A moisture-laden area of low pressure produced 4 to 6 inches of rain in 6 hours in southern New Hampshire.
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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 GYX wrote it up.
A moisture-laden area of low pressure produced 4 to 6 inches of rain in 6 hours in southern New Hampshire.
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 Gray, ME wrote its last area forecast discussion before the first event at Sep 18, 5:46 AM EST, 2 hours 14 minutes earlier.
Area Forecast Discussion National Weather Service Gray ME 646 AM EDT Tue Sep 18 2018 .SYNOPSIS... Heavy rainfall will continue across southern New Hampshire and extreme southwest Maine today due to the remnants of Florence moving through the region. Over central and northern areas mainly dry conditions expected. The system will be fast moving and exit by this evening followed by clearing, cooler and drier air for the mid to latter part of the week as high pressure builds into the region. A more substantial cold front arrives Friday bringing more dry weather and fall like temperatures to the area. && .NEAR TERM /TODAY/... 645AM UPDATE... Have made some adjustments to forecast rainfall and rain chances based on latest radar trends and observations. Lebanon, NH has already reported an inch of rain, so this activity is dropping moderate to heavy rain. It is moving fairly quickly, though, and should be offshore by early afternoon. ORIGINAL DISCUSSION... Axis of rainfall has begun orienting itself such that southern and central portions of New hampshire will likely see the most persistent rainfall, extending eastward into southern Maine. This is occurring along and north of a developing frontal boundary extending eastward from the remnants of tropical system Florence. With a very humid air mass in place, and tropical moisture being advected into the frontal boundary, expect a solid 1 to 3 inches of rainfall within this axis before it moves offshore this evening. Although flash flooding is possible especially if some deeper convection can develop, the threat remains too low for a watch. Temperatures today will be cooler due to cloud cover and rainfall, but will still make the mid 70s in most places. Meanwhile, a cold front drops in from the north later in the day shifting winds to the north and bringing drier air in. && .SHORT TERM /TONIGHT AND WEDNESDAY/... After the cold front moves through, expect cool and dry air to move in from the north. Some showers may linger into Tuesday night or even Wednesday morning. Temperatures will be 10 to 15 degrees colder for highs on Wednesday in the cooler air mass. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... A high amplitude ridge of high pressure builds across the eastern U.S. Wed night and Thu with cool and dry conditions. By Thu night into Fri a return south to southwest flow will increase after the passage of a warm front and then briefly bring a return to warmer temps and higher humidity. By Fri night a strong Canadian cold front associated with a Canadian clipper will move through the area, a few showers will accompany the front. Behind the front a large Canadian ridge of high pressure builds east from the Great Lakes across the northeast with much cooler and drier air making it feel more like fall. The cool dry conditions will last into early next week. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... Short Term... IFR conditions are likely in the heavier rain moving through southern New Hampshire and southern Maine today, but conditions may remain VFR north of this. Should return to VFR tonight or at latest Wednesday morning. Long Term...Mainly VFR except MVFR in scattered showers Thu night through Fri night. && .MARINE... Short Term...Low pressure tracks across southern New England and exits through the Gulf of Maine today. Winds may occasionally gust to 20 or 25 KT but not widespread enough for a Small Craft Advisory. A cold front drops down from the north tonight with northeast winds behind it tonight into Wednesday again gusting to near 25 KT. Long Term...Winds and seas will remain below SCA levels Thu into early Fri. By Fri afternoon an increasing south to southwest flow in advance of an approaching cold front will likely require a SCA. The cold front moves across the waters Fri night with SCA conditions possible for a time over the outer waters behind the cold front as winds become north and then northeast. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && NEAR TERM...Marine SHORT TERM...Marine LONG TERM...Kimble
Hazardous Weather Outlook National Weather Service Gray ME 318 AM EDT Tue Sep 18 2018 MEZ018-023-NHZ007-008-010>015-190730- Interior York-Coastal York-Sullivan-Merrimack-Strafford-Cheshire- Eastern Hillsborough-Interior Rockingham-Coastal Rockingham- Western And Central Hillsborough- 318 AM EDT Tue Sep 18 2018 This Hazardous Weather Outlook is for southwest Maine, New Hampshire, central New Hampshire and southern New Hampshire. .DAY ONE...Today and Tonight. The remnants of Florence are forecast to move through New England today and exit the region by this evening. A stripe of heavy rainfall is likely across southern New Hampshire and extreme southwest Maine today with rainfall mainly in the 1-2 inch range with some locally higher amounts. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to Standard Operating Procedures. MEZ007>009-012>014-019>022-024>028-NHZ001>006-009-190730- Northern Oxford-Northern Franklin-Central Somerset-Southern Oxford- Southern Franklin-Southern Somerset-Interior Cumberland-Androscoggin- Kennebec-Interior Waldo-Coastal Cumberland-Sagadahoc-Lincoln-Knox- Coastal Waldo-Northern Coos-Southern Coos-Northern Grafton- Northern Carroll-Southern Grafton-Southern Carroll-Belknap- 318 AM EDT Tue Sep 18 2018 This Hazardous Weather Outlook is for Maine, south central Maine, southwest Maine, west central Maine, western Maine, central New Hampshire and northern New Hampshire. .DAY ONE...Today and Tonight. No hazardous weather is expected at this time. .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. ANZ150>154-190730- Coastal Waters from Stonington, ME to Port Clyde, ME out 25 NM- Penobscot Bay- Coastal Waters from Port Clyde, ME to Cape Elizabeth, ME out 25 NM- Casco Bay- Coastal Waters from Cape Elizabeth, ME to Merrimack River, MA out 25 NM- 318 AM EDT Tue Sep 18 2018 This Hazardous Weather Outlook is for Atlantic coastal waters. .DAY ONE...Today and Tonight. The remnants of tropical system Florence are expected to pass south of the waters today. Strongest winds are expected to remain south of the coastal waters, but some heavy rain may result in very low visibility south of Cape Elizabeth. .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.
The Boston radar (KBOX), 106 km away, was scanning. The volume nearest the first event began at 13:00 UTC.
2 flash flood, 1 flood. Local standard time, as filed.
A moisture-laden area of low pressure produced 4 to 6 inches of rain in 6 hours resulting in flooding of 4 businesses on Tinkham Avenue in Derry. Seven people were rescued by boat and 15 cars were submerged.
A moisture-laden area of low pressure produced 4 to 6 inches of rain in 6 hours flooding several streets in Milford. Wall, Alder, and Crosby Streets flooded. Mason Rd. near the Wilton town line was severed after a culvert washed away. Ox Brook came out of its bank flooding Melendy Rd.
A moisture-laden area of low pressure produced 4 to 6 inches of rain in 6 hours causing the Souhegan River at Milford to flood briefly. The river crested at 9.17 feet. Flood stage is 9 feet.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in New Hampshire in 2018Every state in 2018This day in weather historyWarnings in New Hampshire, September 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: 782583, 782579, 782586.