Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 251438
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1038 AM EDT SUN SEP 25 2016

.UPDATE...
Aviation section updated

&&

.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.../This afternoon/
Issued at 1026 AM EDT Sun Sep 25 2016

Vorticity lobe currently located near the Mississippi river is expected
to drift east during the day. This feature may spark off some convection
over the west central and northwest zones by mid to late afternoon. Will
extend the PoPs for later this afternoon into some of the west central
zones as well to cover this feature.

Previous discussion follows.

A cold front will approach the area today. Until later in the day,
high pressure should remain in control with just an increase in
clouds.

Some models bring in rain before 00Z to the western forecast area
ahead of the front. The Hi Res Rapid Refresh has convection into the
area by 19Z. This seems overdone given what little forcing will be
available before the front arrives.

However, the GFS and Canadian bring in rain before 00Z. Although
less weight is given to the GFS since it typically overdoes QPF
coverage, the SREF also hints at this possibility. Given the above,
and after looking at neighboring office`s input, have decided to add
some slight chance PoPs to the far northwest 21Z and beyond.

With some decent sunshine for at least the first half of the day,
feel that MOS is too cold. Went closer to a raw model blend of
temperatures.

&&

.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 frontogentical 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 through Saturday Night/...

Issued at 331 AM EDT Sun Sep 25 2016

The extended period could start out with a few rain showers across
the northern counties as a low pressure systems departs to the
east. After that, a large ridge of high pressure will build over
the region, resulting in dry conditions and more seasonable
temperatures through the end of the long term period.
Initialization is handling the pattern well, so no deviations
were needed.

&&

.AVIATION /Discussion for the 251500z IND TAF update/...

VFR conditions are expected to continue. Forecast soundings
suggest convective temperatures will be reached this afternoon
with some sct CU developing. HRRR once again appears a bit over
done...and will hold off on any afternoon precip as it suggests.
Otherwise...ongoing tafs in good shape.

/Discussion for the 25/1200Z TAF Issuance/...

Issued at 720 AM EDT Sun Sep 25 2016

VFR conditions are generally prevailing at most TAF sites with
little fog development at this time. The main focus of the TAF
period though will be showers and thunderstorms with approaching
cold front. Showers and isolated thunderstorms should start
impacting KLAF and KHUF by Mon 03Z, spreading eastward into KIND
and KBMG. The best chances for convection will be in the Mon
09-12Z time frame. Prevailing conditions will generally be at VFR
levels, but they could quickly deteriorate to MVFR or worse during
any storms. Meanwhile, winds will start out east/southeasterly and
gradually veer to the southwest through the course of the period.
Winds could be breezy at times at KIND tonight with sustained
speeds of 12 to 15 kts.


&&

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

$$

SYNOPSIS...50
NEAR TERM...50/JAS
SHORT TERM...50
LONG TERM....TDUD
AVIATION...TDUD/JP


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