Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 241438
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1038 AM EDT SAT SEP 24 2016

.UPDATE...

The Aviation Section has been updated below.

&&

.SYNOPSIS...
Issued at 252 AM EDT Sat Sep 24 2016

Dry conditions will persist through Sunday morning with ridging
aloft and high pressure centered over Ontario. However, the
pattern will change by Sunday afternoon as a low pressure system
tracks out of the Northern Plains and into Manitoba and Ontario.
This system will break down the current persistent upper ridge,
and its associated cold front will bring shower and thunderstorm
chances to central Indiana starting Sunday afternoon. Showers and
isolated thunderstorms will persist through Monday, but drier
conditions can be expected by Monday night. The dry weather will
then persist through the extended period. So, the main focus of
the extended period will be the much cooler temps with highs only
in the low to mid 70s starting Monday and overnight lows dipping
into the upper 40s/low 50s.

&&

.NEAR TERM /This afternoon/...
Issued at 957 AM EDT Sat Sep 24 2016

Surface analysis shows back door cold front has sagged to
southern Indiana...with light east to NE surface flow across the
forecast area. High pressure was in place across the Great lakes
and across the Tennessee River valley. Area of stratus and fog
were lingering across the area in the wake of the front...however
as daytime heating and mixing resumes in the next few
hours...partly cloudy the skies are expected to become.

A relatively dry column is indicated by the Forecast soundings
and time heights. However low level moisture continues to linger.
What trending high cover higher the next few hours due to
lingering clouds...but trending skies toward partly cloudy this
afternoon. Any bit of sunshine should allow temps to rise rapidly
into the lower 80s...thus have not made any major adjustment to
temps. Should clouds hold on longer than expected...we will need
to trend the highs a bit cooler.

&&

.SHORT TERM /Tonight through Monday Night/...
Issued at 252 AM EDT Sat Sep 24 2016

The main focus of the short term period will be
shower/thunderstorm chances on Sunday and Monday with a cold
front, as well as cooler temperatures.

Dry conditions will prevail through tomorrow morning due to
ridging aloft and high pressure over Ontario. The pattern will
start to change by tomorrow though as a low pressure system slides
out of the Northern Plains and into Manitoba. Its associated cold
front will start impacting central Indiana after Sun 18Z. Shower
and thunderstorm chances will increase from west to east
throughout the day on Sunday. Best forcing with aforementioned
front/isentropic lift is expected to fall between the Mon 06Z-
18Z time frame. So, will continue to carry mention of likely pops
at times from west to east through that time period.

Low precip chances will linger through Monday afternoon, but do
not expect much in the way of residual rain with upper low. So,
trended toward a dry forecast by Monday evening.

The other area of focus in the short term period will be the shift
to more Fall like temperatures by Monday as daytime highs only top
off in the low to mid 70s. And, as skies clear out on Monday
night, radiational cooling will result in lows dipping into the
upper 40s/low 50s, some of the coolest in awhile.

&&

.LONG TERM (Tuesday through Friday)...
Issued at 203 AM EDT Sat Sep 24 2016

The initialization from Region will be used.

Confidence is high the period will be dry, with all models
agreeing about that.

There is not good agreement about how much cold air will come south
Tuesday and Wednesday, with the European model considerably warmer
than the GFS.As a result, errors of 2-3 degrees or so are
possible in the forecast that will be issued today.

Potential errors drop to around 2 degrees Thursday and 1 degree
Friday as the models come into alignment with how fast warmer air
will return.

&&

.AVIATION (Discussion for 241200Z TAFs)...
Issued at 1038 AM EDT Sat Sep 24 2016

Fog and low ceilings will persist for another few hours,a lthough
some gradual improvement is likely. Previous discussion follows.

Issued at 655 AM EDT Sat Sep 24 2016

A weak front will cause extensive fog and stratus this morning.
Expect mostly mvfr ceilings and visibilities, with areas of ifr.
The stratus and fog should burn out as morning goes on with
ceilings rising to about 4 feet and visibilities becoming greater
than 6 miles.

Stratus and fog may produce mvfr again late tonight. Since the front
causing them will be dissipating, conditions should not be as
low as this morning.

Winds will be mostly east at 7 knots or less.

&&

.IND Watches/Warnings/Advisories...
NONE.
&&

$$

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


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