IWX issues Area Forecast Discussion (AFD) at Jan 16, 2:43 AM EST
471
FXUS63 KIWX 160743
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
243 AM EST Thu Jan 16 2025
.KEY MESSAGES...
- Areas of slippery travel this morning as a clipper system
moves through. Lake effect snow to follow into the afternoon.
- Rain and snow Friday night through Saturday. Not as cold.
- Dangerous cold with lake effect snow early next week. Wind
chills of 20 below zero expected.
&&
.DISCUSSION...
Issued at 240 AM EST Thu Jan 16 2025
The clipper system is presenting less impressive in reality when
compared to 24 hours ago. The associated precipitation shield is
moving swiftly and has become more organized within our forecast
area. Snowflakes are small at the office but the volume is high
resulting in estimated visibility of somewhere between 1/2 and 1
mile. This feature will have exited the great South Bend area by the
heart of the morning rush, but elevated surface can be slippery due
to pavement temperatures in the teens. This feature may be ongoing
for the early part of Fort Wayne's rush our. Accumulations will be 1
inch or less this morning.
Lake effect snow activates late morning as cold air advection spills
over the lake in tandem with the trough axis. Some lake enhancement
is already noted over central Lake Michigan. With the synoptic help,
lake effect should spread well inland resulting an an additional few
tenths of an inch inland to this morning's snow total. The evolution
of the LES through the day is a little murky owing to possible dry
air intrusion. In spite of this, am erring on the site of
persistence and pattern recognition with at least 30-40% chance of
LES showers through the afternoon, tapering off near/by sunset.
Upper-level ridging builds in tonight. Ridging occurs as a trough
off the Baja of California tracks east seemingly in tandem with a
second trough descending from the Canadian Prairie. Warm air
advection Friday not only allows us to rise above freezing but
brings a chance of rain changing to snow by Friday night. The
rain/snow mix will be most common south of US 30, while those north
(especially by the Michigan state line) see all snow.
Forecast soundings are a little messy Friday night. There is some
indication that, prior to deep moisture arriving, a period of
freezing drizzle is possible after sunset. Confidence is low on this
and duration would be brief. Once the column saturates, a period of
rain is favored unless strong forcing permits wet-bulbing of the
profile to freezing, in which case snow would be dominant. Soundings
are marginal overall with the above-freezing layer barely making it
900mb (2k FT). In contrast to these clipper systems and lake effect
snow that has frequented the area the past week or so, we're facing
a wet/slushy snow Friday night to Saturday morning.
A cold front clears the area by Saturday evening which will spark
lake effect once more and usher in an Arctic blast colder than this
week's. A period of heavy lake effect snow is possible for Berrien
and Cass counties Sunday and Monday if impressive soundings verify.
Temperatures at 850-mb bottom-out at -28C Monday and Tuesday
according to the in-house suite of ensembles. Wind chills will be in
the 20s below zero at times. High temperatures will be in the single-
digits Monday and Tuesday. Northwest and westerly flow through this
cold air outbreak will keep lake effect snow showers in play Sunday
through Wednesday. We'll break out of the single-digits Wednesday
(teens for highs) and Thursday (20s).
&&
.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1250 AM EST Thu Jan 16 2025
A clipper type system will continue to dig across the region for
the remainder of the overnight as a strong channeled vort max
and accompanying upper jet streak shift across the region. Snow
has overspread far NW Indiana/SW Lower Michigan over the last
hour, and expecting these IFR vsbys to overspread KSBN in the
06Z-07Z timeframe. Strongest forcing appears to be focused in a
3 to 5 hour window for the terminals overnight into early
morning, before shifting to more of a lake effect/enhancement
snow shower potential during the day. Low level thermal trough
dropping across the southern Great Lakes this afternoon could
provide some uptick in multiband setup, but drying mid levels
offer some hesitancy to hit this hard with the 06Z TAFs.
Greater potential for afternoon lake effect snow showers may
reside across west central Lower Michigan. Gusty southwest winds
will shift to west-northwest today, with gusts into the 20 to
25 knot range. Did consider including a LLWS mention from
06Z-09Z to begin this TAF period, but these conditions still
appear marginal and short-lived. Otherwise, a period of MVFR
cigs below 2k feet and IFR cigs are possible toward daybreak
this morning through around midday.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory until 4 AM EST Friday for LMZ043-046.
&&
$$
DISCUSSION...Brown
AVIATION...Marsili
Source: IWX issues Area Forecast Discussion (AFD) at Jan 16, 2:43 AM EST (https://mesonet.agron.iastate.edu/p.php?pid=202501160743-KIWX-FXUS63-AFDIWX)
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