Area Forecast Discussion
Issued by NWS Indianapolis, IN

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418
FXUS63 KIND 210449
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1249 AM EDT THU JUL 21 2016

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

&&

.SYNOPSIS...
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 /Overnight/...
Issued at 946 PM EDT Wed Jul 20 2016

One lone convective cell has popped up in the northeast Indy
suburbs over the last 20-30 mins...likely from remnant outflow
from isolated storms earlier this evening. Stifling...muggy
airmass this evening with dewpoints in the mid and upper 70s over
much of the forecast area. 0130Z temps ranged from the mid 70s to
the lower 80s.

As has been the case throughout the evening...these cells pop up
in the moist unstable airmass as they interact with old outflow...
then weaken and diminish within 15-30 mins as they move away from
the boundary. Expect this shower near Fishers to do likewise by
02-0230Z and with little to no forcing aloft present for
additional convection to form overnight and a slowly stabilizing
boundary layer with the loss of daytime heating...will continue
with a dry forecast.

Should see clouds gradually diminish as well as the high centered
to our east pokes back into the region. Have introduced patchy fog
mention everywhere for late tonight as the combination of stagnant
boundary layer flow and dewpoints likely to remain at or above 70
are supportive for localized diminished visibilities. nudged low
temps up a degree or two as well with most areas remaining in the
70s through the night.

Zone and grid updates out.

&&

.SHORT TERM /Thursday through Saturday/...

Issued at 137 PM EDT Wed Jul 20 2016

Mainly dry...hot 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 part...in 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
Frosty!

&&

.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 thunderstorms 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
precipitation.

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 21/0600Z TAF Issuance/...

Issued at 1247 AM EDT Thu Jul 21 2016

Crossover temperatures should be reached or exceeded after
210600Z tonight, so expecting areas of IFR visibility restrictions
in fog to develop after that time. Chances of IFR restrictions at
KIND are lower due to the urban heat island.

Surface winds less than 7 kts tonight.

&&

.IND Watches/Warnings/Advisories...
Heat Advisory from 10 AM Friday to 8 PM EDT Saturday for INZ021-
028>031-035>049-051>057-060>065-067>072.

&&

$$

SYNOPSIS...PUMA
NEAR TERM...RYAN
SHORT TERM...PUMA
LONG TERM....DWM
AVIATION...JAS



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