670
FXUS63 KIWX 052307
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
607 PM EST Wed Feb 5 2025

.KEY MESSAGES...

- Period of freezing rain/drizzle still on track this evening
  into the overnight hours with untreated surfaces likely to be
  very slippery.

- Another fast moving system may bring a wintry mix Saturday.

&&

.DISCUSSION...
Issued at 250 PM EST Wed Feb 5 2025

Several challenges remain on the evolution of the approaching winter
event, with high confidence on most, if not all areas seeing a
period of freezing precip. Where confidence decreases is exact onset
of precip, mix of sleet across the north and lingering freezing
drizzle for the morning commute.

Freezing rain/drizzle that started back across Missouri this morning
was working northeast and attempting to expand in coverage across
IL, but is encountering a somewhat drier layer below 900 mb. Unlike
many of the past systems, column above 900 mb is already
generally saturated which should allow for onset of precip
within a few hours of the arrival of the deeper lift and
moisture. Temperatures have struggled to warm today, but should
make a run at freezing briefly across the south before falling
some this evening. Many models have trended towards a slower
onset of precip for the entire area with locations along the
US-30 corridor maybe not seeing anything until 2 or 3Z and even
later further north. In addition the warm nose may not penetrate
as far north as previously thought with 850 mb temps only 1 to 2
C and more shallow vs the deeper warm nose further south.
Despite these concerns, the only change to headlines was to slow
the start time north of US-30 to 10 PM based on the trends.
Once precip starts, we are looking at a 3 to 6 hour window of
accumulation of ice or possibly sleet across the north. Overall
accumulations will likely remain under a tenth of an inch, but
only a few hundredths is needed to make for difficult driving
conditions. Locations in the SE may see more of a convective
element that could allow for brief heavy rain that would limit
efficient accruing of the ice. The precipitation will wind down
quickly by morning, maybe ending at some drizzle (freezing?).
Slgt chc pops have been maintained through 12Z Thu to account
for this. Temps will warm Thursday above freezing, but it may
take much of the morning across the north for this to occur.

Few changes beyond tonight as yet another system arrives for
Saturday with a mix of precip expected once again. Warm nose may not
be as pronounced as the current system and confined mainly to SE
areas resulting in more of a snow/sleet/freezing rain setup with
frozen precip chances greatest across the north. Plenty of time to
sort out details on this system, but some minor travel issues could
arise. Struggle between high pressure to the north and additional
disturbances passing west to east into next week leaves lots of
uncertainty in the forecast.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 601 PM EST Wed Feb 5 2025

Existing TAFs were generally on track; only a few minor
adjustments to start and end times for FZRA. Dry air continues
to win-out in the short term, though dew points are rising
slightly and radar returns are on an upward trend. This has
resulted in a delay by one hour for the FZRA start at KFWA.
Duration of FZRA at KSBN is highly questionable based on some
guidance that offers a glancing blow. In contrast, the upper-
level trough, per water vapor, is beginning to amplify and lift
northeast which should result in an blossoming precipitation
shield.

FZRA perhaps ends sooner than advertised by an hour or two. Low
clouds scatter out very late in the afternoon with breezy
conditions.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Winter Weather Advisory from 10 PM this evening to 10 AM EST
     Thursday for INZ005>009-104-204.
     Winter Weather Advisory until 10 AM EST /9 AM CST/ Thursday
     for INZ012>015-017-018-020-022>027-032>034-103-116-203-
     216.
OH...Winter Weather Advisory from 10 PM this evening to 10 AM EST
     Thursday for OHZ001-002-004-005-015-016.
     Winter Weather Advisory until 10 AM EST Thursday for OHZ024-
     025.
MI...Winter Weather Advisory from 10 PM this evening to 10 AM EST
     Thursday for MIZ078>081-177-277.
MARINE...Small Craft Advisory from 1 PM Thursday to 5 AM EST Friday for
     LMZ043-046.

&&

$$

DISCUSSION...Fisher
AVIATION...Brown