Rain and snow cometh

An extreme moist storm system is already affecting New England and will continue to into the day on Monday.

Flood watch in effect for Southern New England.  Winter Storm Warning for Northern VT and Northern NH and into most of Maine.

Today:  Rain, heavy at times.  Transitioning to snow north later in the afternoon north.  Highs in the 50s south, 40s north with temperatures falling throughout the day.

Tonight:  Rain continues, heavy at times, snow pushes further south across Northern New England.  Accumulations of 6-12 inches overnight.  Lows in the 20s north, 40s south.

Tomorrow:  Rain and snow comes to an end in the afternoon.  Daytime highs will occur in the morning with temperatures falling or holding steady through the day, 40s south, upper 20s to low 30s north.  Total accumulations of 20-30 inches, see image below.

Tuesday:  Mostly sunny, cooler, highs upper 30s to near 40 south, 20s and 30s north.

Discussion:  A large and complex low pressure system is approaching the region.  This will bring heavy rain and heavy snow later today and tonight.  It is already raining in some places, particularly in Central and Northern New England.  The rain will overspread all areas this afternoon and become heavy at times.  The center of the low pressure system will essentially pass directly over New England tomorrow and it get closer, colder air will start moving in.  This will change over the precipitation to a wintry mix and then to all snow.  This will start in northwestern New England first and then push southeastward.  Eventually the snow spread all the way down into Southern VT, Western MA and Southwestern NH.  There is going to be significant accumulations with this storm in Northern and Central New England, as much as 20 to 30 inches.  There is so much moisture available and with the cold air coming in, its going to create a lot of heavy, wet snow.  I'll include a forecast snow total image below, pulled directly from a forecast model.  Unfortunately the complexity of the forecasted amounts is too difficult to depict using MS Paint.

Total liquid equivalent amounts will range from 1.5 to 4 inches.  That is a lot of water and as a result, flood watches are in effect for places that are going to see strictly rain, Southern New England.  Low lying areas and where there is poor drainage, I expect to see some flooding.  Also, some of the smaller streams and rivers might spill their banks.  The worst of the flooding will likely occur on Monday.

Beyond tomorrow, conditions will quiet down for a few days with seasonable temperatures.  Our next storm system will affect the region late in the week and looks like mainly a rain event right now.

Here is the forecast snow totals:

Complicated storm

We have one more pleasant day today, even if it did start off rather cold.  We will see abundant sunshine through at least the first half of the day before some clouds develop.  Temperatures should make it to 40 degrees in Southern New England and 30s for Central and Northern NE.  The clouds that will start to move in will be in response to the approaching storm system set to arrive on Friday morning.

After reviewing some computer guidance this morning, the system appears to be moving a bit slower than previously forecast.  Instead of the precipitation getting started around 3 AM, it will probably start around sunrise now, closer to 7 AM.  Precipitation type is proving difficult to forecast, as surface temperatures in many locations will get close to or below freezing for a time on Friday morning.  I will provide 2 maps today, one indicating precipitation type and the other indicating snow totals, much easier to show you rather than describe it.

Green is all rain, the pinkish color is where there will be a period of a mix and then the light blue is all snow.  Below is snow total map.

As you can see VT and most of NH are going do well in terms of snow with this storm.  I left the accumulation range pretty wide as there is going to be banding in spots which will give some areas high amounts.  It would be far too difficult to pin those locations down.  The purple area will see a few hours of sleet and freezing rain before changing over to mainly rain.  Fortunately this won't produce much accumulation, but will make the road messy.  The green area should be mostly rain, with some northern areas in this zone seeing some mixing, but hardly any accumulation.

There is going to be quite a bit of liquid associated with this storm and there is going to be flooding problems.  The flooding problems will obviously be in the locations that have mostly rain.  Eastern MA and RI may have to deal with the worst of any flooding that occurs.  This will be caused by ice daming of small tributaries and street drains that are still clogged with ice.  Just be mindful of this tomorrow and avoid driving across water covered roadways.

Beyond Friday, we'll see another light snow on Sunday morning, followed by a gradual warm up leading to what looks like storm on Tuesday that provides mainly rain.  More to come on this, but I think you have plenty to chew on for now.  :-)

Thanks for reading and post any questions in the comments area below!

-Jon K.