723 
FXUS63 KIND 290300
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
959 PM EST Sat Nov 28 2020

.UPDATE...
The Near Term and AVIATION Sections have been updated below.

&&

.SYNOPSIS...
Issued at 232 PM EST Sat Nov 28 2020

High pressure will hold across the area through Sunday. A low 
pressure system is expected to affect the area from Sunday night 
into early next week. High pressure will return for the middle to 
later parts of next week.

&&

.NEAR TERM /Rest of Tonight and Sunday/...
Issued at 959 PM EST Sat Nov 28 2020

Clear skies are in place across central Indiana at 930 pm. 
Temperatures are in the mid to upper 30s with light southwesterly 
winds and dew points in the middle to upper 20s. Surface high 
pressure centered east of the area continues to block northward 
advancement of clouds and this will continue through most of the 
overnight. Could see an increase in clouds in the southwest by the 
morning sent in this direction by a system currently strengthening 
over western TX/OK. No appreciable changes in the forecast. Previous 
discussion follows...

Model data suggest a gradually weakening surface ridge will hold 
across the local area through Sunday, as an amplifying northern 
stream trough digs into the northern Midwest by Sunday evening.

A decent amount of lift may be generated across the area during the 
day Sunday, ahead of the approaching trough. However, models suggest 
condensation pressure deficits within the precipitation bearing 
layer will remain insufficient for precipitation through the day 
Sunday. As a result, only expecting a gradual increase in mid and 
high level cloud, starting by the pre dawn hours of tonight and 
continuing through Sunday.

Low level thicknesses suggest the GFS MOS temperature guidance for 
tonight and Sunday look reasonable for the most part, so only minor 
adjustments planned.

&&

.SHORT TERM /Sunday Night through Tuesday/...
Issued at 232 PM EST Sat Nov 28 2020

Model data suggest the amplifying northern stream trough will evolve 
into a deep upper low over the area by Monday night, with this low 
drifting slowly east by Tuesday. In addition, a southern stream 
system will get absorbed by the developing upper low. Models suggest 
this southern stream system will shear out across the Ohio Valley 
Sunday night and Monday.

It appears the deeper moisture will get tied up with the southern 
stream system, and get shunted off to the southeast of the local 
area. However, sustained lift associated with the developing upper 
low, will result in a gradual saturation of the air mass from the 
top down by the early morning hours of Monday. Will bring in PoPs 
starting Sunday night, and continue them into Monday night. Will 
start to taper off the PoPs from west to east later Monday night 
into Tuesday, as the upper low drifts off to the east. The highest
PoPs appear to be from late Sunday night into Monday night, 
coinciding with the development and passage of the upper low.

Thicknesses should be low enough under the developing upper low for 
most of precipitation to fall in the form of snow, except for the 
beginning of the event where thicknesses may still be high enough 
for the precipitation to start as rain. Most of the area has 
potential for light accumulations by Tuesday. Potential exists for 
somewhat higher amounts over the far east zones, where models 
suggest the western fringes of a deformation zone may intrude into
the those areas for a time Monday afternoon and night.

Progged low level thicknesses generally support the GFS MOS 
temperature guidance during the short term. Any adjustments should 
be minor.

&&

.LONG TERM /Tuesday Night through Saturday/...
Issued at 156 PM EST Sat Nov 28 2020

ECMWF shows high pressure building across the Ohio Valley on
Tuesday night through Thursday in the wake of the departing low
pressure system. Dry air and subsidence appear to be in place 
across Indiana on Tuesday through Thursday as ridging passed from 
the southeast.  

On Thursday through Saturday...the ECMWF continues with a highly
amplified...wavy pattern aloft as another area of low pressure 
dives south to the southern plains before turning northeast for 
the Ohio Valley on Friday and Saturday. This will bring more 
chances for precipitation to Central Indiana late this week. At 
this time enough cold air appears in place that some of the precip
type could be snow...although significant accumulations are not 
expected. Temps will be at or near normals.

&&

.AVIATION /Discussion for 290300z TAF issuance/...

Issued at 959 PM EST Sat Nov 28 2020

Updated current conditions only. Previous discussion follows...

IMPACTS:
-VFR thru the period.
-Light (0 to 5 kt) southwesterly winds thru the night.

DISCUSSION: Quiet weather is expected for the next 24 hours, with
clear skies tonight and light southwesterly winds and high
pressure sliding off to the east.

CONFIDENCE:
-High confidence in VFR through 0z Monday. 
-High confidence in light to calm winds overnight.

OUTLOOK: A strengthening low pressure system will bring lowering
ceilings, gusty northwesterly winds, and rain and snow to the TAF
sites starting late Sunday night.

&&

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

$$

SYNOPSIS...JAS
NEAR TERM...JAS/CP
SHORT TERM...JAS
LONG TERM....Puma
AVIATION...CP