Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 300433

Area Forecast Discussion
National Weather Service Indianapolis IN
1232 AM EDT FRI SEP 30 2016


The Aviation section has been updated below.


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 /Overnight/...
Issued at 948 PM EDT Thu Sep 29 2016

showers slowly increasing in coverage over the forecast area this
evening as energy aloft spreads west back into central Indiana.
Skies were mainly cloudy with 0130Z temps ranging from the mid 50s
to the lower 60s.

Upper low centered over southern Kentucky this evening will slowly
drift N/NW through the night. Vort energy aloft will be drawn west
back into the forecast area overtop of the upper low and will set
the stage for gradually increasing coverage in showers from the
north and east overnight. Will maintain likely pops during the
predawn hours when rainfall coverage is expected to be highest.
With little in the way of instability noted on mesoanalysis this
evening...will remove mention of thunder overnight. Bumped low
temps up a degree or two based on current readings and expectation
of temps falling only about 3 to 5 degrees the rest of the night.

Zone and grid updates out.


.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 30/06Z TAFs/...
Issued at 1232 AM EDT Fri Sep 30 2016

Conditions will deteriorate overnight to MVFR and periods of IFR as
an upper low continues to spin over the region.

Cannot rule out isolated thunder mainly during the day Friday. Will
include prob30 mentions of this.

Winds will be less than 10kt through the period, initially with a
northerly component. Winds will become more easterly/southeasterly
through the period.





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