Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 152034

Area Forecast Discussion
National Weather Service Indianapolis IN
434 PM EDT Thu Mar 15 2018

The AVIATION Section has been updated below.


Issued at 246 AM EDT Thu Mar 15 2018

Central Indiana will remain under the influence of high pressure
through today, yet.  However, clouds and precipitation chances will
start increasing from the southwest tonight as the next system
approaches from the Central Plains.  At the initial onset Friday
morning, precipitation will be in the form of a wintry mix, but it
will quickly transition to rain with daytime heating.  Nonetheless,
the transition back to a wintry mix will start again on Friday night
before turning back to rain once again on Saturday.

Rain will taper off from west to east on Saturday as high pressure
strengthens over the area with dry conditions by Saturday night.
After that, Sunday will be a dry day before the next system
brings much of the same pattern early next week.


.NEAR TERM /Rest of Today/...
Issued at 958 AM EDT Thu Mar 15 2018

Great start to the day as the Ohio Valley resides under a large
area of high pressure. 14Z temperatures ranged from the mid 30s to
the lower 40s over much of the forecast area.

Essentially just cosmetic changes were needed for the morning
update as the forecast is in excellent shape. Expect mostly sunny
skies throughout the day with temperatures ranging form the mid
and upper 40s northeast to the upper 50s over the southwest.
Winds will predominantly remain out of the northwest for much of
the day.

Zone and grid updates out.


.SHORT TERM /Tonight through Saturday Night/...
Issued at 246 AM EDT Thu Mar 15 2018

The main focus of the short term period will be precipitation
type tomorrow night, mainly the threat for freezing rain.

First, cloud and precipitation chances will start increasing
across the southwestern portions of central Indiana late tonight
as a low pressure system approaches from the Central Plains.
There is the threat for a wintry mix with initial onset, but agree
with previous forecast that precipitation will be light at that
point. Higher precipitation chances will not arrive until mid-
morning when temperatures will be warm enough for all rain,
minimizing the threat on Friday morning.

Best isentropic lift for this event will be during the Sat 00Z-12Z
time frame, and this is where the forecast becomes a bit tricky.
Rain should be the predominant precipitation type through Sat 00Z,
but as colder air starts filtering into the northeastern portions
of central Indiana, the transition back to a wintry mix will
begin. Confidence remains moderate to high in rain being the
precipitation type from Indianapolis and southwestward. However,
confidence in precipitation type and timing becomes low to
moderate for the northeastern half of the forecast area. Forecast
soundings at KMIE and KLAF are indicating a warm nose in the lower
levels followed by sub freezing temperatures at the surface after
Sat 06Z, and latest models are starting to hit the freezing rain
threat a bit harder. So, latest ice accumulation amounts have
increased to the .10 to .15 inch range.

The freezing rain threat should end by mid-morning Saturday with
just lingering rain showers throughout the day. As high pressure
strengthens to the west, dry conditions will return by Saturday


.LONG TERM /Sunday through Wednesday/...
Issued at 235 AM EDT Thu Mar 15 2018

Forecast confidence is high into Sunday night, then moderate.

There is good agreement among the various models the weather will be
dry with seasonal temperatures into Sunday night. Potential errors
are 2 degrees or less.

From late Sunday night through Wednesday, there is overall agreement
the weather will get cooler and wetter. Details are uncertain as the
American and European models handle low pressure over the eastern
USA differently. Potential errors are 5 degrees for temperatures and
10-20 percent for POPs.

Any precipitation through Monday will be rain. Significant snow or
ice accumulation is unlikely, but rain, freezing rain, and snow are
all possible Monday night into Wednesday. What occurs will depend on
exact phasing of temperatures and precipitation.


.AVIATION /Discussion for 152100Z TAF Issuance/...
Issued at 434 PM EDT Thu Mar 15 2018

Updated current conditions.

Previous discussion follows...

VFR conditions throughout the forecast period.

High pressure will remain the dominant influence through midday
Friday as it drifts across the Great Lakes. With the exception of
thin cirrus from time to time...expect clear skies for the rest of
today and through tonight. Northwest winds this afternoon will
transition to northerly then northeast overnight.

High level cloud cover will begin to increase by early Friday
afternoon as moisture is drawn north into the region ahead of low
pressure tracking through the central Plains. More substantial
cloud cover however will hold off until late day Friday with the
chance for precipitation following Friday night. Expect east-
northeast winds on Friday.





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