03/31/10  8:06 AM

So how much rain has fallen over the northern Mid Atlantic the past few days?

Well, for most locations east of the Delaware River, over 2 inches have fallen with the highest rainfall totals found over eastern Connecticut and Long Island with over 5 inches of rainfall!

Northeastern Pennsylvania did get some periods of heavy rain, but generally dodged the heaviest rainfall.  Most locations had over an inch of rain with lesser amounts to the northwest.  Above 1000 feet, some of the rain changed over to snow, which lead to snowfall accumulations of over 6 inches at the highest elevations!

The Philadelphia metropolitan area received 1 to 2 inches of rain with isolated amounts over 2 inches for Delaware and southern Philadelphia counties.

Much of southern and central New Jersey had over 2 inches with 3 to 4 inches of rain along the immediate coast.  Meanwhile, northern New Jersey pushed to 1 to 2 inches of rain.  The heaviest rainfall was focused along the coast due to a strong 850 MB to 700 MB front that set up over the immediate coastal waters.  The mid level front lead to increased lifting, which enhanced rainfall totals.

The New York City metropolitan area, Long Island, and Connecticut were also under the influence of strong frontogenesis from Sunday night through Tuesday morning, which produced a prolonged period of moderate to heavy rain to settle over these locations for a long period of time.  The development and intensification of the coastal low on Tuesday lead to additional heavy rainfall and strong winds, however by then the over 2 to 4 inches of rain had already fallen.

7:23 AM

The low pressure system responsible for the heavy rain that had moves through the Philadelphia metropolitan area early this morning and is now driving through Long Island and Connecticut is slowly moving into the northern Hudson Valley.  The cold front associated with the surface low pressure system was responsible for thunderstorms last night the produced very heavy downpours and occasional lightning.

Through today, the upper low that is supporting this storm will continue to move east-northeast off the northern Mid Atlantic coast and into the Atlantic.  Scattered showers will continue to linger over the Philadelphia and New York City metropolitan area through this afternoon.  A few of these showers will be capable of producing heavy downpours, however this will be an isolated threat.

High pressure will take hold by tonight with clearing skies.  Dry conditions and clear skies can be expected Wednesday and Thursday as the high pressure system slides through the region.

Another Sub Tropical disturbance will approach from the southwest, however this time the disturbance will have more interaction with the Polar jet stream.  This storm is expected to move much faster than previous storms with rain entering the Philadelphia metropolitan area on Thursday evening and exit by late Friday morning.  The heaviest precipitation is expected to be focused over southern New Jersey and Philadelphia metropolitan area.  As cold air enters from the northwest, some snow may mix in over high elevations, however no significant snowfall accumulation is expected.

High pressure will once again return for Saturday and Sunday, however the Polar air mass in place will keep temperatures well below normal in the 30′s an 40′s on Saturday and 40′s and 50′s on Sunday.  Another area of low pressure will approach by Monday afternoon, however this storm track is expected to be directed towards the St. Lawrence River Valley or the eastern Great Lakes, thus leading to a strong southwesterly flow and much warmer conditions.  Showers and strong to potentially severe thunderstorms can be expected by Monday afternoon and evening as the cold front moves though.

5:45 PM

Periods of moderate to heavy rain are developing this afternoon over much of eastern Pennsylvania, New Jersey, and into much of eastern New York.

A strong upper low over the Tennessee Valley will continue to slowly move east towards the northern Mid Atlantic tonight.  As the upper low slowly progresses to the east, strong moisture advection from the Atlantic will produce heavy rain throughout the Philadelphia and New York City metropolitan area.  As the 850 MB low level jet stream intensifies this evening, areas of embedded thunderstorms will produce heavy downpours.  The heaviest rainfall will likely be focused over northern New Jersey and the Hudson Valley where upper level dynamics will be strongest.

Showers will linger through tomorrow afternoon as the low pressure system slowly exits into the Atlantic.  Rainfall amounts of 1 to 2 inches is expected for most locations with up to 3 inches in isolated locations due to heavy downpours.  Winds from the southeast will range from 10 to 20 mph tonight with gusts over 30 mph along the coast and over the coastal waters.

By Tuesday night, a Polar high pressure system will build into the East coast with clearing skies yet cooler temperatures.  The afternoons of highs in the 70′s will be a distant yet pleasant memory as more normal conditions will return with highs in the 50′s and 60′s.  Still, overall, dry conditions can be expected through Thursday afternoon.

Another area of low pressure will approach from the Tennessee Valley on Thursday night with period of rain, heavy at times, through Friday morning.  This time, the low pressure track will be further south with the focus of heaviest rain over the Philadelphia metropolitan area and southern New Jersey.  Some snow may mix into the rain over elevations above 1000 feet with all snow potentially developing above 1500 feet before ending on Friday morning.  No accumulation is expected, however.

