National Weather Service Raw Text Product

Displaying AFOS PIL: AFDIWX Received: 2018-01-13 11:23 UTC


382 
FXUS63 KIWX 131123
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
623 AM EST Sat Jan 13 2018

.SYNOPSIS...
Issued at 432 AM EST Sat Jan 13 2018

Lake effect snow showers are expected today over portions of
northern Indiana and southwest Lower Michigan. Accumulations of 1
to 3 inches are possible through tonight in the snow belt region 
before the snow showers end. Highs today will be in the upper 
teens and lows tonight will dip to around zero with some locations
in the single digits below zero. More accumulating snow is 
expected across the entire area Sunday night into Monday with 
1 to 3 inches possible. This will be followed by more lake effect
snow Monday night into Wednesday. A warming trend looks likely late
in the week and into next weekend.

&&

.SHORT TERM...(Today and Tonight)
Issued at 431 AM EST Sat Jan 13 2018

Ongoing lake effect and temperatures main concern in the short 
term period. Upper level trough to swing through the area today 
with some weak DPVA. Polar airmass remains dry and not expecting 
much with this wave outside of lake effect region. Slight increase
in inversion heights today as trough passes but not much more 
than 5-6kft. However, long NNW fetch with some pre-conditioning 
from Superior along with sfc-850mb delta Ts in the lower to mid 
20s should be enough to support lake effect snow showers through 
the day and into tonight. Bufkit soundings show strong lift packed
within saturated shallow lower levels so some moderate snow 
showers possible at times. Low level flow will back today and 
transitory band should gradually shift east today and northward 
tonight as flow becomes southwest. Accumulations always difficult 
in these shallow unstable events but expect generally 1 to 3 
inches with some 4 inch amounts not out of question through this 
evening. 

Low temperatures next concern for tonight as arctic high builds into 
the region. Skies will clear in the west as lake band shifts 
northeast. Winds should also become light or calm as ridge axis 
expands east. Have lowered temps across the west and south by 
several degrees into the single digits below zero. Central and 
northern areas will drop into single digits above zero but may end 
up colder as well depending on how fast lake plumes shifts north. 
  

&&

.LONG TERM...(Sunday through Friday)
Issued at 431 AM EST Sat Jan 13 2018

Clipper system remains on track to impact the region Sunday night 
into Monday. Surface low track remains just to our north as left 
front region of cyclonically curved 100+kt jet streak moves over the 
area. Modest system relative isentropic lift develops Sunday 
night ahead of this feature and light snow should spread east 
through the late evening and overnight. As typical with these 
clippers there is not a lot of moisture available but good lift 
with diffluence aloft from jet streak and 1.5 PVU surface dropping
to around 600 mb should help system maximize pcpn/snowfall. Model
QPF has been rather consistent around two tenths of an inch and 
this matches well with WPC values. Snow ratios should be near or 
slightly above climo and close to 15:1 - 18:1 for this event. 
Rather deep DGZ being depicted but not supersaturated and 
strongest lift still near top or above this zone which will keep 
ratios lower than models despite the very cold temps. Forecast 
remains on track with general 1 to 3 inches across the area. Could
see some enhancement toward end of event in the far NW near the 
lake as winds become westerly and some lake enhancement kicks in. 

Attention then turns to lake effect potential behind this synoptic 
wave. Low level winds initially will be westerly Monday night into 
Tuesday as an east-west surface trough will be left across 
central Lake Michigan and interior Michigan. This feature will 
move south Monday night and should lead to development of another 
Type VI snow event with meso low/vortex development west of Big 
Sable Point MI late Monday night. This feature will drop south 
Tuesday and likely will come onshore between Berrien and Laporte 
counties followed by a strong single band in its wake. Models have
been rather consistent showing this band type but have some 
differences in orientation of trough axis as well as when and where
meso vortex will come onshore. Short duration intense rates would
be expected with the vortex while a more prolonged period of 
moderate to heavy snow would be likely in the single band. 
Increased pops in the NW to likely and high chance Tue and Tue
night with refinement coming over the next few days. 

A short but nice break in the weather appears likely after this lake 
effect event with a gradual warming trend late week into the 
weekend. 

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday Morning)
Issued at 623 AM EST Sat Jan 13 2018

Cold nnw flow will allow lake effect plume and associated snow 
showers to work into KSBN shortly after issuance with periodic 
IFR/MVFR visibility restrictions and some light snow 
accumulations. Could even see a few flurries briefly at
KFWA...best chances later this afternoon with little impact
anticipated. Lake effect snow showers end tonight as winds back 
and ridging settles in. Mainly VFR otherwise outside of any snow 
shower activity. 

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...Small Craft Advisory until 7 PM EST this evening for LMZ043-046.

&&

$$

SYNOPSIS...Lashley
SHORT TERM...Lashley 
LONG TERM...Lashley 
AVIATION...Steinwedel


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