Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 181437

Area Forecast Discussion
National Weather Service Indianapolis IN
1037 AM EDT Wed Apr 18 2018

The AVIATION section has been updated below.


Issued at 200 AM EDT Wed Apr 18 2018

A quick moving area of low pressure will sweep into Central
Indiana this afternoon and exit tonight. This will bring chances
for light precipitation amounts to Central Indiana late this
afternoon and evening.

A Large high pressure system is expected to arrive in the are on
Thursday and linger across the region through at least the first
half of the weekend. This will bring dry weather with moderating
temperatures each day through Saturday.

A quick moving low is then expected to push across the Tennessee
River valley on Sunday. This system may bring some rain chances to
the Ohio valley on Sunday into Monday...however overall
precipitation chances remain low.


.NEAR TERM /Rest of Today/...
Issued at 958 AM EDT Wed Apr 18 2018

Forecast is in pretty good shape. Adjusted morning sky cover based
on latest satellite imagery, but trend of increasing clouds looks
good as low pressure approaches the area.

Upped winds some based on latest data, so gusts near 40 mph are
possible this afternoon, especially south.

Left PoPs capped at 50 percent for now as am still unsure about
coverage. Did change wording though to scattered to imply some rain
in the area though. Will adjust this afternoon if necessary.

Temperatures could be tricky with a surface low moving through the
area this afternoon, leading to a temperature gradient in the
vicinity. Until trends can be seen better, made no changes at this

Previous discussion follows...

Surface analysis early this morning shows a ridge axis of High
pressure stretching from the upper midwest...across Nrn Indiana to
SE OH. A deep low pressure system was found across eastern Kansas.
Aloft water vapor was showing a ridging in place across
Illinois...building eat toward Indiana. Strong subsidence was
seen in the wake of the low over western and Central Kansas.

Models suggest the upper ridge to west will quickly push over
Indiana today. Meanwhile the low over Kansas is expected to also
arrive in Central Indiana by late afternoon. National Radar
mosaics show precipitation only on the north side of the
approaching low...over NB. Lower level moisture fails to arrive
today as lower level flow only becomes east to southeasterly. The
GFS fails to show moisture arriving until really late this morning
and given that its rather shallow ahead of the approaching low.
Furthermore GOES16 is showing very little cloud cover with the
approaching system. Given current radar trend and expected chances for precip should be on the north side of
the system. GFS mid level RH fields support this also. THus will
trend best pops this afternoon across the northern parts of the
forecast area. Central Indiana should spend much of the day within
the warm sector with excellent sunshine and mixing, Will trend
High temperature above the forecast builder blends.


.SHORT TERM /Tonight through Friday Night/...

Issued at 200 AM EDT Wed Apr 18 2018

GFS and NAm both suggest the quick moving low will exit Central
Indiana this evening. Associated moisture on the north and
backside of the low should allow for some precip chances early in
the evening...particularly across the northern parts of the
forecast area. In the wake of the low and associated cold
front...Time Heights keep some lower level strato-cu
trapped...providing mostly cloudy skies overnight. Furthermore an
upper trough will be passing across state overnight...which could
provide some weak forcing to the lower level moisture...resulting
in drizzle or even a flurry. THus will trend toward mostly cloudy
with stick close to the forecast builder pops...however
measurable precip will be most likely in the evening as the
system and stronger forcing departs. Will stick close to the
forecast builder blends on temps.

Quiet weather is then poised to settled across the area for the
rest of this forecast period. The GFS and NAM show strong ridging
building over the Central Plains on Thursday through Friday Night.
This will result in lee side subsidence and produce a strong
surface high pressure system in place across the Mississippi and
Ohio valleys. Forecast Soundings at this point show a very dry
column along with unreachable convective temps. Thus mostly sunny
days and clear nights will be expected to end the work week.
temperatures through Friday night will be warmer...however will
still remain below seasonal normals. Northerly surface flow ahead
of the surface high will keep our source air approaching from the
Great Lakes and Ontario. Thus will trend temps at or below the
forecast builder blends.


.LONG TERM /Saturday through Tuesday/...

Issued at 338 AM EDT Wed Apr 18 2018

Latest blended initialization continues to trend toward a dry
forecast for most of the extended period and do not see any reason
to deviate from it. Focus then turns to rain chances very late in
the period as a low pressure system tracks from the Central Plains
into the Mississippi Valley. Confidence in the forecast is high up
until this point because the models are differing on the path of
that system after it crosses the Mississippi. The Euro is wanting
to take a more northerly track with it into the Tennessee Valley,
while the GFS trends toward a southeasterly track toward the
Carolinas. This will largely impact rainfall amounts across
central Indiana for Tuesday. For now, the latest blended
initialization seems to be favoring the Euro a bit, but this is a
low confidence forecast due to the variability in both timing and
track of the system. Meanwhile, temperatures will initially start
out below normal then trend toward normal through the course of
the long term period.


.AVIATION /Discussion for the 181500Z TAF Update/...
Issued at 1037 AM EDT Wed Apr 18 2018

Adjusted wind direction and speed based on latest trends. Still
looks like MVFR will develop this afternoon along with gusty winds.
Tweaked wind direction later in the period as well based on latest

Previous discussion follows...

TAF sites will initially start out with VFR conditions. However,
they will deteriorate to MVFR category by this afternoon when rain
showers enter the area with a quick moving low pressure system.
MVFR should then be the prevailing flight category through the end
of TAF period at all sites except KLAF, which will receive the
brunt of it this evening into tonight with IFR conditions.
Meanwhile, east/southeast winds will shift to the west/northwest
and become strong this evening and tonight with sustained speeds
of 12 to 17 kts and gusts up to 30 kts.





NEAR TERM...Puma/50
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