Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 050444

Area Forecast Discussion
National Weather Service Indianapolis IN
1144 PM EST Sun Dec 4 2016

The AVIATION Section has been updated below.


Issued at 154 PM EST Sun Dec 4 2016

After more zonal flow aloft and dry conditions tonight and
tomorrow, the next 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 /Rest of Tonight/...

Issued at 909 PM EST Sun Dec 4 2016

Precipitation has moved off to the east of the area and the rest
of the night should be dry. Going low temperatures in the lower
30s are on track and see no need for adjustments there. Did bump
cloud cover up to completely cloudy through the overnight based on
satellite observations of cloudy skies well back into Iowa,
Missouri and Arkansas. Increased wind speeds over the next several
hours also based on observations and high res model output.

Could see some patchy fog develop late with small dewpoint
depressions over the area and no dry air advection. However the
stronger winds could abate this and will not see much cooling at
all with the cloudy skies, so confidence is low. Included patchy
fog over the western and southern counties where winds will drop
off quickest making fog development more likely there.


.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 050600z TAF issuance/...

Issued at 1138 PM EST Sun Dec 4 2016

MVFR ceilings at all sites but KLAF (already IFR) should drop to
IFR after a few hours as stratus deck sinks. After that
visibilities could drop to MVFR as well if the winds can drop off
as forecast. There is a chance KLAF could see visibilities drop
to around a mile or less for a few hours around daybreak, but
confidence not high in the possibility given the winds there so
will leave out anything lower. Hi res models indicate ceilings
will be slow to scatter/rise even with high pressure building in
and may not see improvement until late morning. By early afternoon
should be seeing VFR everywhere. Then Monday night another system
moves in and brings more rain chances to the area. Westerly to
northwesterly winds through the night around 8-14 kts now will
drop in speed later during the overnight and then back to the
southeast during the morning before backing to the east Monday




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