Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 230950
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
550 AM EDT SAT JUL 23 2016

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

&&

.SYNOPSIS...
Issued at 326 AM EDT Sat Jul 23 2016

Hot and humid weather will continue through the weekend. Only small
chances for storms are in the forecast until Sunday night and Monday
when a cold front will move through the area. After that
temperatures will be closer to normal for the rest of the week.
After a dry day on Tuesday thunderstorm chances return midweek as
another frontal system passes through.

&&

.NEAR TERM /Today/...

Issued at 326 AM EDT Sat Jul 23 2016

Early this morning through mid morning expect to see patchy dense
fog to areas of fog around the forecast area, with ample low level
moisture available and light winds. At this point, cirrus moving
in is helping keep some visibilities bouncing around and
preventing widespread dense fog. A few observations have already
dropped to a quarter mile though, and may need to issue a dense
fog advisory. Will reserve decision for just before package
issuance.

Solid cap in place with 700 mb temperatures 11-12C over the area
should keep dry weather for most of the area through the day. During
the late afternoon/evening could see isolated locations get enough
heating to break the cap, but with no real focusing mechanism don`t
expect to see anything widespread. Will go with dry pop through the
morning and then ramp up to a 20 pop for late afternoon/evening.

For temperatures expect a hot and humid day with highs in the low
to mid 90s. Think area will see more sunshine than yesterday
given the lack of storms early this morning and thus high
temperatures should be a few degrees warmer. With dew points still
expected to be in the mid 70s through the day looking at max heat
index values in the solid 100 to 110 degree territory and thus
will continue with heat advisory for today.

&&

.SHORT TERM /Tonight through Monday night/...

Issued at 326 AM EDT Sat Jul 23 2016

Some differences in the models in the details on the progression of
shortwaves through the main flow and as a result lower than average
confidence on thunderstorm chances during the short term, especially
for tonight through Sunday. A shortwave looks like it will move into
northern Illinois/Indiana overnight, but how far south this prompts
convection depends on the model you choose. thus will put some pops
in but confine the highest values over the northern counties and may
go dry south for Saturday night. Sunday the GFS wants to bring
precip across the entire area early and keep it here through the
day. The NAM and ECMWF seem to keep the area capped through the day
and shift the precip focus north until Sunday night and then bring
it through with the cold front. This solution seems more reasonable
and will lean this way, but will keep some lower chances going on
Sunday with the potential there. Will increase pops for Sunday night
into Monday with better model agreement on QPF during that time and
better overall forcing with the front.

High temperatures will be highly dependent on whether or not
precip/clouds arrive to mitigate heating. With the preference for
lower pops will lean toward warmer high temperatures and thus heat
advisory conditions possibly extending into Sunday. Monday`s frontal
passage should bring some relief with highs dropping back into the
80s and lower dewpoints advecting in behind the front.

&&

.LONG TERM /Tuesday through Friday/...

Issued at 221 AM EDT Sat Jul 23 2016

Superblend keeps at least chc pops each day in the forecast as
humid air remains across the Ohio Valley and Diurnal showers and
storms cannot be ruled out. However...synoptically speaking...the
ECMWF brings two systems across Central Indiana during this
period. The first is a quick moving short wave that sweeps across
the area on Wednesday night into Thursday. This system appears to
be accompanied by ample moisture along with a surface low pushing
through the region. Thus better chances for pops here. The second
arrives on Friday night into Saturday as the ECMWF suggests a
broad trough in the upper flow. Again...with better organization
in place that that time better chance for rain are expected then.

With no real intrusions of Canadian Air...typical summertime
temperatures in Indiana are expected.

&&

.AVIATION /discussion for the 231200z tafs/...

Issued at 550 AM EDT Sat Jul 23 2016

LIFR fog across the taf sites is expected to burn off quickly this
morning...leading to VFR conditions by 15z.

Surface obs show many of the taf sites at IFR or worse. Heat
island effects keeping visibilities at IND VFR. Surface high
pressure was in place across the region...providing mainly clear
skies and light winds.

Very High dew points combined with heating will lead to SCT-BKN CI as
suggested by the forecast soundings. Forecast soundings through
Sunday morning never show deep saturation...suggesting storms
never develop. However...confidence in this remains low as ample
CAPE remains available and water vapor imagery shows a shortwave
within the ring of fire over Nebraska and South Dakota poised to
spill into or toward Indiana. Will not be surprised is VCTS or
prevailing thunderstorm occur this taf period...but confidence too
low for a mention.

More IFR fog expected tonight with the similar air mass remaining
in place.

&&

.IND Watches/Warnings/Advisories...
Heat Advisory until 8 PM EDT this evening for INZ021-028>031-
035>049-051>057-060>065-067>072.

Dense Fog Advisory until 9 AM EDT this morning for INZ051>053-
060>063-067>071.

&&

$$

SYNOPSIS...CP
NEAR TERM...CP
SHORT TERM...CP
LONG TERM....PUMA
AVIATION...JP


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