Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 072337
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
637 PM EST Thu Dec 7 2017

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

&&

.SYNOPSIS...
Issued at 318 PM EST Thu Dec 7 2017

Quiet and cold tonight and a bit warmer Friday. Friday night a
clipper system will bring snow to central Indiana through
Saturday with light accumulations expected. Dry, cold and quiet
conditions then expected Saturday night through Sunday night.
For the rest of the seven days, chances for precipitation will
remain in the forecast for most periods under continued
northwesterly upper flow.

&&

.NEAR TERM /Tonight/...

Issued at 318 PM EST Thu Dec 7 2017

Clouds will move out tonight from northwest to southeast and winds
will slowly decrease. This will allow temperatures to drop rather
quickly, and think a guidance average in the mid teens is
reasonable. Even though winds will decrease from their current
speeds of 10-18 mph with sporadic gusts around 25 mph, they
shouldn`t drop off completely. This will produce wind chills in
the single digits at times near daybreak.

&&

.SHORT TERM /Friday through Sunday/...

Issued at 318 PM EST Thu Dec 7 2017

The focus of the short term is on arrival of snowfall and amounts
Friday night and Saturday.

Friday will start off cold but with mostly sunny skies highs will
top off in the low to mid 30s. Friday night, though, a clipper
system will swing out of the northwest flow pattern toward Indiana
and bring snowfall with it. Models are in good agreement on
arrival after at least 1 am in the northwestern counties, and
later elsewhere. At this point given model consistency have high
confidence in snow occurrence and at least medium confidence in
timing after 1 am in the northwest and after 3 or 4 am in the
central and north. Lesser confidence of snowfall occurrence as you
head southwest and south where forcing will be weaker. Snow will
continue through Saturday morning, but high confidence that snow
will come to an end over the western and southwestern counties by
1 pm Saturday if not before.

Medium confidence in snowfall totals, with the latest NAM coming
in with higher numbers than other models. Given the better
agreement of other solutions, think numbers around an inch near
I-70 with 1-3 inches north and half an inch or less in the south
and southeast looks reasonable especially given the lack of deep
moisture.

Saturday night looks dry and cold, with Sunday looking dry but
with increasing temperatures.

&&

.LONG TERM /Sunday Night Through Thursday/...
Issued at 237 PM EST Thu Dec 7 2017

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

The eastern half of the country will continue to be dominated by a
large upper level trough. Various waves riding through the trough
will bring occasional chances for precipitation to the area during
the long term. In addition, lake effect snow showers from
reinforcing shots of cold air may impact northern and eastern
sections of the forecast area.

Thus kept the initialization`s PoPs through the period.

As for temperatures, it looks like the initialization is being
influenced by climatology again, so reality will likely be colder
than its forecast.

&&

.AVIATION /Discussion for the 08/00Z TAF Issuance/...

Issued at 632 PM EST Thu Dec 7 2017

VFR conditions will prevail for the duration of the TAF period
with winds out of the southwest at 4 to 10 kts.

&&

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

&&

$$

SYNOPSIS...CP
NEAR TERM...CP
SHORT TERM...CP
LONG TERM...50
AVIATION...TDUD



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