May 15, 2018 - Decision Support Briefing #1. As of: 6:00 AM May 15, 2018 ... Large Hail : Much of the Lower Hud Valley,
Severe Thunderstorms Possible This Afternoon/Early Evening... Decision Support Briefing #1 As of: 6:00 AM May 15, 2018
Current Hazards
What Has Changed? Severe Weather Threat for entire Tri-State Damaging Winds Main Threat This afternoon/Early Evening
Weather Forecast Office
New York, NY
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Presentation Created 5/15/2018 6:51 AM 1
Main Points Hazard
Impacts
Location
Timing
• Downed trees and powerlines, along with isolated structural damage associated with the strongest storms.
Entire Tri-State Region
This afternoon and early this evening
• Isolated flash flooding is possible, especially where multiple storms train over the same area. Rainfall rates of around 1 to 2 inches an hour possible. Rapid flooding of Urban Areas, Low-lying Roads, and Small Streams and Creeks.
Entire Tri-State Region
This afternoon and early this evening
Large Hail
• Large hail can cause damage to vehicles and other property.
Much of the Lower Hud Valley, NE NJ, and Interior SW CT
This afternoon and early this evening
Isolated Tornadoes
Isolated tornadoes possible with damage to structures, trees, and powerlines. Power outages possible.
Much of the Lower Hud Valley, NE NJ, and Interior SW CT
This afternoon and early this evening
Damaging Winds
Flash Flooding
Weather Forecast Office
New York, NY
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Presentation Created 5/15/2018 6:51 AM 2
Summary of Greatest Impacts Damaging Winds: Entire Tri-State Region None
Limited
Elevated
Significant
Extreme
Flash Flooding : Entire Tri-State Region None
Limited
Elevated
Significant
Extreme
Large Hail : Much of the Lower Hud Valley, NE NJ, and Interior S CT None
Limited
Elevated
Significant
Extreme
Isolated Tornadoes: Much of the Lower Hud Valley, NE NJ, and Interior S CT None
Limited
Elevated
Significant
Weather Forecast Office
New York, NY
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Extreme
Presentation Created 5/15/2018 6:51 AM 3
Severe Weather SPC Convective Outlooks 32 Day 1
Hazards:
Wind Gusts up to 65 mph Hail up to 1” Weak tornadoes possible
Impacts:
Localized/Scattered/Widespread downed trees and powerlines Localized/Scattered/Widespread structural damage
Timing and Location:
Heaviest rain from 4 to 9 pm
Uncertainty: Impact of Marine Influence from NYC on East. Exact magnitude of Severe Gusts (could be stronger than 65 mph in places)
Weather Forecast Office
New York, NY
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Presentation Created 5/15/2018 6:51 AM 7
Flash Flooding
Hazards:
Rainfall of 1/2 to 1 inch, with locally higher amounts Rainfall rates of around 1to 2“/hr possible
Impacts: Day 1 2 3 Excessive Rainfall Outlook
Rapid Flooding of Urban Areas, Low-lying Roads, and Small Streams and Creeks. Isolated Flash Flooding Most Likely over NE NJ/NYC.
Timing:
Heaviest rain from 3 to 9 pm
Uncertainty: Most likely to see just minor flooding.
Weather Forecast Office
New York, NY
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Presentation Created 5/15/2018 6:51 AM 9
Forecast Uncertainty or Scenarios
Exact impact of Marine Influence will determine how far east and south Severe Threat gets. Magnitude of wind gusts is uncertain. There is a low end potential for 70-80 mph wind gusts. Extent of flash flooding – most likely will not occur due to fast moving storms. However if 1+” an hour rates do happen over urban/poor drainage areas, then isolated flash flooding could happen.
Weather Forecast Office
New York, NY
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Presentation Created 5/15/2018 6:51 AM 14
Event Summary
Severe Thunderstorms Possible Across Entire Tri-State This Afternoon/Evening Main Threat from Damaging Wind Gusts Lower Threat from Large Hail, Isolated Tornadoes and Flash Flooding Severe Storms most likely across NE NJ/Lower Hudson Valley/Interior SW CT
Weather Forecast Office
New York, NY
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Presentation Created 5/15/2018 6:51 AM 15
Contact and Next Briefing Information This will be the final briefing
Web: http://www.weather.gov/okx/
Facebook: http://www.facebook.com/NWSNewYorkNY
Phone (public): 631-924-0517
Twitter: http://www.twitter.com/NWSNewYorkNY
YouTube: https://www.youtube.com/user/NWSNewYor kNY
Disclaimer: The information contained within this briefing is time-sensitive, do not use after 6 PM Tuesday (05/15/18).
Weather Forecast Office
New York, NY
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Presentation Created 5/15/2018 6:51 AM 16