A vigorous upper level disturbance that brought damaging thunderstorms across Ontario province moved into northern NY during the early morning hours. Damaging winds were centered near Potsdam/Canton but other isolated wind damage occurred as well.
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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 BTV wrote it up.
A vigorous upper level disturbance that brought damaging thunderstorms across Ontario province moved into northern NY during the early morning hours. Damaging winds were centered near Potsdam/Canton but other isolated wind damage occurred as well.
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 Burlington, VT wrote its last area forecast discussion before the first event at Jul 8, 2:24 AM EST, 1 hour 33 minutes earlier.
Area Forecast Discussion National Weather Service Burlington VT 324 AM EDT Sat Jul 8 2017 .SYNOPSIS... An upper level disturbance across the eastern Great Lakes will track eastward allowing showers to redevelop across northern New York toward daybreak, and across Vermont during Saturday morning. A few embedded thunderstorms are possible, and portions of central and eastern Vermont may see a stronger storm or two with hail and gusty winds before activity exits eastward during Saturday afternoon. A cold front will sweep across the North Country Saturday afternoon with partial clearing and drier conditions late in the day. Slight cooler temperatures and lower humidity levels are expected on Sunday. && .NEAR TERM /THROUGH TONIGHT/... As of 201 AM EDT Saturday...Shower and thunderstorm activity continues across Ontario and southern Quebec along weak surface trough extending towards Buffalo and Lake Erie. Over the North Country, a break in clouds has allowed for fog development, especially in areas that received greater amounts of precipitation during the day. This trend will continue into the early morning hours before mid level shortwave approaches from southeastern Ontario. This stronger shortwave trough is evident in IR imagery and will result in redevelopment of shower activity toward daybreak across nrn NY, and across much of VT 12-18Z Saturday. Anticipate an additional 0.25-0.5" with this activity. May see a few embedded convective elements with a few rumbles of thunder. Though deep-layer shear is stronger tomorrow (sfc-6km bulk shear near 40kts), timing is a bit off (early) for a significant severe threat. Best chances for stronger storms should be central/ern VT where atmosphere may begin to destabilize before passage of sfc cold front during the early aftn. We'll need to monitor that potential in ern VT, but otherwise the early timing and widespread cloudiness should limit overall instability across most of the North Country tomorrow. Localized hail/wind threat should be limited to central/ern VT. Then, should see clearing from west-east later Saturday aftn, with drier air on nw low-level flow during the evening and overnight hours Saturday night. High temperatures on Saturday generally a few degrees cooler, mainly in the mid-upr 70s. Lows Saturday night expected to fall back into the mid 50s. && .SHORT TERM /SUNDAY THROUGH MONDAY/... As of 321 AM EDT Saturday...Large scale picture shows mid/upper level trof prevailing across the northern lakes into the ne conus during this time period. The fast westerly flow aloft will remain active with embedded 5h vorts and ribbons of enhanced 850 to 500mb rh...crossing from west to east. This will produce an unsettled pattern with chances for showers both Sunday and Monday...but given the lack of significant pws and limited instability svr and widespread heavy rainfall not anticipated. Both NAM/GFS show first vort on Sunday midday, followed by another one on Monday. Instability ranges from 300 to 700 j/kg with highest values pooling across the SLV and parts of the northern CPV...so a rumble or two of thunder is possible in any stronger convective elements. Progged 850mb temps cool to 10c by Sunday behind boundary today...combined with some clouds support highs mainly in the 70s areawide. The areal coverage of clouds will play a big factor in overnight lows on Sunday night...but thinking clouds hang tough and will trend toward warmer guidance...mid 50s to l/m 60s. Little change in thermal profiles expected on Monday with highs climbing back into the 70s...maybe a few lower 80s southern SLV/CPV with more sun. Bottom line...not expecting a complete washout either day...but several rounds of scattered showers could but a damper on outside activities at times. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... As of 321 AM EDT Saturday...A fast westerly flow aloft continues across our region for Tuesday into Weds...as a surface cold front swings from west to east. Once again this front seems to pass in several pieces with limited low level convergence and upper level dynamics not aligning with boundary or surface instability. Like many previous boundaries this summer...expecting scattered to numerous showers/storms to develop on Tuesday...but magnitude of convection should be limited. Latest guidance indicates sfc based cape values climbing between 600-1000 j/kg...especially slv...with pws only 1.20 to 1.40 and some increasing shear as 500mb winds approach 40 knots. Plenty of uncertainty develops on Thursday into Friday...with limited run to run consistency and plenty of spread between the different solutions. Thinking 1022mb high pres will build behind boundary for Weds into Thurs...suppressing our the heat/humidity...along with higher pws values to our south. Thinking boundary will push into the mid Atlantic states by Weds...while cool and dry northerly flow prevails across our cwa...as advertised by the 00z Ecmwf. Have cut superblend pops by 20 to 30%...during this time period...but continue to place a token chance pops in forecast given uncertainty. Temps with lower humidity values and northerly flow will range mainly in the upper 60s to mid/upper 70s with lows mainly in the 40s mountains to mid/upper 50s valleys. Of course if the front stalls across our region during this time period...much higher humidity values and warmer temps along with greater chances for rain will need to be added to the forecast. