Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 222239

Area Forecast Discussion
National Weather Service Indianapolis IN
539 PM EST Wed Nov 22 2017

The AVIATION Section has been updated below.


Issued at 302 PM EST Wed Nov 22 2017

High pressure from Kansas to northwest Illinois is providing a
cool air mass over the area with just a scattering of clouds this
afternoon. Skies will clear going into the evening and tonight as
this high moves over the Ohio Valley. Looking for some clouds to
come in from the northwest possibly by morning from a low pressure
system upstream over the Upper Great Lakes.


.NEAR TERM /Tonight/...

Issued at 302 PM EST Wed Nov 22 2017

As stated in the synopsis, high pressure will be slifing eastward
across the Ohio Vally tonight keeping skies clear across the
region. Had a little bit of an issue as forcast soundings indictae
that temperatures drop just below freezing given the inversion
that will set up in the boundary layer. Also, GFS/Euro bring some
high clouds over the northeast and central parts of the forecast
area, which may impede the falling a few more degrees, but then
given the model blend is only talking a few degrees with light
winds, kept temperatures in the middle 20s for lows by
Thanksgiving morning.


.SHORT TERM /Thanksgiving Day through Saturday/...

Issued at 302 PM EST Wed Nov 22 2017

High pressure will continue to move off to the east and southeast
giving a southwest flow on the backside of the high late Thursday
and Thursday night. Thus, it will not be as cold Thursday night
as warm air advection moves acros the area. There may be some
high clouds on the edges of the storm system moving eastward north
of the Great Lakes, but with warmer and dry air from the southern
Plains, a mild day is in store for the area on Friday. On Friday
night, a cold front is forecast to move towards the area from the
northwest. Thought about a slight chance for some light
rainshowers across our north central and northeast parts, but
given the dry air in place and lack of any significant moisture
advection, it will be up to what the mid/upper level trough can
produce in the way of moisture if it will rain or just what could
make it through the dry boundary layer. Thus, went with a mostly
dry forecast on Friday night/Saturday morning along/ahead of the
cold front that will move through Saturday morning. That will
leave Saturday as another nice day all in all with temperatures
about 10 degrees cooler than Friday.


.LONG TERM (Saturday night through Wednesday)...

Issued at 1248 PM EST Wed Nov 22 2017

There is good model agreement and high confidence in the forecast
through Monday night. The weather should stay dry. Possible
temperature errors are 3 degrees or less.

Forecast confidence plummets starting Tuesday.  The American and
European models have different handling of a large weather system
over eastern North America. The American model brings in both cold
air and rain chances much faster.

While the consensus is still the best forecast in such situations,
possible temperature errors for Tuesday though Wednesday are 6
degrees. Possible POP errors for the same period are 10-20 percent.


.AVIATION /Discussion for the 230000Z TAFS/...
Issued at 539 PM EST Wed Nov 22 2017

Increasing layered cloud above 050 expected at the terminals
tonight, along with unrestricted visibility. Surface wind at or
below 6 kts.




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