621
FXUS63 KIWX 050838
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
338 AM EST Wed Feb 5 2025

.KEY MESSAGES...

- Freezing rain is expected Wednesday night with slippery travel
  conditions likely into Thursday morning. The morning commute
  will likely be affected.

- A wintry mix is expected once again on Saturday.

- Cool, but seasonable to slightly above normal temperatures
  are expected through much of this period aside from the warm
  up into the 40s for much of the area on Thursday.


&&

.DISCUSSION...
Issued at 330 AM EST Wed Feb 5 2025

A high pressure center situates east of the area by this afternoon
and warming ensues overnight as the warm front waffles and attempts
to lift northward. Models do still show slight differences in the
exact location of the warm front. Moisture advection ensues during
the afternoon and into the evening with the ECMWF indicating the
best area of columnar moisture moves through between 00z and 12z.
However, time sections indicate that low level dry air may cut into
initial precipitation limiting residence time of preciptiation
across the area. High temperatures on Wednesday range between the
upper 20s and mid 30s, but road temperatures are in the upper 20s in
the South Bend area to around freezing in the Grissom area. We`ll
need to see how warm road temperatures can get today because that
may impede initial ice accretion with initial light rain potentially
aiding in lowering temperatures in a similar process to how sweat
lowers temperatures on skin. Surface winds out of the east also look
to impede warmth reaching the surface until they can turn to a
warmer trajectory and that doesn`t look to occur until after 9z at
the earliest. It may take until after sunrise to finally warm
pavement surfaces. Models` adjustment to the south of the freezing
rain area during the day Tuesday provides additional uncertainty
because it may mean better moisture doesn`t get far enough northward
to bring adequate precipitation to cause freezing rain in the north.
If ptype is more drizzle, the accretion process may be more
efficient, but accretions could end up lower. The southward shift
also may mean that temperatures from White county to Allen OH county
are too warm allowing more ice accumulation in this area. Some
sporadic power outages could occur overnight where a combination of
accretion occurs and winds gust up to 20 mph. With all this mind,
have gone with a winter weather advisory to highlight the threat of
freezing rain/icing.

Models indicate surface temperatures warm above freezing Thursday
morning allowing melting to ensue. A surface low forms north of the
Great Lakes and cold advection ensues on its backside Thursday night
as the temperature gradient sinks south in the form of a cold front.
Any wet surfaces could refreeze Thursday night with temperatures
dropping back into the mid 20s, but gusty winds Thursday between 20
and 30 mph may be able to elicit drying of road surfaces to restrict
that some. Dry weather is back for Friday and Friday night with high
pressure passing through.

For Saturday, another system with a similar look to the mid levels
moves through. However, this system arrives during the morning hours
as opposed to the nighttime. Dry air at the onset may be able to
delay precipitation arrival and limit the amount of snow that falls.
Then, as dry air advances with the diurnal curve, models indicate
that a wintry mix takes over. With the low pressure center east of
the area Saturday night, lingering moisture pairs with encroaching
cold air to change over to snow with some lake enhancement on the
back end.

Aside from Thursday`s highs that look to surpass 40 degrees in many
OH and IN counties, every other day sees high in the 30s or
below.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1130 PM EST Tue Feb 4 2025

Dry air advection out of the northeast was somehow just enough
to be able to scatter out most of the lower clouds under a
rather spectacular subsidence inversion with temperatures aloft
a full 10C warmer than at the base of the inversion. The dry
conditions in the low levels should prevail until around 00Z.
Even as precipitation develops and lower levels saturate, it
should be some time before IFR clouds are able to develop. With
the warm layer well above +5C, virtually no chance for snow and
not cold enough nor deep enough for sleet, so really solid
support for freezing rain from 02Z to 12Z.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Winter Weather Advisory from 7 PM EST /6 PM CST/ this evening
     to 10 AM EST /9 AM CST/ Thursday for INZ005>009-012>015-
     017-018-020-022>027-032>034-103-104-116-203-204-216.
OH...Winter Weather Advisory from 7 PM this evening to 10 AM EST
     Thursday for OHZ001-002-004-005-015-016-024-025.
MI...Winter Weather Advisory from 7 PM this evening to 10 AM EST
     Thursday for MIZ078>081-177-277.
MARINE...None.

&&

$$

DISCUSSION...Roller
AVIATION...Skipper