Recap: Saturday's Severe Weather Event | WNYT.com

Recap: Saturday's Severe Weather Event

Allison Finch
Updated: August 31, 2020 03:33 PM
Created: August 31, 2020 03:04 PM

Ahead of the severe weather on Saturday, the Storm Prediction Center (SPC) issued their convective outlook forecast. This forecast issued on Friday, August 28th placed our viewing area under a marginal risk for severe weather and a 2% chance of a tornado forming. On Saturday morning an updated forecast was issued by the SPC for the time period of 6AM Saturday to 6AM Sunday. In the second forecast provided by the SPC, they upgraded our viewing area to a slight risk and brought the tornado percentage up to 5% for a part of our viewing area. If you are curious about the different categories within these forecasts, check out this article here

SPC Forecast for Saturday, August 29th, 2020.  | Storm Prediction Center SPC Forecast for Saturday, August 29th, 2020. | Storm Prediction Center
 

On Saturday morning, ahead of a warm front that was starting to push into the region from the southwest, there were widespread rain showers. None of these rain showers were severe at any point in the morning. By afternoon (about 1PM EST) the warm front had advanced through the region, exiting to our northeast. Behind this warm front was a moist air-mass which increased the humidity throughout the region. The skies started to clear which made the surface temperatures rise.

The main ingredients for thunderstorm development are:

  1. Moisture
  2. Instability
  3. Lifting Mechanism

The warmer temperatures and humid conditions created a moist and unstable atmosphere. The only thing needed for thunderstorms to form was a lifting mechanism. Lifting mechanisms help air rise in the atmosphere and there are four different ways that it could happen. There are orographic lifting, convective lifting, convergence and frontal lifting.

WPC surface analysis valid for 08/29/2020 at 21 UTC | Weather Prediction Center WPC surface analysis valid for 08/29/2020 at 21 UTC | Weather Prediction Center
 

Wrapping this back to Saturday’s severe weather event, the lifting mechanism that helped create the thunderstorms was a frontal lift. Since cold air is denser than warm air, the warm air is rapidly pushed up into the atmosphere, making the leading edge of the cold front have a steep slope. Thunderstorms are more likely to form with cold front compared to warm fronts. A cold front started to push into the region from the west by early afternoon, which gave the atmosphere all the ingredients to form a thunderstorm. The National Weather Service (NWS) in Albany, NY was keeping a close eye on these conditions. At 1:30PM EST there were showers and a few thunderstorms popping up on the radar. At about 2:40 PM EST the NWS issued a severe thunderstorm warning for a cell in Fulton, Herkimer and Hamilton counties. Shortly thereafter, the NWS issued a severe thunderstorm watch.

Hoosick Valley School ground | Tori Hackett Hoosick Valley School ground | Tori Hackett
McDermott Rd, Stillwater, NY | Kacie Marzano McDermott Rd, Stillwater, NY | Kacie Marzano
They forecasted that more than one severe thunderstorm was going to occur that afternoon. A watch means that there are ideal conditions for thunderstorms to form. These storms can include gusty winds, hail, heavy downpours and even an isolated tornado. The same cell that was first warned as a severe thunderstorm warning in Herkimer, Hamilton and Fulton counties started tracking east at 30 mph which promoted the NWS to issue more severe thunderstorm warnings for areas that were going to be affected from this storm. It was this cell that gained enough rotation within it to be warned as a tornado warning. A hour and a half after the first tornado warning was issued, there were confirmed reports of a tornado on the ground just outside of Stillwater, NY. This tornado warning tracked east throughout the next two hours producing two different tornados. One EF-1 tornado that started and ended in Stillwater, NY which had estimated maximum winds speeds of 100 MPH and traveled a total of 0.25 miles. Then another EF-1 tornado that started and ended in Schaghticoke, NY. This tornado has estimated max wind speeds of 110 mph and traveled a length of 1.25 miles. The cold front then moved through the area, which sparked a line of severe thunderstorm warning from the north to south of our viewing area. These thunderstorms produced heavy rainfall, hail and gusty winds. Both the thunderstorms and tornados caused extensive damage, power outages and localized flooding to the area. By 8 PM EST most storms had moved out of our viewing area, leaving us with quiet weather, dry for the rest of the evening.  

The SPC creates verification maps to highlight where they forecasted a chance for severe weather and where severe weather was reported. This was the verification map from the SPC of Saturday’s severe weather event.

SPC Verification Map for Saturday, August 20th, 2020.  | Storm Prediction Center SPC Verification Map for Saturday, August 20th, 2020. | Storm Prediction Center


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