National Weather Service Raw Text Product

772 
FXUS63 KIND 072018
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
318 PM EST Sun Feb 7 2021

.UPDATE...
The SYNOPSIS...NEAR TERM...SHORT TERM...LONG TERM
and AVIATION Sections have been updated below.

&&

.SYNOPSIS...
Issued at 309 PM EST Sun Feb 7 2021

Multiple rounds of snow expected from tonight through mid-week
should bring between 3-6 inches of total accumulation across 
central Indiana. Tonight snowfall totals are expected to be light
with up to 0.5 inches in far northern locations of central 
Indiana. Temperatures will still be below seasonal but look to 
rebound slightly early this week with highs in the upper 20s and 
low 30s. 

&&

.NEAR TERM /Rest of Today and Tonight/...

Issued at 309 PM EST Sun Feb 7 2021

Cold air has supplanted itself across the midwest as high 
pressure builds in beneath CAA. Here in central Indiana, 
temperatures range from the single digits to the north all the way
into the 20s in areas without snow cover. Wind chill values are 
near 0 over most locations, with a few exceptions to the south. 

Skies should remain clear though this afternoon and evening prior to 
the emergence of clouds from the west due to a subtle short wave.
Snow reports across MO and IL indicate some snowfall has been 
associated with this wave. Snowfall should continue as it 
approaches central Indiana, however the intrusion of dry air 
created by surface high pressure will limit progression this 
evening. Current dew point depression are between 15 and 20 across
most of central Indiana, further emphasizing the surface dryness.


Expectations are for snowfall to start reaching the ground after 
10PM this evening in far NW portions of central Indiana. Moisture 
through the troposphere out ahead of this wave is lacking in general 
so there still remains a possibility that not enough moisture is 
present for any snow to reach the ground resulting in lower PoPs. 
Current thoughts are for most areas I-70 and north to receive at 
minimal flurries tonight with the possibility of up to 0.5 inches, 
given high snow ratios, in far northern central Indiana. 

&&

.SHORT TERM /Monday and Monday Night/...

Issued at 309 PM EST Sun Feb 7 2021

The main focus in the short term will be the unfolding of another 
shortwave and associated surface low Monday afternoon through Monday 
night. This shortwave is a little more potent, supported by a 
developing upper level jet. Cyclogenesis out ahead of the wave looks 
to ramp up early on Monday over the Mississippi valley as increased 
CVA and upper level diffluence fuel surface pressure depression. 

As the surface low develops, a frontogenetical zone materializes 
over southern Indiana. This will be the primary focus for heavier 
snowfall for Monday evening/night. Vertical lift within the 
deformation is maximized within a near saturated dendritic grown 
zone, optimal for producing heavier snow fall rates. The shortwave 
is expected to quickly move easy and therefor snowfall rates should 
only be heavy for a short period of time. Current expectation are 
for 2-3 inches of snow within this narrow regions of heightened 
rates. Models are just starting to materialize this feature and are 
therefor are rather volatile in its location. This has lead to 
lower confidence in where highest snowfall amount will be located.
As the wave moves eastward tonight, better observation ingestion 
into the models should help with pinpointing accumulations. 

Elsewhere, broad vertical lift associated with the aforementioned 
upper level jet will squeeze out the minimal moisture present in 
the atmosphere. Expectations are for a low qpf but high snow ratio
0.5 to 1.0 inches over areas north of the previously discussed 
deformation zone. A slightly better zone of moisture and 
isentropic lift has been depicted in northern portion of the 
region where closer to 1 inch is more likely. 

Temperatures will increase slightly as the shortwave and stronger 
jets push the cold airmass northward. Temps will still be below 
seasonal however with highs expected to be in the mid 20s to low 
30s and lows in the low 20s to teens. 

&&

.LONG TERM /Tuesday through Sunday/...

Issued at 309 PM EST Sun Feb 7 2021

Tuesday during the day will be quiet with high pressure in control. 

Tuesday night, isentropic lift increases as some upper energy 
approaches from the west. Will have some slight chance to chance 
category PoPs, with highest PoPs south.

Wednesday into Wednesday night, a surface wave will ride along a 
front to our south. The area will be near the right entrance region 
of an upper jet, and there will be some frontogenetical forcing 
around as well. Moisture looks adequate for precipitation, so went 
with likely PoPs across roughly the southeastern half of the area, 
closer to the surface front.

Some questions remain though about this setup which lowers 
confidence on specifics. Will moisture be lower than expected with 
perhaps some convection south of the surface front? How far north 
will warm air aloft get? For now it appears some will get into the 
southern forecast area, so have introduced a wintry mix there. 

Potential is there for a few inches of snow in the north and a mix 
of light incing and light snow south. Will continue to monitor.

Thursday and Friday look to be dry with high pressure in control 
again. Went with some low PoPs Saturday as there is potential for 
another shot of colder air to move in.

Temperatures will be cooler than average mid-week, then very cold 
air will attempt to move in again next weekend. However, models 
continue to delay the coldest air, so confidence in temperatures at 
the end of the period remains very low.

&&

.AVIATION /Discussion for 07/21Z TAF Update/...

Issued at 309 PM EST Sun Feb 7 2021

Minor alterations to match current observations, otherwise no
significant changes made. 


Previous discussion as follows... 

IMPACTS: VFR conditions through 00Z at all TAF sites. Light snow
showers possible tonight. Within snow showers, MVFR ceilings and
visibilities are possible. Brief period of MVFR ceilings expected
after 06Z. VFR conditions tomorrow. 

 DISCUSSION: Clouds will begin to fill in as a weak shortwave
approaches from the west. Light snow showers/flurries should 
develop late tonight, but shouldn't cause too many issues. A brief
period of lower visibilities/ceilings are possible at KLAF.
Another system will pass through tomorrow providing better chances
of snow and larger impacts. 

 CONFIDENCE: High confidence in VFR conditions through 00Z. Low
confidence in deteriorating conditions tonight. 

&&

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

$$

SYNOPSIS...Updike
NEAR TERM...Updike
SHORT TERM...Updike
LONG TERM....50
AVIATION...Updike