Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 240433
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1233 AM EDT Wed May 24 2017

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

&&

.SYNOPSIS...
Issued at 314 PM EDT Tue May 23 2017

Wet weather will move back into central Indiana overnight and hang
around through the day on Thursday. By Thursday night upper ridging
starts to build into the area and conditions should be dry until
midday Friday. An upper wave will approach then along with another
frontal system and they will keep chances for showers and
thunderstorms in the forecast through Sunday.

&&

.NEAR TERM /Tonight/...
Issued at 934 PM EDT Tue May 23 2017

Current forecast looks in good shape at this time. Short term
model guidance suggests lift tonight will be rather disorganized
for the most part, with the better lift holding off until after
sunrise on Wednesday. No updates planned at this time. Previous
discussion follows.

An upper low will swing southeast from Minnesota tonight and bring
some upper forcing in from the west tonight. Chances for rain will
increase from west to east through the night, and eastern counties
will likely remain dry until early Wednesday morning. A broad
surface low looks like it will begin to form over the area late
during the overnight. Low temperatures should still be able to drop
into the low to mid 50s despite ample cloud cover due to cooler
temperatures aloft.

&&

.SHORT TERM /Wednesday through Friday/...

Issued at 314 PM EDT Tue May 23 2017

Wednesday the day will start with surface low pressure centered
possibly directly over Indiana, but it will be pretty broad. The
circulation firms up and strengthens through the day but also moves
off to the southeast before it circles back over the area. This is
due to the stalling track of the upper low. The best upper forcing
will move through the area during the afternoon and thus have
categorical pops during that time. Some instability will be
available as southerly flow ahead of the low draws moisture up into
the low itself. While severe chances look better to the east, the
surface low over the area and a boundary hanging behind the low as
it moves east will allow for a very localized increase in low level
vorticity. LCLs will be low also due to the presence of the surface
low and thus will need to monitor for isolated weak tornado
potential.

The low spends Wednesday night wrapping up before moving out of the
area during the day on Thursday. This will keep rain over the area
through much of Wednesday night, and through at least the morning in
the eastern counties as it exits. The presence of the upper low will
also keep high temperatures in the 60s on both Wednesday and
Thursday as temperatures aloft are cooler in the base of the upper
low and cloud cover will be ample.

Thursday night brief upper ridging moves through the area and should
dry things out and clear out sky cover. Friday should be dry through
midday but by afternoon the upper ridging is moving to the east and
another upper wave is approaching and could bring in chances for
showers and thunderstorms in the warmer southwest flow.

&&

.LONG TERM /Friday Night through Tuesday/...
Issued at 258 PM EDT Tue May 23 2017

Unsettled and active weather is the headline for the upcoming
holiday weekend as a frontal boundary and wave aloft combine to
bring the potential for scattered convection to impact central
Indiana at times through Sunday.

A broad upper low will set up over the Canadian prairies with
pieces of energy ejecting from the base of the parent low east
into the Mississippi and Ohio Valleys within a wavy southwest flow
aloft regime. Aforementioned frontal boundary will align across
the Ohio Valley beginning Friday night and remain over the area
before shifting southeast by late weekend as the upper low drops
southeast.

While model differences in timing remain...some clarity starting
to develop in terms of timing higher impacts to the area and
potential for heavy rainfall and severe weather. An initial wave
tracking through the area and along the boundary Friday night and
early Saturday showing hints of a potential MCS. Additional
impacts appear likely Saturday afternoon and evening with
possibility for robust convection in the vicinity of the frontal
boundary to develop in a warm and modestly unstable airmass. CIPS
analogs strongly suggestive that highest severe weather threat may
exist across central Indiana on Saturday.

Convective threats diminish through the day Sunday as the front
shifts south and region comes under the influence of cyclonic flow
associated with the upper low sagging into the Great Lakes. At
this point...dry and cooler weather is expected for early next
week although a lingering presence of northwest flow aloft as the
week progresses is suggestive of a continued convective threat.

&&

.AVIATION /Discussion for the 240600Z TAFS/...
Issued at 1233 AM EDT Wed May 24 2017

Potential for scattered shower activity in the vicinity of the
terminals overnight, but it appears better threat for more organized
precipitation will probably hold off until towards the late morning
or midday hours of Wednesday, when better lift arrives. Some
lightning strikes possible after about 241600Z-241700Z with rather
low convective temperatures.

Ceilings above 050 expected for the most part overnight, with the
potential for areas of ceilings near the 050 level towards the
midday hours Wednesday. Some diurnal cloud development near 025 also
possible by the late morning or midday hours.

Surface winds generally 6 kts or less through midday Wednesday.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SYNOPSIS...CP
NEAR TERM...CP/JAS
SHORT TERM...CP
LONG TERM....Ryan
AVIATION...JAS/JH


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