Areal Flood Warning 20, NWS Indianapolis, IN

Area Forecast Discussion
National Weather Service Indianapolis IN
628 AM EDT SAT AUG 27 2016

.UPDATE...
The AVIATION Section has been updated below.

&&

.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 271200z tafs/...

Issued at 628 AM EDT Sat Aug 27 2016

Mainly VFR Conditions are expected. Thunderstorms will be expected
this afternoon...MVFR/IFR conditions will accompany any
thunderstorm that strikes a taf site.

HRRR suggesting convection across the taf sites appears
wrong...as Radar fails to show any development
upstream...southwest of the taf sites. for now precip is contained
across mainly Illinois. Thus will keep tafs VFR and contain
convection to this afternoon as forecast soundings suggest
convective temps will once again be reached with plentiful CAPE
and high pwats. No specific timing or prevailing grounds at this
point and will just use VCTS.

As heating is lost and the passing wave departs...will end vcts
window this evening. Very low dewpoint depressions and minimal
mixing along with plentiful lower level moisture should lead to at
least some MVFR fog on early Sunday.

&&

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

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE INDIANAPOLIS IN
438 AM EDT SAT AUG 27 2016

INZ021-028>031-035>049-051>057-060>065-067>072-280845-
CARROLL-WARREN-TIPPECANOE-CLINTON-HOWARD-FOUNTAIN-MONTGOMERY-BOONE-
TIPTON-HAMILTON-MADISON-DELAWARE-RANDOLPH-VERMILLION-PARKE-PUTNAM-
HENDRICKS-MARION-HANCOCK-HENRY-VIGO-CLAY-OWEN-MORGAN-JOHNSON-SHELBY-
RUSH-SULLIVAN-GREENE-MONROE-BROWN-BARTHOLOMEW-DECATUR-KNOX-DAVIESS-
MARTIN-LAWRENCE-JACKSON-JENNINGS-
INCLUDING THE CITIES OF...LAFAYETTE...FRANKFORT...KOKOMO...
CRAWFORDSVILLE...ANDERSON...MUNCIE...INDIANAPOLIS...TERRE HAUTE...
SHELBYVILLE...BLOOMINGTON...COLUMBUS...VINCENNES...BEDFORD...SEYMOUR
438 AM EDT SAT AUG 27 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL INDIANA.

.DAY ONE...TODAY AND TONIGHT.

OUTLOOK: CHANCE FOR THUNDERSTORMS. STRONG TO SEVERE STORMS
POSSIBLE.

HAZARDS: DAMAGING WINDS. TORRENTIAL RAINFALL LEADING TO FLASH
FLOODING. ISOLATED TORNADOES. LIGHTNING.

TIMING: THUNDERSTORMS COULD OCCUR ANYTIME. BEST CHANCES FOR STRONG
TO SEVERE STORMS THIS AFTERNOON AND EVENING.

DISCUSSION: AN UPPER WAVE INTERACTING WITH A STALLED FRONT WILL
KEEP CHANCES FOR THUNDERSTORMS IN THE FORECAST THROUGH THE DAY. A
WEAK LOW LEVEL JET COULD COMBINE WITH THE UNSTABLE AIR AND STALLED
FRONT TO PRODUCE A FEW STRONG TO SEVERE STORMS LATER TODAY.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

OUTLOOK: THERE ARE CHANCES FOR THUNDERSTORMS THROUGH WEDNESDAY. AT
THIS TIME WIDESPREAD SEVERE STORMS ARE NOT EXPECTED.
LIGHTNING...TORRENTIAL DOWNPOURS LEADING TO FLASH FLOODING AND
GUSTY WINDS WILL BE THE MAIN THREATS.

DISCUSSION: UPPER WAVES MOVING THROUGH THE REGION ON THE EDGES OF
AN UPPER RIDGE WILL COMBINE WITH A REMNANT FRONTAL BOUNDARY TO
MAINTAIN PERIODIC CHANCES FOR THUNDERSTORMS THROUGH THE MIDDLE OF
NEXT WEEK.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS UNLIKELY...BUT CANNOT BE RULED OUT FOR THIS
AFTERNOON/EVENING.

&&

MORE INFORMATION...ALONG WITH OTHER WEATHER...HYDROLOGICAL AND
CLIMATE INFORMATION CAN BE FOUND...AT HTTP://WEATHER.GOV/IND (ALL
LOWERCASE)

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