Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 192311

Area Forecast Discussion
National Weather Service Indianapolis IN
712 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 This Afternoon and Tonight/...
Issued at 310 PM EDT Mon Mar 19 2018

Short term models suggest main lift from approaching system will
begin moving into the southwest zones over the next couple of
hours, with this area of lift pivoting across the southern half
of the forecast area later tonight. Will go with high PoPs over
the southern zones, tapering the chance PoPs farther north. Still
appears there will be sharp cutoff to the northern extent of the
precipitation shield, so will keep the far northern zones dry.

Appears most of the precipitation will be in the form of rain,
although there is a potential for some mixed precipitation late in
the night over the central zones along the northern end of the
precipitation shield. Could be some minor accumulations of snow
late tonight, but given current temperatures approaching 60, the
best chances for any accumulations will be on elevated and grassy

Low level thicknesses suggest the GFS MOS lows tonight may be a hair
on the warm side, but overall the guidance isn`t too bad.


.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 20/00Z TAF issuance/...
Issued at 712 PM EDT Mon Mar 19 2018

VFR across northern and western sections through the period.
However MVFR ceilings with rain/snow showers south of KIND
late tonight through midday Tuesday.

Lows pressure over northwest Tennessee will track east northeast
across Kentucky.  An area of rain over southern Indiana and southern
Illinois will move to the northeast overnight.  This will cause
flight conditions to lower over the south half of central Indiana
overnight.  Colder air spreading into the region will also result
in mixed rain and snow showers some areas late tonight and early

Northeast winds 10 to 15 knots with gusts to 20 knots will back to
the north by Tuesday.




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