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Area forecast discussion 
National Weather Service Indianapolis in
348 am EST Monday Nov 30 2015

the long term and aviation sections have been updated below


issued at 248 am EST Monday Nov 30 2015

A frontal system will bring rain chances to central Indiana today
through Tuesday morning. upper system will swing through
the Great Lakes and bring a chance of rain or snow to northern parts
of the area Tuesday night and Wednesday. After that...high pressure
will lead to dry weather through next weekend.

With the exception of Wednesday...when highs will be slightly below
normal...temperatures will be slightly above normal with highs in
the middle 40s and lower 50s.


Near term /today and tonight/...
issued at 332 am EST Monday Nov 30 2015

Main challenge today will be probability of precipitation as overrunning situation sets up.

The 00z operational GFS has now come into better agreement with the
00z NAM and November 29th 12z European model (ecmwf) with regards to evolution of the
Wyoming upper low and a surface low that is expected to spin up this
afternoon near Kansas City. However...ensemble member clustering had
a little to be desired. At any rate...looks like a blend which is
close to wpc forecasted surface low positions will suffice. This
will take the surface low to southwestern Iowa this evening and
southwestern Minnesota by 12z Tuesday. Meanwhile...occluded front
attached to the surface low will sweep east across central Indiana
tonight and hook up with the Tennessee Valley system that will be
lifting northeast.

Models agree that 300k isentropic lift will precede occluded front
today. However...lower levels will take awhile to saturate and
so...not confident that a solid rain shield will make a lot of
progress north and east. Currently...observations across our
southwestern counties had only 10k foot decks with no rain reaching
the ground...despite weak radar echoes. The European model (ecmwf) has been
consistently slower to spread any quantitative precipitation forecast northeast. Thus...will stick
with isolated probability of precipitation mainly south and west of Interstate 74 through
noon and then chance probability of precipitation spreading northeast across the entire area
during the afternoon. 00z NAM MOS probability of precipitation look a bit too high.
Prefer the 00z GFS MOS.

With warm advection opposing thick cloud cover...prefer a blend of
the cooler 00z NAM and warmer GFS MOS numbers with highs in the
upper 40s to the lower 50s.

Tonight...the isentropic lift will increase and shift to the eastern
counties and western Ohio overnight. However...modest 850-500
millibar qvector convergence near the occluded front along with weak
925-850 millibar frontogenesis...will keep the rain around through
the night. The best forcing will be southeast across northern
Kentucky and southeastern Ohio associated with a 40 knot low level
jet and northwest of the area with the occluded low. Will stick with
just light rain and go with probability of precipitation in between the wetter 00z NAM MOS
and not as wet 00z GFS MOS. This would translate to low likely
category most locales...possibly a little higher southeast and

Models hint there could be just enough instability to produce a clap
or two of thunder tonight. However...they would suggest it would be
limited to northern Kentucky and western Ohio at the nose of the low
level jet. So...continued to leave mention of thunder out.

Southerly flow and thick cloud cover should keep temperatures from
dropping much during the night with blend of 00z MOS lows in the 40s
looking good.


Short term /Tuesday through Wednesday night/...
issued at 248 am EST Monday Nov 30 2015

Main focus for the short term will be on any lingering morning probability of precipitation
on Tuesday with the occluded front along with rain or snow chances
with the upper low Tuesday night through Wednesday strong
positive vorticity advection moves over our northern half.

The occluded front should be near or at our eastern border 12z
Tuesday. Although the 12z European model (ecmwf) has been more steady and is
dry...decided to leave small probability of precipitation in for a few hours east central
per the 00z GFS and NAM and 00z NAM MOS as a buffer. The rest of the
day and into the overnight...the area will be dry-slotted. Model relative humidity
time sections reflect this nicely. As such...should see breaks in
the cloud cover Tuesday afternoon and Tuesday night most areas. That
said...should see some more precipitation move back into our
northwestern counties toward 12z Wednesday and spread east over the
rest of the north Wednesday as strong positive vorticity advection rotates around the base of
the upper low. Could see lingering precipitation in our far northeast
Wednesday evening...but for now will keep it dry. BUFKIT
soundingsand partial thicknesses suggest the precipitation could be
a mix of rain and snow. With moisture limited to the surface to
700millibars...went with small probability of precipitation across roughly the northern half
ofcentral Indiana on Wednesday with increasing cloud cover there
as well and less clouds to the south.

With cold advection...the cooler 00z NAM MOS looks good
Tuesday...but with more clearing expected per the 00z GFS
MOS...prefer a blend. Blend of temperatures with slightly below
normal highs in the lower and middle 40s looks sufficient for


Long term /Thursday through Sunday night/...

Issued at 336 am EST Monday Nov 30 2015

Dry benign conditions will prevail for entire extended period as a
large ridge of high pressure aloft and at the surface dominates
the central and eastern portions of the U.S. Temperatures will be
close to normal for Thursday...but a weak warming trend will occur
through the period with highs reaching the upper 40s/low 50s for
the weekend. Overnight lows will generally be in the upper 20s/low
30s for Thursday and Friday nights...increasing to the low to middle
30s for Saturday and Sunday nights.


Aviation /discussion for the 30/0900z taf update/...

Issued at 336 am EST Monday Nov 30 2015

no changes.

Previous discussion...
VFR during the overnight hours gradually becoming IFR ceilings rain
fog on Monday.

High pressure over the eastern Great Lakes will retreat to the east
as low pressure over the Southern Plains moves north towards Iowa.
This will allow an area of IFR ceilings and rain to spread slowly northeast
into central Indiana. Models indciate southern sections may become IFR
Monday morning after daybreak while this may not occur until late Monday
over northern sections. Model soundings indicate LIFR ceilings and rain
possible by Monday evening.

Surface winds will veer to east-southeast by Monday afternoon as a warm
front approaches from the southwest.


Ind watches/warnings/advisories...none.


long term....tdud

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