A pre-frontal trough moved across southern Ontario during the overnight and pre-dawn hours with weak forcing brushing areas close to the Canadian border. A cluster of storms developed over the western end of Lake Ontario and maintained intensity as they crossed the lake, likely due to better nocturnal instability over the very warm lake waters.
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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 BUF wrote it up.
A pre-frontal trough moved across southern Ontario during the overnight and pre-dawn hours with weak forcing brushing areas close to the Canadian border. A cluster of storms developed over the western end of Lake Ontario and maintained intensity as they crossed the lake, likely due to better nocturnal instability over the very warm lake waters. Outflow from these storms came onshore near Stony Point and Sackets Harbor with greater than 40 knots velocity and a still elevated core. This core came down as the storms approached Jefferson County. The storms quickly weakened as they moved onshore and away from the warm waters of Lake Ontario.
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 Buffalo, NY wrote its last area forecast discussion before the first event at Aug 7, 3:22 AM EST, 36 minutes earlier.
Area Forecast Discussion National Weather Service Buffalo NY 422 AM EDT Tue Aug 7 2018 .SYNOPSIS... A broken line of showers and thunderstorms will continue across the area this morning ahead of a weak cold front. By this afternoon the best thunderstorm threat shifts east of the area while a few scattered showers and rumbles of thunder form along lake breeze boundaries. More unsettled weather is expected on Wednesday when a mid level disturbance will pass over the region. Temperatures through the rest of the work week will remain near to slightly above normal. && .NEAR TERM /THROUGH TONIGHT/... A belt of deep subtropical moisture with PW values around 2 inches will advect across the region early this morning while under the broad synoptic lift in the right entrance region of an upper-level jet streak. A broken line of showers will move across the region from west to east in the pre-dawn hours, with scattered thunder also expected. As we near sunrise, this line of showers will push east of the Genesee Valley and into the North country, while also losing a bit of their steam as the upper-level forcing pulls off to the northeast. Otherwise, it is a warm and muggy morning with temperatures mainly in the lower 70s. Shower coverage will taper off from northwest to southeast during the course of the morning as the aforementioned ribbon of deep layer moisture ahead of the approach front shifts to our east, and slightly drier mid-level air works its way in across the region. Lingering low-level moisture will give way to a blossoming diurnal cumulus field as lake breeze boundaries develop inland by midday. The westerly flow in place will develop a typical convergent boundary between Lake Erie and Ontario from Niagara County east- southeastward toward Ontario county, which will provide the focus for some scattered afternoon showers and a few rumbles of thunder. Otherwise, the North Country will remain largely dry, and likewise downstream of Lake Erie from Buffalo south across the far western Southern Tier. Meanwhile, inland across Cattaraugus and Allegany counties, the combination of the lingering pre-frontal boundary and the Lake Erie breeze pushing inland should help develop some scattered showers and thunderstorms there this afternoon as well. In regards to severe potential, the overall threat is minimal but non- zero, with a few isolated wind damage reports not out of the question. The best locations for any severe threat would be across the Cattaraugus and Allegany counties, as well as along the convergence zone as it dives into Ontario County. It will remain humid today, but not quite as warm as temperatures should top out in the low to mid 80s. This will be some five degrees lower than that of Monday. Tonight, any lingering convection will quickly diminish after sunset. The low-level moisture will remain in place, making for another muggy night, although overnight lows will dip into the upper 60s. