Christmas Storm 2020: What you need to know

Weather Blog

ROCHESTER, NY (WROC) — Mother Nature is bringing quite the messy gift just in time for the holiday. Here is the breakdown by timing and impacts.

THURSDAY (CHRISTMAS EVE):

Pockets of light rain starts from west to east early in the morning as a mid-latitude cyclone rapidly develops into the Great Lakes and across the Ohio River Valley. Temperatures will be well above freezing that will warrant all rain. The system may be battling some drier air at first, but slowly but surely, periods of light rain will turn into a soaker for all by nightfall. Expect a breezy Christmas Eve with winds gusting at least 20-30 mph.

THURSDAY NIGHT (CHRISTMAS EVE):

The main surface low in the Great Lakes starts to shift and turn northward just as another low forms right behind it. That means a reinforcing shot of moisture as the cold air rushes in, changing the rain to sleet and freezing rain first, and then eventually to snow. With the timing of everything slowly coming together, a best guess for this transition will happen from west to east beginning in some spots as early as ~5 PM across Wyoming and Genesee counties. Then from there the line will slowly spread eastward through the overnight into Christmas Day. This brief period where rain transitions to mostly sleet and freezing rain will make roads a bit icy during the evening hours. The highest chance to see higher amounts of freezing rain will be south and west of Rochester where the cold air looks to undercut the warm air first.

All in all, many factors still need to be ironed out for us to have a good grasp on how it will all shake out. The path of this secondary low will determine when the cold air moves in and how much moisture is in place as the temperatures drop below freezing.

When looking at the graphic above, be aware of the fact that all of us have the chance to see enough freezing rain to create a few slick spots on untreated roadways, with equal chances it passes quick enough for little to no impacts at all. HOWEVER, the folks highlighted in pink and especially purple should be aware there is a good possibility freezing rain falls for a long enough period where you get very difficult and slick travel conditions. It doesn’t take much for accumulating ice to create issues in an area.

A few models are also now hinting at the possibility of a decent slot of dry air to develop that could heavily affect how much icing ends up occurring for a good chunk of us. This will also limit the amount of snow many of us see waking up Christmas morning.

FRIDAY (CHRISTMAS DAY):

It looks more than likely that folks across Rochester and east see no more than a brief dusting of snow by early Christmas morning. With all the rain and sleet to come beforehand, it’s possible those areas end up with a decent amount of sleet pellets adding to most of the accumulations as far as frozen precipitation goes. For those west of Rochester, you have the better odds at seeing a “white” Christmas with at least a few inches on the ground by morning.

As the storm system picks up and moves out, the cold air continues to take a stronger hold and it will not take long for lake-effect snow bands to form off Lake Erie and Lake Ontario. This should bump up snow totals a bit for some throughout Christmas Day with the highest impacts felt across far WNY. Expect the Lake Erie band to ramp up Christmas afternoon and dump several inches across Southern Erie, Wyoming, and Genesee Counties through the evening. There is some evidence showing the Buffalo Metro could see significant snowfall Friday evening into Saturday.

The National Weather Service Buffalo office has issued Lake Effect Snow Warnings for Wyoming and Genesee County with heavy lake-effect snow expected. Winter Weather Advisories are in effect for Monroe, Livingston, Wayne, Ontario & Yates counties for slick travel conditions due to a brief period of freezing rain/sleet beginning midnight tonight until noon Friday

SATURDAY:

Those few inches could turn into a foot and more east of Lake Erie. The band, if strong enough could send snow accumulations up into Western Monroe County and briefly into Rochester early. Otherwise the winds will shift back southward and the band should taper off.

—IMPACTS—

Rain Thursday means wet roads for most of the day. Expect a wind-driven rain as the storm approaches. Temperatures drop quickly overnight and once those numbers drop below 32°, there will be a risk icy spots on roadways. Bridges and overpasses will be the first to form ice as they are less insulated.

A Flash Flood Watch in effect for Livingston county begins Thursday morning until 1 PM Friday for the combination of mild temperatures and rainfall amounts between 1 to 1.5 inches causing snow melt and possible minor flooding to the Genesee River.

With the possibility of some freezing rain mixed with mostly sleet during the transition from rain to snow, slick spots will no doubt cause tricky and slippery travel especially those south of Rochester and across higher elevations where temperatures will drop close to freezing quicker than most.

Brief bursts of snow early Saturday will mean reduced visibilities and snow-covered roads for the early Christmas morning drive. Reduced visibility could also impede travel as winds may create blowing snow. Once the lake-effect snow band develops off Lake Erie, very difficult driving conditions are expected within this band with near-zero visibility and roads covered in snow. This is only for the specific region where the band forms, and for those within Lake Effect Snow Warnings until late Saturday night.

All will feel the chill as temperatures drop to the 20s and wind chills dip into the teens Friday night, Saturday, and Sunday.

For constant updates on the forecast check out our daily forecast blog HERE.

~WROC Weather Team

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