532 
FXUS63 KIND 080251
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
950 PM EST Mon Dec 7 2020

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

&&

.SYNOPSIS...
Issued at 407 PM EST Mon Dec 7 2020

Surface high pressure will provide dry weather through 
Thursday. Temperatures will warm up to above normal for the 
latter half of the week, then a low pressure system will bring 
rain showers this weekend followed by a return to colder temps 
early next week.

&&

.NEAR TERM /Rest of Tonight/...

Issued at 949 PM EST Mon Dec 7 2020

Increased cloud cover in the forecast based on satellite loop and 
trends. With the increase in cloud cover and all but the easternmost 
counties expected to remain overcast through the overnight hours, 
also increased low temperatures a bit to the middle 20s to lower 
30s. Previous discussion follows...

A weak upper trough will move through the 
area tonight. Only expecting continued cloud coverage as forcing 
will be weak and moisture will be limited. Satellite imagery from 
this afternoon shows clouds extending up to Wisconsin and Minnesota 
from which the airflow is coming from, bringing those clouds to the 
area. The northeast may see more clouds tonight as well as some lake 
enhanced clouds could extend into that area. Overnight lows in the 
mid 20s will occur again tonight. 

&&

.SHORT TERM /Tomorrow through Thursday/...

Issued at 407 PM EST Mon Dec 7 2020

Ridging will move into the area 
throughout the short term prompting subsidence and dry weather. 
Model soundings show that the low to mid levels will remain dry 
through the period, limiting any precip from the upper moisture. 
Clouds will start to thin out tomorrow morning as a weak upper 
trough exits the region and continuing to clear through Wednesday. 
Winds will be shifting throughout the period with the the eastward 
moving ridge, starting off with colder NW flow becoming more 
southwesterly by mid week. This will allow warmer air to advect 
in and high temperatures will get to the mid to low 50s for 
Wednesday and Thursday. 

A low pressure system will start to advance into the area at the end 
of the period, ahead of which cloud coverage will start to increase 
from the NW late in the day Thursday.

&&

.LONG TERM...(Thursday Through Monday)
Issued at 232 AM EST Mon Dec 7 2020 

The long term will start off Thursday night with an upper ridge of 
high pressure over the Great Lakes and Ohio Valley, separate troughs 
over the Southwest and and another over the northern Plains and 
another over the Pacific Northwest. At the surface, a broad ridge of 
high pressure will be moving the eastern states, a warm front will 
lift to the southern Great Lakes and cold front will be over the 
central and southern Plains. South and then southwest winds in 
between the departed high and cold front to the southwest will allow 
temperatures to be well above normal with highs in the middle and 
upper 50s in the offing Friday. Normal afternoon highs for this time 
of year are in the lower to middle 40s.  

Things will start off dry, but increasing moisture and isentropic 
lift on the 300K level will result in widespread rain showers by 
Friday night. The coupling of Great Lakes and southern states 100 
plus knot upper level jets will result in increased divergence. This 
will result in increased vertical motion and a strengthening 40 plus 
knot low level jet across central Indiana Friday night into 
Saturday. This suggest rainfall amounts could be higher than models 
currently are pumping out. Could see an inch or more over all or 
parts of central Indiana by late Saturday. 

The frontal system will be moving through on Saturday, but exact 
timing is problematic, so confidence in temperatures is not high, 
but in general, model blend lower and middle 50s look reasonable. 
May actually see a much tighter temperature gradient, however with 
indirect and direct circulations of the jet streaks. 

Precipitation should be winding down Saturday night as the system 
pushes northeast. Could see a brief mix of snow with rain with any 
lingering shower across northeastern sections.

Much colder but seasonable temperatures will be felt Sunday, in the 
wake of the cold front and under high pressure. Would not rule out a 
snow shower Sunday night though as an upper trough will be dropping 
down southeast and nearby. 

&&

.AVIATION /Discussion for 080300z TAF issuance/...

Issued at 949 PM EST Mon Dec 7 2020

IMPACTS:
-Ceilings should drop over the next few hours back to MVFR.
-Winds will be light and variable overnight and into the morning,
 but become southwesterly around 7 to 12 kts Tuesday afternoon.

DISCUSSION: An upper wave moving SSE through WI will reinforce
the cloud cover over the TAF sites through the night and into
Tuesday. Ceilings should drop from around 3500 ft now to 2500 to
3000 ft over the next few hours and stay there at least into
Tuesday morning. Light and variable winds overnight will become
stronger and southwesterly by Tuesday afternoon.

CONFIDENCE: Medium confidence in MVFR ceilings returning to all
the sites over the next few hours. 

&&

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

$$

SYNOPSIS...KH
NEAR TERM...KH/CP
SHORT TERM...KH
LONG TERM....MK
AVIATION...CP