The Northeast is coming off a warm week (record-breaking for some) and rolling right into a severe threat to start the new week.
A negatively-tilted trough continues its progress eastward this morning. Ahead of it, temperatures are warm and the air is moist. As the lifting mechanism approaches from the west, a potent line of storms is expected to erupt.
This is a forecasted sounding valid for 18z near Allentown, PA.
According to this we have:
- A mostly uncapped atmosphere. Open warm sector development is possible – likely multicellular clusters rather than single discrete cells due to the lack of cap.
- Decent CAPE in the hail growth region (-10 C to -30 C). Indicative of the potential for updrafts capable of supporting decently-sized hail.
- Weaker lapse rates. Updrafts may struggle to strengthen.
- Weak speed shear/not much directional shear. Supercells are not favored. Tornado potential is low, but spin ups can occur in the line where mesoscale conditions/topographical features allow for enhanced directional shear.
- Some dry air in the mid-levels with winds ~40 kts. Damaging winds possible.
Look for pre-frontal development in the open warm sector east of the Appalachians, especially across southeastern PA/NJ/southeastern NY where broken cloud cover will allow for added instability via daytime heating.
Any pre-frontal storms are likely to be more of the multicellular variety with the potential for hail, wind, and heavy rain. Once the line arrives later this afternoon, damaging winds become the main threat, along with some heavy rain. Tornado potential is low today due to the lack of directional shear. However, spin ups within the line are possible, especially where topography favorably enhances the low-level shear.
Though the potential for significant wind (65+ kts) is low due to winds not being as strong aloft, consider sheltering for a severe thunderstorm warning if one is issued. Winds 50+ mph can still bring down trees and/or powerlines.
Stay weather aware this afternoon and evening!