JAMESTOWN-There is a standard “Slight” risk for severe thunderstorms for the western portion of Western New York for Sunday, along with an Areal Flood Watch for the entire region.
The setup: A strong Cold front will wobble its way towards Western New York on Sunday, bringing with it a chance for showers and thunderstorms in a QLCS (Quasi-Linear Convective System) or simply a squall line. The potential exists for this line to carry some pretty heavy rainfall, along with gusty winds and some hail.
The NOAA Storm Prediction Center in Norman, Oklahoma has placed far western Chautauqua County under a standard “Slight” Risk (2/5), with the less-than-average “Marginal” Risk (1/5) surrounding that.
Timing It out: The newer model runs have really slowed the advancement of the developing QLCS way down, and it now looks to be a nighttime severe weather episode, rather than a midday event, like originally thought.
Sunday will be a soggy one, with showers and thundershowers throughout the day, mainly south of Buffalo. The strongest and heaviest storms with the line looks to reach the far western portion of our region by around 7:00 PM, and continuing to sweep across the region through the nighttime hours. The line should be east of Chautauqua County by around 8:30 PM or 9:00 PM, with the entire event finally coming to an end around 11:00 PM for all of Western New York. Storms will weaken the further eastward they advance, due to the less-than-ideal conditions of the nighttime hours to keep storm severity.
Impacts: The main threat with this QLCS feature will be damaging wind gusts of around 60 MPH, along with some very heavy rainfall at times as well. There is the potential that some of these storms could also contain some hail.
Flooding Concerns: This squall line has the potential to lay down some very heavy rain across Western New York, which could lead to some flooding. Combine the rain we see through the day on Sunday, along with the storms associated with the front Sunday night, we’ll be looking at average rain totals between one-and-a-half to two inches, with localized amounts up to three inches. In advancement, the National Weather Service in Buffalo has issued an Areal Flood Watch, which will be going into effect 7:00 PM Sunday, and running through 1:00 PM Monday for ALL of Western New York.
(An Areal Flood Watch differs from a Flash Flood Watch, in the fact that areal flooding is any kind of flooding over a large area from smaller rivers, streams and creeks, that have gone above their banks due to heavy rainfall; whereas flash flooding is the result of heavy rainfall over a short period of time).
Also, please keep in mind, that the textbook definition of a severe thunderstorm is one that is producing wind gusts of 58 MPH or higher, or hail one inch in diameter or larger, which is about the size of a Quarter. Lightning and rainfall do NOT make a thunderstorm severe, by definition.
Stay on top of the weather Sunday night and make sure you have a good way of getting watches and warnings; I personally recommend a NOAA Weather Radio, along with a good smartphone app that pushes warnings.