Area Forecast Discussion
Issued by NWS Indianapolis, IN

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348
FXUS63 KIND 171407
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
907 AM EST Tue Jan 17 2017

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

&&

.SYNOPSIS...
Issued at 217 AM EST Tue Jan 17 2017

Unseasonably warm weather is expected the next few days as
southwesterly flow within the atmosphere continues to keep
arctic...winter air at bay in Canada. Low pressure over Illinois
will quickly exit Indiana today...allowing High pressure over the
Central Plains to build across the Ohio Valley. Clouds are
expected to linger across the area as the High pressure system
arrives.

The high will bring cloudy but mainly dry weather to Central
Indiana on Wednesday...before the active weather pattern resumes
of the end of the work week and the weekend. At that
time...several strong upper level weather systems will push
through the Ohio Valley bringing more chances for periodic
showers...but above normal temperatures.

&&

.NEAR TERM /Today/...

Issued at 217 AM EST Tue Jan 17 2017

Surface analysis early this morning shows Low Pressure over
Illinois...with cyclonic lower level flow in place across Indiana.
A cold front trailed the low...stretching south across SE Missouri
into Arkansas. Water vapor imagery showed a dry slot intruding in
to the system across southern Illinois and Central Indiana. Water
vapor also shows the Highly Amplified and unusual pattern fro
January...with a deep trough across the western plains and
southwest with Southwesterly flow in place across Texas into the
Ohio Valley. Radar shows much of the precipitation exiting Central
Indiana...with a thin band ahead of the cold front over Central
Indiana. Overall...best forcing appears to have left the area as
dry air on the previously mentioned dry slot begins to intrude in
to the area.

Forecast soundings today show drying within the column as the
surface low is expected to pull farther northeast to the Great
Lakes. Time Heights also show the departure of deep moisture...the
the continuation of lingering lower level moisture through the day
and into Tonight.

Aloft the GFS shows Indiana caught between one departing short
wave associated with the departing low and and another arriving
wave within the flow aloft. Thus overall...forcing today remains
weak. Given the lower level clouds a sprinkle of drizzle cannot be
ruled out...but will aim for a cloudy day and try to contain pops
to the morning hours with the departure of the low to the north.
As for temps will use a blend and trend to or below given the
expected clouds and slight cold air advection.

&&

.SHORT TERM /Tonight through Thursday Night/...

Issued at 250 AM EST Tue Jan 17 2017

Time Heights and Forecast soundings continue to keep ample lower
level moisture lingering across the the region through Wednesday
Night. The previously mentioned second short wave looks to pass
across Indiana and the southern Great Lakes tonight...but forecast
soundings fail to show deep moisture. At the surface...High
pressure over the central plains looks to be building across the
Ohio Valley. Thus with a few ingredients for precip but not
everything coming together...including anti-cyclonic flow in the
lower levels...will only include a low chc pops for very Light
precip. Given the expected clouds will trend lows tonight at or
warmer than a Superblend.

GFS and NAM suggest that the large surface High pressure system
will slowly push through the Ohio valley from Wednesday and
Wednesday Night. Forecast soundings and Time height sections keep
the all too familiar pattern of trapped lower level
saturation...indicating that plenty of clouds will continue to
linger across the area. Aloft...the previously mentioned second
short wave departs by wednesday morning...allowing for ridging to
build across Central Indiana and the Ohio Valley ahead of the
next strong upper level weather system over the western Plains.
Thus will continue the mainly mostly Cloudy forecast through
Wednesday Night. Will stick close to a blend on temps.

Our Next weather system will begin to move into the area on
Thursday and Thursday night. The surface high pressure system
will depart to the east allowing a warm front to push toward
Central Indiana from the southwest. Aloft...strong forcing arrives by
late Thursday afternoon and Thursday night as the GFS shows a
strong upper low pushing into Missouri and beginning to influence
the Ohio Valley. Thus will begin to ramp pops higher as the day
progresses on Thursday into Thursday Night.

&&

.LONG TERM /Friday Through Monday/...
Issued at 225 AM EST Tue Jan 17 2017

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

An upper trough will bring rain chances Friday. After a brief dry
period Saturday, a large upper level low (and associated surface
low) will bring additional rain chances through the remainder of the
long term.

In addition to the inherent uncertainty during the long term period,
there is additional uncertainty on exactly how the upper low will
develop and where it moves each day. Thus see no reason to change
the initialization`s PoPs.

Temperatures will continue to be above average through the period.

&&

.AVIATION /Discussion for the 17/1500Z TAF Update/...

Issued at 906 AM EST Tue Jan 17 2017

UPDATE...
Lowered wind speeds a few knots at KIND, otherwise no changes.

PREVIOUS DISCUSSION...
MVFR and IFR conditions are expected to give way to all IFR or
lower conditions this afternoon.

Cold front should be past TAF sites by valid time, taking most of
the rain with it and shifting the winds to west southwest. There is
an area of MVFR ceilings behind it, stretching back into central IL.
These will move across the sites during the early part of the
period, with the exception of KLAF who looks to go to IFR by valid
time.

As another system approaches and moves in this afternoon and
tonight, ceilings will lower to IFR or lower everywhere. There could
be some patchy light rain tonight, but odds are too low to mention.

&&

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

&&

$$

SYNOPSIS...Puma
NEAR TERM...Puma
SHORT TERM...Puma
LONG TERM....50
AVIATION...50/TDUD



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