Scattered showers and thunderstorms developed during the evening of the 11th across portions of Central New York ahead of an approaching cold front. Some of these storms produced excessive rainfall and areas of flash flooding.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS BGM wrote it up.
Scattered showers and thunderstorms developed during the evening of the 11th across portions of Central New York ahead of an approaching cold front. Some of these storms produced excessive rainfall and areas of flash flooding.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Binghamton, NY wrote its last area forecast discussion before the first event at Aug 11, 7:02 PM EST, 1 hour 53 minutes earlier.
Area Forecast Discussion National Weather Service Binghamton NY 802 PM EDT Tue Aug 11 2020 .SYNOPSIS... Thunderstorms expected into tonight with a passing cold front. This front will ease up the heat for tomorrow and any chances for thunderstorms through the rest of the week will be across northeast Pennsylvania and Central New York should remain mostly dry. && .NEAR TERM /THROUGH WEDNESDAY NIGHT/... 800 pm update.. Made only very minor adjustments to temperatures, winds and sky cover overnight. Overall, the near term grids and forecast remain in good shape. As expected a ling of thunderstorms has developed across CNY, and is now approaching the I-88/86 corridor. These storms (some which may be strong to severe, with torrential rain and gusty winds) will continue to slowly move off to the south and east through the late evening hours. The showers and storms should move out of our forecast area before daybreak. Areas of fog are likely once again, especially in the valleys. 320 pm update... Thunderstorm activity will increase this evening as a cold front pushes into western NY. SPC maintains a marginal risk across most of northern and Central NY...as the same short wave that kicked off the significant Derecho yesterday will be entering the Saint Lawrence Valley in the next few hours. Although not nearly as potent as it was, this wave could still kick off some strong storms this evening and CAMs continue to show a line of storms crossing the region from about 5pm to midnight tonight. With ML CAPE around 1500 J/kg and fairly steep mid- level lapse rates of 7C/km, it is possible that a strong line of storms may organize and some damaging wind gusts would be the most likely threat. Also, PWATs of a around 2" means any storms will contain torrential downpours with rainfall rates possibly over 2 inches per hour, and any training of storms or slow moving cells could produce localized flash flooding. High pressure builds in from the west tomorrow and the forecast is looking more and more dry as frontal boundary dips well south of the region. Could still see an isolated shower or thunderstorm in NE PA depending on how far south the front can make it. Temperatures will be cooler than today but highs will still be well into the 80s, however humidity will be much lower. && .SHORT TERM /THURSDAY THROUGH FRIDAY/... 230 PM UPDATE... A frontal boundary will settle across central or southern PA into Thursday, as high pressure edges in from Quebec. This will keep most of the area dry, though some showers and rumbles of thunder will be possible during the daytime hours Thursday and Friday across our northeast PA zones given the proximity to the boundary. Otherwise, looking at quiet weather with morning lows in the upper 50s to lower 60s and highs in the low to mid 80s. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... 230 PM Update... No changes to the forecast with much of the period dominated by high pressure. Previous discussion continues below. 300 AM UPDATE... Period is controlled by high pressure ridging into the area from Southeast Canada. This will keep us dry much of the time, with only isolated or perhaps scattered showers, mainly over NEPA, as waves pass by to the south. Temperatures will be near normal through the period. On Monday, a cold front moving in from the west will bring showers and thunderstorms to the area, mainly in the afternoon. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... The cold front continues to move east central NY and NE PA this evening. SYR, RME, ITH, and ELM have had the front pass with the threat of showers and thunderstorms over. BGM will be getting showers and thunderstorms for the next one to two hours. AVP will likely not see the showers until 2Z. With the loss of daytime heating, the threat of thunder is low at AVP. With the clear skies and recent rain, fog will be a threat at ELM again tonight with IFR or worse conditions possible after midnight. RME will have to be watched as well but confidence was low that fog will develop near the airport. Tomorrow is looking clear with VFR conditions expected everywhere after 14Z Outlook... Wednesday through Friday...Mostly VFR expected...possible afternoon thunderstorms at AVP and possible valley fog at ELM overnight. Saturday and Sunday...Early morning fog possible, especially for KELM. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...None. && SYNOPSIS...MPK NEAR TERM...MPK/MJM SHORT TERM...HLC LONG TERM...DGM/HLC AVIATION...AJG