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... A mid level shortwave will move from Lower Michigan to southern Ontario on Wednesday, with associated forcing supporting the development of a weak wave of low pressure along an east/west oriented frontal zone over Ohio and PA. There are still differences in track and timing details of this frontal wave in the latest 00Z model guidance, but in a general sense it will cross the region from west to east during the day Wednesday. Model consensus places the best juxtaposition of moisture and forcing across the western Southern Tier and western Finger Lakes, where the greatest chances for rain and scattered thunderstorms will be found, with lower chances near the Canadian border. The increase in cloud cover and showers will keep temperatures down somewhat, with upper 70s to lower 80s on the lake plains, and lower to mid 70s for the higher terrain. Showers and scattered thunderstorms associated with the frontal wave will end from northwest to southeast late Wednesday afternoon and evening as an area of drier air in the mid levels and a weak surface ridge builds into the eastern Great Lakes. Expect lows in the mid 60s on the lake plains, and around 60 for the Southern Tier valleys and Lewis County. Thursday the latest 00Z model guidance has moved up the timing of the next mid level shortwave and associated weak surface cold front, moving it into the eastern Great Lakes by Thursday afternoon. This system will be lacking deep mid level moisture, and boundary layer moisture will also be somewhat lower than recent days as surface dewpoints drop into the mid 60s. Despite the negatives, the combination of the approaching trough and added convergence from lake breeze boundaries may be enough to support a few widely scattered showers and thunderstorms during the afternoon. A few of these may continue into Thursday night as the trough crosses our region, and the warm lake waters may support some nocturnal convection over and just east of Lakes Erie and Ontario. Temperatures will trend warmer again on Thursday, with highs in the mid 80s on the lake plains and upper 70s on the hills. Lows Thursday night will range from the mid to upper 60s on the lake plains to around 60 for the Southern Tier and Lewis County. && .LONG TERM /FRIDAY THROUGH MONDAY/... Late this week through early next week looks quite unsettled as a frontal zone stalls over or just south of our area. A mid level trough approaching the Upper Great Lakes Friday will deepen into a mid level closed low over the weekend from the central Great Lakes to the Ohio Valley. This closed low will maintain weak forcing across our region and support a continued feed of moisture from the Ohio Valley, and eventually the Atlantic Ocean by early next week. The close proximity of at least weak forcing and sufficient moisture will maintain a chance of showers and thunderstorms each day from Friday through Monday. Expect much of the convection to be diurnally driven, with a peak in coverage during the afternoon and evening each day. It should be noted that despite a chance of rain in the forecast every day, much of this will likely be scattered in nature with plenty of rain free time. Temperatures aloft remain quite warm through the period, with 850mb temps running around +16C. The resulting surface high temperatures will depend greatly on the extent of clouds and showers each day. If enough sun is realized, highs will reach the low to mid 80s on the lake plains and upper 70s on the hills, with lows generally in the 60s. && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... Mainly VFR conditions will prevail through the TAF period, with a few exceptions. A broken line of showers and few thunderstorms continues to move across the region early this morning with localized MVFR/IFR restrictions. Coverage will decrease by mid- morning, with more scattered showers and thunderstorms developing inland from the lake breezes this afternoon. Most TAF sites will see low VFR conditions in the 3.5 to 5 kft range, with KJHW will be most likely to see a period of MVFR CIGS around 2.5 kft this morning. Outlook... Tonight...Mainly VFR with a chance of showers...and MVFR/IFR in patchy fog. Wednesday...Mainly VFR with scattered showers and thunderstorms. Thursday...VFR. Friday and Saturday...Mainly VFR. A chance of showers and thunderstorms with brief/local MVFR. && .MARINE... A line of thunderstorms will move across the east end of Lake Ontario and up the Saint Lawrence River this morning. While any of these storms could prompt special marine warnings, general winds and their associated waves will remain below small craft advisory criteria. For the rest of today, ongoing convection at the start of the day will gradually push east away from the lakes during the midday and afternoon. Otherwise, moderate to occasionally fresh southwesterlies will be found at the east ends of both lakes, but conditions should remain below Small Craft Advisory criteria. Winds will then become light with negligible waves across the Lower Great Lakes Tuesday night and Wednesday. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && SYNOPSIS...Church NEAR TERM...Church SHORT TERM...Hitchcock LONG TERM...Hitchcock AVIATION...Church MARINE...Church
