As for the Friday night-Saturday system:
1. Looks more & more like 96% & 4% sleet (sleet just at onset). This ups snowfall, even without the deeper moisture.
2. There IS a phasing of the polar & subtropical jets, so there is a moisture feed to bring some decent snow.
3. Deepest moisture is still just south of the area, however.
4. Regardless, looking right now at a solid 2-4″ snow for the viewing area with potential of a 4-7″ snow.
5. Snow/sleet would tend to move in early Friday night with heaviest snow early Saturday morning. Snow would tend to end around Saturday midday.
It is a cold one tonight! Just wait until Wednesday night-Thursday morning. Much of the area will drop below 0. The record for West Lafayette Thursday morning is -8 set in 1977. I am forecasting -3.
The 00z GFS does tend to handle the placement of heavier snow better than the 00z NAM as of 10 p.m. The GFS DOES shift the heavier snowfall south with more like 2-4″ in our north & 1-2″ north of Lafayette & 0.5-1″ elsewhere. I do like the GFS more than the NAM, but I am not 100% with it. It doesn’t seem to handle the lift & forcing the best.
UKMET is farther south, CMC is not. HRRR is handling the snow placement well & brings 2-3″ into east-central Iowa by 2-3 a.m. This is definitely reasonable.
So, went for slight compromise & only slightly shifted 1-2s & 2-4s southward.
Noticed in 00z NAM that it places the heaviest snowfall about 50 miles too far north than where is it actually located at 10 p.m. That said, makes me wonder if it is placing the forcing for 1-5″ snows too far to the north tomorrow. I like what I have so far & given 48-hour trend will not shift. It monitor with wait on 00z GFS, UKMET, GEM & Euro with wait on HRRR (last run was back at 16z).
So, less than 1″ just about everywhere, except for areas north of Morocco to Rensselaer to Winamac to Rochester. I will see if we need to raise it a hair pending other data.
I am going to drop tomorrow night’s lows even a hair more with lows of -5 to 0 area-wide, given development of clear skies & inversion (if inversion can really form well, -5 may be conservative in the far north where deeper snow cover is likely).
As for Friday night-Saturday morning. Two things can be gleaned that looks different compared to earlier today. 1) the forecast lower atmospheric profile is colder (more snow than mix) & 2) there is some merger of the subtropical jet (BUT NOT the deep, deep moisture) here, adding more water to the mix. Looks like a 1-3″ snow now with a bit of mix, unless deeper moisture can overspread the area. If that happens & precipitation is all snow, then a 4-7″ would be more in the works. We will monitor.