Apr 26, 2016 12:54 AM
NH1 First Alert Weather: Late April snow has its limitations
NH1 Chief Meteorologist
Yes, the dreaded four letter word is happening today...SNOW! At least in some parts of New Hampshire! This time of year it is extremely hard for snow to accumulate. It is going up against a variety of limiting factors which make any meteorologist pause before making a snow map with large snow totals. First, there is the Sun Angle. This wintry mix will be happening during the day. A mix of rain and snow will start off light at dawn and be filling in over the course of the morning.
First, The angle of the sun is similar to what we have in August! So the sun is getting higher in the sky. While the clouds will block the sun all day, radiation from the sun penetrates the clouds and reaches the ground and helps to warm the surface.
Secondly, it's just too warm! The last time we had accumulating snow was April 4th. That day was cold and temperatures were in the Lwr-mid 20's. If you remember, snow was quick to stick and roads became slick. Concord received close to 3", while the Seacoast had closer to 8"! Today will be very different. Temperatures will be in the 30's, above freezing from dawn to dusk. Some will be near 40 with a chilly NE winds at the surface. While temps will be 32+ at the ground, temps just above our heads will be just cold enough to support a wet snow which should be able to reach the ground before changing to rain drops. Across Southern New Hampshire, it will likely be too warm for snow. In fact, I expect a fairly rainy day across Southern New Hampshire, and maybe a few wet snow flakes mixing in during the midday and afternoon. The best chance of accumulating snow will be from the Lakes region points north, especially in higher elevations which are closer to the colder air aloft. Due to the temperatures down at the ground and aloft, any snow that does fall will be wet. It will be the kind which will fall and melt instantly it hits the warm ground! Roads will be wet all day, so I expect no issues on the roads either. The roads retain and absorb the heat from the sun. I see no way roads will be slippery tomorrow because of all these factors.
Finally, the speed of this system is fairly progressive. It will be a quick thump of snow from the morning into early afternoon across Central/Northern NH. By afternoon, scattered rain, and snow showers will linger and be ending for the evening commute. No travel problems expected. Accumulations will be minor, but where the heavier band of snow set up we have the potential for 1-3" of snow. Again, due to the wet texture of the snow, accumulations will be difficult. Some wet snow could stick to trees in the north. It will be a cold rain and snow for all. The coast will be raw with a rainy mix and cool onshore winds. It will be a day to prepare for the chilly raw, wet elements.
Skies will be clearing Tuesday night with cooler temperatures arriving. Lows will drop down to near 32 overnight. High pressure builds in for the midweek with sunshine and slightly cooler than average temperatures in the 50's. There will be a persistent trough in the Northeast heading into early May. This will keep temperatures running cooler than the average, so any dreams of warmer temperatures in the 70's surging back into New Hampshire will have to wait. May will get off to a cooler start. As we say good by to April, April will likely being the first cooler than normal month we have seen since last June! It has been a very warm trend which last straight through the winter! It looks like this recent cool trend still has a bit more left to go!