Hazardous Weather Outlook National Weather Service Binghamton NY 408 PM EDT Tue Aug 11 2020 NYZ009-022-044>046-057-062-PAZ038>040-043-044-047-048-072-122015- Northern Oneida-Steuben-Cortland-Chenango-Otsego-Delaware-Sullivan- Bradford-Susquehanna-Northern Wayne-Wyoming-Lackawanna-Luzerne-Pike- Southern Wayne- 408 PM EDT Tue Aug 11 2020 This Hazardous Weather Outlook is for central New York and northeast Pennsylvania. .DAY ONE...Tonight. Scattered thunderstorms will cross the region this evening. A few storms could contain strong winds and torrential downpours. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. NYZ015>018-023>025-036-037-055-056-122015- Yates-Seneca-Southern Cayuga-Onondaga-Schuyler-Chemung-Tompkins- Madison-Southern Oneida-Tioga-Broome- 408 PM EDT Tue Aug 11 2020 ...HEAT ADVISORY IN EFFECT UNTIL 7 PM EDT THIS EVENING... This Hazardous Weather Outlook is for central New York. .DAY ONE...Tonight. Please listen to NOAA Weather Radio or go to weather.gov on the Internet for more information about the following hazards. Heat Advisory. Also, scattered thunderstorms will cross the region this evening. A few storms could contain strong winds and torrential downpours. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. Hazardous weather is not expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BINGHAMTON NY
824 PM EDT TUE AUG 11 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0759 PM TSTM WND DMG 1 N WELLS BRIDGE 42.38N 75.25W
08/11/2020 OTSEGO NY 911 CALL CENTER
TREE DOWN ACROSS ROAD NEAR COUNTY RD 4 AND SAND HILL RD
BLOCKING BOTH LANES OF TRAFFIC
&&
AJGPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BINGHAMTON NY
845 PM EDT TUE AUG 11 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0804 PM TSTM WND DMG MARYLAND 42.53N 74.88W
08/11/2020 OTSEGO NY 911 CALL CENTER
TREE DOWN ON COUNTY RD 42
&&
AJGPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BINGHAMTON NY
921 PM EDT TUE AUG 11 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0907 PM FLOOD UNION CENTER 42.15N 76.07W
08/11/2020 BROOME NY LAW ENFORCEMENT
FLOODING ON NATICOKE CREEK BRIDGE
&&
MJMPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BINGHAMTON NY
923 PM EDT TUE AUG 11 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0917 PM FLOOD N JOHNSON CITY 42.12N 75.96W
08/11/2020 BROOME NY LAW ENFORCEMENT
MINOR FLOODING REPORTED ON HARRY L DRIVE, BALDWIN
STREET AND OTHER NEARBY ROADS.
&&
MJMPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BINGHAMTON NY
924 PM EDT TUE AUG 11 2020
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0920 PM FLOOD BINGHAMTON 42.10N 75.91W
08/11/2020 BROOME NY LAW ENFORCEMENT
NUMEROUS REPORTS OF URBAN AND UNDERPASS STREET
FLOODING. WATER UP TO THE BOTTOM OF CAR DOOR AT EMMET
STREET UNDERPASS.
&&
MJMSpecial Weather Statement
National Weather Service Binghamton NY
929 PM EDT Tue Aug 11 2020
NYZ045-056-057-062-PAZ039-040-120230-
Chenango NY-Broome NY-Sullivan NY-Delaware NY-Susquehanna PA-
Northern Wayne PA-
929 PM EDT Tue Aug 11 2020
...A LINE OF STRONG THUNDERSTORMS WILL AFFECT...SOUTHERN BROOME...
DELAWARE...SOUTH CENTRAL CHENANGO...NORTHWESTERN SULLIVAN...
NORTHEASTERN SUSQUEHANNA AND NORTHERN WAYNE COUNTIES UNTIL 1030 PM
EDT...
At 929 PM EDT, Doppler radar was tracking strong thunderstorms along
a line extending from Bovina Center to Deposit to near Brackney.
Movement was southeast at 20 mph.
Wind gusts up to 50 mph will be possible with these storms.
Locations impacted include...
Rockland, Binghamton, Vestal, Johnson City, Kirkwood, Conklin,
Jackson, Walton, Delhi and Sanford.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Heavy rainfall is also occurring with these storms, and may lead to
minor flooding. Do not drive your vehicle through flooded roadways.
These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.
&&
LAT...LON 4215 7450 4215 7453 4212 7456 4202 7478
4194 7461 4180 7501 4175 7570 4207 7609
4220 7581 4235 7474 4223 7452 4220 7453
4217 7446
TIME...MOT...LOC 0129Z 314DEG 19KT 4228 7477 4208 7545 4197 7585
MJMThe Binghamton radar (KBGM), 11 km away, was scanning. The volume nearest the first event began at 01:52 UTC.
3 flash flood. Local standard time, as filed.
Heavy thunderstorm rainfall produced flash flooding across Nowlan Road.
Flash flooding was occurring along Conklin Forks Road.
Heavy rainfall produced flash flooding of Belden Brook over Route 79.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in New York in 2020Every state in 2020This day in weather historyWarnings in New York, August 2020
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 917690, 917697, 917703.