Verification And Sunday Forecast

Well, it looks like the SREF products did a really good job with pinpointing the possible severe weather today. As seen below there several reports of severe wind and hail across south central New York. It was here where the sun was out much of the day allowing for teh atmosphere to become destabalized. This combined with 30-40kt of 0-6km shear allowed for the few severe thunderstorms to develop and maintain themselves. This area was pinpointed almost exactly by the SREF shear and instability product shown in my previous post. It also lined up really well with teh SREF probability of severe thunderstorms product. The other severe reports were in eastern PA just south of a stratus layer. This allowed for ample heating, and wind shear was higher in eastern PA compared to teh rest of the state. This area was also pinpointed by the SREF data. The SREF data also indicated that any severe weather would be isolated and this was indeed correct. Across the rest of PA most storms were terrain induced. Wind shear was lower which prevented most storms from becoming organized enough to become severe. Also, a stratus layer, which was predicted well by the NAM and GFS, impacted central PA for much of the day limiting instability

Now on to Sundays severe potential. The SPC currently has a 5% probability of severe weather tomorrow for eastern PA up to CT. I beleive this area is correct, but that future forecasts will up this probability. The SREF products used for todays forecast did so well, that theres no reson to stray far from them tomorrow. The probability of 1000j/kg of CAPE and 30kts of 0-6km shear is higher than it was today. It is centered over northeast PA, southeast New York and western CT, so it is here where I expect a few to several severe thunderstorms. A alcak of upper level support should limit overl extent of seevere weather, but expect more reports than there where today. This is backed up by the SREF severe probabilities, which are maxamized over teh same areas and are higher than todays probabilities. Further south across southern New Jersey and southeast PA the CAPE will be higher, but they will be displaced from the weak surface front and the higher wind shear, and thus only expect pulse type storms that shoudl remain below severe limits.

Intro and Possible Severe Weather Saturday

First off I would like to introduce myself. My name is Marc Chenard and I am a recent graduate from The Pennsylvania State University with a B.S in Meteorology. I will be starting a job at the National Weather Service in Blacksburg,VA on June 1st. In this blog I will discuss anything interesting that happens at work as well as discuss possible severe weather events across the central and eastern part of the country.

Severe Weather

There appears to be a chance of a few severe thunderstorms Saturday afternoon across mainly northeast PA and south central New York. Increasing low level moisture on the back side of a departing ridge will increase instability across the area. The image above shows the SREF probability of Most Unstable Capes being greater than 1000 j/kg. You can see there is a pretty good chance of this happening across PA. So the instability will be present, we just need a forcing mechanism and wind shear. The forcing looks meager at best with no upper level support. At the surface there will be a weak front helping to aid convergence, but this will not be enough to allow for widespread thunderstorms. wind shear will be rather weak, but will be highest the further north you go with SREFs showing near 40kts of 0-6km shear near the NY-PA border. The next image shows the combined probability of 500 j/kg of CAPE and 0-6 km shear greater than 30kts and convective precip greater than .01. This pinpoints the highest probabilities over northeast PA and south central New York. It is hear where the combination of CAPE and wind shear may allow for some storms to briefly organize and approach severe limits. The overall severe threat will depend on the amount of sunshine and how high dew points can get. Across the rest of PA expect some afternoon popcorn thunderstorms, but given lack of wind shear and weak winds aloft think overall severe threat is low. So overall, I am not expecting a big severe outbreak, but instead think we will see a few to several reports across the previously mentioned areas. I'll leave you with an image showing the SREF probability of severe weather. I have been looking at this product a lot recently it seems to do a very good job of pinpointing possible severe weather areas.