Mid and upper 50s really bring on the spring fever and that’s exactly the type of temperatures we are going to see this afternoon. There will be water running down the roads, off your rooftop and even under the snow, although you won’t be able to see that.
If you look at the snow on your lawn you are likely to see it melting unevenly. The slope of your yard, water traveling under the snow and even the way the sun hits the surface all contribute to the uneven melting. If you have water moving under the snow this will further erode the snow from the bottom up.
There’s a lot of stuff happening out there with regard to snowmelt. Over the past three days the temperature of the snowpack has increased by 4-6 degrees and in many areas is poised to rapidly melt. We should see a loss of 2-5 inches of snow today, depending on where you live. Those areas whose snow is closest to 32F will see the most snow melt. The map below shows the temperature of the snow as of this morning.
The sun is about as strong as it would be in the final days of September and those areas which face south are already seeing bare ground becoming exposed. If you drive along the highway, you are likely to see a lot of grass by the end of today, at least on the side of the road pointing to the sun.
The snowbanks themselves are pulling further back from the road as the asphalt heats up. The long-wave radiation from the surface melts the snow quickly and snow loss can be dramatic.
Before we get too excited and start thinking the snow and cold are over, we need to look at the long range forecast. You should prepare mentally for a frustrating end to March. Although we will be past the vernal equinox, I think it’s going to be a cold end to this month.
The 8-14 day outlook gives a 70% chance of the area seeing below average temperatures and only a 3% chance of above average readings. As a matter of fact, if you break up the next 30 days into 5 day increments, I don’t see any 5 day period of constantly above average readings.
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Of course averages are quickly rising, so even if we are 5 or 10 degrees below average for our high temperatures, it will still be warm enough to melt some of the snow, but it’s not going to melt very quickly.
There is a weather system coming into the picture this weekend with some rain and wet snow. Temperatures are going to be mild enough so most of the precipitation falls as rain; however, there could be some minor accumulation of snow.
Beyond mid-March it becomes more and more difficult to get accumulating snow in minor precipitation events. As the overall atmosphere warms, the best chance of snow starts to come at night as well as in more dynamic situations (larger storms), which can pull cold air from above down to the ground.
The chart below shows the average last date of measurable snow in Boston and other cities. It’s not until the close of the month this usually occurs, so patience will be needed as we slowly climb out of winter and into spring.