Area Forecast Discussion
Issued by NWS Indianapolis, IN

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216
FXUS63 KIND 300359
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1200 AM EDT Thu Mar 30 2017

.UPDATE...

The Aviation section has been updated below.

&&

.SYNOPSIS...
Issued at 236 PM EDT Wed Mar 29 2017

A frontal system is expected to move through the area on Thursday
and Friday. Another frontal system is expected to affect the area
early next week.

&&

.NEAR TERM /Rest of This Afternoon and Tonight/...
Issued at 956 PM EDT Wed Mar 29 2017

Latest hourly numerical guidance and observational trends suggest
the min temp forecast for tonight is a bit low. Have bumped these
numbers up a few degrees. Remainder of forecast is in good shape and
required only minor tweaks. Previous discussion follows.

Issued at 236 PM EDT Wed Mar 29 2017

Some showers presently occurring over parts of Illinois in
association with an upper wave. Could see the potential for a few
showers over parts of the west central and northwest zones later
this afternoon and evening as this upper wave lifts up through
Illinois.

Otherwise, short term model data suggest a stronger upper wave,
originating over the southern Plains, will be moving into the
western zones towards sunrise Thursday. Degree of lift, aided by a
40 kt low level jet and plume of steeper lapse rates, suggest there
may be quite a bit of shower and thunderstorm activity associated
with this wave. Will bring in high PoPs over the western zones
towards sunrise to cover this feature, with PoPs tapering off
farther east.

Progged low level thicknesses suggest the GFS MOS lows for tonight
may be a little on the warm side. Will nudge the lows down a few
degrees.

&&

.SHORT TERM /Thursday through Saturday/...
Issued at 236 PM EDT Wed Mar 29 2017

Model data suggest upper low currently over the southern Plains,
will drift into the local area by Thursday night, and push east of
the area by Friday night. An associated surface low and cold
front expected to move through the area Thursday night.

Will keep PoPs rather high for Thursday and Thursday evening as the
remnants of tonight`s activity move through early in the day
Thursday, and for expected convective development along the cold
front late Thursday afternoon and evening. Models suggest marginally
favorable lapse rates, and generally adequate deep layer shear for
severe convection near the cold front, but the better jet structure
looks to be farther south over the Tennessee Valley. Amount of
convection earlier in the day Thursday will have an affect on
whether steeper lapse rates, and resultant better instability, can
hold locally the time of cold frontal passage.

Will keep some PoPs going for showers on Friday as the upper low
moves through. Drier conditions expected by Friday night and
Saturday in the wake of the system.

Based on progged low level thicknesses, it appears the GFS MOS highs
for Thursday and Friday are probably too warm. Will nudge the highs
down 3-5 degrees in those periods. The guidance lows look good for
now.

&&

.LONG TERM (Saturday night through Wednesday)...
Issued at 150 PM EDT Wed Mar 29 2017

Confidence is high the period will see a lot of wet weather, with
the chance for rain especially high Monday and Monday night.
There is good agreement about trends, but major model differences
about specifics. POP errors could be as much as 20 percent.

It`s probable temperatures will be above normal. However,
uncertainty about the rain forecast brings uncertainty about the
temperature forecast also.  The consensus from Central Region will
be used, with potential errors 2-4 degrees.

&&

.AVIATION /Discussion for the 30/06Z TAFs/...
Issued at 1200 AM EDT Thu Mar 30 2017

VFR conditions will be likely much of the night. MVFR conditions may
overspread LAF and briefly IND/HUF tomorrow as a low pressure system
moves into the area.

Showers and a few thunderstorms will approach the area late tonight,
but uncertainty will preclude much more than a TEMPO mention and/or
VCTS mention.

Winds will be easterly early in the period, generally around
10-15KT. Occasional gusts may occur but will be too infrequent for
prevailing inclusion. Winds will become more southerly with time
as the low approaches.

Visibilities may be reduced at times in showers mainly tomorrow.
Fluctuations will be likely as is often the case.

&&

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

&&

$$

SYNOPSIS...JAS
NEAR TERM...JAS
SHORT TERM...JAS
LONG TERM...JK
AVIATION...NIELD



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