Monday, November 24, 2014
Inquirer Daily News

Bolaris: One last whack from winter

A Northern Cardinal flies from its snow-covered perch on Monday, April 14, 2014, at the Heckrodt Wetland Reserve in Menasha, Wis. The cold and perhaps some snow are headed this way. (AP Photo/The Post-Crescent, Dan Powers)
A Northern Cardinal flies from its snow-covered perch on Monday, April 14, 2014, at the Heckrodt Wetland Reserve in Menasha, Wis. The cold and perhaps some snow are headed this way. (AP Photo/The Post-Crescent, Dan Powers)

Let's face it, the past few days have been our ultimate weather fantasy. Temperatures have soared into the 70s and the 80s helping our psyche rebound from one of the worst winters of all-time.

As we strolled around with renewed energy in our dusted off summer clothing we felt good knowing that finally that Old Man Winter has been beaten back by the spring gods, knocked out and left on the canvas for months to come.

When I was your local TV forecaster here in Philly, I always used April 15th as the cut-off for snow, because by looking back on the history books there was still a low-to-moderate chance of accumulating snow by the 15th of April.

Well, it looks like Old Man Winter, although staggered, still has enough left in him to throw us (hopefully) one last left hook before leaving this part of the planet.

The set-up

An early season Bermuda high (high pressure that circulates over the Bermuda region in the Atlantic and sends very warm air up and along the Eastern Seaboard) is in place. I like to call it the "heat pump effect." In the spring it's a gift as it allows for a very pleasant change to much warmer temperatures, except along coastal sections due to the cold ocean influence. In the summertime, the Bermuda high positioning is much more common and we bake as temperatures soar into the 90s and, at times, triple digit heat.

This Bermuda high effect will start to break down as a very dynamic and powerful cold front for this time of the year and will bump heads with the very mild air still in place. The battle zone of clashing air masses will start to take place on Tuesday as mild and moist air will be squeezed out by an advancing Arctic front accompanied by a huge temperature drop. On the east side of the front temperatures will be near 70 degrees and on the western flank of the front readings will be in the 40s, 30s and 20s.

The result and forecast

Dress for two seasons on Tuesday, as the day itself will be unseasonably mild as temps near 70 degrees.

After 2 p.m. rain will become heavy at times.

Between 4-7 p.m. a band of thunderstorms may develop as the winter air mass forms a defining line (thunderstorms) or the leading edge of the Arctic front.

The evening rush will feature heavy rain with plenty of ponding of the roadways and perhaps some isolated stream flooding along with wind gusting to 30-40mph from the south.

After 8 p.m. dress for winter, as a rapid temperature plunge will take place. When the front crosses your town expect a quick 15-20 degree drop within an hour with a dramatic wind shift to the west and gusts to 40mph plus.

After 10 p.m. temps will be cold enough for snow, but by that time moisture should be limited so I'm not anticipating any snow accumulations in the city, southern New Jersey or Delaware. Still, I can't rule out some accumulating snow in the Lehigh Valley, Poconos and perhaps northern Bucks County. 

Temps by Wednesday morning will be around 32 degrees in town and in the 20s across our suburbs to the north and est.

Since plants have already started blooming you might want to protect those vulnerable to a possible freeze.

Temperatures on Wednesday will be some 20-30 degrees colder than the past few days as readings struggle to get above 50.

One significant side note: I can't rule out the possibility of rogue severe thunderstorm popping up late in the day on Tuesday.

Reality, sometimes, bites you right in the #@%.

John Bolaris

John Bolaris For Philly.com
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