Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 020441
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1141 PM EST Thu Dec 1 2016

.UPDATE...
The AVIATION Section has been updated below.

&&

.SYNOPSIS...
Issued at 241 PM EST Thu Dec 1 2016

Quiet and cool weather is expected through the first part of the
weekend as weak high pressure slowly builds and moves across
Central Indiana through Saturday.

A weak warm front in combination with passing upper level weather
disturbance will bring chances for precipitation on late saturday
night and into Sunday. It may be cold enough for some of the
precipitation to start as snow showers on Saturday night...before
changing over to all rain on Sunday. No accumulations are expected
at this time.

A pair of storm systems are then expected to impact the region
next week. The first bringing rain to the area on Monday night and
Tuesday. The second and stronger cold front will arrive on
Wednesday night and Thursday...beginning as rain showers that may
change over to snow...followed by a blast of winter air.

&&

.NEAR TERM /tonight/...

Issued at 241 PM EST Thu Dec 1 2016

Surface analysis early this afternoon shows broad cyclonic flow
across Indiana around low pressure centered over Quebec. Visible
Satellite Images shows an extensive cloud shield covering the
Great Lakes and much of Indiana. Westerly Surface flow remains in
place across Central Indiana with temperatures holding in the
upper 30s.

Forecast soundings and Time heights across the area maintain the
status quo....showing lower level moisture trapped beneath an
inversion aloft. Upper flow continues to suggest broad cyclonic
flow aloft influencing the lower level flow also. Thus will keep
the trend of a mostly cloudy sky tonight with temps a blend for
low temps. Given the expected clouds...the cooler MET values for
lows appear too cold.

&&

.SHORT TERM /Friday through Sunday/...

Issued at 241 PM EST Thu Dec 1 2016

Quiet weather is expected to continue on Friday as the GFS and
NAM continue to suggest plentiful lower level moisture
continuing to linger across the region. Lower level flow fails to
become anticyclonic...as the deep upper over the northeast slowly
pulls away. The overall lack of ridging in the mid and upper
levels will help prevent much in the way of Clear. Thus a Mostly
Cloudy sky again is expected on Friday. Given the expected clouds
and a lack of warm air advection...will trend highs at or below
MAVMOS values.

GFS and NAM shows weak ridging beginning to build across the
region aloft on Friday Night and Saturday as high pressure builds
across the region at the surface. Forecast soundings and Time
height sections begin to scour out the lower level moisture
showing convective temps that are unreachable. Thus will aim for
clearing skies and use a blend on temps again on Friday night and
Saturday.

Surface high will move east of Indiana on Saturday night and into
Sunday...along with the ridging aloft. NAM and GFS shows an
approaching short wave pushing toward Indiana. 290K GFS Isentropic
surface also shows good isentropic lift starting late saturday
night and continuing on Sunday with specific humidities surging
toward 3 g/kg. Forecast soundings show a top down saturation
starting on late Saturday night. As lower level temps may remain
below freezing...a mix type of precip may be possible upon onset.
Little to no accumulations will be expected as ground temps remain
warm. Best forcing and moisture looks to arrive on Sunday as the
isentropic lift and short wave pass during the day. Temps should
warm and allow all the precip to become rain. Thus will raise pops
on Sunday given the expected forcing. Again...will follow
superblend`s lead on temps.

&&


.LONG TERM /Sunday Night through Thursday/...
ISSUED AT 241 PM EST THU Dec 1 2016

ECMWF suggests very active weather pattern next week. The first
system to impact the region on Monday Night and into Tuesday as a
quick moving short wave will sweep along the Ohio River. At this
time...temperatures look warm enough for all precipitation to remain
as rain...however we will note that this system takes an ideal track
for snowfall across Central Indiana. Again...temps look too warm for
snow. Thus will just include rain pops at that time.

After that quick moving wave departs by late Tuesday...Dry weather
is expected to persist through the Wednesday as weak high pressure
remains in the wake of the departing low.

ECMWF then suggests a much stronger cold front and strong...highly
amplified wave to push into the region on Wednesday night and Into
Thursday. Again...precip ahead of the cold front should be rain as
the air mass ahead of the system should be well above freezing.
However...very strong cold air advection is denote in the wake of
the front with 850mb temps falling toward -17c by Thursday
evening...giving us our real first blast of winter air.

&&

.AVIATION /Discussion for the 020600z TAF Issuance/...
Issued at 1141 PM EST Thu Dec 1 2016

Good confidence that stratocu will hang around most if not all of
the TAF period under the influence of low level cyclonic flow and an
inversion. Could see some clearing from southwest to northeast
toward 06z Saturday. Confidence is more toward MVFR through 13z or
so at HUF and BMG and after 20z at IND and LAF, per late evening
trends and the GFS lamp.

Winds will continue to have a westerly component 5 to 8 knots
through the TAF period.

&&

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

$$

SYNOPSIS...PUMA
NEAR TERM...PUMA
SHORT TERM...PUMA
LONG TERM....PUMA
AVIATION...MK



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