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... Through 06Z Sunday...Mixed flight conditions dependent on precipitation received during the daytime hours. IFR-VLIFR conditions will bounce between these categories through sunrise at all but KBTV. KBTV is holding onto VFR conditions at 06Z but expect MVFR to possible IFR conditions to develop centered around 08Z-10Z this morning. Have TEMPO'd this as KBTV only received 0.10 inch precip Friday. A strong mid-level trough approaching from the eastern Great Lakes and an associated cold front will bring an additional period of showers during the mid morning hours through midday. Can't rule out a few embedded rumbles of thunder. Intervals of MVFR conditions possible areawide during 12-20Z Saturday. Outside of showery activity expect VFR conditions into Saturday evening. Fog development possible Saturday night into Sunday morning as clouds look to clear overnight. Outlook... Sunday: VFR. Breezy. Chance SHRA. Sunday Night: VFR. Chance SHRA. Monday: VFR. Chance SHRA...Slight Chance TSRA. Monday Night: VFR. Chance SHRA...Slight Chance TSRA. Tuesday: VFR. Likely SHRA...Slight Chance TSRA. Tuesday Night: VFR. Chance SHRA...Slight Chance TSRA. Wednesday: VFR. NO SIG WX. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && SYNOPSIS...Banacos NEAR TERM...Banacos/KGM SHORT TERM...Taber LONG TERM...Taber AVIATION...KGM
Hazardous Weather Outlook National Weather Service Burlington VT 419 AM EDT Sat Jul 8 2017 NYZ026>031-087-VTZ001-002-090930- Northern St. Lawrence-Northern Franklin-Eastern Clinton- Southeastern St. Lawrence-Southern Franklin-Western Clinton- Southwestern St. Lawrence-Grand Isle-Western Franklin- 419 AM EDT Sat Jul 8 2017 This Hazardous Weather Outlook is for northern New York and northern portions of the Champlain Valley in northwest Vermont. .DAY ONE...Today and Tonight. Showers and thunderstorms will develop across the Saint Lawrence Valley, moving across the Adirondacks and Champlain valley throughout the morning, before continuing across Vermont during the midday. Cloud to ground lightning and periods of heavy rainfall are expected to be the primary threats. .DAYS TWO THROUGH SEVEN...Sunday through Friday. No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. NYZ034-035-VTZ003>012-016>019-090930- Western Essex-Eastern Essex-Orleans-Essex-Western Chittenden- Lamoille-Caledonia-Washington-Western Addison-Orange-Western Rutland- Windsor-Eastern Franklin-Eastern Chittenden-Eastern Addison- Eastern Rutland- 419 AM EDT Sat Jul 8 2017 This Hazardous Weather Outlook is for northern New York, central Vermont, northeast Vermont, northwest Vermont and southern Vermont. .DAY ONE...Today and Tonight. Showers and thunderstorms will develop across the Saint Lawrence Valley, moving across the Adirondacks and Champlain valley throughout the morning, before continuing across Vermont during the midday. A few stronger storms are possible, containing gusty winds and small hail, in addition to dangerous cloud-to-ground lightning and heavy downpours. .DAYS TWO THROUGH SEVEN...Sunday through Friday. No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
Special Weather Statement
National Weather Service Burlington VT
348 AM EDT SAT JUL 8 2017
NYZ026-029-087-080845-
Northern St. Lawrence-Southeastern St. Lawrence-Southwestern St.
Lawrence-
348 AM EDT SAT JUL 8 2017
...A LINE OF STRONG THUNDERSTORMS WILL AFFECT ST. LAWRENCE COUNTY...
At 348 AM EDT, radar indicated strong thunderstorms were located
along a line extending from 9 miles north of Kring Point State Park
to near Redwood. Movement was east at 30 mph.
Winds in excess of 40 mph and dime size hail are possible with these
storms.
Locations impacted include...
Potsdam, Gouverneur, Canton, Ogdensburg, Norfolk, Oswegatchie,
Lisbon, De Kalb, Fowler, Colton, Morley, Degrasse, Richville,
Hammond, Cranberry Lake, Madrid, Rensselaer Falls, Norwood,
Edwardsville and Hermon.
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
LAT...LON 4441 7579 4442 7579 4442 7581 4443 7579
4443 7577 4444 7579 4444 7577 4445 7576
4445 7578 4447 7577 4447 7579 4451 7575
4468 7552 4483 7488 4413 7470 4420 7541
4437 7580 4441 7584
TIME...MOT...LOC 0748Z 263DEG 27KT 4451 7588 4426 7586The Ft Drum radar (KTYX), 102 km away, was scanning. The volume nearest the first event began at 08:57 UTC.
6 thunderstorm wind. Local standard time, as filed.
Numerous trees and wires downed by thunderstorm winds.
Numerous trees and wires downed by thunderstorm winds.
Numerous trees and wires downed by thunderstorm winds.
Numerous trees and wires downed by thunderstorm winds.
Numerous trees and wires downed by thunderstorm winds in Duane.
Trees down on Algiers Road and boat overturned on Lake Champlain.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in New York in 2017Every state in 2017This day in weather historyWarnings in New York, July 2017
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: 702285, 702286, 702288, 702289, 702290, 702291.