Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 101157
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
657 AM EST Sat Dec 10 2016

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

&&

.SYNOPSIS...
Issued at 155 AM EST Sat Dec 10 2016

Cold...Arctic High pressure will push across Indiana today. This
will result in mainly dry but cold weather across Indiana. Tonight
a weak upper level weather disturbance will push across the Great
lakes. This may result in some light snow or flurries across the
northern parts of Central Indiana late tonight.

Active...changeable weather is in store for Sunday. As the
surface High drifts east of Indiana...warmer southerly flow is
expected to arrive. Furthermore...a warm front will begin to
sweep inti Indiana ahead of a developing low pressure system. This
may result in chances for snow or mixed precipitaion on
Sunday...however as warm air continue to push into the
region...all precipitation will change over to rain.

A cold front will the sweep across Indiana on Sunday night into
Monday...ending the precipitation threat and allowing cold air to
return.

Active weather is expected to continue into next week as several
weather systems are will push across the state...bringing chances
for snow along with more cold air.

&&

.NEAR TERM /Today/...

Issued at 155 AM EST Sat Dec 10 2016

Surface analysis shows broad high pressure in place over the Ohio
and Tennessee River valleys. Water Vapor Imagery shows quick and
slightly northwest flow in place aloft while satellite shows some
passing mid and high clouds within that flow. Radar shows a few
flurries associate with those clouds across the northern parts of
the forecast area. Temps were in the 20s.

Main forecast Challenge today will be temps. Forecast soundings
and time height sections shows mainly a dry column today...with
subsidence as expected under the influence of the surface high.
However some clouds will be expected from time to time as the
quick flow aloft allows for some passing clouds. Given the
expected passing clouds and minimal temperatures advection a blend
on temps will work nicely.

&&

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

Issued at 155 AM EST Sat Dec 10 2016

Models remain in pretty good agreement with the overall pattern.
GFS forecast soundings tonight continue to show a top down
saturation ongoing as warm air advection appears ongoing. Forecast
sounding through the evening and toward 12Z continue to show a
very dry lower lever...thus precipitaion in most spots should not
reach the ground...should it start rather late tonight. Thus will
try to trend toward a cloudy forecast with minimal to no pops and
steady or slowly rising temperatures given the ongoing warm air
advection.

290K GFS Isentropic surface shows excellent lift...starting
mainly on Sunday afternoon with specific humidities surging over 4
g/kg during the afternoon. Good dynamics remain in place as a
quick moving short wave looks to push out of the Central Plains
toward the Ohio Valley. Forecast soundings continue to trend
warmer as sunday progresses within the  warm air advection and
also continue a top down type saturation. Again...with evaporative
cooling with expected onset of precipitation...some mixed
precipitation appears possible given top down
techniques...especially across the northern parts of the forecast
area. Will try and trend pops above guidance given this strong
forcing and dynamics. Slowly rising temps are expected through the
day as the warm front passes on Sunday and into Sunday evening. By
Early Sunday evening...forecast soundings have warmed entirely
above freezing...and all precip types should be in the form of
rain by that point. However...best moisture and forcing is quickly
departing to the east along with the departing short wave. 290K
Isentropic surface shows forcing shut off by 06Z. Thus will again
raise pops...focusing mainly during the evening hours as the last
of the best dynamics exit. Any icing/snow that does occur with the
onset of precip should quickly melt with the arrival of warmer air
and rain.

Cold front will then pass late on Sunday night as subsidence and
High pressure builds across Indiana and the ohio Valley.
isentropic surface shows subsidence and forecast soundings show a
dry column. Monday could remain rather cloudy as the ridge axis
remains west of Indiana and lower levels within the forecast
soundings show trapped stratocu amid a broad cyclonic flow. Will
trend temps at or below a blend at that point.

Better clearing should arrive on Monday night as lower level flow
becomes more anti-cyclonic as the surface high builds across the
area. Again...forecast soundings show a dry column. Thus will work
a blend beneath partly cloudy skies.

&&

.LONG TERM /Tuesday through Friday Night/...

Issued at 332 AM EST Sat Dec 10 2016

The extended period will start out dry with lingering high
pressure in the area. However, the pattern will quickly change by
Wednesday when focus then shifts to the next system, which is
expected to bring some light snow accumulations to the forecast
area. Earlier model runs had precipitation starting out with rain
mixed in, but now models are trending toward all snow for the
duration of the event. Current Superblend initialization looks
good, so will not deviate from it. Further out, dry conditions
will return from Wednesday night through Friday, and then additional
snow showers will return on Friday night.

&&

.AVIATION /Discussion for the 10/12Z TAF Issuance/...

Issued at 642 AM EST Sat Dec 10 2016

Conditions will bounce around the MVFR/VFR mark this morning, then
improve to VFR by late morning for most of the day as high
pressure strengthens over the area. However, KLAF can expect MVFR
to be the prevailing flight category once again by this evening as
an upper level disturbance passes across the Great Lakes. Light
snow showers will also accompany the disturbance and affect KLAF
during this TAF period. Winds will start out southwesterly and
back to the southeast at 4 to 8 kts.

&&

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

&&

$$

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



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