Hoosier

Report of 8.3" in Kane county.

I was curious what downtown Chicago looks like. Webcams from there show mainly wet roads, certainly a big difference compared to outside the core of the city.

The only calendar day snow left to challenge will be that one from 1961. 3.0" at the Midway co-op observer as well.

Haven't been out but I'm hearing that the main roads are in terrible shape around here.

Noticeable difference, exactly 1 hour later

Dry slot will get here later but the activity around Champaign should swing up this way.

Street looks worse than an hour ago. Should still have some lingering precip after peak "heating" so conditions may get worse.

Like I said, there is something particularly cruel about sleet at this time of year. Just think, 70 in 2 days.

I think they might have been quicker to issue an advisory had it been a weekday. I also think that the lack of experience with mid April snows of this amount could have played a role in being hesitant. This is an outlier in terms of climo. Models did do a good job though in general in showing the potential.

Had a mixy period earlier but it appears to be all snow now and coming down nicely. Temp hanging around 33-34.

Some models like the HRRR and NAM are too slow with the northward progression of precip.

Looking at obs in central IL, they are dropping about 3 degrees within the first half hour or so after precip onset.

Corrected a mistake with 1936... had the wrong date. Btw, in regards to the 2.6" on 4/3/1903... it was 77 degrees the day before.

I think one would be more likely if it were a weekday. May get a last minute one anyway though. It has hardly snowed for 2 months and people may have forgotten how to drive.

MLI has not been below freezing at all since April 3. ORD not since April 1.

Still snowing at end of run. Would not be surprised to see a localized 6+ if things go right.

Here's an illustration of the warm layer aloft So if you're near the edge, hope for heavy/convective type precip to try to beat back the warming to some extent. We all know how this goes though, more often than not.

Setting the stage

Wetbulb zero levels on the 00z DVN and ILX soundings were around 2500 and 3200 feet respectively. Also have quite a spread in current temps/dews. Temps should drop fairly rapidly later with evap cooling.

RAP has been hinting at dual snow maxes.

Thanks for chiming in. It is a couple weeks later in the season now but still, no reason to think it won't stick to paved surfaces with the kind of precip rates that look to occur.

Not taking the snow maps at face value, but it is impossible to ignore the signal for accumulating snow. I do still think that there will be a band of about 3-5", which I'd favor JUST north of here.

Hopefully this is the last snow call I make this season. I'll go with 2-3" on the coldest surfaces here. If it stays snow after flipping over, then amounts could be higher but I have low confidence in that as models want to bring in a bit of a warm nose for a while especially around 850-700 mb. Thinking back to April 18-19 last year when I got about 1", it eventually began to stick to paved surfaces despite temps being a bit above freezing. I think there will be some sticking on the pavement this time as well, especially during heavier precip, but obviously not to the extent of colder/elevated surfaces.

Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 408 PM CDT Sat Apr 13 2019 .SHORT TERM... 340 PM CDT Through Sunday night... Rare late season accumulating snow event is on the way, with the potential for amounts on colder surfaces that have not been seen in decades in some locations this late in the season. Have forecast overall amounts of 1-4" on colder surfaces. In the heaviest swath wherever it sets up, 2-4" will be probable, with localized accums of up to 5" or so not out of the realm of possibility. However, travel impacts outside of sharply reduced visibility at times are uncertain given the mild antecedent road temps after full sun today. It`s certainly possible to get some brief slushy accums on less heavily traveled roads during the heaviest snowfall, but will not be issuing a Winter Weather Advisory due to this uncertainty about magnitude of travel impacts. To add to the possible items to consider, northerly winds gusting to 25-35 mph could plaster elevated/colder surfaces with the very wet and heavy snow, with some concern due to this for tree damage despite leaves still being bare. This system does have the necessary ingredients going for it to produce appreciable accums at least on grassy surfaces this late in the season. PWAT values will be over 0.7", with 0.6" generally seen as favorable for heavy rates. Model cross sections indicate strong low and mid-level frontogenesis favorably topped by saturated negative EPV (instability). In addition, the mesoscale lift will be augmented by strong synoptic lift from the negatively tilted trough lifting across the region, with mid 990s mb surface low tracking just north of Ohio River Valley. Finally, forecast soundings show that steep mid-level lapse rates will be present, with even some minor MUCAPE that could yield convective enhancement to the rates and a non-zero chance for thundersnow. The heaviest precipitation/snowfall rates will occur from Sunday morning a bit prior to sunrise through mid day/early afternoon. During the heaviest rates, snow could be coming down at 1"+ hour at times for rate of fall but not necessarily in actual accumulation rate given warm ground temps and air temps a few degrees above freezing. For this reason, capped snow ratios at a maximum of 7:1, though in the absolute heaviest rates ratios could briefly be higher. The initial surge of warm advection driven precip will quickly spread northward tonight into pre-dawn Sunday, with p-type mixing with or changing to snow except likely for far southeast areas where it will be a bit warmer aloft and at the surface. The system deformation, tied to the precip shield currently seen on radar mosaic over parts of OK and west/central TX will then spread northeast and will be narrower in focus and be accompanied by f-gen driven banding. There could be a gap between the 2 slugs of moisture, so precip rates between these two areas could tail off for a time. Big wild card is exactly where the heaviest banding sets up, because this will be the area in which the snow will likely come down hard enough to overcome the warm ground conditions to accumulate. Models do a good job of indicating conditions favorable for mesoscale banding, but exact placement is often a now-cast type item and we`re still about 18 hours out. We`ll also have to see if the widespread intense convection in the warm sector of the cyclone plays any role in modulating the placement and intensity of banding. Outside of the heaviest banding, lighter rates will limit accumulation potential and p-type could oscillate between rain and snow since thermal profiles are so close to the snow/rain line. There also at times may be a loss of deep saturation aloft outside of the heaviest banding, so drizzle mixed with snow or plain drizzle may occur. Finally, the immediate lakefront of Chicago and just inland is a wildcard for accumulations. With the strong northeast winds coming over Lake Michigan water temps in the upper 30s to 40s, this may make it tougher to get an appreciable accumulation, along with the urban heat island effect and lingering warmest pavement temps from today. During the afternoon, the magnitude of the forcing will gradually wind down in the system deformation, so snow rates should taper off and lower ratios farther/limit accum efficiency. Precipitation will finally end by/during the evening as the system exits east, with a small chance of brief lake enhancement into NW Indiana. Temperatures will drop back to the upper 20s to lower 30s tomorrow night, so any snow that doesn`t melt once rates taper off in mid- late afternoon will stick around for one night and then quickly melt on Monday. Will have to watch for some patchy fog in spots after midnight Sunday night, especially where this any lingering snow cover. Castro

For Chicago, there have only been 5 instances of not having a 1" calendar day snow in March followed by a 1" calendar day snow in April. Here are the dates/amounts of the last Jan/Feb 1" snow and the dates/amounts of the April 1" or greater snow that broke each streak. How about that stretch in 1910. 2/15/1903: 4.7" ------> 4/3/1903: 2.6" 1/14/1910: 1.6" ------> 4/23/1910: 2.1" 2/26/1936: 1.3" ------> 4/1/1936: 2.1" 2/18/2000: 11.1" ------> 4/7/2000: 1.6" 2/25/2007: 2.3" ------> 4/11/2007: 3.0" 2/18/2019: 1.8" ------> 4/14/2019: ???