IWX issues Area Forecast Discussion (AFD) at Jan 17, 6:43 AM EST
649
FXUS63 KIWX 171143
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
643 AM EST Fri Jan 17 2025
.KEY MESSAGES...
- Above freezing temperatures persist today, which will allow for
continued snowmelt.
- A strong cold front arrives overnight tonight into early
Saturday, which will bring in precipitation that starts as
rain and quickly changes over to snow. Brief, slushy snow
accumulations up to 1" are possible.
- Dangerous cold begins filtering into the area Sunday and lasts into
the middle of next week. Monday and Tuesday will be the
coldest days of the season thus far with highs in the single
digits! Wind chills as low as 20 to 25 below zero are expected
especially Sunday night through Tuesday night.
- Depending on how frozen Lake Michigan will be, lake effect
snow could occur from Sunday to Tuesday.
&&
.DISCUSSION...
Issued at 250 AM EST Fri Jan 17 2025
Enjoy another day with highs above freezing! Today, dry weather
persists and highs will warm into the upper 30s. With gradual
clearing throughout the afternoon and evening, the combination
of above freezing temperatures and sunshine will help with
snowmelt.
Our area will be sandwiched between two areas of low pressure
on Friday night, with one passing through the northern Great
Lakes region and the other through the Ark-La-Tex region. From
these two systems, an expansive cold front will sweep across the
area Friday night into early Saturday. Precipitation initially
falls as rain with temperatures above freezing, but will
quickly changeover to snow as temperatures drop below freezing.
With low snow to liquid ratios at the onset, snow will likely be
a slushy, wet snow with up to 0.5 to 1" of snow accumulation by
early Saturday. Pavement temperatures have been above freezing
the past few days, so I wouldn't anticipate a widespread travel
Saturday morning, but there could be some slick spots on bridges
and overpasses. Snow will be heavy, but brief, which will likely
limit accumulations on the roadways.
The coldest air since December 2022 is on the way! A large area of
high pressure will allow for bitterly cold Arctic air to spill into
the central CONUS and Midwest starting as early as Sunday through
the middle of next week. Monday and Tuesday will be the coldest days
of week with highs only in the single digits. Several nights with
lows below zero are likely from Sunday night to Tuesday night. With
wind gusts between 20 to 25 mph, wind chills values will be as low
as -20 to -30 degrees from Sunday night through Wednesday morning.
This dangerous cold will be brutal, with frostbite possible in as
little as 30 minutes! Limit prolonged exposure outdoors and take
precautions to protect pets and exposed pipes from this bitter cold.
Cold Weather Advisories (-15 degrees) and/or Extreme Cold Warnings (-
25 degrees) will likely be needed for this prolonged stretch of
dangerous cold. Temperatures will begin to warm up back towards
seasonable levels (but still below freezing) by mid to late
next week.
Lake effect snow will also be possible (especially along the I-94
corridor) in the midst of this Arctic blast. At this time, lake
effect snow looks most likely behind the cold front on Sunday. Low
level winds converge and theta e lapse rates are favorable for lake
effect snow. Some continuation of lake effect snow is possible early
in the week, however, limiting factors include dry air, unfavorable
fetch, and the potential for Lake Michigan to freeze over in our
nearshore zones. There is already some shelf ice/ice pancakes seen
on webcams at Michigan City and St Joseph, but the Arctic air Sunday
through Wednesday will likely lead to the ice coverage expanding.
Depending on how much Lake Michigan freezes over, this could inhibit
lake effect snow from forming.
&&
.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 640 AM EST Fri Jan 17 2025
A progressive short wave upper ridge will shift to Mid Atlantic
states this afternoon allowing broad sfc anticyclone across the
Ohio Valley to depart to the east. The combination of this
ridge, and upstream broad low level troughing associated with a
southern and northern stream disturbance will create a strong
low level height gradient today with latest guidance continuing
to indicate a 50 knot low level jet developing this afternoon.
Despite surface gusts to around 25 knots today, did continue to
include LLWS mention given persistence of sharp low level
inversion. Stronger low level moisture transport will be
somewhat delayed until after this evening, and latest data
still suggests precip onset time of late evening/early overnight
at terminals. Evaporative cooling effects could allow precip to
begin as a brief period of snow, but should quickly change to
rain or rain/snow mix as better moisture is drawn northward.
Colder profiles on backside of this system should allow precip
to end as mainly snow Saturday morning. VFR conditions to begin
this period will transition to MVFR later this evening, and
possibly to IFR during the overnight hours.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory from 10 AM this morning to 4 PM EST
Sunday for LMZ043-046.
&&
$$
DISCUSSION...Johnson
AVIATION...Marsili
Source: IWX issues Area Forecast Discussion (AFD) at Jan 17, 6:43 AM EST (https://mesonet.agron.iastate.edu/p.php?pid=202501171143-KIWX-FXUS63-AFDIWX)
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