High pressure will regain control for Saturday and Sunday with clearing skies yet very cool conditions with temperatures struggling in the 30′s and 40′s on Saturday and 40′s and 50′s on Sunday.  Another low pressure system will follow on Monday, however the storm track is expected to be towards the St. Lawrence River Valley, leading to temperatures returning to the 50′s throughout the region and periods of heavy rain by the afternoon.

9:30 AM

High pressure has exited the New Jersey coast this morning as a warm front slowly moves north towards the Hudson Valley and Connecticut this afternoon.

The warm front is currently north of Philadelphia cutting through Monmouth County and is just south of Long Island. Clear skies and dry conditions are being observed throughout the region due to the strong lifting and convection over the Tennessee Valley and Southeast, which is essentially robbing the moisture advection associated with the warm front and creating an area of sinking air over the northern Mid Atlantic.  Note the air of dry and red color on the water vapor satellite image to the left.

However, increasing clouds can be expected by this afternoon with showers entering the region late this evening and overnight.  The strong Sub Tropical disturbance will drive towards New Jersey by tomorrow afternoon with periods of rain, heavy at times.  The heaviest rain is expected over the Delaware River Valley through the Hudson Valley.  A half inch to an inch of rain is expected along the coast and through much of Long Island into eastern Connecticut.  Heavier rain, over an inch to as much as 3 inches of rain, is expected just to the west where mid and upper level dynamics will be the strongest.

The rain will exit by Tuesday morning with clearing skies by Tuesday afternoon.  Flash flooding will be a significant threat for portions of northern New Jersey and the Hudson Valley considering the state of the rivers throughout the region this morning.  Caution should be taken!

High pressure will return on Wednesday and Thursday with dry yet cooler conditions with highs generally in the 50′s and 60′s.  It should be noted that these temperatures are generally within normal ranges.

Another area of low pressure will move through the northern Mid Atlantic on Friday with periods rain and possibly some snow mixing in at the highest elevations.  Otherwise, a light to moderate rain is expected from late Thursday night through Friday afternoon.

High pressure will regain control with significantly colder conditions on Saturday and Sunday.   Temperatures will struggle on Saturday with highs in the 40′s for most locations however by Sunday afternoon temperatures will rebound into the 50′s and 60′s once agin.  Those with farming concerns should take heed on Saturday and Sunday morning as temperatures will be near to slightly below freezing on both mornings!

9:26 AM

There is no doubt what the major feature on the water vapor satellite picture is this morning.  A strong Sub Tropical disturbance is supporting the development of a strong and moisture loaded area of low pressure over the Gulf Coast that will move towards the New Jersey coastal waters by Sunday night.

Meanwhile, we can see the Polar disturbance over eastern Canada was not able to dig into the Northeast and Mid Atlantic, all but ensuring an all rain event for the majority of the New York City and Philadelphia metropolitan areas.  The intensity and movement of the Polar disturbance will lock up a cold Arctic air mass over Ontario, thus ensuring no significant phase will occur while this storm passes through the northern Mid Atlantic.

Today through tomorrow morning, clouds will being to increase with temperatures ranging from the upper 30′s to mid 40′s for most locations, which is near normal.  No precipitation is expected through Sunday morning.

On Sunday afternoon, the low pressure system will be moving through Tennessee Valley as precipitation spreads north into southern New Jersey by 4 PM and spreading throughout the northern Mid Atlantic by 7 PM.  The rain may mix with snow and sleet at the onset for elevations about 1000 feet in Northeastern Pennsylvania, northwestern New Jersey, the Hudson Valley, and interior Connecticut; however the precipitation will quickly change over the rain.  This storm is going to move quickly, however the rainfall rates through Sunday evening into Monday morning will support rainfall amounts over an inch in many locations and possibly over 2 inches in localized banding within the precipitation shield.  As the low pressure system jumps to the New Jersey coast on late Sunday night, the low pressure system will begin to quickly intensify supporting a strengthening northeasterly wind with gusts over 30 mph.  Some minor coastal flooding will be possible, however the more significant threat will be from flash flooding of small stream, small rivers, and urban locations due to the heavy downpours.

The storm will exit on Monday morning with clearing conditions throughout by Monday afternoon.  High pressure will remain in control through Tuesday and into Wednesday with a continuation of moderating temperatures as the position of the high will support southwesterly winds from the surface to 850 MB.  However, this warm stretch will not last long.  A cold front will approach with a developing area of low pressure over the Gulf Coast on Thursday.  The cold front will introduce a modified Polar Air mass which will cause temperatures to fall on Thursday and through Friday back into the mid 30′s for most locations.  Minor low pressure development on Friday morning will lead to a mix of rain and snow down to the coastal locations as the Polar air mass builds into the region.

Temperatures will continue to remain in the 30′s for highs for next weekend as a negative EPO pattern begins to take hold over North America by next weekend with a quick end to the thaw of January 2010.