The models have essentially remained unchanged since yesterday for Thursday night, and some of the short range meso-scale models are now out to Friday morning, adding some clarity to the situation.
The 12z NAM, 12z GFS, and 0z European model runs all show 850mb temps of -5 over the lake and much of Ohio by 0z Friday, and quickly advect in 850mb temps of -6 to -8 over the course of the evening. This is in response to an upper level shortwave and secondary cold front moving through the area Thursday evening. As the shortwave moves through, the models develop a deep cyclonic flow over the lakes and show an increase in mid level humidity, resulting in steep low level lapse rates, high inversions and some mid level moisture to help seed lake effect.
The 12z NAM skew-t for Cleveland right along the lake shore valid 9z Friday, courtesy of wunderground.com shows a relatively uniform WNWrly flow of 20-30 knots in the lowest 20k feet of the atmosphere, with reasonable moisture and instability up through about 13-14k feet. This moisture and instability go through the whole dendrite growth zone. This would certainly support lake effect activity through much of the night.
As the secondary cold front passes through Thursday evening, it is reasonable to assume that scattered showers might break out area wide across a good chunk of northern Ohio as some synoptic lift moves through. After this front passes, the flow will start shifting from westerly to WNWrly and potentially more NWrly by early Friday morning. Given a deep cyclonic flow with deep moisture through the lower-mid levels, high inversions and plenty of instability with lake-850mb delta-t’s of -16 to -18C and the lake-500mb differential around -40C, this supports robust lake effect development over the lake starting around 0z Friday.
Given the wind direction the best banding may initially be concentrated along the eastern lake shore. However, the winds will slowly gain more of a northerly component, shifting the initial band inland into the primary Snow Belt and perhaps favoring another convergence band for a period of time along the western lake shore into the southern/eastern suburbs. If the flow goes almost northwesterly like some models do show by early Friday, the convergence bands may dissipate and be replaced by more of a multi-band setup, which favors the higher terrain inland from the lake.
Accumulations remain tricky…temperatures will start out in the lower 40s Thursday evening which supports rain or mixed showers initially. However, with sufficiently cold temperatures not far above the surface I believe that it will not take long to switch to snow as the evening progresses. Areas along the lake shore and the lower elevations are the exception, where I’m not sure there will be a period of all snow or notable accumulations. Snow should be accumulating in the higher elevations by midnight Friday. My guess is areas above 800 feet will see some accumulations under any heavier bands and that areas above 1000 feet will do well.
The shifting of bands may make it hard for any one area to really cash in. However, the 12z NAM shows .1-.25” of liquid equivalent over most of the Snow Belt and the 12z NMM/ARW mesoscale models show a large area of .25”-.5”+ liquid equivalent. Given instability into the dendrite growth zone and a rather unstable environment I believe over a quarter inch of liquid equivalent could occur where bands persist, and I do think there could be decent snow rates in the higher elevations where the whole column will be at or below freezing overnight. So, I believe a general 2-4” seems possible above 1000’ from eastern Cuyahoga county eastward. Between 800-1000’ 1-3” seems possible in the Snow Belt. Lower elevations will likely remain too warm for much accumulation. The higher elevations in southern Cuyahoga, northern Medina, northern Summit and northern Portage counties could also see 1-3”, especially if winds do become more northwest overnight Thursday into early Friday. The event should wind down Friday morning.
First guess snow map, valid Thursday 5pm-Friday 12pm: