severe weather/flooding threats in Mid Atlantic today.....
Posted: Fri Jun 25, 2004 3:34 am
Looking at severe potential this Friday reveals a fairly widespread area of severe thunderstorms forecasted to occur this afternoon and evening from southeastern New York including New York City southward through east central Pennsylvania, New Jersey, Maryland, Delaware, eastern West Virginia Panhandle, east central Virginia and northern North Carolina including the District of Columbia. Isolated tornadoes, hail to 2 inches in diameter, thunderstorm wind gusts to 70 mph, and dangerous lightning are all possible in this particular region. There is also an additional concern due to slow forward motion that is expected with these thunderstorms today. Thus with 2-3 inch per hour rates in slow moving storms that move at less than 10 mph, we're gonna flood in some locations too. The famous weather service flash flood logo "Turn around, Don't Drown" will likely be put to the test across the Middle Atlantic states later today as well as supercells and some bow echos will likely be slow movers.
The question is why this severe weather??? An upper level trough continues to rotate around in the Great Lakes and northeastern part of the United States. A deep vortex is centered over James Bay with upper disturbances rotating around the base of this deep vortex. This in conjunction with abundant gulf moisture ahead of an approaching cold front, a developing lee side trough with a surface low along it, and finally a weak disturbance over the Tennessee Valley will all combine over the Mid Atlantic to result in strong to severe thunderstorms later today. As this surface low organizes later today along the leeside trough over Virginia, expect an organizing line of supercell and bow echo type severe thunderstorms with hail to golfball sized possible as well as damaging wind gusts from the Mid Atlantic into southern New England. The reason for that is due to strong deep layer shear 0-6 km of 35-45 knots. Despite weak low level flow/SRH, short lived tornadoes are possible today across the Middle Atlantic region as very strong instability and very moist air is in place in conjunction with the modest directional shear.
Another threat today for the Mid Atlantic in particular is flooding rainfall given the high levels of low level moisture in place combined with the expected slow forward motion of these storms. As a result of that, the most intense storms could produce rainfall rates of 2-3 inches per hour. If this occurs for an extended period of time over one given area, that area is going to flood whether it's good drainage or poor drainage. Once again if you come across a roadway covered by water, don't risk it. Turn around, don't drown. It could save your life.
This has the potential to be a very dangerous day today across the Mid Atlantic and into southern New England. Keep an eye out for future watches and warnings later today as well as severe thunderstorm warnings and possibly tornado warnings as well. Some of these supercell storms could easily spin up a tornado, keep an eye on it!!!!
Jim
The question is why this severe weather??? An upper level trough continues to rotate around in the Great Lakes and northeastern part of the United States. A deep vortex is centered over James Bay with upper disturbances rotating around the base of this deep vortex. This in conjunction with abundant gulf moisture ahead of an approaching cold front, a developing lee side trough with a surface low along it, and finally a weak disturbance over the Tennessee Valley will all combine over the Mid Atlantic to result in strong to severe thunderstorms later today. As this surface low organizes later today along the leeside trough over Virginia, expect an organizing line of supercell and bow echo type severe thunderstorms with hail to golfball sized possible as well as damaging wind gusts from the Mid Atlantic into southern New England. The reason for that is due to strong deep layer shear 0-6 km of 35-45 knots. Despite weak low level flow/SRH, short lived tornadoes are possible today across the Middle Atlantic region as very strong instability and very moist air is in place in conjunction with the modest directional shear.
Another threat today for the Mid Atlantic in particular is flooding rainfall given the high levels of low level moisture in place combined with the expected slow forward motion of these storms. As a result of that, the most intense storms could produce rainfall rates of 2-3 inches per hour. If this occurs for an extended period of time over one given area, that area is going to flood whether it's good drainage or poor drainage. Once again if you come across a roadway covered by water, don't risk it. Turn around, don't drown. It could save your life.
This has the potential to be a very dangerous day today across the Mid Atlantic and into southern New England. Keep an eye out for future watches and warnings later today as well as severe thunderstorm warnings and possibly tornado warnings as well. Some of these supercell storms could easily spin up a tornado, keep an eye on it!!!!
Jim
However have some hope here if the expected low to develop in se VA can hold the marine influence at bay and allow for some better development here.