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Area forecast discussion 
National Weather Service Indianapolis in
400 am EST sun Nov 23 2014

Update...
the synopsis...near term...short term...long term
and aviation sections have been updated below.

&&

Synopsis...
issued at 308 am EST sun Nov 23 2014

Two separate systems will affect central Indiana through the
forecast period. The first will continue its track from the lower
Mississippi Valley into Indiana today...producing rain/isolated
thunderstorms and some snow showers through Monday night. After a
brief lull in activity early in the week and a return to colder
weather...the next system will arrive around Thanksgiving day. Due
to the colder air mass...precipitation with the second system will
generally be in the form of snow and a wintry mix on Wednesday and
Thursday.

&&

Near term /today/...

Issued at 308 am EST sun Nov 23 2014

The main focus of the near term period will be precipitation and
thunderstorm chances with surface low approaching from the
southwest.

Upper trough will continue to deepen across the Central Plains
today while a surface low tracks across the Missouri Valley and
into central Indiana. That surface low will provide the best
dynamics for the forecast area today.

Lift with aforementioned surface low will be minimal until this
afternoon. As a result...kept probability of precipitation at slight chance through the
morning hours and then start increasing them more rapidly after
sun 18z. Vorticity maximum strengthens in middle levels around late this
afternoon through late evening...so went with probability of precipitation near 100
percent during that period. As central Indiana falls into a warm
sector with some weak instability but decent shear...isolated
thunderstorms will be possible during late afternoon and evening.
Storm Prediction Center has all of central Indiana under mention for non severe
thunderstorms.

Temperatures...highs this afternoon will climb into the middle to upper 50s
as forecast area slides into a warm sector. Trended on the warmer
side of guidance as a result.

&&

Short term /tonight through Tuesday night/...

Issued at 308 am EST sun Nov 23 2014

The main focus of the short term will be precipitation chances and type
as surface low exits central Indiana on Monday.

Thunderstorm chances should end by Monday 03z...but decent rain
chances will continue through Monday as the associated cold front
sweeps across the forecast area. Colder air will transition precipitation
to snow by middle to late afternoon. However...the best moisture and
lift will already be out of the area...so accumulations will be
minimal.

The main focus of Monday will be the strong southwest winds as a 120
knots upper level jet sweeps across central Indiana. Sustained speeds
will range between 20 to 25 miles per hour with gusts up to 40 miles per hour.
Contemplated issuing a Wind Advisory...but this far out will only
highlight in severe weather potential statement.

Tuesday will be dry and cool with weak ridging in place. Highs
will only top off in the 30s after starting out in the 50s on
Monday. Overnight lows will plummet back into the 20s on Monday
and Tuesday nights in wake of cold front. Temperatures were handled best
with a model blend.

&&

Long term /Wednesday through Saturday/...

Issued at 308 am EST sun Nov 23 2014

A broad long wave upper trough from Hudson Bay to the Great Lakes
and upper Midwest will be the rule through much of the long term.
Models bring a weak upper disturbance across our region very late
Wednesday into Thursday. Then an area of high pressure will dominate
our weather rest of the long term as it moves east across our
region.

Models have trended drier with the upper disturbance late Wednesday
into Thanksgiving day. Thus went slight chance probability of precipitation most areas with
still chance probability of precipitation north half Wednesday night and far north into
Thursday. Models have trended a little warmer Wednesday...so went
with mostly rain south half and mixed precipitation elsewhere late
Wednesday. Low level thickness favor snow north and central with
mixed precipitation far south Wednesday night and Thursday.

In regards to temperatures models have trended a little warmer
Wednesday. Meanwhile there are big differences between models in
temperatures with the rest of the long term. The GFS is a warm
outlier...while the gemnh and European models are significantly
colder. Went with a blend most periods. The GFS begins warm
advection Friday as low pressure moves into the northern plains.
Meanwhile the Euro and gemnh models do not indicate this..and in
fact keep high pressure over the upper Midwest Friday and move it
our way Saturday.



&&

Aviation /discussion for the 21/09z kind taf update/...

Issued at 308 am EST sun Nov 23 2014

Minor tweaks made to kind taf to better match current conditions.
No other changes are needed at this time.

Previous aviation discussion follows...
VFR expected through at least the first 6 to 10 hours of the taf
period. Will see light showers overnight...but not expected to
significantly impact conditions.

Next system approaching will begin lowering ceilings near daybreak
along with some drizzle...but sref probabilities and lamp guidance
suggest conditions remain low end VFR through about late morning.
Should see conditions deteriorate to MVFR with onset of steadier and
more widespread rain tomorrow afternoon...then perhaps to IFR late
in the period toward tomorrow evening as the low approaches and a
low level jet works into the area.

Winds will likely be southerly...then become southeasterly toward
morning. Speeds will likely be in the 07-14kt range through the
period. Some gustiness may occur tomorrow afternoon...but at this
point it looks too spotty to include. As low level jet moves in late
in the period...low level wind shear will become a concern at most
sites. Have included a mention despite uncertainty on details to put
the word out there.

&&

Ind watches/warnings/advisories...none.

&&

$$

Synopsis...tdud
near term...tdud
short term...tdud
long term....jh
aviation...nield/jh

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