Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 151908

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

The LONG TERM 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 Night through Thursday/...
Issued at 308 PM EDT Thu Mar 15 2018

The elusive search for spring will continue through the extended
period as much of the eastern U S remains locked in under a deep
upper trough within an amplified pattern aloft.

A dry start to the extended will transition quickly to a much more
unsettled pattern for early next week as a fast moving cutoff
upper low tracks out of the southern Plains on Monday and
eventually becomes absorbed within the expanding upper trough by
midweek as heights once again tumble across the eastern part of
the country.

Precip type will become a factor over parts of the region...
especially from Tuesday into Wednesday as much colder air aloft
once again expands across the Ohio Valley. Low level thermals are
supportive of rain initially Monday...with snow mixing in on the
northern flank late Monday night into Tuesday and again Tuesday
night into Wednesday. There is still a lot to iron out at this
early stage and it will likely be the weekend at the earliest
before more precision can be placed into the precip type forecast.
That being said...the main message here is that winter is not done
just yet for central Indiana. Potential is there for a light...
slushy snow accumulation in spots but overall impacts are likely
to be more of a nuisance than anything else. Such is wintry
weather in late March.

After a mild day Monday in the 50s...expect temperatures topping
out only in the 30s and 40s Tuesday through Thursday as the
influence of the broad upper trough is felt.


.AVIATION /Discussion for 151800Z TAF Issuance/...
Issued at 1221 PM EDT Thu Mar 15 2018

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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