National Weather Service Raw Text Product

Displaying AFOS PIL: AFDIWX Received: 2018-01-13 23:36 UTC


589 
FXUS63 KIWX 132336
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
636 PM EST Sat Jan 13 2018

.SYNOPSIS...
Issued at 626 PM EST Sat Jan 13 2018

Lake effect snow will continue to gradually dissipate through the
overnight hours. Less than an inch of additional accumulations 
are possible, mainly near Lake Michigan. Low temperatures will 
fall to around zero tonight. Quiet but cold weather is expected 
Sunday, with high temperatures only reaching to around 20 degrees.
A clipper system will bring a widespread 2 to 3 inches of snow 
late Sunday night into Monday, with areas west of US 131 possibly 
seeing amounts up to 4 inches. Another lake effect snow event will
develop in it's wake, bringing additional accumulations to north 
and northwest wind favored snowbelts late Monday night into 
Wednesday.

&&

.SHORT TERM...(This Evening through Sunday)
Issued at 402 PM EST Sat Jan 13 2018

Ongoing lake effect snow showers and flurries in northwest wind 
favored areas, enhanced this afternoon by a shortwave aloft, will 
gradually become more west-east oriented before lifting out of our 
CWA early Sunday morning on SW Winds. Subsidence in the wake of the 
shortwave, combined with infiltrating dry air from our west 
southwest will cause a diminishing trend, with limited convective 
depth and moisture to work with. This will also keep amounts 
conservative, generally up to 1" accumulation, with the greatest 
amounts near Lake Michigan. 

The strong arctic high will settle in overhead through Sunday 
afternoon, with dry conditions, lightening winds, and clearing skies 
in the forecast. This brings us to tonights low temperatures, which 
will be especially chilly in the southwestern CWA. Lows will range 
from around 3 below zero in the southwest to around 4 above in the 
northeast. High temperatures on Sunday will only reach into the 
upper teens and low 20s.

&&

.LONG TERM...(Sunday Night through Saturday)
Issued at 402 PM EST Sat Jan 13 2018

Clipper System: Sunday Night-Monday

Still a little bit of a discrepancy with regards to the start of 
snow with the clipper system Sunday evening, but otherwise models 
seem to be in agreement as to the placement of the surface low and 
the larger synoptic scale features. Kept a similar forecast to the 
previous in terms of locations of highest pops, just increased 
slightly due to increasing confidence in the event occurring as 
planned, at least through Monday evening, when system snow 
transitions to more of a lake enhanced situation (more on that 
later). 

Snow ratios again were lowered slightly from consensus given ratios 
(which have been overdone all season). Used a blend of the consensus 
with WPC's grids in the interest of collaborating with neighboring 
offices. While the depth of the DGZ is deep during the event, the 
most favorable ingredients are not always in sync. At several 
points, as mentioned in previous AFD, conditions are not 
supersaturated, or the best lift is above/below the DGZ. 
Nevertheless, still think we'll have a solid 2-3" for most 
locations, with areas west of US 131 (in Michigan) and US 31 in IN 
seeing amounts between 3-4" (due to lake enhancement later Monday 
evening on westerly winds). Things could get a little hairy in terms 
of travel Monday as winds will gust up to around 25 mph at times, 
causing blowing/drifting of any accumulated snow (worst near Lake 
Michigan). Held off on any headlines for now with this event, as 
we'll be able to refine more tomorrow-but it looks like we're into 
solid advisory criteria/impacts at this point. Stay tuned for 
updates.

Type VI Lake Effect Snow: Late Monday night into Wednesday

The Lake effect aspect of things is a little trickier to nail down, 
largely due to the mesoscale nature of things and the models still 
varying with the exact placement and strength of the roughly WSW-ESE 
oriented surface/upper level trough. This lowers confidence a bit 
with regards to exact placement/timing/strength of things, but 
feeling confident we'll see snow showers across the area in NW to N 
favored regions, thus have higher pops with limited QPF at this 
time, though I did increase slightly. The general idea remains the 
same, with the mesolow developing in northern Lake MIchigan and 
dropping southward into La Porte and Berrien counties, before 
morphing into a nice long lake effect band oriented N-S. This band 
will then traverse eastward as winds become more west-southwest and 
gradually diminish by Wednesday evening. Right now, have amounts of 
1-3" through Tuesday, but the event will be ongoing through 
Wednesday. We'll have a better idea on amounts as we get closer and 
models refine the details.

High Pressure and Slight Warming: Thursday into Friday, Chances of 
Rain/Snow to round out next week

Quiet weather will return with mainly dry conditions Thursday into 
Friday night, with highs climbing from the 20s into the mid-upper 
30s. On saturday another system (which models disagree largely on at 
this time) will approach the area, leading to low chance pops across 
the CWA. This will be a rain/snow mix based on temperatures at this 
time, with highs Saturday reaching to the low 40s. 

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 626 PM EST Sat Jan 13 2018

Drier air will continue to push in from the west as high pressure
moves in so any MVFR conditions under remnant snow will only last
for a few hours at most. 

Clearing skies will be the norm overnight and only a mix of sun
and clouds will start Sunday, but clouds will be back on the
increase as we head into Sunday night ahead of a clipper system.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...Small Craft Advisory until 10 PM EST this evening for LMZ043-046.

&&

$$

SYNOPSIS...MCD/Roller
SHORT TERM...MCD
LONG TERM...MCD
AVIATION...Roller


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