Last week I warned that the upper-level pattern was showing signs of becoming blocked and a pattern change to below- average temperatures is likely the second half of April across much of the eastern United States.
Potent Nor’easter May Impact Mid-Atlantic and New England Friday and Saturday
A very potent upper-level low pressure system depicted in the forecast model above (courtesy pivotal weather) will slide across the northern Mid-Atlantic states on Thursday, likely spawning the development of a coastal storm (Nor’easter) on Friday.
Depending upon the exact track of this system wet snow may accumulate in spots from the Alleghenies to the Poconos with a cold rain, gusty winds, and temperatures running twenty degrees below average (or more) for the lower elevations.
Just as the famous Yoshino cherry trees begin to blossom along the Tidal Basin, the North Atlantic Oscillation (NAO) is forecast to dive providing an ominous and reliable warning that a blocking pattern across the northern Atlantic Ocean is setting up as we head into early April.
The image above (courtesy NOAA) shows the NAO index plunging this week. When the NAO is negative, high pressure builds over the north Atlantic Ocean causing the jet stream to dip into the eastern United States. This dip in the jet stream typically initiates east coast storms followed by a blast of cold air.