Area Forecast Discussion
Issued by NWS Indianapolis, IN

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171
FXUS63 KIND 102007
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
307 PM EST Sat Dec 10 2016

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

&&

.SYNOPSIS...
Issued at 307 PM EST Sat Dec 10 2016

A high Plains system will lift northeast across the great lakes
Sunday night. This system will bring snow to central Indiana
tonight. The snow will transition to a wintry mix and then rain
Sunday afternoon and evening as a warm front lifts northeast
acrossthe area. Colder air will move in Monday in the wake of a
associated cold front.

Two more systems will bring much colder air in as well as chances
for accumulating snow Wednesday and Wednesday night and also next
weekend.


&&

.NEAR TERM /TONIGHT/...

Issued at 307 PM EST Sat Dec 10 2016

Main focus tonight will be onset of snow in warm air advection
ahead of a high Plains system.

Models in good agreement that a Rockies system will move into the
Oklahoma and Texas panhandle area overnight. Warm air advecttion
will start kicking in especially toward daybreak. 290K isentropic
condensation pressure deficits suggests the northern half of the
forecast area will saturate down enough to result in overruning
precipitation, which critical thicknesses and model soundings
suggests will be all snow. Will go with likely pops extreme north
across part of Carroll county, where a couple of inches are
possible by morning, and tapper off to slight chance pops as far
south as a Franklin to Rockville line. South central parts of the
forecast area should hold off on any precipitation until Sunday
morning.

Issued a Winter Weather Advisory starting at 7 pm tonight and
going through 1 am Monday.

With thick cloud cover and warm air advection, will side at or above
MOS.


&&

.SHORT TERM /Sunday through Tuesday/...

Issued at 307 PM EST Sat Dec 10 2016

Snowfall amounts and timing of changeover will be the main
concern for the short term.

Models now in decent agreement that 295K isentropic lift will ramp
up as a low pressure system lifts northeast from the Plains to
Lake Huron Monday morning. This will result in increasing chances
of precipitation. Based on critical thickness progs, model
soundings and Bufkit, model blend has the far southwestern
counties dry until 15z Sunday at which time the precipitation type
should be either rain or freezing rain. The other areas should all
be snow. The freezing line will be working its way northeast and
should reach Greensburg, Indianapolis and Crawfordsville around 2
pm and extreme northern parts of the forecast area after 6 pm. Far
northern parts of Carroll county may remain snow the whole event
before it ends overnight Sunday night. Model QPF has increased a
bit and looks reasonable seeing as specific humidities reach 4 to
6 g/kg Sunday afternoon. In addition, the area will be in the
right rear quadrant of a 140 knot upper jet over southern lower
Michigan. Could see over 4 inches of storm total snow in the
advisory area with an inch or less from Indianapolis and south.
Could also see light freezing rain accumulation Sunday afternoon
with less than .05 expected. The remainder of the short should be
dry and cold with some breaks in the clouds.

&&

.LONG TERM /Tuesday night through Saturday/...

Issued at 229 PM EST Sat Dec 10 2016

A large upper low traversing northern Ontario will bring mostly
dry and colder weather to central Indiana to start the long term.
What once looked like potential for a strong storm mid week now
looks anemic in terms of forcing and moisture and thus only have a
slight chance for snow across the northern half or so of the area
during the day on Wednesday, and accumulations are very light.
Wind chills could drop below zero Wednesday night and Thursday
night.

By Friday though models indicate that an upper ridge axis could
move east of the state and allow a strong frontal system to form
in the southwestern states and quickly bring some moisture and
forcing back to the area on southwesterly flow. Thus have chances
for snow going from Friday on. The southwest flow should also
allow the area to warm some, which will introduce a precipitation
mix on Saturday before the precipitation comes to an end.

&&

.AVIATION /Discussion for the 10/18Z TAF Issuance/...
Issued at 1133 AM EST Sat Dec 10 2016

Good confidence that VFR conditions will prevail through tonight.
Could see snow moving in to LAF after 03z associated with moist
upglide ahead of a high Plains system. MVFR possible toward the end
of the TAF period as this system gets closer and warm and most
advection increases.

Winds will southwest through 23z 7 knots or less and south and
southeast tonight 5 knots or less. Winds will pick up to 10 knots or
more after 15Z Sunday.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 7 PM this evening to 1 AM EST
Monday for INZ021-031.

&&

$$

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



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