127 
FXUS63 KIWX 062311
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
610 PM EST Sat Feb 6 2021

.SYNOPSIS...
Issued at 400 PM EST Sat Feb 6 2021

Snow will spread across the area tonight with 1 to 2 inches for most 
locations and higher amounts near the lake. It will also be cold 
with temperatures around zero and wind chill values of 5 below to 20 
below through Sunday morning. Several additional chances for light 
snow are expected during the upcoming week along with continued cold 
conditions.

&&

.SHORT TERM...(This Evening through Sunday)
Issued at 400 PM EST Sat Feb 6 2021

Next shortwave is rapidly approaching the area at press time. A 
modest wave on water vapor imagery that is paired with an additional 
vort max exiting Oklahoma. These two waves will largely split our 
area tonight with better moisture locked to our south and best CVA 
just to our north. Pivoting 110+ kt 400mb jet streak does provide 
some modest right entrance support with good fgen noted from 925-
700mb (driven largely by good low level convergence ahead of 
shortwave and along attendant cold front). However fgen signal 
weakens with time and eastward extent as parent shortwave lifts NE 
and weak jet streak is absorbed into larger, faster jet across New 
England. Vertical cross-sections show this well along with an 
increasingly stable environment. Again, some brief, tenuous 
instability above the frontal slope in our west based on theta-e and 
geostrophic EPV but the signal is increasingly muted with eastward 
extent. Forcing also becomes oriented increasingly north-south with 
a very narrow time window (3-5 hours) for accumulating precip. 
Therefore...incoming snow band likely to produce a quick burst of 
moderate snow (perhaps down to 1/2SM vis in a few spots) but it will 
not last long and will weaken as it crosses the area in the 02-08Z 
timeframe. Forecast soundings indicate relatively deep DGZ with 
light winds but max omega is largely focused above that layer... 
promoting more plates and columns. Snow ratios will be on the higher 
side (particularly in our west) but still less than 20:1. All of 
this yields around 2" west to around 1" east. Slightly higher 
amounts in Berrien County with longer duration and perhaps some 
minor lake enhancement. Some brief lake effect snow is possible 
immediately behind the front early Sun AM but inversion heights 
crash to a paltry 3 kft with dry air entrainment in WNW fetch 
keeping cloud thickness only around 1 kft by later Sun AM per latest 
forecast soundings. This will make hydrometeor production nearly 
impossible and have lowered lake effect PoP's/amounts through 
Sunday. No changes to inherited advisory. Still think Berrien County 
will get close to 3" and wind gusts near 20 mph will lead to some
blowing and drifting issues. Certainly on the low end of the 
spectrum though.

Other main story for tonight is cold temps/wind chills. As feared, 
overnight lows this morning dropped lower than expected and latest 
guidance came in slightly colder for temps tonight. Clouds will 
scatter in our SW by early morning and winds hold steady around 10 
mph. Latest concensus guidance gives temps below zero in our SW and 
leaned even further on the cold side with lows around -5F there. 
Went colder for the rest of the CWA as well (low single digits) with 
cold front/snow expected to be largely out of here by early morning. 
With a steady 10 mph wind this yields wind chill values in the 
-15F to -20F range for much of our Indiana counties and therefore
 issued an advisory. Residual clouds and later exit of snow only
 yield apparent temps in the -5F to -10F range for our OH and MI 
 counties so no advisory planned there. Wind chills may struggle 
 to reach magic threshold on the eastern fringes of advisory but 
 it will certainly be close and final minimum wind chills are 
 often slightly colder than anticipated. (Actually reached 
 criteria this morning in a few spots.)

&&

.LONG TERM...(Sunday Night through Saturday)
Issued at 400 PM EST Sat Feb 6 2021

Next systems follow closely in fast, progressive flow aloft. Weak 
wave crosses Sun night with perhaps a light dusting possible but 
forcing is very limited with no upper jet support and a highly 
sheared midlevel wave. Next decent system will be late Monday with a 
very similar setup to today. Moderate (but gradually decaying) right 
entrance jet support and low level fgen. Once again some potential 
for deep DGZ but with limited forcing and moisture anticipate 
another 1-2" (possibly up to 3" in a few spots). Brief break on Tue 
but will have to watch late Wed-early Fri timeframe for the 
potential for a more amplified system to spin up along baroclinic 
zone to our south. Models beginning to come into slightly better 
agreement on overall picture but still a lot of details to work out 
in the coming days. Also still some potential for colder air to 
return late next week into the weekend though latest runs do call 
the severity and longevity into question a bit.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 610 PM EST Sat Feb 6 2021

Ragged band of light snow in association with upstream arctic front 
to cross the terminals this evening. Brief IFR restriction in light 
snow otherwise MVFR cigs expected to persist within post frontal 
inversion. W/NW winds aob 10kts through the period.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Winter Weather Advisory from 6 PM this evening to 7 AM CST 
     Sunday for INZ003.

     Wind Chill Advisory from 3 AM EST /2 AM CST/ to 1 PM EST /noon 
     CST/ Sunday for INZ003>005-008-012>018-020-022>027-032>034.

MI...Winter Weather Advisory from 7 PM this evening to 8 AM EST 
     Sunday for MIZ077-078.

OH...NONE.
LM...Small Craft Advisory from 1 AM to 11 AM EST Sunday for LMZ043-
     046.

&&

$$

SYNOPSIS...AGD
SHORT TERM...AGD
LONG TERM...AGD
AVIATION...Fisher


Visit us at www.weather.gov/iwx

Follow us on Facebook...Twitter...and YouTube at:
www.facebook.com/NWSNorthernIndiana
www.twitter.com/nwsiwx
www.youtube.com/NWSNorthernIndiana