943
fxus63 kiwx 130002
afdiwx
area forecast discussion
national weather service northern indiana
702 pm est fri dec 12 2025
.key messages...
- lake effect snow showers tonight, primarily for berrien
county. accumulations of less than one inch.
- light snow saturday afternoon (accumulations 1 to 3 inches),
transitioning to lake effect snow showers saturday night into
sunday (additional 2-4").
- wind chills of -15 or colder saturday night and sunday night.
&&
.discussion...
issued at 228 pm est fri dec 12 2025
primary topics of interest this afternoon are 1) incoming clipper
system saturday afternoon and night (snow duration ~6 hours),
followed by lake effect snow, and 2) below-zero wind chills saturday
night and sunday night.
a compact but strengthening upper-level disturbance races across the
northern rockies this afternoon, arriving on our doorstep saturday
afternoon just as an upper-level low drops due south from ontario.
this results in a strengthening area of frontogenesis across central
indiana. forecast soundings depict a shallow dry layer saturating
quickly amid this highly-forced environment and a deepening
dendritic growth zone through time (approaching 500mb after 21z/4pm
est). given the continental polar source region of this air mass,
snow ratios will be high (+/-15:1) resulting in efficient
accumulation despite the brief residence time. snow amounts of 2" to
3" are expected south of us 24 while most of the forecast area will
see 1-2" from this clipper. the exception will be south-central
michigan which will generally miss both the clipper and subsequent
lake effect. wind from the northwest near 10 mph saturday will
result in some blowing and drifting. wind gusts near 20mph will be
confined to those downwind of lake michigan. synoptic ("system")
snow ends before midnight. an advisory was considered for my far
southern indiana counties, but seeing such low-end advisory amounts
amid an above-average snow season so far made me less enthused for
headlines. the incoming shift may update as needed, especially if
the storm track shifts north.
in the wake of this clipper, lake effect snow develops saturday
evening and persists through sunday. this is preceded by a brief
period of lake effect snow tonight, primarily for berrien county and
those along the toll road. equilibrium levels are shallow (< 5k ft)
with an elevated and poorly saturated dgz. thus, amounts by daybreak
saturday will be less than 1". given this < 1" accumulation for
tonight, opted to delay any headline issuance for the time being.
for lake effect snow saturday afternoon through sunday, accumulation
will favor berrien, cass (mi) la porte, and st. joseph (in)
counties. lake effect parameters will be most favorable saturday
night / early sunday morning.
outside of the lake effect snow, temperatures will plummet saturday
night as skies clear and canadian high pressure becomes established
over the ohio valley. those near white and cass (in) counties will
see lows below zero while the remainder of the forecast area will
see single-digit lows. being at the mercy of decreasing clouds, this
decreases forecast confidence for the issuance of any cold weather
advisories at this time. sunday night, with lake effect clouds
decreasing, all areas are expected to be on either side of 0. wind
chills of -15 to -20 may warrant a cold weather advisory.
thawing out tuesday through thursday as upper-level ridging moves
in. highs will creep into the 40s wednesday and thursday. low
pressure moves through the upper midwest late in the week bringing
renewed chances for rain and snow.
&&
.aviation /00z tafs through 00z sunday/...
issued at 654 pm est fri dec 12 2025
mvfr cigs for both taf sites expected through the remainder of
this forecast period with mvfr to ifr category vsbys in light snow
after 16z sat as a disturbance pushes through the area with
heavier snowfall expected south of both terminals primarily
central in as the better deformation band sets up in this
location. the southerly track of this system would also put kfwa
with the better chances of the lowered vsbys and heavier bursts
of snowfall compared to the further north ksbn terminal.
&&
.iwx watches/warnings/advisories...
in...none.
oh...none.
mi...none.
marine...small craft advisory from 10 pm this evening to 10 pm est
sunday for lmz043-046.
&&
$$
discussion...brown
aviation...andersen