Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 172237

Area Forecast Discussion
National Weather Service Indianapolis IN
637 PM EDT Sat Mar 17 2018

The AVIATION Section has been updated below.


Issued at 252 PM EDT Sat Mar 17 2018

A weakening upper low is expected to pass through the area later
this afternoon and evening. Another low pressure system is expected
to affect the area early next week. In the wake of this system, high
pressure will build into the area for the middle and later parts of
next week.


.NEAR TERM /Rest of This Afternoon and Tonight/...
Issued at 252 PM EDT Sat Mar 17 2018

Weakening upper low currently over Illinois will be passing over the
local area later this afternoon and into the evening hours. Radar
indicates there is still some patches of light rain and drizzle
associated with this feature, so will keep some PoPs going into the
evening hours until the upper low passes off to the east. Most of
the lingering precipitation should be in the form of rain, but there
could be a light mix at times over some of the northern zones.

Short term model data suggest the low clouds should start scattering
out from the north around sunset, with the clearing line slowly
dropping south tonight, although the clearing line may not reach the
far southern zones until well after midnight.

There may be some fog development, especially later tonight, as
skies clear with a light gradient and residual moisture.

Low level thicknesses suggest the GFS MOS lows for tonight look
reasonable, so little if any adjustments planned.


.SHORT TERM /Sunday through Tuesday/...
Issued at 252 PM EDT Sat Mar 17 2018

Next upper trough is expected to move into the Midwest by Monday,
with an associated surface low passing near of south of the Ohio
River. Warm advection begins Sunday night, so will bring PoPs back
into the southern zones Sunday night, and spread them northward into
the rest of the area on Monday and Monday night. The highest PoPs at
this time appear to be Monday afternoon and evening over the
southern zones, coinciding with the best lift.

Thicknesses suggest rain will be the predominate precipitation type
Sunday night and Monday, however thicknesses are expected to lower
Monday night, allowing for more of a mixed precipitation threat by
that time. Some light accumulations are possible over parts of the
area Monday night.

Will keep some chance PoPs for mixed precipitation into Tuesday
morning as the system passes off to the east, however some of the
ensembles suggest the precipitation threat may linger longer
into the day Tuesday.

Progged low level thicknesses suggest the GFS MOS highs for Sunday
may be a bit on the warm side. Will nudge the guidance highs down a
category. The remainder of the periods look OK at this time.


.LONG TERM /Tuesday Night through Saturday/...
Issued at 315 PM EDT Sat Mar 17 2018

Models indicate a split upper flow with an upper ridge over
central Canada and an an upper trough over eastern Canada.
There is also an active southern stream during the period.
High pressure will build into our area by Wednesday and keep
us cool and dry Tuesday night through Thursday night.

A low pressure system over the central plains will track east
across Indiana next weekend. The 12Z European model is 12 to 18
hours slower than the GFS and Canadian models.  Will go with a
blend.  As a result slowed down Superblend precipitation timing
slightly.  Indications at this time precipitation will be mainly

Lowered daytime temperatures a little northern sections Saturday.
Otherwise...stayed close to Superblend temperatures other periods.


.AVIATION /Discussion for the 180000Z TAFS/...
Issued at 635 PM EDT Sat Mar 17 2018

Patchy light rain/drizzle and IFR conditions associated with a
weakening upper low expected to move off to the southeast of the
terminal by or shortly after issuance time.

MVFR deck around 015 expected to gradually scatter out from north
to south tonight, based on short term model data. Although, it may
not be until around 180800Z when these lower clouds scatter out at

Some concern for fog potential later tonight as skies clear out
and gradient relaxes. Confidence on widespread development of
visibility restrictions in fog is low at this time, as it appears
there will be some at least weak dry advection in the lower
levels. The best threat for visibility restricitions at this time
appears to be in the KLAF area, where skies will clear off the

Surface winds generally 350-040 degrees at 6-10 kts this evening,
with winds diminishing to at or below 6 kts after 180600Z.




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