Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 200349

Area Forecast Discussion
National Weather Service Indianapolis IN
1150 PM EDT Mon Mar 19 2018

Aviation section has been updated below.


Issued at 310 PM EDT Mon Mar 19 2018

A low pressure system is expected to affect the area from tonight
through Wednesday morning. High pressure is expected to build
into the area for the later parts of the week. Another low
pressure system may affect the area over the weekend.


.NEAR TERM /Rest of Tonight/...
Issued at 1030 PM EDT Mon Mar 19 2018

Radar and weather depiction indicated rain was occurring over much of
central Indiana south of I-70.  This rain was spreading slowly north
and may spread a bit more to the north before pulling on to the east
by morning.  Will go with high precipitation chances south of I-70
and low chances just to the north and completely dry far northwest.

Other concern is the arrival of colder air causing a change over to a
wintry mix.  The NAM seemed much too aggressive and was an outlier.
Have trended toward the rapid refresh which has an area of freezing
rain and sleet occurring in the colder locations possibly mixed
with light snow colder air towards 12Z.  With the road surfaces being
quite not think there will be any significant icing on
Therefore will cover with a special weather statement rather than a
winter weather advisory.

Temperatures have dropped into the lower 30s over northeast Indiana
and western Ohio and current forecasted low temperatures seem to be
on track which had lows from upper 20s far north to middle 30s south.

Only other change was to raise wind speeds slightly overnight.


.SHORT TERM /Tuesday through Thursday/...
Issued at 310 PM EDT Mon Mar 19 2018

Operational and ensemble data are coming into better agreement
during this period, so believe the gradual slowing down of the
system over the past couple of days is about over.

Model data suggest most of the organized lift that will be affecting
the area tonight will be in the process of moving out of the
southeast zones Wednesday morning. Otherwise, lift looks rather
disorganized throughout the morning hours, possibly getting better
organized during the afternoon hours. As a result, there may a
relative lull in the precipitation threat for a time on Tuesday.
Will keep the highest PoPs on Tuesday over the southeast zones for
mainly the morning hours, tapering them off to the northwest. Mixed
precipitation expected during the morning hours, but this should
trend towards rain by midday as the boundary layer warms.

Will keep PoPs high over the eastern zones Tuesday night, as models
suggest a well developed deformation zone may set up in those areas.
Rain is expected to transition back to snow during the night as the
boundary layer cools and thicknesses lower. A few inches of snow
accumulation is possible over the eastern zones Tuesday night,
depending on how fast the change over occurs.

Most of the organized lift appears to be east of the area by
Wednesday morning as the upper low pulls away. Will keep some chance
PoPs for light snow over the eastern zones Wednesday morning.
Dry weather expected for the rest of the short term as high pressure
builds in.

Progged low level thicknesses suggest the GFS MOS temperature
guidance in the later periods looks too warm. Will cut about a
category of the guidance from Tuesday through Wednesday night.


.LONG TERM (Thursday night through Monday)...

Issued at 322 PM EDT Mon Mar 19 2018

Mostly dry weather is likely early in the period. There should be a
wet spell during the weekend, then drying again. Exact timing is
quite uncertain and potential POP errors are 20 percent or higher.

It is also likely most precipitation will be rain, but
there is uncertainty about whether any snow will fall.

For temperatures, possible errors are 5 degrees.

The reason for all the uncertainty is the American and European
models disagree in many aspects about how a low pressure system will
affect our area. They do concur the best chance for precipitation
will be during the weekend and that most of the time temperatures
will be too warm for ice or snow.


.AVIATION /Discussion for 20/06Z TAF Issuance/...
Issued at 1150 PM EDT Mon Mar 19 2018

VFR across northern area through the period.  Otherwise...
MVFR ceilings at KBMG most of the period and at KIND
Tuesday evening.

Low pressure will move east across Kentucky will produce rain
changing to a wintry mix over the southern half of central Indiana
overnight.  This first round of precipitation will move out and
a second upper disturbance will produce another round of mixed
precipitation changing to snow tonight mainly over eastern and
southern sections.

Northeast winds of 15 knots and gusts of 25 to 30 knots possible
through early Tuesday morning.   Winds will become north 15 to 20
knots during the day Tuesday.




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