IWX issues Area Forecast Discussion (AFD) at Jan 3, 12:12 AM EST
118
FXUS63 KIWX 030512
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
1212 AM EST Fri Jan 3 2025
.KEY MESSAGES...
- A clipper system brings light snow to the area tonight.
Accumulations ranging from a dusting to up to 2 inches,
heaviest near and south of the US 24 corridor.
- A winter storm impacts primarily central and southern Indiana
later Sunday and Monday. Snow accumulations are possible
especially south of US 24, but it remains too early for exact
snow amounts.
- Cold with periods of lake effect snow well into next week.
&&
.DISCUSSION...
Issued at 217 PM EST Thu Jan 2 2025
Area of light to moderate snow working steadily west through IA with
the leading edge moving into west central IL. Good deal of dry air
in place which will limit precip reaching the ground initially, but
near/shortly after 00Z Fri should see a rapid ramp up on coverage.
Pretty much slam dunk for a period of snow as far north as the US 30
corridor with the highest amounts closer to US 24 where 1 to 2
inches still appears probable where the strongest forcing exists.
Main questions remain as to how far north measurable snow will
reach. Snow flakes will be observed possibly to the MI/IN state
line, but little if any accumulation is expected at this time. Onset
of pops has been slowed a bit and also allowed to linger a bit
longer in SE areas overnight with the bulk of the snow from the
system gone by 9Z Fri.
Colder air will move in behind the system with 850 mb temps by late
Friday ranging from -12 to -17 C, coldest in NE areas. This yields
delta ts near 20 C, equilibrium levels between 9 and 10 kft, and 0-
2 km thetae lapse rates going slightly negative, even well inland on
a 25 kt or so flow. Stronger flow, lack of convergence and some dry
air in lowest 1000 ft should help keep accumulations check, but some
areas could see 1 to maybe as much as 3 inches through Fri night.
Some flurries may linger into Sat as inversion heights crash.
Collaborated with GRR on possible winter weather advisory closer to
Lk MI to address both Fri commutes, but greatest concerns for our
area seem to start Fri AM with the PM commute possibly seeing
impacts. Will defer for now.
Focus the shifts to a deep upper low still off the western US coast,
which will make landfall by late Friday in the Pacific NW, then dive
SE into Oklahoma by 12Z Sun. The feature will open up once onshore,
but quickly deepens and takes on a brief negative tilt in OK as a
strong jet streak rounds the trough. Abundant moisture will be drawn
north with a major winter storm likely to impact northern MO into
central/southern IL/IN/OH. While confidence is increasing in these
areas, some challenges remain further north as the area more ends up
impacted by an inverted trough/deformation precip area and maybe the
northern fringe of the heavier precip from the main system. Models
have trended a bit north again, but with no significant phasing
occuring to pull the low further northwest, don't think there will
be a lot more N push (but I could be wrong). While still to early
for amounts, we could be potentially looking at travel impacts US 24
south Sunday evening into Monday with a need for
headlines in the next couple of period. Plenty of things to
work out yet, so stay tuned to reliable sources.
The deep low will usher in a shot of even colder air which will not
only get some lake effect going once again, but send highs into the
teens by mid week with wind chills near or maybe below zero.
&&
.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1209 AM EST Fri Jan 3 2025
A clipper system is currently moving through the area, bringing
snow showers and reduced visibilities across (primarily along
and south of US 30). KFWA has seen visibilities as low as 1 mile
and visibilities will remain between 1 to 3 miles in areas where
light to moderate snow is falling early this morning. Snow
should be done around 09Z, with a few hours of quiet weather
this morning before lake effect snow showers ramp up during the
afternoon. Winds will increase as well this afternoon, with
gusts to 20 to 25 kts. In any lake effect snow showers, expect
MVFR visibilities. There may also be some patchy blowing snow
this afternoon with those gusty winds that could also help
reduce visbilities.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory until 10 PM EST Saturday for LMZ043-046.
&&
$$
DISCUSSION...Fisher
AVIATION...Johnson
Source: IWX issues Area Forecast Discussion (AFD) at Jan 3, 12:12 AM EST (https://mesonet.agron.iastate.edu/p.php?pid=202501030512-KIWX-FXUS63-AFDIWX)
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