Ice coming Wednesday?


This NAM model, typically used by the National Weather Service, shows icing in Concord by 1 p.m.

A significant ocean storm that for the last few days looked like it was going to pass just east of New England has seemingly decided its coming ashore. This is partially due to a cold front that was forecasted to boot it out to sea that is now lagging over Canada.

Right now, this looks like an absolute mess. The forecast could certainly change but as it looks currently a large gulf low is heading northward with a ton of tropical moisture. We are locked into the cold air and it is not going anywhere over the next 48 hours.

Cold air + lots of rain = freezing rain and ice!

I have looked at a few models this afternoon and some are picking up on the ice signature and others not so much (yet) so there isn’t 100% consensus at this point (that would come tomorrow).

But enough models are showing the freezing rain/icing elements, and so it is safe to say something is going to happen in the pre-dawn hours of Wednesday through at least the late morning hours of Wednesday (and most likely into the early afternoon).

Precipitation should start 4-7 a.m. on Wednesday. Believe it or not, this is the most humid time of day so there will be plenty of moisture in the atmosphere to convert into precipitation.

There is a bit of a difference in precipitation type based on the two main models. One model has more snow. The other model shows nothing over Concord. However what it is REALLY likely showing is freezing fog and freezing drizzle, which can’t be picked up by this type of forecast model. The resolution is too large.

Between 7 and 10 a.m., things look to be going downhill fast. The Global Forecast System (GFS) model has heavy, wet snow (possibly mixing with sleet) while the North American Mesoscale model (NAM) model has sleet and more likely freezing rain falling at this time.

By 1 p.m., there is a lot of agreement between the models – pink = freezing rain. The NAM also has the isobars compacting so the winds may be increasing from the northeast as well. Great first full day of winter!

By mid-to-late afternoon the center of low pressure will be moving from the Cape Cod region toward the Canadian Maritimes and dragging the moisture with it. A cold front will blow on through in the late evening bringing with it a reinforcing blast of cold, winter air from Thursday.

Lastly, what are the precipitation totals for this storm looking like at this time? See below. The NAM model is not indicating a heavy snow accumulation. This indicates any snow that falls will be mixing with rain.

The main precipitation to worry about is freezing rain. The accretion of ice looks like 0.25-0.50 inch (which is drastic and rather unrealistic). I would think 0.10-0.20 is a fair estimate which is still very dangerous. This seems to be the major hazard of this storm at this moment in time.

The forecast could certainly change and hopefully it does. Ice is not fun. Stay tuned for updates! Your CHS weather desk has you covered!