Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 042037
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
337 PM EST Sun Dec 4 2016

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

&&

.SYNOPSIS...
Issued at 154 PM EST Sun Dec 4 2016

A rather active period has commenced across Central Indiana with the
first of several systems bringing rain and snow today.  After more
zonal flow aloft and dry conditions tonight and tomorrow, the second
system will approach from the southwest on Monday night.
Precipitation will generally be in the form of rain with this system
except for some snow initially mixing in at times across the
northern counties.  After a lull in activity from Tuesday night
through Wednesday, yet another system will bring more of a snow
threat Wednesday night/Thursday morning.  Light snow accumulations
will be possible with this system.  Further out, high pressure will
result in dry conditions for the end of the week.

&&

.NEAR TERM /Tonight/...

Issued at 154 PM EST Sun Dec 4 2016

Heaviest precipitation will enter the forecast area over the next
several hours. Currently, most places are reporting rain or a
rain/snow mix. The best chances for any minor accumulations remain
over the far northwestern counties. Time cross sections show both
lift and moisture decreasing significantly after Mon 00Z though with
mid levels dry by Mon 06Z. As a result, will continue to trend
toward a decrease in pops from west to east rather quickly after
Mon 00Z with almost the entire forecast area dry by Mon 03Z.

As the upper trough pushes farther east this evening, flow aloft
will become more zonal with strengthening high pressure at the
surface. So, dry conditions can be expected overnight. As far as
temps, overnight lows will bottom out in the low 30s. Some
lingering clouds will prevent them from dropping much further.

&&

.SHORT TERM /Tomorrow through Wednesday/...

Issued at 154 PM EST Sun Dec 4 2016

Dry conditions can be expected tomorrow with zonal flow aloft and a
large area of high pressure over much of the Lower Midwest and
Ohio Valley. The pattern will begin to change again by tomorrow
night though as the second of several systems approaches from the
southwest. Rain will start spreading across the forecast area from
the south starting after Tue 00Z. Some snow could initially mix in
across the northern counties early, but it will generally be all
rain by Tue 06Z. Isentropic lift will be best during the Tue
09-15Z time frame, quickly diminishing after Tue 18Z. As a result,
the entire forecast area will be dry by Tuesday evening. The dry
conditions will prevail through the end of the short term period
until yet another system moves in late Wednesday.

&&

.LONG TERM /Wednesday night through Sunday/...
ISSUED AT 147 PM EST Sun Dec 4 2016

ECMWF continues to suggest an active weather pattern during this
period. A quick moving surface low is expected to push along the
Ohio River on late Wednesday Night and Thursday...a most favorable
track for snowfall across Central Indiana. Temps and forecast
soundings suggest the column will be plenty cool for what could be
our first accumulating snow of the season.

High pressure and ridging is expected to build across the area in
the wake of the departing low on Friday...forecast soundings
suggesting trapped lower level stratocu with broad cyclonic
circulation in place over Indiana and points east while high
pressure in place over the plains states. How typical! Ridge axis
remains west of the forecast area until Saturday. Thus will aim for
a dry but cloudy forecast on Friday...and dry and few clouds on
Saturday as High pressure and the ridge axis moves across the area.

ECMWF depicts another warm front moving toward Indiana on Saturday
night and Sunday as low pressure moves through the upper midwest. At
this time...this looks like another snow event as forecast
soundings remain below freezing through the column.

&&

.AVIATION /Discussion for the 041800z Tafs/...

Issued at 1228 PM EST Sun Dec 4 2016

VFR Conditions will quickly deteriorate to MVFR...IFR and LIFR
this afternoon. IFR conditions likely to persist overnight.

Quick moving short wave and isentropic lift to push across the
forecast area this afternoon. Forecast soundings and time height
sections show deep saturation this afternoon and low level
saturation lingering tonight. Rapid refresh shows precipitation
over Illinois spreading eastward across the TAF sites late this
afternoon. Thus categorical rain this afternoon. As previously
mention IFR/LIFR Cigs are expected to linger after the dynamics
pass as time heights show trapped lower level moisture beneath an
inversion aloft.

A return to VFR will be possible on Monday as high pressure
arrives and mixing scours out the lower levels.


&&

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

&&

$$

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


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