The first ten days of May have featured below normal temperatures in the DC-to-Philly-to-NYC corridor (DC: -3.9°F, PHL: -5.0°F, NYC: -5.8°F) and more cold air is coming for the latter part of the weekend and the early part of next week. In fact, overnight low temperatures could drop into the 30’s early next week in some suburban locations along I-95. Looking down the road, it appears this consistently chilly weather pattern of late will dramatically change in about ten days or so and we could very well experience hot weather by late May as we approach the Memorial Day holiday weekend. In addition, there are signs that the tropics could become active for the first time this season by the end of May in a year that should be more active than recent years in the Atlantic Basin (Tropical Outlook).
Sunday/Monday cold shot
One cold frontal system will arrive in the eastern US on Friday and the result is likely to be showers and embedded thunderstorms from DC-to-Philly-to-NYC as we close out the work week. Right on its heels, a secondary cold front will arrive by late Saturday and bring with it another round of showers for this area. Following the passage of the weekend secondary cold front, much cooler air will push into the region for Sunday and Monday. This chilly air mass will be supported by strong, cold Canadian high pressure and temperatures will be well below normal in a large region of the country extending from the Plains to the east coast. Overnight temperatures early next week could actually drop into the 30’s in some suburban locations in the I-95 corridor and snowflakes are not out of the question for higher elevation locations of Pennsylvania, New York, Maryland and West Virginia.
Hot weather pattern likely by late May
In a potential complete reversal of the expectation for the middle of May (i.e., cold period), the latter part of the month looks like it’ll get quite hot in the eastern half of the US. Temperatures could very well soar to well above normal levels in the days before Memorial Day weekend in roughly the same area that will suffer through next week’s cold shot. In addition to the temperature reversal, the overall weather pattern that is likely to unfold during the late stages of May could support tropical activity in the Atlantic Basin for the first time this season.
Last night’s ensemble run of the Canadian computer forecast model features well below normal temperatures in the eastern half of the US from Saturday night through Wednesday night (top image). The same 00Z model run also features above normal temperatures in the 5-day period from Sunday, May 22nd - Friday, May 27th (middle image). Last night’s GFS computer model run indicates the first tropical troubles of the Atlantic Basin season could take place just in time for the Memorial Day holiday weekend (bottom image).
Meteorologist Paul Dorian