thursday

Southerly flow ahead of another system and southwest flow aloft
support the well above normal blend temperatures for the weekend and
small sporadic pops. Confidence is low on timing or coverage of any


Aviation /discussion for the 23/0000z taf issuance/...
issued at 734 PM EDT sun Sep 22 2019

An approaching cold front will bring showers and the chance for
thunderstorms to the terminals this evening through 08-11z early
Monday morning...from northwest to southeast. A dip to MVFR
conditions are expected as the front approaches and the terminals
become impacted with lower ceilings and lower visibilities at taf
sites impacted by rain. Confidence not high in lightning/thunder
potential, but cannot rule it out with some of the stronger

Skies should begin to scatter out behind the front during the
morning hours. Returning terminals to VFR conditions around 13-15z

Most of the gusts seen earlier today have subsided. Currently, we
are seeing south to south-southwest winds across all terminals at
8 to 12 knots. Expect those winds to veer to the west overnight
and then to the northwest during the early morning hours Monday.
Winds look to remain between 5 to 10 knots overnight into


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