Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 280609

Area Forecast Discussion
National Weather Service Indianapolis IN
209 AM EDT Sun May 28 2017

The SYNOPSIS...NEAR TERM and SHORT TERM Sections have been updated below.


Issued at 210 AM EDT Sun May 28 2017

A series of weak fronts will cross Indiana from the west through
Tuesday. High pressure is expected to develop over our state
Wednesday, then another front should arrive Saturday.


.NEAR TERM (Today)...

Issued at 210 AM EDT Sun May 28 2017

The main issue is the threat of thunderstorms today.

This looks high. The GFS and NAM have similar handling of a
disturbance arriving aloft before 24Z. They also agree about large
amounts of CAPE surging over Indiana in advance of the disturbance.

It`s possible clouds will reduce destabilization.  However satellite
shows we`re already on the northern side of the cirrus shield, which
is eroding. Subsidence ahead of the short wave this afternoon will
also work against clouds. We should at least be partly sunny. With
the high late May sun, that supports considerable CAPE.

Likely to categorical POPs for thunderstorms seem best for the
afternoon. As the HRRR indicates, the morning should be dry as
instability builds.

Uncertainty about cloudiness means some uncertainty about
temperatures, but most methods indicate a consensus should be
accurate to within 2 degrees.


.SHORT TERM (Tonight through Tuesday night)...

Issued at 210 AM EDT Sun May 28 2017

The forecast problem is POPs.

For tonight, the eastern CWA needs a chance in case anything that
fires during the afternoon continues past 00Z. In the west,
subsidence behind the previously mentioned disturbance should keep
things dry. The east should be dry as well after this evening.

The models have disagreements Monday through Tuesday night, but
concur the flow will stay basically cyclonic. With the high sun
angle, that means there be at least some chance of storms every
afternoon and evening. Beyond that, consensus should identify
periods when rain chances are highest.

Skies should be partly cloudy as weak perturbations pass through
the cyclonic flow.

Given the models differ about rain chances, they have differences
with temperatures as well.  In absence of a strong reason to go one
way or the other, consensus will be used to minimize errors.  These
should be 3 degrees or less.


.LONG TERM /Tuesday night through Saturday/...
Issued at 204 PM EDT Sat May 27 2017

Ensembles in good agreement is slowly drifting an upper low
across the upper Great Lakes and into southeast Canada during the

Appears an upper disturbance may rotate through the local area
around Tuesday night into Wednesday. Will keep some PoPs going for
parts of the area during that time.

Ensembles continue to be rather aggressive with the precipitation
threat late next week, although there are large differences as to
the timing of this system, ranging from as early as Thursday night
to as late as next Saturday. At this time, the best threat seems
to be Friday and Saturday, so will concentrate the PoPs in those


.AVIATION (Discussion for 280500Z TAFs)...

Issued at 1248 AM EDT Sun May 28 2017

Conditions will start off VFR, but with low dew point
depressions, some MVFR fog may develop and last until a few
hours after dawn.

Good confidence there will be more storms after 17z. Could be MVFR
but for now left model VFR conditions.

Winds will be light and variable tonight. Speeds should stay less
than 10 mph today, while direction will veer from south to
northwest by 24Z as a cold front passes.




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