Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 160831

Area Forecast Discussion
National Weather Service Indianapolis IN
331 AM EST Thu Nov 16 2017

The SYNOPSIS, NEAR TERM, and SHORT TERM sections have been
updated below.


Issued at 331 AM EST Thu Nov 16 2017

Today and tonight will be dry, but then a low pressure system will
bring rain to central Indiana later Friday into Saturday. Dry
weather then returns for Sunday into mid-week next week. For the
most part, temperatures will remain below normal. Saturday will see
warmer than normal temperatures ahead of the low pressure system,
then Sunday will see well below normal readings behind the system.


.NEAR TERM.../Today/
Issued at 331 AM EST Thu Nov 16 2017

Early this morning GOES-16 satellite data shows a large area of
stratocumulus moving across the area. A break in this cloud deck was
across northern Illinois, but more clouds were to the northwest.

Main question today will be cloud cover. By 12Z the clearing line
will have made it into the northwest half or so of central Indiana,
but some concern that more southward moving clouds across and near
Lake Michigan could be impacting the northeastern forecast area.

For later in the morning into early afternoon, some models such as
the Hi-Res Rapid Refresh, the Gridded LAMP, and to some extent the
SREF show more widespread lower clouds moving south well into the
forecast area. Other main models do not have this feature.

As noted above, some of the cloud deck across Michigan is moving
more south than east. Thus cannot discount the models that are
showing higher cloud cover mid day. However, drier air overall will
continue to move in.

With low confidence, will go partly to mostly cloudy northeast half
and partly to mostly sunny southwest half.

With at least some sunshine expected most areas, the model blend
looks good for temperatures.


.SHORT TERM.../Tonight through Saturday night/
Issued at 331 AM EST Thu Nov 16 2017

Models are close enough that the model blend initialization
was accepted for most items.

Mid and high clouds will increase tonight into Friday morning ahead
of the next system. Isentropic lift increases during the afternoon
as the moisture increases. Will go low PoPs during the afternoon for
about the northwest half of the area.

Better forcing moves in Friday night with a low level jet moving in.
Thus went likely or higher PoPs by overnight Friday night.

On Saturday, low pressure will deepen as it moves from Illinois into
lower Michigan, and it will drag a cold front across the area. A 50-
60kt low level jet will bring in forcing and moisture, and the left
exit region of an upper jet will also help produce lift. Will go
high PoPs all areas, with the highest PoPs during the morning ahead
of the front.

There will be some low PoPs Saturday evening as the wrap-around
behind the low moves through. Temperatures get cold enough for
perhaps some snow to mix in with any rain.

Enough instability moves in Friday night to have a thunder mention.
Most-unstable CAPE progs show enough instability to go chance of
thunderstorms on Saturday. With some instability and shear Saturday
along with strong winds not far the surface, would expect the
possibility of some strong storms with the front Saturday. Of course
this is still a developing situation so will have to fine tune
strong to severe chances as the event gets closer.

Outside of the storms Friday night into Saturday, there will be
gusty winds potentially over 30kt as the pressure gradient tightens
across the area.

The model blend temperatures look reasonable given expected


.LONG TERM /Sunday through Thursday/...

Issued at 245 AM EST Thu Nov 16 2017

Main pattern will remain west/northwesterly aloft and resulting in
dry conditions until towards the end of the period. Several mid/
upper level troughs will skirt eastward off to the north of the
forecast area mainly over the Great Lakes.

High pressure will be over the southern Plains eastward across the
southeast states efficiently blocking any low level moisture
northward. As that high moves off the southern Atlantic coast, a
dry southwesterly flow out of the southern and central Plains
will warm the area to near 50 across the southern parts of the
area before the next cold front drops in Tuesday afternoon.

Looks like the next chance for precipitation will not be until
early Thursday morning (Thanksgiving) as a frontal system comes
into the area with the chance for snow flurries/light rain.
Confidence is low at this time being so late in the period and
will have to see how this develops over the next several days.


.AVIATION /Discussion for 160600Z TAF Issuance/...
Issued at 1100 PM EST Wed Nov 15 2017

The GFS LAMP is bullish on cu re-development overnight into Thursday
morning. The SREF is much more favorable. In addition to the
potential for more low clouds to re-develop, low level rh progs
combined with satellite trends from the stratocu over northern
Illinois and northwestern Indiana strongly suggest LAF and possibly
IND will see MVFR conditions through 09z or so. So, strong
confidence in MVFR conditions at LAF overnight and moderate
confidence in mostly VFR elsewhere. After 10z, the terminals should
be be mostly clear with just some afternoon cu in cyclonic flow, per
the cu development progs.

Winds will be southwest and west through the overnight 11 knots or
less and shift to northwest overnight into Thursday. LAF could see
some gusts to 20 knots as well through 10z.




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