Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 291818
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
220 PM EDT Thu Sep 29 2016

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

&&

.SYNOPSIS...
Issued at 129 PM EDT Thu Sep 29 2016

A low pressure system will stay close to Indiana through the
weekend, resulting in a damp, cool, spell. From Monday through
Thursday our weather should be dominated by high pressure from the
deep south to New England, causing drier and warmer conditions.


&&

.NEAR TERM (Tonight)...

Issued at 129 PM EDT Thu Sep 29 2016

The models all agree low pressure through a deep level and nearly
saturated air will remain over Indiana. They also agree synoptic
scale forcing, as shown by strong Q vector convergence, will develop
over most of the area from 03Z-09Z.

The result is going to be widespread rain. Categorical POPs will be
forecast most areas. Likely will be used in the northwest, which
should have more of a glancing blow from the forcing. There is a
chance of thunder given the cold air aloft, but most rain should be
stratiform considering forcing is going to cover a lot of saturated
air simultaneously.

Last night a consensus forecast worked well for temperatures. The
same should work tonight given most guidance is again in agreement
and the basic situation hasn`t changed.

&&

.SHORT TERM (Thursday through Sunday)...

Issued at 129 PM EDT Thu Sep 29 2016

POPS are the forecast problem.

The model deterministic fields all have a vertically stacked low
pressure nearly over the area until Sunday, when it leaves to the
northeast. The result will be plenty of clouds and showers, and
possibly thunder.

Exactly when rain occurs will be controlled by weak impulses
embedded within the larger low pressure. At times there are
relatively large differences in the model POPs, suggesting different
handling of these impulses. Using a consensus will minimize errors,
but POPs with this forecast may change by 10-20 percent.

There is excellent agreement on temperature predictions. This
indicates a consensus will work well, as it has recently. Based on
the range of what different methods forecast,the consensus should
have errors of 2 degrees or less.

&&

.LONG TERM /Sunday Night through Thursday/...
Issued at 220 PM EDT Thu Sep 29 2016

Sunday night through Wednesday will be dry as the upper low
which will be over the eastern great lakes Sunday evening moves
on to the east and a ridge of high pressure builds in across
our region.  The dry weather may end by Thursday as an upper trough
moves into the northern and central Plains.  Some models indicate
a cold front may make it as far east as Illinois by the end of
day 7.   Will mention a slight chance of showers over western
sections late Wednesday night and low chances of showers and a
few thunderstorms all but far east Thursday.

Temperatures will become a little warmer by the middle of next
week as an upper ridge of high pressure builds into the Ohio
valley.  Stayed close to super blend temperatures in most cases.

&&

.AVIATION /Discussion for the 29/18Z TAF Issuance/...
Issued at 1258 PM EDT Thu Sep 29 2016

Generally VFR Ceilings through early evening followed by IFR
Ceilings with rain showers late tonight and Friday morning. Then
improving again toward midday Friday.

An upper low pressure system will continue across Indiana through
the period.  Radar indicates scattered light showers were occurring
across the region and ceilings generally ranged from 3 to 5 thousand
feet. With daytime heating expect slightly higher ceilings as the
afternoon wears on.  Could see an isolated thundershower as well.
Model indicate showers will become more numerous late tonight and
model soundings indicate ceilings and visibilities will become IFR
as well late tonight and Friday morning.  Should see some
improvement again by midday Friday with ceilings improving to 2 to 4
thousand feet.

Winds through the period will be northerly at 5 to 10 kts.


&&

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

$$

SYNOPSIS...JK
NEAR TERM...JK
SHORT TERM...JK
LONG TERM....JH
AVIATION...JH


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