12:10 PM (Monday) | ***Another cold shot for the Mid-Atlantic/NE US region with frost possible next two late nights…summer-like warmth at week’s end…recap of remarkable weekend cold***

It’ll turn summer-like in the Mid-Atlantic/NE US at week’s end with the development of a “Bermuda'-high” type of pattern. Map courtesy NOAA, tropicaltidbits.com

Overview

Another cold shot is coming to the Mid-Atlantic/Northeast US for the first half of the week and it could lead to more record or near record low temperatures and the possibility of frost during the next couple of late nights. As with the remarkable cold air outbreak this past weekend, attention should be paid to sensitive vegetation with this unusual late season chill.  The end of the week will bring about a dramatic turnaround and summer-like warmth is quite likely on Friday as a “Bermuda-high” type pattern develops over the eastern US and Atlantic Ocean.

Numerous records or near record lows were achieved on Saturday, May 9th in the central and eastern US. Map courtesy coolwx.com, NOAA

Recap of the remarkable weekend cold

The cold air outbreak over the past weekend brought about many daily record lows temperatures across the central and eastern US, numerous sites recorded their lowest temperatures ever for so late in the season, and some spots actually recorded their lowest temperatures ever for the entire month of May. In addition, the changeover of rain-to-snow in many parts of the Mid-Atlantic/NE US early Saturday as the cold air mass arrived early Saturday resulted in the latest measurable snowfall for many spots in this same part of the country.

Numerous records or near record lows were achieved on Sunday, May 10th in the central and eastern US. Map courtesy coolwx.com, NOAA

In the Mid-Atlantic region, there were some interesting measurements this weekend with New York’s Central Park at the top of the list.  First, the low temperature of 34 degrees on Saturday, May 9th, was a record low and it was the lowest temperature ever for so late in the season beating the previous record by three days set in 1891.  Any record at Central Park is rather impressive as they have been keeping records there for quite a long time. The temperature of 34 degrees at Central Park on May 9th was the first sub-40 degree reading in May since 1978 and they dropped to 39 degrees on Sunday, May 10th.  In addition, the snow that fell at Central Park early Saturday was the latest snow there since 1977.  Another interesting observation took place on Long Island In New York State station OKX) on Saturday where the 500 millibar (~`8,000 feet) temperature dropped to -38.1 degrees (C) which not only became the record for May, but was very close to matching the April record. The significance of a temperature record at the middle part of the atmosphere (i.e., 500 millibars or approximately at 18,000 feet) is that it signifies just how deep this cold air mass was on Saturday.

Elsewhere, in upstate Pennsylvania, record lows were set on Saturday in Altoona (26°F), Bradford (22°F), Johnstown (23°F), State College (27°F, tied the record from 1966) and Williamsport (29°F).  A few of these locations also had their lowest maximum temperature ever for the date as well.  In Philadelphia (PHL), Saturday featured the first sub-40 degree temperature on May 9th or later since 1966 when a low of 35°F was recorded and it dropped to 39°F on Sunday, May 10th.   In the DC metro region, Reagan National Airport (DCA) dropped to 37°F on Saturday which was the coldest there in the month of May since 1966.  Baltimore Washington Intl (BWI) Airport broke the low temperature record on Saturday, May 9th, when it bottomed out at 34°F breaking the 1966 record of 36°F with records going all the way back to 1872.

Yet another cold shot is pushing into the Mid-Atlantic/NE US and frost is a possibility each of the next two late nights. Map courtesy NOAA, tropicaltidbits.com

Cold shot for the first half of the week

Another rather impressive cold shot is moving into the Mid-Atlantic region as we begin the new work week with the passage of another strong cold frontal system.  That frontal system has caused some shower activity in the region on Monday - perhaps an afternoon thunderstorm - and winds will soon pick up in intensity from the all-too familiar northwesterly direction as another cold air mass arrives in the region.  Overnight lows for both late tonight and late tomorrow night are likely to be in the low-to-mid 30’s along the DC-to-PHL-to-NYC corridor and there can be frost in the normally colder suburban locations to the north and west of the major cities. As with the weekend cold, it would be prudent to protect sensitive vegetation for this unusual late season chill.

High pressure will push off the east coast later this week and it’ll pump summer-like air into the Mid-Atlantic/NE US at week’s end on increasingly strong southwesterly winds. Map courtesy NOAA, tropicaltidbits.com

Summer-like warmth at week’s end

High pressure that will push over the Mid-Atlantic region at mid-week will push off the east coast in the late week time period.  As a result, the flow of air on the backside of the high will become southwesterly in the eastern US – similar to a summer-time “Bermuda-high” scenario.  In a similar fashion, temperatures will take off in the eastern US with a noticeable warm up on Thursday and then summer-like warmth on Friday in the DC-to-Philly-to-NYC corridor where temperatures can reach into the 80’s.  With the significant warm up at the end of the work week will come an increased chances of showers and thunderstorms in much of the eastern US and the summer-like warmth will continue into the weekend as well.

Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com

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