Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 031905
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
205 PM EST Sat Dec 3 2016

.UPDATE...
The SYNOPSIS...NEAR TERM and SHORT TERM Sections have been updated below.

&&

.SYNOPSIS...
Issued at 205 PM EST Sat Dec 3 2016

High pressure over Indiana will quickly move east exiting the
region but bringing generally quiet weather tonight. A quick
moving upper level weather disturbance will sweep into the Ohio
Valley on Sunday...ahead of a weak cold front. This may bring a
mix of precipitation initially to central Indiana on Sunday
morning...before changing over to all rain during the afternoon.

Another high pressure system will arrive on Sunday night and
Monday...brining a return to dry weather to start the work week.
However...active weather is expected in the week ahead as a pair
of weather systems will push across Indiana during the
week...brining chances for rain and Monday night and Tuesday and
some snow on Wednesday night into Thursday.

&&

.NEAR TERM /Tonight/...

Issued at 205 PM EST Sat Dec 3 2016

Surface analysis early this afternoon shows High pressure in
place across Illinois and Indiana. Water vapor shows a plume of
moisture streaming northeast from Texas into the Ohio Valley. A short
wave was found across the western plains states...moving quickly
eastward. Satellite shows cloud cover associated with the
approaching plume advancing across Indiana.

Forecast soundings tonight and time height sections continue to
shows a top down type saturation occurring through the night as
the high pressure system departs and the trough and short wave to
the west approach. Thus will keep skies cloudy tonight...and stick
close to a blend on temps.

Forcing associated with the advancing wave may arrive in the
western parts of the forecast area by daybreak. This may result
light precip amounts near 12Z...thus some low chance pops may be
needed...although confidence in a pre 12Z measurement is low.

&&

.SHORT TERM /Sunday through Tuesday/...

Issued at 205 PM EST Sat Dec 3 2016

Active weather is in store for Sunday as both the GFS and NAM
suggest a moderate negatively titled short wave to push into
Illinois and Indiana through the course of the day. Excellent
dynamics aloft appear in place ahead of this system. Additionally
the 295K isentropic surface shows good lift through the day with a
surge of Specific humidities to over 3 g/kg. Forecast soundings
and time height sections also show deep saturation. Thus hopefully
superblend will allow a near 100 pop. Forecast soundings show
lower levels starting the day below or near freezing...thus some
mix in precipitaion type will be possible with the onset as temps
warm through the day due to daytime heating and broad warm air
advection. Given the expected precipitation through the
day...will trend highs cooler than the MAVMOS.

GFS and NAM suggest the upper wave quickly departs on Sunday
evening...and isentropic forcing is shut off. Mid levels show good
subsidence arriving through the night as High pressure is
expected to build at the surface. Cannot rule out a stray
lingering shower across the eastern parts of the forecast area
around 00z-02z as the forcing departs...but for the most
part...precip will be ending and will trend pops toward dry.

High pressure is then expected to settle across the region on
Monday. Forecast soundings remain quite dry with an inversion
aloft and unreachable convective temps. Thus will trend toward a
partly cloudy sky and a blend on Highs.

Next up...the GFS and NAM once again suggest a strong low
pressure system and associated upper wave to sweep out of the
southern plains and push in to the ohio valley on late Monday
night into Tuesday. A similar set-up appears once again within the
forecast soundings...with a top down type saturation. Once again
the 295k Isentropic surface shows excellent lift with specific
humidities over 5 g/kg. Thus again will ramping pops higher than
guidance on Monday Night and Tuesday as these features arrive.
Fortunately the column appears a bit warmer with this second
system...thus precip type should remain all rain.

&&

.LONG TERM /Tuesday through Saturday/...
Issued at 331 AM EST Sat Dec 3 2016

Rainmaker will be moving through the Ohio Valley early in the long
term period, with conditions turning sharply cooler later in the
week as a slug of cold air drops into the region. Models continue to
differ in their handling of Wednesday night system but are coming a
bit closer together on timing. Euro produces are more robust surface
reflection in contrast to the GFS near complete lack of identifiable
surface features. This impacts the blended initialization, and may
be biasing precipitation amounts low if the Euro verifies - in which
case a light but potentially low end advisory level snowfall may be
possible - particularly considering the relative lack of wintry
precipitation thus far this season. Made adjustments to blended
initialization Wednesday night to better capture this potential.

&&

.AVIATION /Discussion for the 03/1800Z TAF Issuance/...

Issued at 1222 PM EST Sat Dec 3 2016

Conditions will continue to fluctuate around the MVFR/VFR mark
through this afternoon as low clouds linger. Expect conditions to
predominantly become VFR category by this evening and persist into
tomorrow. Focus then turns to an upper level disturbance progged
for tomorrow morning. Precipitation will initially start out in
the form of a rain/snow mix, but chances are still too low to
mention in TAFs at this time. The rain/snow mix will eventually
transition to all rain by tomorrow afternoon, which is conveyed
in the KIND TAF. Conditions will quickly deteriorate to MVFR or
worse late tomorrow afternoon though when the bulk of the
precipitation moves through. Winds will initially be
northwesterly, becoming southeasterly by tomorrow morning.
Sustained speeds will range between 5 to 10 kts.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SYNOPSIS...PUMA
NEAR TERM...PUMA
SHORT TERM...PUMA
LONG TERM...NIELD
AVIATION...TDUD



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