Area Forecast Discussion
Issued by NWS Indianapolis, IN

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KIND 160321
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1121 PM EDT Mon Jul 15 2019

.UPDATE...

The Aviation section has been updated below.

&&

.SYNOPSIS...
Issued at 321 PM EDT Mon Jul 15 2019

The remnants of Barry will lift into the Ohio Valley through Tuesday
night bringing scattered strong storms with heavy rainfall to
central Indiana. The remnants will shift east of the area Wednesday
with focus shifting to the arrival of the hottest and most humid air
of the season beginning Thursday and continuing into next weekend.

&&

.NEAR TERM /Tonight/...
Issued at 321 PM EDT Mon Jul 15 2019

After a sunny first half of the day for many...the cirrus shield
associated with the remnants of Barry have made steady progress into
the southern half of the forecast area. Steadier rainfall associated
with the remnants have drifted into the lower Wabash Valley but made
little further movement north to this point. Scattered convection
has fired in the vicinity of a differential heating boundary where
instability was pooling just east of the forecast area along the
Indiana-Ohio border. 19Z temperatures ranged from near 80 in the
southwest where clouds and rain were...to around 90 further north
where more sun had been realized.

Am a bit less optimistic about Barry induced convection developing
the rest of the afternoon as the thicker cloud shield is limiting
heating with an already paltry instability profile over much of the
forecast area that may be courtesy of subsidence immediately ahead
of the remnants. An axis of minimum precip water values at around
1.4 inches that is just now beginning to increase would also support
this idea. Would appear that the primary convective threat will
reside over far eastern and northeast portions of the forecast area
where CBs are already better developed and congested in the vicinity
of the differential heating boundary into the early evening with
more isolated activity elsewhere.

As for the area of widespread steady rainfall moving into the lower
Wabash Valley...overall model trends off the CAMs suggest coverage
diminishing and becoming more scattered into the evening as it moves
further into central Indiana and considering an overall lack of
forcing aloft...that seems reasonable at this point. In addition...
that process appears to have already started as overall rainfall
rates have weakened a bit. Really hard to justify much more than
chance pops into the evening at this point as the deeper moisture
gradually advects into the region.

As the upper level circulation associated with the remnants approach
the region overnight...better forcing aloft will expand into central
Indiana with a low level jet nosing in as well. This may serve to
increase the convective threat a bit late tonight but with lack of
heating and more substantial instability...not expecting any more
than scattered convection.

Temps...with the arrival of the tropical moisture fetch into the
region tonight...most if not the entire forecast area will remain
above 70 degrees. Trended towards the warmer MET guidance.

&&

.SHORT TERM /Tuesday through Thursday/...
Issued at 321 PM EDT Mon Jul 15 2019

Forecast challenges focus on two primary storylines through the
period: the impact from the remnants of Barry on Tuesday and
possibly the first part of Wednesday...and the arrival of oppressive
heat and humidity in wake of the system beginning Thursday.

Some changes noted on model guidance today with respect to the
remnants of Barry. Now appears the upper level circulation will
weaken to an open wave and shift east quicker than previously
thought. The result here is likely to be now that the main potential
for greater convective coverage will shorten to Tuesday and Tuesday
night with activity becoming more scattered Wednesday as the
weakening remnants depart off to the east faster.

CAMS continue to advertise the greatest potential for numerous
storms to develop focusing Tuesday afternoon and night as the upper
energy moves into the region and some weak diffluence aloft develops.
Model soundings showing a moist airmass up through 15kft with narrow
CAPE profiles and a broad above freezing layer extending to about 13-
14kft. Precip water values will surge above 2 inches and with warm
rain processes in play...any shower or storm will produce enhanced
rainfall rates with the potential for localized flooding. Remain a
touch concerned about a threat for a few cells to rotate with
favorable hodograph profiles...increased shear and helicity
values...and LCLs likely to settle near 1000ft...especially by late
day. Overall instability levels may not be quite enough to
support...but considering the presence of a deep tropical airmass
and that much of the forecast area is likely to be to the right of
the weakening surface wave track where shear may briefly
maximize...this will be something to keep an eye on Tuesday.

The precip water values will peak on Tuesday night at 2.3 to 2.4
inches as the center of the remnants pass through central Indiana.
Storms may be limited with instability levels diminishing further
but expect convection to continue across the area with showers
producing heavy rainfall akin to what you might see in the tropics.
Likely pops are warranted across the entire forecast area Tuesday
night and early Wednesday. More extensive convection will shift east
of the region by midday Wednesday with a transition back to
isolated/scattered storms Wednesday afternoon influenced heavily by
better instability and lingering deep moisture. That being
said...the window for convection will narrow rapidly Wednesday
afternoon and evening as soundings show an increasing capping
inversion developing with heights aloft rising.

Wednesday night and Thursday will see a full transition to our
second headline regarding the heat and humidity as deep ridging
aloft expands into the Ohio Valley. The presence of a lingering
layer of tropical moisture in the wake of the remnants of Barry will
ensure downright filthy dewpoints that may rise into the 74 to 77
deg range by Thursday afternoon. The result will be the hottest and
most humid airmass of the season to date and potentially the most
uncomfortable heat experienced in central Indiana in the last few
years. Cannot rule out a few storms developing during peak heating
but most will remain dry. And this is just the beginning as the high
heat and humidity continues into the upcoming weekend.

Temps...Tuesday and to a lesser extent Wednesday will provide a
brief reprieve from the hotter weather as more clouds and storms
will keep highs primarily in the 80s. With the faster departure of
Barry Wednesday...nudged temperatures up a bit with the possibility
that a few locations get to 90. The real heat and humidity though is
set for Thursday with low level thermals supporting going above
guidance with many areas into the mid 90s. With the dewpoints
mentioned above...heat indices peaking at 105 to 110 appear possible
Thursday afternoon. Will continue to highlight via the HWO but a
foregone conclusion that heat headlines will be needed by Thursday
extending into the weekend.

&&

.LONG TERM /Thursday night through Monday/...
Issued at 240 PM EDT Mon Jul 15 2019

Models and ensembles in agreement that broad ridging will persist
through the long term. This will keep the heat and humidity around
and supports the 90 plus degree afternoon highs from the blend
through at least Sunday. Dew point temperatures in the 70s combined
with the plus 90 degree temperatures will result in afternoon heat
indices in excess of 100 degrees.

The ridge will also support mainly dry weather, although would not
rule out a few heat of the day storms during the weekend.

&&

.AVIATION /Discussion for the 16/06Z TAFs/...
Issued at 1121 PM EDT Mon Jul 15 2019

VFR initially and overnight will likely give way to MVFR on
Tuesday as the remnants of Barry approach.

Showers and storms are likely to be in the area, and will carry
showers with vicinity thunder much of the period tomorrow onward.

Winds will generally be southerly through the period, and may gust
to around 20KT or so at times. Ceilings will be the primary
limiting factor, but visibililies may drop in the heavier showers
and storms at times.

&&

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

&&

$$

SYNOPSIS...Ryan
NEAR TERM...Ryan
SHORT TERM...Ryan
LONG TERM...MK
AVIATION...Nield


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.