Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 230622

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

The LONG TERM Section has been updated below.


Issued at 355 PM EDT Fri Jul 22 2016

A large ridge over much of the nation will keep a hot and humid
airmass in place across central Indiana through the weekend.
Isolated thunderstorms cannot be ruled out, although most areas
appear likely to be dry through the early portion of the weekend.
A frontal boundary will approach the area later in the weekend
into next week, increasing the thunderstorm chances, primarily
late in the weekend into Monday, and from mid week onward. This
boundary will bring some slight relief from the heat.


.NEAR TERM /Overnight/...
Issued at 958 PM EDT Fri Jul 22 2016

Muggy conditions continue with mainly clear skies this evening as
the forecast area residing on the edge of the heat ridge. 0130Z
temps largely remained in the lower to mid 80s.

Soundings showing some instability present above a well developed
cap sitting between 5kft and 9kft. Drier mid level air has
advected into the region from the north in the wake of the upper
level wave that has moved into the Tennessee and lower Ohio
Valleys. With ridging aloft strengthening overnight and 700mb
temps hovering at not see available low level moisture
or instability above the cap being sufficient enough to generate
even any isolated convection across central Indiana. Plan on
removing pops for the rest of the night as a result.

Primary focus as the night progresses is likely to focus on areas
of fog developing with the stagnant flow and deep moisture present
within the lower levels of the atmosphere. Have introduced fog into
the grids after 06Z across the entire forecast area. Expect
another steamy night with lows in the mid to possibly upper 70s
and dewpoints in the 70s.

Zone and grid updates out.


.SHORT TERM /Saturday through Monday/...
Issued at 355 PM EDT Fri Jul 22 2016

Will increase pops to 30 Saturday afternoon as there is at least
some chance that remnant circulation or boundaries from prior
convection to our west would be able to spark slightly more
expansive activity across our area, but again with a lack of
substantial upper level support and 700 mb temps remaining 10 to
12C, expect that widespread organized convection is unlikely
through Saturday evening. There is some indication that as the
frontal boundary approaches and the ridge weakens slightly, more
substantial thunderstorm activity could move into the area late
Saturday night into Sunday, followed by the front itself, which
will necessitate increased thunderstorm chances Sunday into
Monday. Significant uncertainty remains, obviously, as this will
depend heavily on how convective activity lays out over the next
24 to 36 hours.

Consensus temperatures appeared reasonable, although did bump them
up slightly, particularly tomorrow when models appear to be
overdoing potential coverage of precip.

Model dewpoints have been slightly too aggressive in recent days
and bumped them down slightly, but this still results in peak heat
indices Saturday and Sunday in excess of 100 across the entire
area, and in excess of 105 in portions of central Indiana. Will
continue heat advisory through Saturday as it currently stands.
May require extension into Sunday, but this will depend
significantly on thunderstorm activity which as previously
mentioned remains highly uncertain.


.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 23/0600Z TAF Issuance/...

Issued at 1150 PM EDT Fri Jul 22 2016

Latest analysis of the Rapid Update Cycle shows that high pressure
is elongated over the Ohio River Valley. Winds are calm at most
locations and will continue to be so throughout the night.
Temperature/depoints are getting close in outlying areas meaning
that moisture is present for the development of fog reducing
visibilities to IFR/LIFR during the early morning hours...mostly
after 23/0800Z.

High pressure will be slow to move off to the east on Saturday, so
the fog/low clouds will be around for IFR to MVFR through the
morning hours.  Should see improvement to VFR going into early
afternoon on Saturday.


.IND Watches/Warnings/Advisories...
Heat Advisory until 8 PM EDT this evening for INZ021-028>031-



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