ACCUWEATHER: The temperature roller coaster ride in the northeastern United States will continue on Monday, setting the stage for severe thunderstorms over a part of the region.
Cooler air pressed into the Northeast on Sunday, holding temperatures 15 to 25 degrees below Saturday's highs in many communities.
The change was even more dramatic in Boston. After coming close to breaking Saturday's record high of 85 F, Sunday's high of 66 was recorded at midnight EDT. Temperatures then fell to 50 by daybreak and held around that mark into the afternoon.
An exception to the cooldown on Sunday was in locations west of the Appalachians, where the next warm surge has begun.
Along the boundary separating the warmth and cooler air, spotty thunderstorms will rattle western Pennsylvania and the southern Appalachians on Sunday afternoon. One or two of the thunderstorms can produce strong wind gusts.
On Monday, temperatures in much of the mid-Atlantic and central New York will climb into the upper 70s and 80s due to strong southerly winds.
Exceptions to the warmth on Monday include the south-facing shoreline areas and eastern New England due to wind blowing off the cool water. Temperatures will be held to the 40s in Portland and Bangor, Maine.
Monday's warmth will occur ahead of another cold front, which will trigger more thunderstorms from the Florida Panhandle to Virginia and western New York. Some of the thunderstorms will become severe with hail and damaging winds. The threat will be greatest along the I-79 and I-81 corridors.
The thunderstorms may weaken below severe criteria upon reaching the I-95 corridor from Washington, D.C., to New York City on Monday night.
The passage of this front will slash highs by 10 to 20 degrees around the eastern Great Lakes for Tuesday. Highs in the lower to middle 70s will be more common from New York City to Washington, D.C., this day.
"We expect more significant cooling to take place during the first weekend and second week of May," according to AccuWeather Lead Long-Range Meteorologist Paul Pastelok.
"We have been getting mixed signals as to the magnitude of the cooling trend before the middle of May, but we suspect temperatures may dip below average a bit for much of the second week, followed by near- to above-average temperatures for much of the second half of the month in the Northeast," Pastelok said.
On one hand, there is a scenario that will bring showers and thunderstorms with hail and chilly air during next weekend. Another scenario would bring another brief wave of cool air followed by a big warmup next weekend.
Pastelok remains concerned about the potential for a chance of a brief frost over parts of the interior Northeast prior to the end of May.
Gardeners may be able to plant warm-season vegetables and annual flowers during the upcoming warmth, provided they have a means to protect their investment should a spell of frosty air come calling before the Memorial Day weekend.