1.11.2018 -- Here We Go
Good evening, here we go. Our most significant storm system of the season thus far will be moving in late tonight and lasting into Sunday. We're going to take this and break it down day by day given the myriad different things going on.
Here is a look at the current advisories/warnings/watches.
HEAVY RAINFALL AND FLOODING POTENTIAL: High forecast confidence.
HEAVY SNOWFALL: High forecast confidence.
SIGNIFICANCE ICE ACCUMULATIONS - CNY: Moderate forecast confidence on placement and amount.
Dang, it's warm. Too warm for upstate NY in January. The snow is melting. Flood warnings are already posted for portions of Erie and Chautauqua Counties. The NWS is anticipating ice jam flooding at Versailles, as well as Cattaraugus Creek / Sunset Bay and Cazenovia Creek, Buffalo Creek, and Cayuga Creek tonight. A Flood Watch is up for all of western/central/eastern New York through late Friday night. Per NWS Buffalo, "The primary risk for flooding will be due to ice jams. Flooding from snowmelt and ice jams have already been reported across parts of far western New York...including in Erie and Chautauqua counties. Rapid rises in water level tonight due to the rainfall can break up remaining ice, which can then become jammed where there are constrictions in the river or creek channel, such as in curves or other restrictions. People living in areas that are prone to ice jam flooding should take the time in advance to prepare for the potential for flooding. There is also a risk of general river and creek flooding. This will primarily depend on where the heaviest rainfall occurs and may be localized to a few basins in the watch area. Even so, there is a significant risk of localized rainfall totals of greater than an inch which may result in river and creek flooding. The combination of snow melt and rain also may cause basements to flood."
High-res guidance shows rain moving into extreme western/southwestern NY by 9 PM and advancing from SW to NE, covering much of the state during the overnight hours. Rain will be heavy at times.
This rain is being caused by rapid increase in the low-level jet stream transporting in unseasonably warm and moist air from the Gulf. Precipitable water, which is an element meteorologists use to determine atmospheric moisture, is running between 1 and 1.25 inches. This means, if you were able to take a 3D "box" of atmosphere, rain out all the moisture, every drop, it would accumulate 1 to 1.25 inches. Well, this is surging NNEward toward CNY. Add in uplift as the air goes up and over elevated areas, you get increased resultant precipitation (the same process that causes the Tug to get clobbered with so much lake effect). At any rate, all ingredients have come together nicely for heavy rain tonight and Friday.
Rain continues Friday... but should taper in overall coverage and intensity as this low-level jet continues to move out of here. An Arctic front will begin to approach the region... pushing into western New York around midday or so. As this front begins to march across the state, temperatures will, obviously, begin to cool down.
Rainfall amounts of around an inch to an inch and a half are likely across the vast majority of the state. However, the higher elevations from Redfield to Old Forge could see up to 2 inches of rain from this event.
(Just a side note... drawing rainfall maps... stinks.)
Now by Friday afternoon, low pressure will be getting its act together, moving from northern Alabama to western Virginia by late in the day. This will bring in a renewed shot of steady precipitation. As the cold air comes in at the surface from the north and west, rain will change to freezing rain and sleet, and then eventually to snow.
Here are some views of the "future radar" models for 7 AM Friday, 11 PM Friday evening, and 7 AM Saturday illustrating the changeover. This is all dependent, of course, on the eventual storm track. Models have once again shifted the storm track just a tad farther south and east. If this trend continues, the axis of heaviest snowfall and axis of heaviest freezing rain accumulations will shift in-kind.
Notice that there is expected to be a very sharp cutoff on the back edge of the precip. When it ends, it will ... just ... end.
Very heavy snowfall is expected over western and northern New York for the overnight Friday night into Saturday. We have painted a stripe of 12- to 18-inch snowfall over Rochester, Warsaw, Pike, Franklinville, to C attaraugus as a deformation band establishes in this area. The exact location of this band will determine where the highest snowfall totals will be, and there could be a westerly or easterly jog with this placement. Snowfall amounts taper as you head eastward, as there will be a longer duration of freezing rain and sleet. Again, this could all shift depending on the storm track.
Significant ice accumulations are LIKELY in a stripe from Elmira NNE through Cortland, Utica, Gloversville, Lake Pleasant, and Lake George, where ice buildup could be from a quarter to a third of an inch (closer to a quarter of an inch). A tenth to quarter inch ice accumulation is possible from Syracuse and Watkins Glen through Old Forge and Plattsburgh, as well as the Capital Region and the I-88 corridor into the Catskills. Lesser amounts, but still enough to cause bad travel headaches, will occur in western New York as precip changes over to snow more quickly.
After this storm pulls out of here late Saturday ... we return to very cold temperatures with a nice Arctic air flowing overhead. The next weather system looks to head toward the region Monday afternoon into Tuesday with some accumulating snows, followed by lake effect off of Lake Ontario through the middle of next week.