May has brought about freeze warnings, frost advisories, rainy weather, and now a possible Nor’easter? According to meteorologists, a possible Nor’easter may affect the coast and parts of the mid-atlantic for Mother’s Day weekend. Whenever we hear the word Nor’easter, we think of snow and bitter cold temperatures. The term “nor’easter” most often is used for strong winter storms crawling up the Northeast coast, but, in fact, snow isn’t a requirement for such a storm. Nor’easters are simply stronger areas of low pressure along the Eastern Seaboard of the U.S. featuring winds typically from the northeast. They’re usually strongest from fall through early spring, but can happen any time of the year. That includes, unfortunately, mid-May.
This Mother’s Day weekend, a low pressure system should form somewhere off of the Northeastern coast. Here is an outlook for the region:
Friday: Best chance of rain along and south of the Mason-Dixon line in the Mid-Atlantic States, Appalachians, Ohio Valley, Showers possible in other parts of the interior Northeast.
Saturday: Low pressure may develop near or off Mid-Atlantic coast. The best chance for rain is along the coast from the Mid-Atlantic states to southern New England, extending inland to New York state. Winds may increase along the coast and coastal flooding possible north of the low IF it develops.
Sunday: The area of low pressure may hover off southern New England coast. The best chance for rain/wind is from New England westward into Upstate New York.
Another system may swing through the Great Lakes and interior Northeast Sunday, prolonging rain showers in those areas into next Monday or even Tuesday. But don’t worry, the weekend won’t be a total washout. Parts of the mid-Atlantic states may also dry out a bit by Mother’s Day, as well. So, what is to blame for the cold weekend and the possible Nor’easter?
The North Atlantic Oscillation (NAO), an index based on the pressure difference between typical Atlantic subtropical high pressure and typical low pressure near Iceland and southern Greenland, has turned negative so far this month.
When the NAO is in this negative phase, blocking high pressure in the upper atmosphere near Greenland causes the jet stream over North America to plunge southward across the eastern half of the United States, resulting in a period of cooler-than-average temperatures. No worries, this negative NOA will relent sometime next week.
(Image source: The Weather Channel)