Hazardous Weather Outlook National Weather Service Buffalo NY 553 PM EDT Mon Aug 6 2018 NYZ001>008-010>014-019>021-085-072200- Niagara-Orleans-Monroe-Wayne-Northern Cayuga-Oswego-Jefferson-Lewis- Northern Erie-Genesee-Wyoming-Livingston-Ontario-Chautauqua- Cattaraugus-Allegany-Southern Erie- 553 PM EDT Mon Aug 6 2018 This Hazardous Weather Outlook is for western and north central New York. .DAY ONE...Tonight. The probability of widespread hazardous weather is low. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. Scattered thunderstorms are expected on Tuesday. There is a marginal risk that a few of these storms may contain strong, gusty winds. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. This product, along with other watches, warnings, advisories, and statements issued by the National Weather Service office in Buffalo can be found on the internet at http://www.weather.gov/buf LEZ020-040-041-LOZ042>045-062>065-SLZ022-024-072200- Upper Niagara River and Buffalo Harbor- Lake Erie nearshore waters from Ripley to Dunkirk- Lake Erie nearshore waters from Dunkirk to Buffalo- Lake Ontario nearshore waters from the Niagara River to Hamlin Beach- Lake Ontario nearshore waters from Hamlin Beach to Sodus Bay- Lake Ontario nearshore waters from Sodus Bay to Mexico Bay- Lake Ontario nearshore waters from Mexico Bay to the Saint Lawrence River- Lake Ontario open waters from the Niagara River to Hamlin Beach- Lake Ontario open waters from Hamlin Beach to Sodus Bay- Lake Ontario open waters from Sodus Bay to Mexico Bay- Lake Ontario open waters from Mexico Bay to the Saint Lawrence River- Saint Lawrence River from Cape Vincent to Ogdensburg- Saint Lawrence River from Ogdensburg to Saint Regis- 553 PM EDT Mon Aug 6 2018 This Hazardous Weather Outlook is for portions of Lake Erie, Lake Ontario and Saint Lawrence River. .DAY ONE...Tonight. The probability of widespread hazardous weather is low. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. Scattered thunderstorms are expected on Tuesday. There is a marginal risk that a few of these storms may contain strong, gusty winds and locally higher waves. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. This product, along with other watches, warnings, advisories, and statements issued by the National Weather Service office in Buffalo can be found on the internet at http://www.weather.gov/buf
Special Weather Statement
National Weather Service Buffalo NY
414 AM EDT TUE AUG 7 2018
NYZ007-070915-
Jefferson-
414 AM EDT TUE AUG 7 2018
...A LINE OF STRONG THUNDERSTORMS APPROACHING JEFFERSON COUNTY...
At 414 AM EDT, radar indicated strong thunderstorms were located
along a line extending from 12 miles west of Cedar Point State Park
to 15 miles northwest of Oswego. Movement was northeast at 35 mph.
Wind gusts up to 50 mph are possible with these storms.
Locations impacted include...
Watertown, Stony Point, Clayton, Adams, Dexter, Glen Park, Kring
Point State Park, Adams Center, Henderson Harbor and Wellesley Island
State Park.
This includes Interstate 81 between exits 39 and 52.
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.
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 4440 7583 4372 7585 4368 7626 4378 7629
4383 7636 4387 7635 4384 7645 4387 7650
4391 7650 4396 7644 4396 7634 4402 7636
4405 7642 4410 7643 4414 7635 4420 7631
4422 7619 4424 7617 4429 7615 4440 7586
TIME...MOT...LOC 0814Z 247DEG 32KT 4421 7644 4365 7666
HitchcockThe Ft Drum radar (KTYX), 38 km away, was scanning. The volume nearest the first event began at 08:54 UTC.
1 thunderstorm wind. Local standard time, as filed.
A large tree was reported down across Ridge Road between Route 3 and 75.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in New York in 2018Every state in 2018This day in weather historyWarnings in New York, August 2018
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: 781518.