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Footprints and paw prints in last evening's snow, now turned to melting slush as today's rainy thaw began moving into the St. Albans, Vermont area this morning. |
Welcome to the first truly rainy, mild day of spring, 2025 in Vermont.
It will indeed rain most of the day statewide, and temperatures in many areas will warm to levels not seen since late December.
Yes, rain and warm temperatures equals snow melt and a risk of flooding and ice jams.
However, the conditions of the snow cover before the rains started, and the middling amount of rain in the forecast means this time around, flooding shouldn't be very extensive.
Ice jams are possible, of course but unless one forms in a very, very bad spot near a village or town along a river, we should be largely OK.
Knock on wood, there should only be a few scattered ice jams. Take it seriously though. f there is any kind of high water or jammed up ice, it's most likely tonight or tomorrow.
Also, as we always know in early March, winter is NOT over so of course we'll need to deal with some of those issues coming up.
OK, the big picture is out of the way, let's get into the details:
TODAY
After a burst of snow and a little rain in northern Vermont last evening, things got quiet and warm-ish overnight. It was in the 30s to low 40s and western Vermont as of 6 a.m. but still a little below freezing east of the Green Mountains.
Meanwhile, rain was moving in from the southwest, and should get through most of the Green Mountain State by mid to late morning.
Sprinkles of rain have already made it into Vermont as of 7 a.m. but the main bands of it were still just approaching southwest parts of the state.
There might briefly be a few patches of freezing rain at the start where it's cold in eastern Vermont, but that should resolve itself pretty quickly. The National Weather Service in South Burlington has issued a special weather statement that warns of potential black ice, especially on bridges, overpasses and around curves through this morning's rush hour in central and eastern Vermont.
There's even a couple of pockets of cold air left in parts of Rutland County, so it could get slick there, too, for a little while this morning.
The bulk of the rain should come through during the day today and the first half of tonight. Rainfall amounts might be as little as a quarter inch in the far northern Champlain Valley to up to an inch in southern Vermont.
If there were no snow and ice to melt, that amount of rain we expect is absolutely no big deal. Just a routine amount for any storm system.
But there is snow and ice to melt. Plenty of it in some areas. Obviously, only some of it will melt in this episode. And especially in high elevations and in eastern Vermont it might take awhile for it to start melting.
Meteorologists say the snow has to "ripen" first. That means the temperature of the snow cover has to rise enough so that it starts spewing water from melting. By the time the snowpack "ripens" in areas with deeper snow especially, the bulk of the rain will be over.
It will stay warm overnight. In fact, high temperatures today in the mid and upper 40s to near 50 probably won't be reached until we get toward evening. Readings will stay at those levels overnight and into Thursday morning.
The air will have an oddly humid, springlike feel to it, too. Humid air melts snow much more effectively than dry air, so even after most of the rain is over, the snow in many areas will be melting pretty rapidly.
FLOOD/JAM POTENTIAL
If we have any flooding or ice jams at all in this episode, they are most likely to happen overnight and through Thursday.
There is a lot of water in the snow pack. The National Weather Service estimates the amount of water coming out of the snow through melting tonight and Thursday would be the equivalent of 1.5 to two inches of rain in parts of central and southern Vermont.
That might well be enough to make river levels rise enough to break up the thick ice covering parts of those rivers. The ice starts to flow downstream, hits an obstruction, so the ice just backs up behind that obstruction and voila! You have an ice jam.
These things form quickly, so if you live in a flood-prone area, keep an eye on the river ice and be prepared to skedaddle if you see water backing up behind an ice jam. You won't have all that much time to deal with it.
Again, this won't be a widespread problem. But where any of those few ice jams form, it could be locally a very, very big problem. Any river from about the Winooski south in Vermont is at some risk of an ice jam or two.
Even without ice jams, some rivers, like the Otter Creek, Mad River and Winooski, might get pretty high, and could peak just a little under minor flood stage during and just after this thaw.
In northern Vermont, where it will take longer for the snow to "ripen" only about the equivalent of an inch of rain will ooze out of those big snowbanks through melting. That reduces the chances of ice jams in northern Vermont.
COLD RETURNS
It's only early March, so the cold will return, though not to the subzero levels we saw Monday morning.
The storm's cold front will come through Thursday afternoon with little precipitation but falling temperatures. Early afternoon will be balmy, and by the time the sun sets, you'll be starting to notice a chill in the air.
You'll need to watch it a bit Friday morning. By then, everything will have frozen back up again. Including any standing water left on untreated roads. Light snow showers will add to the back-to-winter scenario.
Snowfall won't amount to much. Most of us will see less than an inch, though the central and northern Green Mountains might pick up one to as much as four inches of new snow between Thursday afternoon and Saturday morning.
Friday itself will be blustery and cold with temperatures staying at or below freezing. It should stay below freezing all weekend, including during the days. Though banana belt towns in low elevation southern Vermont could poke into the mid 30s both Saturday and Sunday.
Early guesses are the next week or so should be fairly mellow, with frequent chances of a little snow or even rain later in the week, but nothing heavy.
Next week will be a bit changeable and unpredictable too. As is typical in March, Vermont will be right near the springtime battleground between mild air to the south and still-wintry air encompassing most of Canada.