ITHACA, N.Y. — If you’ll be doing any work outdoors or driving around running errands today, be advised: the National Weather Service is expecting a major outbreak of severe thunderstorms this afternoon and evening.

After pushing a warm front through the area this morning, and area of low pressure and its cold front will swing east-southwest across upstate later this afternoon. Meanwhile, directly overhead is a branch of the jet stream. The combination of being in the warm sector of the low and having the jet stream means there will be a large amount of energy and very unstable conditions, which will allow for the development of thunderstorm supercells and potentially bow-echo squall lines.

The timing of maximum risk for Ithaca and Tompkins County will be from 3 PM to 7 PM. The storms will begin to develop to the northwest by around 1 PM, and push east-southeastward as the day progresses. These storms will be numerous, with a few more intense and dangerous cells embedded. The risk for severe weather will continue through the afternoon and evening, until more stable moves into the region after sunset.

The biggest risks from these storms are damaging strong winds, large destructive hail, frequent cloud-to-ground lightning and flash flooding. Tornadoes will also be possible. Winds guests will be in the 60-75 MPH range, and hail will grow to 1″-2″ in diameter. Locally heavy rainfall may cause street flooding, especially in areas with poor drainage.

Secure or move indoors any light objects that could become airborne. If possible, move your vehicles to a sheltered space. Large hail can damage vehicles and roofs, and pose an imminent safety hazard – immediately take cover if large hail stones begin to fall, and stay away from glass doors, windows and skylights. The winds and hail may bring down trees and power lines, so be prepared for power outages and, if traveling, use caution and plan more time for your travels in case roads become inaccessible. Make sure your sump pumps are working, especially if you live in a low-lying or poorly-drained area. Keep an eye out for severe thunderstorm and tornado warnings on your phone or TV, as that will mean a damaging storm or tornado will arrive shortly.

Once the storms pass, skies will clear out and partly cloudy conditions can be expected overnight, with lows in the mid 60s. Friday will be much calmer, with highs in the upper 70s and low 80s and partly cloudy skies.

Brian Crandall

Brian Crandall reports on housing and development for the Ithaca Voice. He can be reached at bcrandall@ithacavoice.com.