Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 240458

Area Forecast Discussion
National Weather Service Indianapolis IN
1258 AM EDT SAT SEP 24 2016

The AVIATION Section has been updated below.


Issued at 141 PM EDT Fri Sep 23 2016

A large ridge of High Pressure over the plains states is expected to
build across the Ohio valley and Great Lakes tonight and Saturday.
Meanwhile...High pressure over Ontario will also build
southwest...providing dry but warm temperatures for central Indiana
this weekend.

The upper ridge will moves east of Indiana by Sunday
night...allowing a cold front to approach the area for Sunday night
and Monday. This will be the next best chance for showers or storms
as this front passes early next week. Cooler high pressure in the
wake of the front is expected to arrive by the middle of the next
work week. This will lead to more seasonable temperatures then.


.NEAR TERM /Rest of Tonight/...
Issued at 950 PM EDT Fri Sep 23 2016

More clouds should fill in from the north as the night wears on and
boundary washes out across the area. Have low level moisture in
place but uncertain whether low clouds or fog will win out. With low
clouds across northern Indiana and Illinois right now, think low
clouds may wind up being more prevalent at least across the northern
counties. Overall change was to increase cloud cover in the north
and add patchy fog across the area during the overnight. Low
temperatures in the low to mid 60s still look right on track.
Parts of previous discussion follows...

Back door cold front is expected to make slow and steady progress
southwest tonight as the ridging aloft to our west builds across
Indiana. The lower level boundary may help to provide some clouds
during the night as time heights suggest some lower level moisture
available. Thus will trend toward a partly cloud sky
overnight...with a blend on temps.


.SHORT TERM /Saturday through Monday/...
Issued at 141 PM EDT Fri Sep 23 2016

Dry Weather is expected for much of the weekend as HIgh pressure
northeast of Indiana and the previously Mentioned ridging aloft
continue to dominate Indiana/s weather. Models suggesting
cooler...northeast flow on Saturday and Sunday and this should
provide slightly cooler temperatures...however it will still be
above seasonal normals. Forecast soundings on both Saturday and
Sunday Afternoon indicate convective temperatures that can be
reached...however CAPE is very limited. Thus will just trend
toward partly Cloudy skies both afternoons...again trending
slightly warmer than a blend on Highs.

Late Sunday night and Monday appear to be the better times for
precip. NAM and GFS push the upper ridge east of Indiana by that
time as a deep upper low pushes out of the Central Canada and into
the Great lakes and Ohio valley. This feature looks to push as
cold front across the state with ample dynamics and will include
raise pops...particularly monday as these features pass. Forecast
soundings show best saturation on Late Sunday night and on Monday. We
should continue to be mindful that these features often progress
more slowly due to the strong departing ridge ahead of the front.


.LONG TERM /Monday Night through Friday/...
Issued at 159 PM EDT Fri Sep 23 2016

Models are more progressive in recent runs with large low pressure
system moving through the Great Lakes early to mid week. The cold
front is now progged to be through the area prior to the start of
the Long Term period, with broad surface high pressure moving into
the area and dominating through the remainder of the period. Thus
will carry a dry forecast throughout the period. As is noted
above, however, there remains uncertainty in the departure of this

Temperatures throughout the period will be pleasant, and much more
in line with climatological normals than recent days.


.AVIATION (Discussion for 240600Z TAFs)...

Issued at 1255 AM EDT Sat Sep 24 2016

There will be areas of mvfr and local ifr visibilities in fog until
mid morning.  Otherwise high pressure should bring vfr with
scattered to broken clouds around 5 thousand feet and light, mostly
east, winds.

However, this is a very low confidence forecast, especially until
mid morning. The reason is a very weak front moving in from the
northeast.  The front is too subtle for most forecast models to
handle it well. Sometimes in such situations widespread stratus and
fog can develop with little warning.


.IND Watches/Warnings/Advisories...


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