Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 230837
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
337 AM EST Thu Feb 23 2017

.UPDATE...
Aviation section updated

&&

.SYNOPSIS...
Issued at 258 AM EST Thu Feb 23 2017

A series of frontal systems will move through central Indiana during
the next week, creating occasional chances for precipitation. The
warm streak will come to an end after Friday as closer to normal
temperatures return for the weekend behind a strong cold front. This
front could bring severe thunderstorms Friday.

&&

.NEAR TERM.../Today/
Issued at 258 AM EST Thu Feb 23 2017

Satellite imagery and observations show lower clouds starting to
develop across the forecast area this morning. This trend should
continue as weak lift increases ahead of an approaching cold front.

Thus stayed close a model blend for sky cover today which depicts
mostly cloudy skies across most areas for the bulk of the day.

The front will move into the northern forecast area before stalling
out, as most of the push for the front is well off to the north with
an upper wave in the northern stream aloft. With limited forcing, do
not expect any rain with the front this morning.

During the afternoon flow aloft increases from the south, which will
create some lift across the front. Lift isn`t impressive, so will
keep PoPs low.

With the expected cloud cover, kept temperatures below the very warm
MET MOS, but still a little warmer than the MAV. These values are
similar to persistence.

&&

.SHORT TERM.../Tonight through Saturday night/
Issued at 258 AM EST Thu Feb 23 2017

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

A similar setup to this afternoon will continue across the area this
evening, with flow aloft over the surface front. Forcing looks a
little better so went with higher PoPs than this afternoon but still
no higher than the chance category. Highest PoPs will be across the
north, closer to the surface front.

As the front moves north as a warm front overnight, forcing weakens
and PoPs will lower from south to north during the night.

On Friday morning, there won`t be much forcing with the area in the
warm sector. Kept some low PoPs north to account for any lingering
rain from the exiting warm front.

As the upper trough and a cold front approach the area during the
afternoon, PoPs will increase once again. Instability builds in the
warm sector and shear increases. A couple of lines of showers and
storms could develop across the area, one with a pre-frontal trough
and one with the front itself.

Will go with chance PoPs most areas during the afternoon, with some
likely PoPs far northwest close to the surface front. Severe storms
will be possible with decent instability and good shear. The Storm
Prediction Center`s Day 2 Convective Outlook covers this well and
should be read for details.

The NAM allows for clearing and temperatures into the low and mid
70s (The MET MOS for Indy has a high of 75, 1 degree shy of the all
time record high for the month of February). Feel this is too
optimistic as cloud cover should keep readings down.

As the upper trough and cold front move through Friday evening, went
likely or higher PoPs most areas. The threat for severe storms will
continue for areas ahead of the front. Overnight, have some low PoPs
to account for any wrap-around precipitation.

These low PoPs will continue into Saturday north. Otherwise dry and
much colder conditions will be the rule.

&&

.LONG TERM /Sunday through Wednesday/...

Issued at 209 AM EST Thu Feb 23 2017

ECMWF suggests high pressure across the area on Sunday along with
a mainly zonal flow in place aloft and no forcing. Thus cool and
mainly dry weather will be expected. By Late Monday...ECMWF
suggests a warm front returning to the Ohio Valley as the surface
high is well east of Indiana...again little forcing appears in
place...however moisture returns and will carry pops at that time.
Disagree with forecast builder here. Timing is off...forcing is
limited. It/s blend appears poor.

A better chance for precip appears to return on Tuesday night and
into Wednesday as the ECMWF shows SW flow developing aloft as a
strong trough deepens across the western plains states. Several
embedded shortwaves look to push toward Indiana within the flow
aloft Late Tuesday night and into Wednesday as Indiana finds
itself within the warm sector as a strong low moves through the
Great Lakes. An accompanying cold front is then dragged across
Central Indiana on Wednesday. These are all good ingredients for
precip...thus feel best chances will be on Tuesday night and into
Wednesday.

Strong High pressure then looks to build across the region on
Wednesday night into Thursday in the wake of the front.

&&

.AVIATION /Discussion for the 230900Z IND TAF Update/...

VFR conditions are expected to continue the next several hours.
MVFR FOG near 12Z has been removed by CONSSHORT as High cloud
appears poised to push across Central Indiana over the next 1-3
hours and pressure gradients seem to support some mixing that
could prevent fog. However dew point depressions remain at 2F.
Would not be surprised to seem MVFR Fog near daybreak still.

Previous Discussion Below

/Discussion for 230600Z TAF Issuance/...
Issued at 1145 PM EST Wed Feb 22 2017

Flying conditions lowering to MVFR Ceilings and fog towards daybreak
with pockets of IFR.   Then improving some Thursday afternoon.

Low pressure will move east across the northern great lakes and
a trailing cold front over the upper midwest will move to the
northern portions of central Indiana by late Thursday afternoon
and then become stationary.

Main aviation impacts will be VFR be areas of stratus developing
late tonight and early Thursday morning.  Model soundings indicate
widespread IFR appears less likely.   On Thursday...areas of MVFR
ceilings may temporarily improve to VFR Thursday afternoon and
then lower again Thursday night. Could see an isolated thundershower
north portions late Thursday afternoon and evening...but chances are
too low to mention in TAF.

Winds will be from the south or southwest around 5 to 8 knots through
the period.  Marginal low level wind shear may occur overnight...but
it should remain just below criteria.


&&

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

$$

SYNOPSIS...50
NEAR TERM...50
SHORT TERM...50
LONG TERM....Puma
AVIATION...JH/JP



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