Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 291738
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1238 PM EST Tue Nov 29 2016

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

&&

.SYNOPSIS...
Issued at 305 AM EST Tue Nov 29 2016

A low pressure system is expected to move through the Ohio Valley
tonight into Wednesday. In the wake of this system, high pressure
will build into the area for the latter parts of the week. Another
frontal system may affect the area late this weekend and early next
week.

&&

.NEAR TERM /Rest of Today/...
Issued at 945 AM EST Tue Nov 29 2016

Forecast is on track. Skies are mostly cloudy across the area as
some low clouds have overspread much of central Indiana. These
should move out by this afternoon, but satellite shows some thicker
mid and high clouds upstream. Thus, while there may be some sun from
time to time, the day should average mostly cloudy for many areas.

Forecast temperatures have already taken the above into account, so
made no changes at this time.

Previous discussion follows...

Dry conditions expected today in the wake of yesterday`s upper
trough, currently lifting off to the northeast across the Great
Lakes. Short term model guidance suggest low clouds currently
across the area should clear out of the eastern zones around
sunrise. However, extensive mid and high level cloud upstream
should begin moving into the area later this morning and this
afternoon. This should result in quite a bit of cloud cover in one
form or another today.

Low level thicknesses suggest the GFS MOS highs for today look good
for the most part.

&&

.SHORT TERM /Tonight through Thursday night/...
Issued at 305 AM EST Tue Nov 29 2016

Model data suggest another short wave trough, currently dropping
southeast through the southern Rockies, will eject out across the
Ohio Valley during the day Wednesday. This will help to induce a
surface wave on the trailing frontal zone tonight. Based on the
location of the low level jet associated with this system, the best
lift will probably be located near and south of the Ohio river.
However, the northern fringes of this system may affect parts of the
local area tonight into Wednesday. Will go with chance PoPs for
rain over about the southeast two thirds of the area from late
tonight into Wednesday.

Rest of the short term looks dry at this point, as remnants of old
upper low shear off to the east, and surface high pressure noses
into the Tennessee Valley.

The GFS MOS highs for Wednesday look too warm, given cloud cover and
precipitation potential. Will nudge the guidance highs down about a
category in that period. Remainder of the guidance temperatures look
reasonable based on progged low level thicknesses.

&&

.LONG TERM /Friday Through Monday/...
Issued at 305 AM EST Tue Nov 29 2016

Model Ensembles indicate high pressure will dominate our weather
early in the long term followed by an area of low pressure and
an upper trough early next week.   Models are in pretty good
agreement Friday and Saturday and poor agreement early next week.

One difference regards timing as the GFS brings the bulk of
precipitation our way Monday...while the GEMNH and EURO brings
most of it our way Sunday and Sunday night.  The GFS brings
an initial upper disturbance our way early Sunday as well and
then weakens it with it bringing the main system Monday.

There are more similarities between the GEMNH and EURO with the
main difference is that the EURO may be overly deep with the surface
low.  With this in mind...will lean more towards the GEMNH and EURO
timing and the GEMNH with a weaker surface low.   Low level
Thickness of the EURO and GEMNH favor mostly liquid precipitation
early next week and even the GFS is all liquid as well.  As a result
decided to down play mention of snow and also bumped up low
temperatures a little Saturday night.    Another adjustment was to
increase sky cover a little Sunday to coincide with the EURO and GFS
solution.

The model blend and GEMNH and EURO indicate should end Monday and
will follow suit with this forecast.

&&

.AVIATION /Discussion for the 291800 TAF Issuance/...

Issued at 1216 PM EST Tue Nov 29 2016

Mainly VFR conditions at all TAF sites through approximately
30/0600Z...with patches of high cloud remaining across the area.
Kept a SCT to BKN mid-level deck this afternoon and
evening...owing to clouds upstream of the TAF sites early this
afternoon.

Tonight into tomorrow morning...expect a lowering of ceilings as
a frontal boundary approaches and moves eastward across the TAF
sites. Currently expect ceilings to drop to around 800 feet
during the early morning hours. Also...if winds subside in the
early morning hours more than currently expected...would not be
surprised to see a drop in visibilities as well. Not confident at
this time that this will occur. Conditions look to improve back to
VFR by around 14-1600Z.

Surface winds during the TAF period look to veer from south
currently...to west by late tomorrow morning. Speeds look to be
around 5 to 10 knots.

&&

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

$$

SYNOPSIS...JAS
NEAR TERM...JAS/50
SHORT TERM...JAS
LONG TERM....JEH
AVIATION...MRD



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