Monday, May 16, 2022 Northeast Thunderstorm Potential

 A shortwave trough is expected to move across the Northeast Monday with cold front moving through at the surface. As the cold front moves across the Northeast, a line of showers and thunderstorms is expected to organize across western New York and western Pennsylvania and propagate east-northeast through the region. 

Combination of temperatures climbing well into the 70's (with some localized lower 80's) and dewpoints pushing into the 60's will contribute to about 1,000-1,500 J/KG of MLCAPE. This will help aid in the development of showers and thunderstorms along with strengthening of this activity. Strong jet stream dynamics will also be present with 40-50 knots at 500mb and 35-50 knots at 700mb. This will help contribute to about 35-45 knots of vertical shear - plenty sufficient for storms to become organized.

Given the combination of a modestly unstable airmass and strong winds aloft, the potential will exist for the strongest thunderstorms to produce damaging wind gusts and hail. Forecast models also indicate increasing helicity through the day as stronger low-level winds at 850mb overspread the region so a brief tornado is also possible.

Noting the Storm Prediction Center has placed has placed much of New York and Pennsylvania in an enhanced risk (level 3/5) for severe thunderstorms with the greatest potential being damaging winds with widespread damaging wind gusts possible. This line is expected to rapidly weakening as it moves across southern New England as instability quickly begins to wane, however, localized wind damage will still be possible within the region. 

When assessing the potential environment to distinguish a more typical Northeast severe weather event versus a more substantial threat there are several red flags to note;

1) Weak mid level lapse rate - 700-500mb lapse rates are forecast to be on order of 5.5 - 6 C/KM. Weak lapse rates will put cap onto how much instability can materialize during the day as well as limit overall updraft (and subsequent) downdraft strength. 

2) The strongest of the low-level jet winds are confined to the 850mb level with winds forecast to strengthen to around 30-40 knots with a general 25-35 knots at 925mb. While these winds are rather adequate for these levels, they are a bit shy of what you would like to see for a higher magnitude damaging wind event. 

3) Questions regarding low-level lapse rates - The BIGGEST discriminator between more mundane and higher magnitude damaging wind events in the Northeast is low-level lapse rates. Stronger low-level lapse rates (> 8-8.5 C/KM) correlate much higher to widespread damaging wind potential. While these values may be achieved locally, there are questions about this on a widespread or region-wide level. 

Based on everything stated above, showers and thunderstorms rapidly develop by mid-to-late Monday morning across western New York and Pennsylvania and propagate east-northeast across the region with this line strengthening through the morning and early afternoon. Given the modestly unstable airmass and strong wind shear aloft, some strong-to-severe thunderstorms are likely with scattered damaging wind gusts, some hail, and the risk for a brief tornado. Given some of the uncertainties a more widespread damaging wind event doesn't appear likely, but there may be localized areas of more concentrated damage. 

(Note: Defining a higher magnitude damaging wind event - Several-plus reports of 65+ mph winds).