Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 202025

Area Forecast Discussion
National Weather Service Indianapolis IN
424 PM EDT WED JUL 20 2016

The AVIATION Section has been updated below.


Issued at 137 PM EDT Wed Jul 20 2016

A large area of High pressure over the southern plains...filled
with heat and humidity will build across central Indiana over the
next few days and through much of the weekend. This will result in
hot and very humid weather into Sunday.

An isolated afternoon or evening showers or storms will be
possible...particularly on Friday...however no well organized
storm systems look to arrive in the area until Sunday night.

Thus hot and humid weather is expected to continue into the
weekend...with a cool down expected by Monday as a cold front is
expected to pass.


.NEAR TERM /Tonight/...

Issued at 137 PM EDT Wed Jul 20 2016

Surface analysis early this afternoon shows High pressure in place
across NY and PA...with southerly flow pouring into the ohio
valley and Indiana. Water Vapor Imagery shows a large area of
high pressure aloft over the southern plains states. Tropical
moisture streaming around the high was found across the four
corners to Nebraska and then east to Illinois and Indiana. A few
shra/tsra were embedded within this flow across illinois.

Upper flow suggests a ridge axis over Wisconsin and the Western
Great Lakes that should build across Indiana Tonight and into
Thursday. This will result in subsidence and suppression of
convection. As time heights and forecast soundings continue to
suggest a dry column. Thus will trend toward a partly cloudy sky
and very warm low. Given the little change in air mass and the
very high dew points will trend toward warmer side of a blend on


.SHORT TERM /Thursday through Saturday/...

Issued at 137 PM EDT Wed Jul 20 2016

Mainly and very humid weather is expected through this
period. Upper ridge axis is expected to settle across the state as
850mb thermal ridge with temps near 22c is expected to sag south
across Central Indiana. With Dew points across the region in the
70s expected...heat index values will surge into advisory criteria
for friday...above 105. This looks to continue into the weekend as
little chance of air mass is expected until sunday night. Forecast
soundings through the period remain dry...but decent instability
remains in place each afternoon as forecast soundings show
convective temps...for the most the middle 90s with
plentiful CAPE each afternoon. However 700mb temps near 11C along
with ridging aloft...may provide a good cap...particularly on
Thursday. THus will try and trend toward a dry forecast through
Friday afternoon.

Models are also hinting at a weak ridging riding short wave on
Friday night...which due to some weakness within the ridge could
result as a trigger for showers/storms or possible MCS development
for Friday night and into early Saturday. Thus will try and focus
low chance pops at that time for these features...however
confidence remains low.

Another Set of short waves looks to push across Indiana within the
flow aloft on Saturday...again confidence remains very low at this
point...however with the hot and very humid air mass
expected...any triggering mechanism cannot ignored.

Daily Highs on Friday and Saturday should easily reach the lower
90s...this in combination with the expected high dew points in the
lower 70s will resulting in heat advisory criteria...105...being
met on Friday...and potentially on Saturday. Will kick off the
heat advisories for Friday with this issuance. Try and Stay


.LONG TERM /Saturday night through Wednesday/...

Issued at 207 PM EDT Wed Jul 20 2016

Mid level ridge will still be in full force from the Rockies
eastward through the Ohio Valley at the beginning of the period.
The center of this ridge is expected to be over southern MO, so
Saturday night and Sunday will be hot (temperatures low/mid 90s)
and humid. The ridge gets squeezed eastward as a trough begins to
sweep south and east into the Upper Great Lakes on Monday. The
trough will move from northwest IL into northwest and west
central IN Sunday night. Think rain and tunderstorms will be
scattered along this front going into Monday morning. As the ridge
continues to move off into the mid-Atlantic region, the cold front
looks to get hung up over central/southern IN Monday due to
heights at mid levels still forecast to be at 5910 gpm. This will
keep precipitation around on Monday as the trough moves off to the
east. Confidence: Medium-High on temperatures, medium on

Tuesday looks warm with temperatures in the mid 80s (around normal
for now) as does Wednesday as the next shortwave trough moves
towards IN Wednesday night/Thursday time period.


.AVIATION /Discussion for the 212100Z KIND TAF Update/...

Issued at 424 PM EDT Wed Jul 20 2016

Widely scattered convection currently across the area associated with
an instability axis over western Indiana. This will probably continue
through about sunset, but activity should remain sparse enough in
coverage that threat for direct impacts at any one particular terminal
is low.

Previous discussion follows.

VFR conditions expected to remain in place through tonight. All
sites with the exception of KIND may see MVFR conditions during
the early morning hours on Thursday due to some fog.

High pressure is centered over eastern Lake Erie with a quasi
stationary front that lies over the Ohio River region on IN/IL.
There has been a band of clouds from NNW to SSE that have been
flowing SSEWD with the mid level flow. These clouds are on the
immediate periphery of mid/upper level high over the central
Plains. This high will be extending east over central Indiana
next few days bringing very warm conditions accompanied by some
haze. Low confidence of -TSRA at this time so have not included it
with the TAFS for Thursday afternoon/evening.


.IND Watches/Warnings/Advisories...


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