Please tell me this is a joke!
I wish I could... It may be mid-May but unusually cold air associated with a deep upper trough will affect Upstate New York and other areas of the upper Midwest and Northeast one more time (this should be the last frost for northern New York until fall). Lows Sunday night will drop into the low 30s, resulting in frost in some areas of northern New York. By Monday night, temperatures will likely drop into the upper 20s for regions away from Lake Ontario. This will result in a widespread frost for many areas of northern New York. As if this was not enough shock for everyone who has been waiting to kick Old Man Winter for good this year, some residents to the east of Lake Ontario may witness a certain white precipitation on Sunday night into early Monday morning. I am talking of course about snow.
The Technical Stuff
Sunday night surface air temperatures will drop into the low 30s, as mentioned previously. Meanwhile 850 mb temperatures are forecast to drop at least to the low 20s and perhaps the upper teens. This magnitude of cold air aloft will be enough to create instability across Lake Ontario, as the current water temperature of the lake is 44. Typically, at least a 13 degree Celsius temperature difference between the 850 mb temperature and the lake temperature is needed to be favorable for lake effect snow development. Sunday night this temperature difference will exist from shortly after sunset into Monday morning. The temperature profile will also be conducive to any precipitation that does form to fall in the form of snow away from the lake shore area. Other parameters that are needed for lake effect snow development that will be in place Sunday night include less than a 30 degree wind shift between the surface and the 850 mb level, with most of the night having less than a 15 degree shift, and abundant moisture for the majority of the night in the boundary layer. Additionally, the lake equilibrium level will be right around 10,000 feet the entire night, which is also favorable for lake effect snow development.
Where might this occur?
Taking all of this into consideration, it appears likely that at least a band of lake effect snow showers will set up on Sunday night to the east of Lake Ontario. The band appears at this time that it will form over central Jefferson and north/central Lewis Counties and shift southward throughout the overnight. The snow band will likely fall apart around sunrise Monday morning over the Tug Hill region.
Do I need to break out my shovel and snowbrush again?
Probably not. While snowflakes will be in the air across the region, accumulations are probably not likely at this point. Due to recent warm weather, ground temperatures have warmed significantly and the snow will probably not become heavy enough or last long enough in any one area for accumulations to occur. However, minor accumulations under a half inch are not impossible if the band happened to become heavier or sits in one place for a few hours. Minor accumulations are most likely on elevated surfaces, such as your car or hand railings.
Optimistic Closing Remarks (for those of you I just severely depressed...)
Now that I have you dreading Sunday night and contemplating your choice of living in northern New York, I will tell you that after this cold snap the weather will turn nice again. Next week temperatures will slowly climb back to normal and next weekend we may even see slightly above normal temperatures again! And there are some indications that more summer like weather may start to set in by late May into early June.
Lake effect rain and snow showers will likely get started shortly after sunset tonight and will continue throughout the overnight. At this point it looks like if you are inland of Lake Ontario that the atmosphere should be cold enough in the low levels for a complete changeover to snow by midnight. This activity will start across the northern half of Jefferson and Lewis Counties and sink south to around southern Jefferson and central Lewis Counties around midnight. By sunrise the lake effect rain and snow will centered across the Tug Hill area. As temperatures warm with sunrise, the lake effect snow will begin to change back to all rain by late morning and the band itself will continue to sink south slowly, perhaps reaching a few areas just south of the Tug Hill region. By early afternoon if any lake effect rain is around it should begin to break up quickly as 850 mb temperatures warm and create a less favorable environment for lake effect. The band may also move slightly north before dissipating. To the right is what I expect for snowfall totals tonight and early tomorrow morning. The gray area will have snowflakes possible tonight, the light blue area will have snowflakes likely with a dusting of snow possible, and the darker blue area will probably see a dusting a snow and perhaps up to an inch or so in some areas.
