Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 241820
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
220 PM EDT WED AUG 24 2016

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

&&

.SYNOPSIS...
Issued at 325 AM EDT Wed Aug 24 2016

A closed upper low will continue its track across southern
Saskatchewan and Manitoba, while a surface low and associated cold
front enter the Mississippi Valley. These features will be the
leading contributors to weather across Central Indiana through the
end of the week. First though, a weak wave ahead of the
aforementioned surface low will track across Wisconsin today,
triggering the first round of showers and thunderstorms across
Central Indiana early this morning. Further enhancement will be
provided as a cold front tracks across the forecast area tomorrow,
resulting in showers and thunderstorms into Friday morning. After
that, a brief lull in activity will commence on Friday afternoon
through Saturday morning. But, another upper trough will push into
the Upper Midwest late Saturday, bringing yet another round of
showers and thunderstorms to Central Indiana into next week.

&&

.NEAR TERM /Rest of Today/...
Issued at 944 AM EDT Wed Aug 24 2016

Area of showers and thunderstorms across Illinois continues to
evolve with northern areas weakening and the storms over central
Illinois strengthening. Have upped PoPs to likely this morning
across the far northwest to account for the stronger convection in
central Illinois.

Later today evolution of the convection is a bit murkier as the
storms move into less favorable air initially but with instability
increasing again during the afternoon. Short term hi res models are
still playing catch-up with current storms so confidence in their
solutions is low. Thus left afternoon forecast alone and will modify
when trends become clearer.

Lowered high temperatures a bit northwest given better chances for
convection this morning. Otherwise left them alone for now.

Previous discussion follows...

The main focus of the near term period will be shower and
thunderstorm chances as a shortwave enters Wisconsin.

Current radar mosaic is showing some sporadic showers and isolated
thunderstorms upstream across Iowa and Illinois. This activity
should start filtering into western portions of the forecast area
around daybreak, spreading eastward throughout the morning.
Thunderstorm chances will increase by late morning/early afternoon
with best forcing across the northwestern quadrant of the forecast
area due to enhancement from both 300 and 850 mb jets. As a
result, most of the area is under a Marginal risk for severe
weather.

High temperatures will soar into the mid to upper 80s, further
enhancing instability across the area this afternoon.  Generally
stuck close to a model blend for today`s highs.

&&

.SHORT TERM /Tonight through Friday Night/...

Issued at 325 AM EDT Wed Aug 24 2016

Thunderstorm potential will become further enhanced across the
northwestern counties tonight and tomorrow morning as low level
jet increases just ahead of approaching cold front. As a result,
will go with likely pops across the northern counties for tonight.
Meanwhile, SPC keeps the northern half of Central Indiana under a
Marginal risk for severe weather once again for Thursday as
aforementioned cold front passes through the area providing
forcing.

Showers and thunderstorms will linger across the southern counties
into Friday morning, but the remainder of Central Indiana will be
dry by then as high pressure strengthens at the surface across the
Midwest.

Temps through the period will climb into the upper 80s/low 90s
tomorrow with decent warm advection ahead of cold front. However,
temps will take a dip on Friday in the wake of the cold front,
falling back into the low to mid 80s. Meanwhile, overnight lows
will generally be in the 60s and 70s.

&&

.LONG TERM /Saturday Night through Wednesday/...

Issued at 218 PM EDT Wed Aug 24 2016

The blended forecast from the Regional initialization can be used
with moderate confidence.

The models generally agree in depicting a short wave trough moving
across the Great Lakes early in the period with a frontal
boundary gradually sinking south across our area Monday and
Tuesday. Prior to the fronts arrival in warm and unstable air
with upper troughing aiding in lift...expect the potential for
scattered convection. Once the front moves in and across the area
Monday the storm threat will be slightly higher. As that front
settles south of our area heights remain high and with humidity
still lingering...day time heating may still trigger some
isolated storms. By Wednesday another upper trough approaching
from the west will return a slightly higher storm threat and
slightly higher coverage as well.

With relatively high heights this will be a relatively warm
period with lows in the upper 60s or lower 70s...similar
to guidance...while highs generally reach mid 80s to around
90. Once the front moves through these readings will only drop a
category with lows into the low/mid 60s and highs mid 80s.
Dewpoints will only be slight drier.


&&

.AVIATION /Discussion for 241800z TAFs/...

Issued at 1257 PM EDT Wed Aug 24 2016

Winds this afternoon above 10 knots gusting to 20 knots from
south to southwest but drop off before sunset.

Thunderstorm threat is most likely for KLAF through 241900Z.
Remaining TAF sites much more questionable for thunder. Air
does continue to destabilize and potential does exist for current
line of storms KVPZ to KCMI to develop further south of KCMI and
thus affect KHUF, KIND and KBMG. Rapid Refresh model suggests
potential as well so will carry a VCTS threat for these sites this
afternoon.

Short wave causing current convection over IL and IN will exit
with its rain threat by 250000z. Some models continue a threat
this evening but probabilities are too low to carry even as a
mention in TAFs. Some light fog near daybreak Thursday especially
at KLAF where rain has occurred.

Next rain threat is with cold front but that occurs after 252100Z.


&&

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

$$

SYNOPSIS...TDUD
NEAR TERM...TDUD/50
SHORT TERM...TDUD
LONG TERM....TUCEK
AVIATION...TUCEK



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