Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 212307

Area Forecast Discussion
National Weather Service Indianapolis IN
610 PM EST Tue Feb 21 2017

Aviation Section has been updated below.


Issued at 339 PM EST Tue Feb 21 2017

Rain showers will linger over eastern portions of Central Indiana
this evening as a low pressure system traverses the Deep South.
However, dry conditions will return tonight and persist into
Thursday. That is when rain and thunderstorm chances will
increase with a rather potent system. In addition, latest models
continue to trend toward possible severe thunderstorms on Friday
in the warm airmass. Further out, the warm temperatures will
abruptly end on Saturday though as cooler air filters in on the
back side of the aforementioned system. Any wraparound rain
showers could even have some snow showers mixed in on Saturday
morning. After that, dry conditions will return from Saturday
evening through Sunday.


.NEAR TERM /Tonight/...

Issued at 339 PM EST Tue Feb 21 2017

The main focus of the near term period will be rain chances in
association with a low pressure system over the Deep South.

Latest radar mosaic continues to show bulk of moisture over
south/southeastern portions of the forecast area where it should
stay confined to through the evening hours. However, time cross
sections show much drier air in the mid and upper levels after Wed
06Z, so trended toward a dry forecast overnight. Nonetheless,
patchy fog is expected to form overnight, reducing visibilities.


.SHORT TERM /Tomorrow through Friday Night/...

Issued at 339 PM EST Tue Feb 21 2017

The main focus of the short term period will be a rather potent
system progged for the end of the week and possible severe
potential on Friday.

Benign weather will prevail tomorrow into Thursday with zonal flow
aloft. However, focus quickly shifts to a low pressure system
entering the area on Thursday. Rain showers will initially start
on Thursday afternoon, but as forcing increases with associated
warm front on Thursday night, so will the possibility of
thunderstorms. SPC continues to keep the forecast area
highlighted for severe potential on Friday/Friday night as a cold
front enters an unstable environment of high temperatures in the
upper 60s/low 70s and dewpoints in the 50s.

The above normal temperatures will prevail for duration of short
term period with highs generally in the 60s and 70s and lows in
the 50s. Colder temperatures in the 30s will quickly follow the
cold front on Friday night though. Latest Superblend
initialization will be used for temperatures.


.LONG TERM /Saturday through Monday Night/...

Issued at 339 PM EST Tue Feb 21 2017

ECWMF and GFS20 have a strong upper level longwave trough exiting
central Indiana Saturday leaving behind an area of high pressure and
more seasonable temperatures. A few lingering showers will be
possible Saturday morning before more dry conditions move in for the
rest of Saturday and early Sunday.  Light showers and snow showers
are possible Sunday evening through early Monday associated with a
weak shortwave in the wake of the passing trough.

Another period of wet weather is likely for Monday night and Tuesday
ahead of a strong upper level system. The global models do not quite
have a handle on it`s evolution. The 12Z ECWMF showed a much more
deep and robust system which contrasted against a more progressive
12Z GFS.  Confidence is low on the timing and intensity of this
system with inconsistencies seen between model runs.


.AVIATION /Discussion for the 22/0000Z TAF Issuance/...
Issued at 610 PM EST Tue Feb 21 2017

Flying conditions lowering to IFR or lower late tonight and then
improving to VFR Wednesday afternoon.

Low pressure over the southeast U.S. was producing area of light
rain over southern Indiana.   This will begin to pull out by
late evening....but radiational cooling will cause areas of
fog/stratus to develop late tonight with conditions lowering
to MVFR towards midnight and IFR towards daybreak.   This
will slowly break up with daytime heating by midday Wednesday.

Winds will be from the south around 5 knots this evening...then
light overnight and Wednesday morning and becoming south to southwest
up to 8 knots by midday Wednesday.





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