Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 181059

Area Forecast Discussion
National Weather Service Indianapolis IN
600 AM EST Mon Dec 18 2017

Aviation Section has been updated below.


Issued at 256 AM EST Mon Dec 18 2017

There continues to be a split flow pattern mainly over the
southwest and north central parts of the U.S. Central and southern
Indiana is underneath the southern regime of this flow. On the
surface, weak area of high pressure is across the south central
and southeast states which is leaving a light southwest flow over
the area. This has kept temperatures mostly in the lower 40s and
some upper 30s overnight, and there is patchy fog and low clouds
from light moisture across the area on Sunday.


.NEAR TERM /Today/...

Issued at 256 AM EST Mon Dec 18 2017

West to southwest flow will remain over the area today as a weak
low over the eastern Great Lakes moves off further to the east.
The patchy fog and low clouds will remain until later his
afternoon when some comparatively drier air tries to make it way
into the region. Think visibilities from the fog will improve a
bit this morning, but the low clouds will remain for much of the
day, and there could be some drizzle from these clouds. Not much
mixing is going to occur to thin out the clouds, but there may be
just enough insolation as the Sun works on the low clouds later
today. Temperatures may warm a bit then into the mid/upper 40s
with some lower 50s in the southern counties.


.SHORT TERM /Tonight through Wednesday/...

Issued at 256 AM EST Mon Dec 18 2017

A cold front will be making its way slowly southward as it is
embedded underneath the westerly flow at low/mid levels between
these two flow regimes. By Tuesday morning, there will still be a
west-southwest flow in the boundary layer enough to mix things up
enough for some low clouds, but allow more heating to get the
temperatures into the low-mid 50s. The front will make its way
into areas to the north of central Indiana impeded a bit from a
storm system that will stay to our south from Texas through MS and
AL. High pressure over central Canada will become more persistent
by Tuesday evening pushing the cold front into central Indiana by
Tuesday evening. Front will move through dry as any moisture from
the south will be tied up with that southern storm system. North
winds will then fall in behind the front Tuesday evening taking
lows back down into the low 30s and keeping highs Wednesday only
in the 40s.


.LONG TERM /Thursday through Sunday/...
Issued at 310 AM EST Mon Dec 18 2017

The upper flow becomes more amplified over the weekend as a
strong upper trough digs into the upper midwest and eventually
the great lakes.  Models indicate a deepening area of low pressure
will track across the central plains Thursday...upper midwest
Friday and over the great lakes late Friday and early Saturday.
It will become much cooler late Friday night on.

There are some differences between models over the weekend as the
GFS is colder and drier as most of the moisture remains in the
southern stream.  The European and Canadian are not as cold...but
a little wetter late Sunday on.   Will split the difference for
now.  Overall superblend temperatures seem reasonable and only
minor tweaks made.  Also deleted mention of freezing rain in some
of the grids for Sunday that forecast builder had inserted.


.AVIATION /Discussion for 181200z TAF Issuance/...
Issued at 600 AM EST Sun Dec 17 2017

IFR or LIFR ceilings will gradually improve to VFR by this evening.

Satellite and weather depiction indicated low clouds were trapped
across Indiana and Illinois. This resulted in areas of LIFR
ceilings. There will be slow improvement today as some mixing
occurs and lower clouds break up late today.  There is a chance
of some light fog and lower ceilings again late tonight...however
it is too iffy to mention in the TAF`s yet.

Winds will be from the southwest at 5 to 8 knots.




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