Monday 10 AM
Now that cold air has enveloped the Great Lakes and Northeast, it appears likely to persist all week. It appears this will be the chilliest January cold outbreak in four years.
In 1992, meteorologists Steve Nogueira and Weir Lundstedt wrote about a type of trough that was involved in generated unexpectedly great amounts of snow. The troughs under study extended northwest from a low pressure area and were located underneath a pool of cold air several miles overhead. Most common in central and northern New England, these features can produce localized bands of very heavy snow, in some cases producing a foot of snow in areas where standard computer models were only suggesting a couple of inches of snow would fall.
By taking the first three letters of the last names of the scientists writing about these troughs, you get Nor Lun, and so the troughs became known as Norlun Troughs. Such a system might develop tomorrow along or near the New England coast, perhaps between Boston and Portland.
Aside from the possible Norlun Trough development and lakes related snows downwind from the Great Lakes the weather maker coming through should only create small accumulations. Of course, it does not take much snow falling in metropolitan area to cause travel problems.
Another weak low pressure area and frontal system could cross the Great Lakes on Wednesday and move of the East Coast Thursday. After that, there is a chance that a stronger storm could take shape to cause accumulating snow from (at least) Maryland to Massachusetts on Friday. This video has more.
Here is a working draft of snow expectations for the Northeast from later today into tomorrow. I use the term "draft" because the map is updated frequently. Our other stories and forecasts on AccuWeather.com can keep you current.
However, rainfall is increasing south of New England, and southerly flow aloft should bring rain to Providence, Boston and other parts of New England.
Early this morning, the most concentrated rain was falling in a band from Maryland to southern Michigan.
With a high pressure area over Maine, a low pressure area over western Indiana and an upper-air storm spinning over the western Great Lakes, the stage is set for wet weather in the Middle and North Atlantic states.
This map is a rainfall forecast from the NWS Middle Atlantic River Forecast Center located in State College, PA.
The upper-air flow forecast for this evening shows the trough that helps to support rainfall ahead of the cold front.
After reaching the 80s today from NYC to Boston, it might not be that warm again through much of next week.