It's been quite a while since we've had the opportunity to discuss a potential severe weather event at this range. Severe weather events, synoptically favorable ones at least, come few and far between in this part of the nation. It's almost (emphasis on almost) interesting to note how far between they have become over the past few years. One can probably name the past few biggies around here on one hand over the past 10 years. There was one event last year (09) which featured some significant damage, a big event on July 18, 2006 , another big event in 2004 and a few in 2001 and 2002. Obviously there have been a whole plethora of events between the big ones, but snuffing out the big one in this part of the nation can be tough.

Where are we going with this post? To the weekend of course! Forecast guidance has trended fairly robust with the potential for a severe weather event over the Ohio Valley, Pennsylvania and possibly portions of New York. The trend has been slower and more wrapped up with a surface low which is forecast to track from the Plains states northeast towards the Great Lakes. The slower trend means a few things. First of all, the warm sector can strengthen and push northward as the warm front progresses through our area. Second, the better dynamics can wrap up to the west of our area over the Great Lakes and push eastward with good timing during diurnal max temperatures. This is evidenced by the map to your left, the NAM's forecast for 18z Saturday where we see a remarkable H5 trof signature for this time of year


That's a 110kt H5 jet streak which eventually pushes eastward and off the Mid Atlantic coast by 03z Sunday morning. A very impressive jet structure with a powerful shortwave that would provide more than enough forcing for convection should the airmass be moist and unstable enough. As we mentioned, the guidance has trended slower and more wrapped up with the surface low...which has led to a more widespread warm sector, which in turn leads to higher forecasted 2m dew points. You can see the result to your right--an axis of 65 F surface dew points extending into Central/Northern New Jersey with more widespread 60 F readings ahead of these impressive dynamics. This obviously sets the stage for some convection amidst this aforementioned environment. The NAM, the model we are using to showcase this potential event, is indicating MLCAPE values around 750-1000j/kg. Not overly impressive, but we have seen plenty of significant events with that type of instability. The bottom line is, when you have the impressive dynamics aloft, you can survive with 750-1000j/kg of ML/MUCAPE.

There are a few other facets that are important to maintaining a good severe weather event in this area--one of them being the mid level and bulk shear. One good benchmark to check out, to see the atomspheric support for organized updrafts and convection, is the 0-6km bulk shear. The NAM from this afternoon is fairly robust with it's forecast of 60-70kts of bulk shear. That's more than suffice to support updrafts, and in fact may become a concern for being too strong..especially should convection remain low topped. It's also interesting to note that the NAM is indicating extremely robust 0-3km helicity values, in excess of 250 m2/s2 in some areas. Very impressive especially considering the presence of the impressive dynamics and sufficient instability. So where do we stand at this point? The potential definitely exists for a severe weather event this Saturday, but much hinges on the guidance's ability to forecast the track of the surface low. Is the slower and more wrapped up/further northwest trend legit? If it is, we are getting a sneak peek into the parameters that could be lining up---these are parameters along the lines of those seen in the more robust events in this area over the past several years. Keep a close eye on it, we certainly will, and we will keep you informed!