Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 280447
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1247 AM EDT Sun May 28 2017

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

&&

.SYNOPSIS...
Issued at 134 PM EDT Sat May 27 2017

A pair of weather disturbances are expected to pass through the
region bringing showers and thunderstorms Central Indiana Tonight
and again on Sunday afternoon and evening. Some of the storms
could be severe...particularly across southern Central Indiana.

Weak high pressure is then expected to slowly build across Central
Indiana from Monday through the middle of the work week. This will
bring dry weather along with cooler temperatures for much of next
week.

&&

.NEAR TERM /Tonight/...
Issued at 925 PM EDT Sat May 27 2017

Tweaked pops a bit to match adjacent offices, otherwise, the bulk of
the convection should stay south of the forecast area overnight per
radar trends and High Resolution Rapid Refresh. That said, one upper
wave will move across the lower Great Lakes early overnight followed
by another across the Ohio Valley. In addition, a warm front will
lift north across central Indiana. With this synoptic forcing
combined with the deep moisture, will keep in at least chance pops
with the highest chances south, closest to the current
upstream convection and the second wave.

Previous discussion follows...
Issued at 134 PM EDT Sat May 27 2017

Surface analysis early this afternoon shows High pressure in
place across the Great Lakes. A weak trough of low
pressure/boundary was in place from Central Ohio...across Indiana
to southeast Missouri. Visible satellite imagery continues to
show linger low cloud across the area...however this is expected
to dissipate through the late afternoon. GOESR Shows a convective
cluster over Eastern Kansas...and it is this feature that we will
need to watch closely.

Dry weather will be expected through much of the evening hours as
forecast soundings and time heights keep a dry column in place
across the area. GFS and NAM have change a bit with the handling
of the approaching short wave...focusing best development to the
south...toward southern Indiana after 03Z. We will expect a sharp
cut-off across our forecast area on precip...with northern areas
perhaps seeing little to no rains overnight...much high pops
expected from I-70 southward as forecast soundings in these
locations show deep saturation as the upper wave passes. All of
this plus the surface boundary that appears in place seem
reasonable include high pops across the southern parts of the
forecast area...but tapering quickly lower to the north.
Again...given the convective nature of the expected MCS severe
storms...mainly due to straight line winds will not be ruled out.
As for temps will trend toward expected wet bulbs or use a blend.

&&

.SHORT TERM /Sunday through Tuesday/...

Issued at 134 PM EDT Sat May 27 2017

Mainly dry weather will be expected on Sunday morning as the
previous wave should be exiting or will have already exited
Central Indiana by 12Z Sunday as suggested by the GFS. Thus the
day should start out dry. However models suggest that our second
short wave and an associated cold front will sweep across Central
Indiana during the afternoon. Forecast soundings have begun
hinting at much more instability available on Sunday afternoon
than previous runs showing steep lapse rates. GFS IND soundings
suggests CAPE of 2500-3700 J/KG through the afternoon with easily
attainable convective temperatures in the upper 70s. MAVMOS
suggest good surface moisture available with dew points in the
lower 60s. Thus as daytime heating progresses on Sunday...and the
dynamics advance through the afternoon...storm chances will
increase. Will trend toward a categorical Pop by late afternoon
given the expected instability and dynamics lining up. Will stick
closer the the MAVMOS on Highs.

Convection across the area should continue into the early evening
hours as the previously mentioned forcing departs prior to 03Z.
Thus will need to continue to carry pops across the
area...especially across the southeast...where forcing will depart
last. After 06Z...forecast soundings suggest drying within the
column along with subsidence. Thus will trend to dry pops
overnight.

Model then suggest broad lower level cyclonic flow across the
area Monday...around low pressure well north of Indiana...near
northern Ontario. A weak trough looks to pass across Indiana on
Monday...however the forecast column appears very dry. Thus will
try to get to a dry forecast on Monday. A blend on temps will
work fine.

Monday night through Tuesday also appears dry as forecast
soundings suggest a dry column. At the surface...high pressure
over the central plains appears to slowly move east...building
across the Ohio valley. Support aloft remains minimal...as best
forcing within the broad cyclonic flow remains well north of
Indiana...over Ontario and the great Lakes. Thus will continue to
trend toward a dry forecast here along with a blend on temps.

&&

.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
period.

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
periods.

&&

.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.



&&

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

$$

SYNOPSIS...Puma
NEAR TERM...Puma/MK
SHORT TERM...Puma
LONG TERM....JAS
AVIATION...MK/JK



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