Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 131655

Area Forecast Discussion
National Weather Service Indianapolis IN
1155 AM EST Thu Dec 13 2018

The AVIATION Section has been updated below.


Issued at 316 AM EST Thu Dec 13 2018

A couple of low pressure systems will bring rain to central Indiana
at times today through Saturday. Dry conditions will then return for
Sunday and persist into mid-week next week. Temperatures will remain
from near normal to above normal through the period.


.NEAR TERM...(Today)
Issued at 316 AM EST Thu Dec 13 2018

Early this morning, the southern forecast area was covered in
clouds, with temperatures in the 30s to lower 40s. Meanwhile, the
northern forecast area was mostly clear with temperatures in the
20s for the most part.

The area of clouds will continue to slowly march north through the
early morning hours as southerly flow begins to assert itself ahead
of an approaching system.

Thus expect the daylight hours to be mostly cloudy to cloudy across
roughly the southern 2/3 of the area. Clouds will increase across
the remainder of the north.

Isentropic lift increases from the south during the day as warm
advection continues aloft, with the best forcing across the western
half of the area. With decent moisture arriving with the southerly
flow, will go likely or higher PoPs across the western half of the
area at some point today, with chance PoPs east. Temperatures will
be warm enough for all rain.

The model blend looks ok for highs today given expected conditions.


.SHORT TERM...(Tonight through Saturday night)
Issued at 316 AM EST Thu Dec 13 2018

Unless noted below, models are close enough that the model blend
initialization was accepted for most items.

The initial forcing from today will diminish from south to north
during the evening, allowing PoPs to diminish to chance PoPs or
lower by the early overnight period.

On Friday, as an upper low moves into the lower Mississippi River
Valley, difluent flow aloft will allow for more rain to develop.
Some models hint at a possible split in the forcing with better
forcing to the west and east of the area. However, am not confident
enough to go with this solution at this time. Accepted the
initialization`s PoPs, which ends up with likely PoPs far south
(closer to the better forcing) and lower PoPs to the north.

Friday night into Saturday, the upper low will move into the eastern
Tennessee area. The NAM goes farther north with the low and is an
outlier from the other models. Thus disregarded its solution, and
adjusted the initialization`s PoPs downward across the north based
on this. The result is likely category or higher PoPs across the
southern 2/3 of the area, with the highest PoPs overnight Friday

The left exit of an upper jet along with a potential area of
deformation across the area could lead to some moderate to perhaps
briefly heavy rain across the area Friday night or early Saturday.
However, confidence is low due to the models changing their tracks
of the upper and surface lows.

PoPs will diminish Saturday afternoon into Saturday evening as the
system moves east out of the area.


.LONG TERM /Sunday through Wednesday/...

Issued at 302 AM EST Thu Dec 13 2018

Through the long term period, high pressure from the plains will
build east toward and then across central Indiana. This will keep
conditions dry across the area during that time. Temperatures Sunday
will be above normal, but after that a return to near normal
temperatures will occur with more northwesterly flow.
Higher than average confidence forecast with models in fairly good


.AVIATION /Discussion for 131500z TAF Issuance/...
Issued at 1155 AM EST Thu Dec 13 2018

The SREF and even moreso the GFS LAMP suggest MVFR or worse flying
conditions will hang around through 08z or so at LAF and 00z-04z at
the other sites. However, would not rule out MVFR after that time
and occasional VFR at times prior.

The High Resolution Rapid Refresh shows the area of showers,
currently over southwestern Indiana, gradually fill in and lift
northward through the afternoon and evening. The showers should last
the longest at LAF, perhaps through 08z. The showers should exit
elsewhere 00z-04z. Confidence in exact timing is low but in trends
is good.

Winds will mostly be southeast up to 7 knots.




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