Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 271826
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
226 PM EDT TUE SEP 27 2016

.UPDATE...
The SYNOPSIS...NEAR TERM and SHORT TERM Sections have been
updated below.

&&

.SYNOPSIS...
Issued at 221 PM EDT Tue Sep 27 2016

An upper level low is expected to drift southeast from the
upper Great Lakes into the Appalachian mountain region towards
the end of the week.

&&

.NEAR TERM /Tonight/...
Issued at 221 PM EDT Tue Sep 27 2016

Upper low currently located over Lake Superior is expected to
drop south through the Great Lakes tonight. Cloud cover should
increase tonight as the cloud shield associated with the upper low
drops south. Model guidance suggests a rather strong vorticity
lobe rotating around the low will be approaching the area from
the northwest during the pre dawn hours of Wednesday. Will go
with chance PoPs after about 280800Z over about the northwest
two thirds of the area to cover this feature.

Low level thicknesses generally support the GFS MOS lows for
tonight, so any adjustments will be minor.

&&

.SHORT TERM /Wednesday through Friday/...
Issued at 221 PM EDT Tue Sep 27 2016

Models suggest strong vorticity lobe, in conjunction with upper
low, will move through the local area during the day on
Wednesday. Will continue with chance PoPs all areas on Wednesday.
Steepening mid level lapse rates during the day suggest some
lightning strikes are possible, especially over the southeast
zones, where passage of vorticity lobe will coincide with peak
heating.

Appears some shower threat will probably linger through Friday
as upper low gradually drifts southeast into the Appalachian
mountain region towards the end of the period. Will keep chance
PoPs in the forecast through Friday all areas for now, but it
appears the best threat will be over the eastern and southeastern
zones after Wednesday, closest to upper low.

Based on progged low level thicknesses, the GFS MOS highs for
Wednesday and Thursday look too cool. Will raise the guidance a
category or so in those periods. Guidance lows look OK for now.

&&

.LONG TERM /Friday Night through Tuesday/...

Issued at 220 PM EDT Tue Sep 27 2016

The ECMWF continues to keep the persistent upper low over the
Ohio Valley Friday night through Saturday...before it finally
begins to drift farther north on late Saturday night and Sunday.
ECMWF then suggests ridging aloft build across the
region...nudging the low to the northeast. Thus have kept with
superblends low chance pops from Friday Night into Saturday...then
trended toward a dry forecast early next work week as ridging and
high pressure resume. Expect below normal temperatures to continue
on Friday and early Saturday as the low lingers in the area...a
return to near normal highs is expected next work week as high
pressure builds across the region and warmer southerly flow tries
to develop.

&&

.AVIATION /Discussion for the 271800z tafs/...

Issued at 1254 PM EDT Tue Sep 27 2016

VFR conditions are expected to deteriorate to MVFR after 10z-12z
Wed.

Clear skies are expected to remain in place across the state late
this afternoon and evening as the upper low to the north begins to
approach the area.

Upper low over the Great lakes is expected to sink south across
the ohio valley...sending a series of short waves spinning around
the low across the taf sites late in the period. Forecast
soundings show steep lapse rates with good saturation...thus will
expect sct light rain showers and mvfr CIGS in the area on
Wednesday as the Low lingers across the state. Isolated TSRA will
be possible...but confidence is too low for specific timing.

&&

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

$$

SYNOPSIS...JAS
NEAR TERM...JAS
SHORT TERM...JAS
LONG TERM....PUMA
AVIATION...JP



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