IWX issues Area Forecast Discussion (AFD) at Feb 18, 12:33 PM EST322
FXUS63 KIWX 181733
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
1233 PM EST Tue Feb 18 2025
.KEY MESSAGES...
- Very cold conditions will persist through the week with highs
in the teens to lower 20s and overnight lows in the single
digits to lower teens. Wind chills will be as cold as 5 to 10
below zero each morning.
- Snow accumulation chances this week exist mainly in the
northwest flow lake effect prone areas downwind of Lake
Michigan. Lake effect snow showers will persist in northwest
Indiana and southwest Lower Michigan today into tonight, with
additional chances Wednesday night into Thursday.
- Temperatures climb back above freezing by weekend.
&&
.DISCUSSION...
Issued at 228 AM EST Tue Feb 18 2025
After a brutally cold day yesterday where wind chills struggled
to reach above zero, another very cold morning is on tap today.
Temperatures have fallen into the single digits once again as
recent snowpack aids in radiational cooling at the surface. Have
opted to issue another SPS as morning wind chills of 5 to 15
below zero will be just shy of Cold Weather Advisory criteria.
Continue to use caution on area roadways today, especially on
secondary and untreated roads. Snow has blown onto roadways over
the past few days and quickly frozen into black ice in some
areas. Keep this in mind for the Tuesday morning commute, as
there could still be some lingering slick spots! Temperatures
will once again only be in the teens for highs this afternoon as
high pressure spreads east.
Lake effect snow showers persist today downwind of Lake Michigan in
northwest Indiana and southwest Lower Michigan. Winds have started
to gradually switch from west to northwest overnight; northwest
winds will persist today before flow becomes north-northwest
tonight. The lake effect snow showers will likely be scattered
and light to moderate in intensity today and tonight as low
convergence is weak as are lapse rates and Delta-Ts. Overall,
snow accumulations will be 1-2" (with isolated higher amounts
to 3" in northern Berrien County) through early Wednesday.
The next chance for system snow comes Wednesday into Thursday as an
upper level low pivots through the Great Lakes and an area of high
pressure builds over the Dakotas. These two features will allow for
a winter storm to develop to our south across the Mid
Mississippi and Ohio River Valleys tonight through Wednesday
night. A few light snow showers are possible during the day
Wednesday (mainly along the US 24 corridor) as our forecast area
is on the northern fringes of this system. As the
aforementioned upper level low pivots through late Wednesday
with an attendant 500 mb shortwave, this will allow for some
light snow to overspread the area and illicit a lake effect
response as winds become northwesterly once again. The lake
effect setup Wednesday evening into Thursday morning appears
much for favorable than the lake effect today will be. Low level
convergence is much more pronounced late Wednesday and there
will be a Lake Michigan to Lake Superior connection with a
northerly fetch along the long axis of Lake Michigan. Other
favorable parameters include delta- Ts of -15C, inversion
heights around 6-8 kft, and negative theta e lapse rates. Given
the lake to lake connection, it's certainly possible that this
setup results in one dominant lake effect snow band that extends
far inland as opposed to a multi band setup. Few changes were
made to PoPs and snow amounts, but this remains something we
will monitor in the next 24-36 hours in case adjustments are
needed.
Temperatures finally climb above freezing by the weekend and another
dry stretch ensues as high pressure builds across the eastern
CONUS.
&&
.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1232 PM EST Tue Feb 18 2025
Lake effect snow strengthens the first few hours of the TAF period
allowing for MVFR CIGs and times of MVFR and potentially IFR VISBY.
It then weakens this afternoon and into the evening as an area of
warmer temperatures passes through before reinvigorating from
overnight into Wednesday. A return to VFR conditions will be
possible overnight before MVFR conditions return Wednesday morning.
FWA appears to remain in VFR conditions, but an increase in winds
and mixing heights may be able to carry LE snow and clouds down
during the afternoon to lower conditions into MVFR. The best chance
of that appears to be during the first half of the afternoon before
winds die down again.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory until 11 PM EST this evening for LMZ043-
046.
&&
$$
DISCUSSION...Johnson
AVIATION...Roller
Source:
IWX issues Area Forecast Discussion (AFD) at Feb 18, 12:33 PM EST---------------
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