Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 201048
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
648 AM EDT Sun Aug 20 2017

.UPDATE...The NEAR TERM section has been updated below.

&&

.SYNOPSIS...
Issued at 324 AM EDT Sun Aug 20 2017

Dry weather is expected through Monday morning. Then, a strong cold
front will interact with a very warm, moist and unstable atmosphere
and result in unsettled weather over central Indiana Monday night
through Tuesday night. A few strong or severe storms are possible.
Northwestern parts of central Indiana could even see a few storms as
early as Monday afternoon.

Broad surface high pressure will build in behind the cold front and
result in dry and cooler weather.

&&

.NEAR TERM /Today/...
Issued at 648 AM EDT Sun Aug 20 2017

With an area of storms about to move into Knox county, will thrown
in 20 percent pops there through 13z. After that, the cap should
strengthen, discouraging any cell from forming or at least lasting
long, despite the front being around.

Previous discussion follows...
Issued at 324 AM EDT Sun Aug 20 2017

Main concern for the near term is potential for isolated storms to
form along a stationary front that stretched from around Sullivan to
Bloomington to Greensburg. Convergence along this line, in proximity
of a 500 plus J/KG CAPES, was responsible for a few evening pop up
storms. However, models were showing upper ridging over the area
today even as the surface high moves to the Appalachians and east
coast. With an upper ridge over the area and 700 millibar
temperatures increasing to around 10 degrees Celsius, there will be
a decent cap in place and there will be very little of chance
anything developing along the front based on research with August
700 millibar temperatures over the area and thunderstorm initiation.
Still, with convective temperatures in the mid 80s, and a weak upper
wave approaching, can not completely rule out a stray pop up south
central. Still, chances will be too low to mention.

Cu development progs suggests there could be a few to scattered
diurnal fair weather cu. Otherwise, could see some cirrus blowoff
from the Iowa storm complex.

Light southerly flow and plenty of sunshine support above normal
blend highs in the upper 80s and lower 90s, around or slightly
warmer than yesterday. The heat index could reach the mid 90s over
southwestern sections during the middle and late afternoon.

&&

.SHORT TERM /Tonight through Tuesday night/...
Issued at 324 AM EDT Sun Aug 20 2017

Due to the looming eclipse, not only severe weather will be a
concern, but also the cloud cover for Monday afternoon, prior to the
bulk of the unsettled weather.

Models in good agreement that a strong cold front will dive
southeast across central Indiana Tuesday night. The front will
interact with deep moist and very warm, moist and unstable air. This
will result in scattered to numerous thunderstorms mainly Monday
night through Tuesday evening. Also, models are trending quicker
with the convection supporting moving up thunderstorm chances to
areas near and north of Interstate 70 to Monday afternoon.
Coordinated with adjacent offices and the general feel is fairly
thick upstream cirrus blowoff shield is an increasingly very real
concern regarding viewing the eclipse over central Indiana. Thus,
will raise cloud cover to near more than 40 percent with the highest
over the northwestern half of the area.

Low level jet will pump 2 inch plus precipitable water amounts over
the area overnight Monday night and Tuesday. This should bring more
widespread storms to the area with the potential for some heavy rain
in addition to the possibility of severe weather. 30 to 50 knots
deep shear in addition to 500-1500 mixed layer CAPE support the SPC
Day2 Marginal Risk northwest and Day 3 Slight Risk southeast with
damaging winds the main severe threat.

With the front expected to be southeast of the area by 06z
Wednesday, will end pops overnight Tuesday night from northwest to
southeast per the blend.

With the eclipse, high clouds and possible nearby convection, will
cut blend highs Monday, otherwise blend has a good handle on cooling
behind the front. Should see temperatures some 5 degrees or so below
normal by Tuuesday night.

&&

.LONG TERM /Wednesday through Saturday/...
Issued at 244 AM EDT Sun Aug 20 2017

Ensembles are in good agreement during this period, depicting a long
wave trough over the eastern parts of the country, resulting in
northwesterly upper flow locally.

Ensembles suggest a dry and stable air mass will reside over the
local area, with little threat for precipitation in the extended.
Will go with a dry forecast.

&&

.AVIATION /Discussion for 201200Z TAF Issuance/...
Issued at 635 AM EDT Sun Aug 20 2017

BMG and HUF have seen IFR conditions in fog overnight. However,
moderate to good confidence that fog will burn off by 13z or shortly
thereafter. Then, good confidence VFR conditions with just diurnal
cu and passing cirrus through at least 09z Monday. Then, would not
rule out brief fog again at the smaller airports, but too far out
too throw in there at this point.

Winds will become south less than 5 knots.

&&

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

$$

SYNOPSIS...MK
NEAR TERM...MK
SHORT TERM...MK
LONG TERM....JAS
AVIATION...MK



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