Profiling More Precipitation

2015-03-02 20:01:13.000 – Nate Iannuccillo, Summit Intern


You have probably noticed that we have gotten quite a bit of snow this winter, and if you have been paying attention to the forecasts, you know that there’s more en route to New England tomorrow night. However, this storm system will be a little different from those experienced in the past month. It will begin as a typical “Alberta Clipper” with low pressure forming over northwestern Canada. This time, instead of moving towards New England, upper air patterns will keep the low pressure center far to our North. This will have a few different implications on New England weather…
With the bulk of the cyclone largely to our North, it will be a notably warmer storm than those of the past few months as warm air gets cycled in from the southwest.
This storm is expected to develop a significant occluded front as it moves east. The actual occlusion (think sharp spike in temperature) should stay to our north, but its vicinity means that we will experience a very brief warm sector because the cold front and warm front will be so close to each other.
With most of our snow affiliated with these developing fronts, their proximity means that the swift snowfall will be accompanied by a fleeting temperature spike. This will make for a wet heavy snow that we have rarely seen this winter.
Because of these factors, we are likely to see a much different spread of precipitation across New England throughout the storm’s passage. Ahead of the warm front on Tuesday night, New England looks like it should receive consistent snowfall throughout the region, but as things warm up Wednesday morning, the chances of mixed precipitation look increasingly likely for southern New Hampshire.
Let’s take a look at some different models for the time period in question:
Here we can see the NCEP (National Centers for Environmental Prediction) GFS model output displaying precipitation types for 1:00 am EST early Wednesday morning. Shades of green represent rain, blues display snow, pink is ice pellets, red is freezing rain, and yellows show mixed precipitation.
GFS precip forecastImage of Courtesy of the UQAM-Montreal Weather Centre
The GFS shows New Hampshire pretty safe from the mixed precipitation territory.
Here is the same time period displayed by the CMC (Canadian Meteorological Centre) GEM model.
GEM precip forecastImage of Courtesy of the UQAM-Montreal Weather Centre
The Canadian model shows a wider berth of mixed precipitation, extending into southern NH.
And lastly, we’ll look at NCEP’s NAM model.
NAM precip forecastImage of Courtesy of the UQAM-Montreal Weather Centre



The NAM shows a wide spread of mixed precipitation and freezing drizzle scattered over the northeast. If the NAM turns out correctly things could be a little damper than expected.
The fringe areas are more difficult to forecast for, but I would expect southern NH on down to get a little mixed precipitation Wednesday morning, whereas in the North Country, I think most of our snow should be on the ground before temperatures rise high enough for any notable mixed precipitation.
Things will begin to cool down again on Wednesday night, maintaining some nice conditions for later in the week.


Nate Iannuccillo, Summit Intern

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