Wednesday, June 12, 2013

"If you knew then, what you know now..."

NOAA Storm Prediction Center 
Day 2 Severe Weather Outlook

6:35 PM EDT 6/12 (Mid-Atlantic Severe Weather Team) Concern is rising among our team and in the meteorological community for a significant severe weather event on Thursday across central and eastern portions of the Mid-Atlantic. For today, an isolated threat is present for brief periods of severe weather from late this afternoon into the overnight hours along the I-81 corridor in MD, WV and VA. 

SYNOPSIS: The NOAA Storm Prediction Center currently projects a considerably high 45% probability of severe weather for a large, heavily populated part of the Mid-Atlantic. 

  • This scenario would contain strong damaging winds, hail and possibly tornadoes in some areas, as indicated on this map and linked below. 
  • Given that the event is roughly 24 hours out, it is too early to tell what precise areas will receive potentially damaging weather, however, we can say that when NOAA postes a 45% probability this early, it is a very serious concern for those in public safety, infrastructure, and the public in general.

TIMING & IMPACTS: The period of highest impact could be between 12 Noon and 5 PM, but could start earlier or extend into the evening. 

  • Recent heavy rains, low level instability and upper level wind flow, combined with high sun angle may easily produce very large Supercell-like thunderstorms, or even multi-cell complexes across Virginia, Maryland, Delaware and southern Pennsylvania. 
  • These storms would be capable of producing tornadoes similar to what was observed earlier this week in Maryland and also like June 1, 2012. If large supercell type storms develop and produce what is called an "outflow boundary" it is not unrealistic to expect multiple lines of storms to develop from west to east - and affect large areas with potentially damaging winds, heavy rain and large hail.
HISTORY: Regarding comparisons to the "Derecho" of June 29, 2012 -- this event has the potential to produce similar *damage* to that event in some areas-- but may not actually *become* a Derecho, which is a different atmospheric dynamic altogether. The severity of this event is also not likely to cause extremely widespread damage across large areas, but in those which are impacted by a thunderstorm complex may interpret the weather to look similar to what they observed in the Derecho.

NEXT UPDATE: We will have additional information this afternoon as analyses become available, and will post an expanded version of this report on our main site at

NOAA Storm Prediction Center Day 2 Outlook:

MD Forecasters Jason M., Connor M., Josh O., Meagan B.
PA Forecaster Zach F.
Meteorologists: Greg B., Alex D.
Emergency Management Liaison Aaron S.
Senior Advisor Rich F.


EternalReedFan said...

I am disappointed in the lack of updates. I rely on this site. Is something wrong with my computer?

Mike Natoli said...

@EternalReedFan - Since we are all a volunteer organization, we unfortunately do not have the staffing to keep the main website maintained. As a result, this page is typically only updated during major weather events. However, our facebook pages are updated very frequently. Our "flagship" page is the Central MD page (, but you can also check out the general United States page (