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National Weather Service Indianapolis IN
448 AM EDT SAT AUG 27 2016

.UPDATE...
Aviation section updated

&&

.SYNOPSIS...
Issued at 343 AM EDT Sat Aug 27 2016

A front meandering across central Indiana will interact with upper
waves on the periphery of an upper ridge to prompt thunderstorm
chances for the next several days. Temperatures will run higher
than normal until the latter part of the work week, when they will
drop to near normal.

&&

.NEAR TERM /Today/...

Issued at 343 AM EDT Sat Aug 27 2016

Radar mosaic at 330 am shows a large area of thunderstorms over
much of Illinois and some weakening echoes moving north through
southwestern Indiana. Over the next few hours expect the storms
over eastern Illinois to move into the northwest forecast area and
could still see some scattered development along an outflow
boundary that stretches from those storms southeast across the
area. Thus have likely pops going across western portions of the
forecast area at times over the next few hours with lesser pops
heading southeast.

An upper wave moving through the area to the north will provide a
focusing mechanism for more convection throughout the day today.
With high pressure centered southeast of the area have the lowest
pops going in the southeast but have likelies for parts of the day
in the north and west closest to the best upper forcing. The
front, which had settled near the Ohio River, could move north
again and stall in the forecast area, but bring dew points back
into the 70s. With that juicy air, heavy rain and flooding will
again be a threat. And while low level jet will not be impressive,
and enhancement of 15-20 kts does move across the area during the
afternoon and evening. Combining this with the front, low LCLs
from moist airmass and based on recent days, cannot rule out an
isolated tornado.

&&

.SHORT TERM /Tonight through Monday night/...

Issued at 343 AM EDT Sat Aug 27 2016

A series of upper waves moving through the periphery of an upper
ridge will impact central Indiana through the short term, bringing
chances for thunderstorms to the area. Models are showing
discrepancies in timing of the individual waves so low confidence
on that, but moderate confidence there will be some storms around
the area at some point during the days and lesser confidence of
storms at night without additional help from daytime heating. For
temperatures generally leaned on warmer end of guidance envelope
based on recent verification. Very humid air will continue across
the area through the period and thus heavy rain will remain a
threat throughout.

&&

.LONG TERM /Tuesday through Friday/...

Issued at 238 AM EDT Sat Aug 27 2016

ECMWF suggests NW flow persists aloft on Tuesday as a weak short
wave sweeps through Great lakes and brushes Indiana. Best forcing
looks to remain well north of Central Indiana...however and
associated cold front is expected to push across Indiana and the
Ohio valley On wednesday. Change in air mass is expected with
much less humid air arriving on Northerly winds. Thus expected at
least low chc pops for Tuesday and into Wednesday as these
features pass.

Dry weather is expected on Thursday and Friday. ECMWF suggests
high pressure building across the area along with ridging in the
upper levels. Furthermore excellent subsidence is seen in the
middle levels streaming into Indiana on dry NE winds. Thus have
trended dry at time with a return to near normal temperatures.

&&

.AVIATION /Discussion for the 270900z ind taf update/...

VFR conditions will continue the next few hours as another short
wave streams northward into central indiana this morning. Ongoing
taf remains in good shape. With dew point depressions being so
small... some mvfr fog cannot be ruled out. Ongoing Tempo group
handles that well.

Previous Discussion below

/Discussion for the 270600Z TAFS/...
Issued at 1227 AM EDT Sat Aug 27 2016

Can't rule out widely scattered convection overnight given the weak
frontal zone in the area, but 850mb flow looks fairly weak tonight, 
so don't think the convective threat is all that high overnight.

Model guidance suggests remnant vorticity center from convection over
the Tennessee Valley will be drifting north into the local area 
by the mid morning hours of Saturday. As a result, convective threat
should increase across the terminals by that time.

Some concern for the development of IFR ceilings/visibilities 
overnight given the nearly saturated air mass, but with expected
higher level cloud cover, confidence in IFR is low.

Light surface winds overnight expected to become 120-160 degrees at
5-8 kts by late morning Saturday.


&&

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

$$

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

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