IWX issues Area Forecast Discussion (AFD) at Nov 27, 11:42 AM EST
337
FXUS63 KIWX 271642
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
1142 AM EST Wed Nov 27 2024
.KEY MESSAGES...
- Rain mixes with snow this afternoon/evening through early Thursday,
primarily south of US-30. No snow accumulation is expected.
- Lake effect snow showers with accumulations up to 1-2"
possible for Berrien and Cass counties beginning late tonight
through Friday.
- Cold Friday through early next week. Highs in the upper 20s
to low 30s with lows in the teens. There is another
possibility for some lake effect snow Sunday into Monday.
&&
.DISCUSSION...
Issued at 238 AM EST Wed Nov 27 2024
Zonal flow and surface high pressure over the Ohio River Valley are
making for dry and quiet weather through the early afternoon today.
Recent runs of high-res and mid range model guidance continues to
agree regarding the track of the surface low across
Kentucky/Tennessee tonight. As the surface low tracks across
the Ohio River Valley, light rain showers will start to
overspread the area between 18-21Z today. Initially,
precipitation will have dry air to overcome in the low levels.
As the rain showers slowly edge northward, most locations along
and south of US-30 should experience some light rain tonight.
Locations north of US-30, especially in northwest Indiana and
southern Lower Michigan, have the best chances of staying
completely dry. At times tonight and early Thursday, snow may
mix in with the rain showers. Hi-res guidance, particularly the
HRRR, shows a mesoscale band of snow just clipping our southeast
CWA early Thursday. It is certainly possible that Blackford,
Grant, and Jay counties in Indiana do end up seeing more snow
showers than the rest of our CWA, based on if/where bands of
snow showers form across central/north central Indiana. However,
any snow accumulations would be light, likely an inch or less
on elevated surfaces. With road surface temperatures above
freezing and rain mixing in with snow due to temperatures above
freezing, we do not expect any snow accumulations overnight.
There shouldn't be any impacts to Thanksgiving travel today or
tomorrow.
Precipitation comes to an end Thursday morning across northern
Indiana and northwest Ohio as the surface low exits to the east. The
surface low will deepen as it departs, and as it does, it will
likely wrap around some cold air into our forecast area on Thursday.
With colder air moving over a mild, unfrozen Lake Michigan (delta T
values around 20C Thursday (becoming 25C to 30C by Friday)) and low
level winds converging, this will allow for a few inches of lake
effect snow to be possible Thursday into Friday. Also aiding in the
development of lake effect snow is a strong 500mb shortwave that
traverses over Lake Michigan early Friday morning. With low level
winds coming from the north early Thursday, it is possible that
initially La Porte County, IN gets in on a few lake effect snow
showers. Then, as winds switch to be coming from the Northwest
Thursday afternoon and west by Thursday night, the areas most
affected by lake effect snow showers will be Berrien County, MI
and areas downwind of Lake Michigan east/southeast of there. We
will continue to monitor this timeframe as post-Thanksgiving
travel will likely be busy along the I-94 and I-80/I-90
corridors. At this time, the NBM has the highest probabilities
(50-70%) for 1-2"+ of snowfall in northern Berrien and Cass
counties.
From Friday through early next week, highs will be below freezing,
lows will be in the teens, and wind chills could be as low as the
single digits at night. Lake effect snow showers may also persist
Sunday and Monday as a clipper system moves through the Great Lakes.
Otherwise, it should be mainly dry away from Lake Michigan through
early next week.
&&
.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1142 AM EST Wed Nov 27 2024
A shortwave and attendant sfc low over the Central Plains will
track east through KY tonight. A blossoming precip shield along
a leading elevated baroclinic zone is expected to barely clip
KFWA this evening into the early overnight on the far northern
fringe of this system. Ptype at KFWA looks to be primarily
liquid, though a brief mix or changeover to wet snow cannot be
completely ruled out by mid-late evening. Opted to drop KFWA
into MVFR during this time, with better chances for IFR cigs/vis
just south of the terminal into tonight. No impact at KSBN
otherwise with light winds through the period.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Johnson
AVIATION...Steinwedel
Source: IWX issues Area Forecast Discussion (AFD) at Nov 27, 11:42 AM EST (https://mesonet.agron.iastate.edu/p.php?pid=202411271642-KIWX-FXUS63-AFDIWX)
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