Frost vs. Freeze. First Snow in NY?

What is the difference?
A frost can develop with air temperatures as mild as 38F or 40F. It's the surface of your car, or blades of grass that can drop lower and allow condensing moisture to form ice crystals. A freeze however is when the air temperature actually drops to freezing (32F). The difference can lead to an abrupt end to the growing season for plants and late season crops. A hard freeze pretty much takes care of everything growing as temps drop below freezing for at least 4 hours. This morning, temperatures dropped into the 20s and 30s. That was the core of this cold spell and thanks to clear skies and Sunday's temps only reaching the upper 50s.

First Snow in NY
Beside my personal connection of 4 years in Cornell (Ithaca), working in Syracuse and Binghamton... I think it is worth mentioning the seasonal shift- even if it's not here.
Let's jump past the next cold front and into Wednesday morning. Here you can see the 850mb temperature map (the most efficient for measuring temperature forecasts).
Here you can the blue shading indicating colder air spilling in across the lakes. This is actually 6C-8C- which would translate to near freezing surface temperatures. No big deal, right? We just had that this morning. However, this profile of sub freezing temperatures near the Great Lakes- along with the proper wind flow, will allow bands of snow to develop.


Here is the surface weather map for Wednesday morning, showing a small and weak Low Pressure forming off of the New England Coast. That will enhance the North West flow across Lake Ontario and dump across central New York the first snow of the season. Considering the warm water temperature in contrast to the colder air, there could be some heavy bands of snow- but where will depend on the precise wind direction. I will focus more on this as the snow develops...but isn't that exciting? Not for us. The same northwest wind rides down the mountains and dries out. So this type of set up is not going to bring us snow. It's confined to the mountains and lee side of the lakes in NY. I'm jealous. First ski areas opening up in Colorado last week, and now snow on the way in my old stomping grounds. On a side note, Ithaca, NY had a Halloween snow storm in 1993 that dumped between 2 and 6 inches of snow. I don't find that a scary thought, but some of you may.

April Out Like March

What happened to the warm air? A Frost Advisory was issued for the northern and western counties as expected, and we had the temperatures to support that. Was it a record?- Not quite. That was 32F back in 1961. That's not the latest freeze on record. that was May 11, 1966.
It's the radar that surprised me. While High Pressure is usually dry- it is an upper level disturbance feeding off of the cold air and the Great Lakes that produced flurries just to our west this morning.


We do expect a quick rebound into the 60s and 70s over the next few days, but that will come with more clouds and showers. It did not look like much on the maps this morning, but here is the Canadian Model outlook for Saturday Evening. I've highlighted the surface features with a typical spring Low near St. Louis that will provide a severe weather outbreak in the Ohio Valley and down south. Unfortunately this includes the Kentucky. The 134th running of the Kentucky Derby is this Saturday, and that is prime target for stormy weather. These storms often slow down and take their time moving east. So, we may end up with a warm dry day on Saturday, but I had to put in a chance of a thunderstorm since there may be some that fire up ahead of the main system, or reach us in the evening. This is one of those situations when the right forecast may still be wrong, like last weekend. The simple weather graphic has rain, and I even wrote (Afternoon/Evening), but that can get lost in short time I have on the air. This would make 10 out of the last 11 weekends with rain- so I will do my best to pay extra close attention to the timing of the rain until then.

Virgina Tornadoes! Frost Tonight?

Yesterday's storm gave us about 1 inch of rain locally, but that was nothing compared to the severe weather in south east Virginia. Here you can see the peak of the storms as captured around 4pm. If you see the map I posted in yesterday's blog- it was a strong cold front that sparked the storms.
Here is an example of wind sheer similar to what caused yesterday's tornadoes... Winds at the surface were from the south east, while the storm was moving cloud level winds from the south west to north west. A different direction and speed with height. That caused the wind to sheer or rotate with height. For the record, a Tornado Watch was posted for this region by The National Weather Service. A 75 mile path of at least 3 separate tornadoes straddled North Carolina and Virgina. Ironically this was the 6 year anniversary of the La Plata tornado. Today is the day that the NWS will survey the damage and confirm the strength. Early Doppler estimates of perhaps an EF 3- which would mean winds of 138mph-167mph.
For a comparison of the original Fujita Scale and the new Enhanced Fujita Scale- click here.

What I find most interesting, was that this morning, the cold upper level low was passing through Ohio, and brought snow to the mountains of West Virginia - see here at 6am. Due to this upper level Low, I am not sure we will clear out and get back to 60F today. I think clouds will likely hang on longer, and many of us will stay in the upper 50s. When we do clear out tonight, frost is likely just inland with temperatures back into the mid 30s... The sun will be back tomorrow.