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.
A coastal storm will begin impacting the northern Mid-Atlantic states and New England Wednesday through Thursday with rain likely in the big cities and accumulating snow across the higher elevations.
Temperatures are forecast to plunge behind the departing storm system, with a hard freeze likely across the Washington Region on Friday and Saturday morning.
The image below (courtesy Pivotal Weather) shows January-like highs on Thursday with temperatures only rising into the middle 40s in DC.
Low temperatures on Friday morning will likely dip into the lower to middle 20s in our western zones and upper 20s in the immediate DC Area.
Wind Chills overnight Thursday into Friday morning are forecast to dip into the middle to upper teens!
On average the last frost or freeze in the immediate Washington Area occurs in mid April, use caution when planting sensitive plants this early and ask your local Merrifield Garden Center expert for advice on when the best time is to plant.