Area Forecast Discussion
Issued by NWS Indianapolis, IN

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855
FXUS63 KIND 260152
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
951 PM EDT SUN SEP 25 2016

.UPDATE...
The Near Term Section has been updated below.

&&

.SYNOPSIS...
Issued at 304 AM EDT Sun Sep 25 2016

A cold front will move through the area tonight into early Monday
bringing showers and a few thunderstorms to the area. An upper low
could bring a few showers to northern areas mid week. Dry conditions
will then prevail. After one more warm day today, cooler and more
seasonable readings will continue into next weekend.

&&

.NEAR TERM /Tonight/...
Issued at 951 PM EDT Sun Sep 25 2016

Left likely pops in overnight as radar was national radar
mosaic was showing decent upstream coverage.

Previous discussion follows...
Issued at 618 PM EDT Sun Sep 25 2016

Moved pops about 25 miles or so further east over the next few hours
based on radar trends.

Previous discussion follows...
Issued at 220 PM EDT Sun Sep 25 2016

Vorticity lobe currently drifting through western Illinois may spark
off some convection later this afternoon and evening, especially
over the western zones.

Appears better precipitation threat will arrive later tonight as
model data suggest cold front will be moving into the northwestern
border zones around 260400Z. There appears to be decent upper
support aloft associated with this front, given a mid level jet max
around 70 kts, but most of the support lags behind the front. As a
result, think most of the precipitation will be near the front and
in the post frontal zone. Will go with the highest PoPs during the
late night hours tonight and into the pre dawn hours of Monday,
timed with the better upper support.

Low level thicknesses generally support the GFS MOS guidance lows
tonight.

&&

.SHORT TERM.../Tonight through Tuesday night/
Issued at 304 AM EDT Sun Sep 25 2016

Focus is on chances for rain. Models are close enough that a blend
was used.

The cold front will move through the area tonight. An upper jet will
provide additional forcing while 850mb winds over 30kt bring in
additional moisture. Decent frontogenetical forcing will be around as
well. Thus went likely PoPs most areas at some point during the
night, with later timing in the east.

Current expected timing of the system keeps rain still likely over
the east 3/8 of the area or so during the early part of the morning.
However, dry air moves in rapidly, so that by 15Z most areas are dry
and by 18Z everywhere is. Instability on Monday looks quite low so
removed any thunder mention.

Dry conditions should then prevail through Tuesday high pressure
nosing in.

An upper low will begin to move south out of the Great Lakes late in
the period. Models differ on path and how far south the rain gets by
late Tuesday night. Forcing doesn`t look impressive, and given the
uncertainty, was only comfortable adding in slight chance PoPs in
the extreme northeast forecast area.

For temperatures, generally stayed close to the model blend. Given
the dry air that will be in place for much of the short term, there
should be some decent diurnal ranges. The blend captures this pretty
well.

&&

.LONG TERM /Wednesday Night through Saturday/...

Issued at 242 PM EDT Sun Sep 25 2016

ECMWF showing some differences from superblend this period as the
ECMWF suggests that an upper low will settle across the Ohio
Valley through this period...pivoting several waves through the
area. GFS keeps this feature farther east...mainly over the middle
atlantic states. Thus confidence is low for now and have included
superblends low pops where it has been allowed. Confidence remains
low. However northwest continental flow does seem prevalent through
the period which should result in near normal tempertures.

&&

.AVIATION /Discussion for 260000z TAF issuance/...

Issued at 703 PM EDT Sun Sep 25 2016

A cold front will move through the sites during the period and
bring showers and thunderstorms with it. These will bring brief
MVFR conditions, but outside of the storms ceilings at the sites
look VFR for the most part. Some scattered prefrontal showers and
storms will continue sporadically for the next six hours or so
and could impact the sites but confidence and coverage are not
high enough to go with any more than vicinity mention. Then around
6-8z HRRR shows prefrontal storms increasing in coverage near the
sites, and around 9-10z a line of storms associated with the front
should move into KLAF and KHUF and the other sites an hour or so
later. Could see a brief period of MVFR ceilings behind the
frontal passage, but upstream observations indicate the post
frontal clouds may stay VFR, and the rest of the day should be VFR
with wind gusts picking up to around 20-25 kts out of the NW by
midmorning.

&&

.IND Watches/Warnings/Advisories...
NONE.
&&

$$

SYNOPSIS...50
NEAR TERM...JAS/MK
SHORT TERM...50
LONG TERM....PUMA
AVIATION...CP



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