774 

FXUS63 KLOT 301102

AFDLOT



Area Forecast Discussion

National Weather Service Chicago/Romeoville, IL

502 AM CST Tue Dec 30 2025



.KEY MESSAGES...



- Light snow likely late this afternoon/early this evening,

  mainly northeast of a Rockford to Rensselaer line.



- A period of snow again Wednesday afternoon.



&&



.DISCUSSION...

Issued at 244 AM CST Tue Dec 30 2025



Northwest flow aloft in the wake of the big weekend storm system

should remain in place the rest of the week. A series of low 

amplitude shortwave troughs are likely to ripple through the 

northwest flow at fairly regular intervals. 



The first wave, has crossed the Canadian border into the 

northern Plains early this morning and will rapidly move 

southeast toward reaching the mid-Mississippi Valley later this

afternoon. Air mass in advance of this system is dry, but top-

down saturation is likely to result in snow developing

southeastward mid-late afternoon along the I-90 corridor. Not

only is moisture limited, but time/height X-sections depict a

short window (2-4 hours) with deep ascent and column saturated

enough for precip to reach the ground. Within a few hours of

snow reaching the ground, ascent is progged to weaken and mid

levels will begin to dry out. This should result in snow ending

or transitioning to a light snizzle by mid-late evening. 



Overall, looks like a low QPF event with fairly modest

snow:liquid ratios given the expected mostly smaller flake size.

Accumulations looks to be generally an inch or less, but with

temps well below freezing and snow likely hitting during or

toward the end of the evening commute, there could still be

travel impacts. 



Temperatures will remain cold today, likely struggling to reach 20

degrees during the daytime near the Wisconsin border and only

climbing into the lower 20 south of I-80 today. Temps tonight 

will likely slowly rise reaching the mid to upper 20s by 

daybreak Wednesday.



Clipper number 2 will be right on the heels of today's system.

Snow looks to start earlier in the day tomorrow than today and

could fall with a bit more gusto than today's snow. Stronger and

deeper ascent, aided by fairly strong divergence in the left 

exit region of a 130kt+ 250mb jet streak could provide for a 

period of some slightly beefier snowfall during the afternoon. 

Still, with moisture still pretty limited and only a 3-5 hour 

window of accumulating snow expected, it looks like the hardest 

hit areas could end up with an inch or two of snow by the time 

the snow ends Wed evening. It looks fairly windy during the snow

Wednesday, but not as windy nor as cold as it was during Sunday

night's snow. 



Quick shot of seasonably cold air is expected Wednesday night 

into Thursday. As winds veer to more northerly direction and 

prior to column really drying out, there could be a short window

of some lake effect snow into northeast Porter County Wed 

evening, which could bump totals there up a bit. 



There are indications that we could temporarily transition to

more of a zonal flow pattern over the weekend. This would allow

for some moderation in temps and with dry conditions. 



- Izzi



&&



.AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/...

Issued at 502 AM CST Tue Dec 30 2025



Key Aviation Messages for the current TAF period:



- Period of IFR/LIFR snow this afternoon/evening



VFR conditions are expected through the morning. With an air

mass as cold as it is, an stray flurry is possible, but no

impacts are expected.



A quick moving system will drop south over the air space this

afternoon and provide another period of snowfall. Wind gusts

around 20 knots are expected to blow around the otherwise small

snow flakes and drop vis down to IFR, locally LIFR, conditions. 

Snow is expected to end by mid-late evening. There is a chance 

for some snizzle to mix in as the snow end, but confidence was 

too low to add it during this TAF package. MVFR cigs and 

occasional flurries are expected overnight as winds remain out 

of the west-northwest around 10 knots through Wednesday morning.



DK



&&



.LOT WATCHES/WARNINGS/ADVISORIES...

IL...None.

IN...None.

LM...Small Craft Advisory until 3 PM CST this afternoon for the IN 

     nearshore waters.



&&



$$



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