A weak warm front pushed north of the region allowing a hot and unstable airmass to move into southern New Hampshire. A weak mid-level shortwave moved across the state during the day which increased the shear and mid-level lapse rates.
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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 weak warm front pushed north of the region allowing a hot and unstable airmass to move into southern New Hampshire. A weak mid-level shortwave moved across the state during the day which increased the shear and mid-level lapse rates. A few storms developed by late afternoon across southern New Hampshire with one particular cluster of storms in Hillsborough county becoming severe.
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 Aug 24, 11:25 AM EST, 2 hours 25 minutes earlier.
Area Forecast Discussion National Weather Service Gray ME 1225 PM EDT Mon Aug 24 2020 .SYNOPSIS... Scattered showers and thunderstorms will develop today and again Tuesday before a cold front moves offshore. Behind the front relative humidity levels will drop and winds will become gusty at times. High pressure builds in for midweek before rain chances return for the end of the work week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Noon update... have adjusted pops, bringing higher amounts further south into NH later this afternoon in line with radar trends in VT. While mainly stratiform at this point along the Canadian border starting to see a few cells pop ahead of the main precip shield. Expect these scattered storms to increase in coverage over the afternoon. 930am update... Have adjusted the PoPs to reflect current radar trends. Added gusty winds to the thunder areas for this afternoon and increased fog areas for the midcoast tonight. 715 AM Update... A few showers are continuing to fall over the mountains this morning. Fog is improving already with only a couple sites at or below a quarter mile. This should briefly turn to haze before clearing out completely. There is still a great deal of cloud cover and this will continue as convection arrives from the west and fires ahead of and along a boundary. Not much change to the forecast which covers the current situation well. Previous discussion... Surface analysis showed a weak frontal boundary across northern sections this morning. A subtle short wave was poised to move into the area, and this was supporting a cluster of showers and thunderstorms moving through VT and into NH presently. Area soundings show an inversion around 1kft, and this was keeping moisture trapped in the lower levels closer to the coast. Fog and stratus have increased as a result for much of the coastal plain, and this should gradually improve after daybreak. Expect convection to continue this morning, becoming more widespread later today with daytime heating and forcing for ascent increasing gradually. Deep layer westerly flow of about 30 kts should support some isolated to scattered storms this afternoon, a few of which may have gusty winds and heavy rainfall. Temperatures will range from the lower to upper 70s north and east, to the mid 80s to lower 90s south and west. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... We remain in the warm sector overnight tonight with onshore flow increasing ahead of a pre-frontal trough. This should result in another round of stratus and fog, especially for the Mid Coast, but also extending inland. We may see some drizzle as well in the Rockland area. Overnight lows will be warm as a result. Tuesday will be another warm and active day weather-wise. A relatively strong cold front for this time of year moves through during the day Tuesday and should be offshore by the late afternoon. Due to widespread stratus and fog ahead of the front and ongoing WAA showers in the morning, the potential for severe storms is unsure. However, a strong wind field throughout the column could be brought to the surface easily at times with heavy rainfall. SPC has kept us in slight risk due to this and also the likelihood of fast moving storms, making wind damage that much easier. We will see more very localized but quickly accumulating rainfall, and may see some flash flooding if training occurs. Residual showers will continue into the evening in upslope flow and with cyclonic flow aloft. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... A cold front will be pushing well southeast of the area Tuesday evening with cooler and drier air working into the region on northwest flow overnight. Dry northwest flow continues Wednesday as low pressure stalls over the Canadian Maritimes and high pressure remains centered to our west. Flow aloft becomes zonal the second half of the week with a weak low pressure system passing over southern New England late Thursday into Friday morning. An upper trough will approach from the west this weekend that has potential to bring beneficial rain, especially if it can draw moisture from the remnants TC Laura into the region. Temperatures will run well below normal to start the forecast period and generally run below normal through the weekend. Tuesday night will be cool and dry under northwest flow with lows ranging from the low 40s in northern valleys to mid 50s along the coastal plain. Dry northwest winds continue Wednesday with plenty of sunshine and highs ranging from the 70s south of mountains to near 60 near the international border. Weak low pressure will dive southeast from the Great Lakes towards southern New England Thursday. This system will bring low chances for showers primarily to SW New Hampshire as the bulk of the precipitation passes to our south. Going into the weekend attention turns to a short wave approaching the Great Lakes as the remnants of TC Laura move towards the Ohio Valley. Global models in the 00Z model suite are at odds with each other in the strength of the approaching short wave and the northward extent of moisture from Laura. The ECMWF and CMC show that there is potential for widespread beneficial rain from these features over the weekend while the GFS is drier with a weaker trough and moisture restricted to our south. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... Short Term...IFR/LIFR in stratus, fog, and -TSRA will improve later this morning, however showers and thunderstorms will become more widespread as the day goes on, resulting in MVFR conditions possible everywhere. Expect another night of fog and stratus tonight into tomorrow morning, especially for western ME, with drizzle possible at KRKD in onshore flow. A cold front will cross during the day Tuesday and move offshore by Tuesday late afternoon. +TSRA is likely for all terminals during this time. NW winds will pickup behind the front Tuesday evening. Long Term...Mainly VFR into Friday. NW winds will gust to 20 mph at times Wednesday. && .MARINE... Short Term...Winds and seas will increase but remain just shy of SCA conditions Tuesday with a cold front crossing the waters in the later afternoon and evening. Fog and stratus will improve later this AM, but another round is likely tonight into Tuesday morning with very poor visibility for the waters. Long Term...NW winds will remain elevated Tuesday night into Wednesday with gusts to 25 kts at times. Winds relax Thursday and seas will be 5 ft or less. && .FIRE WEATHER... NW winds will become gusty at times behind a cold frontal passage Tuesday and Wednesday. Gusts could reach 30 mph in the higher terrain. RH values will begin to fall behind the front, resulting in minimum RH values between 30 and 45% Wednesday afternoon. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && SYNOPSIS... NEAR TERM...Curtis SHORT TERM...Hanes LONG TERM...Schroeter AVIATION... MARINE... FIRE WEATHER...
Hazardous Weather Outlook National Weather Service Gray ME 945 AM EDT Mon Aug 24 2020 MEZ007>009-012>014-018>028-033-NHZ001>015-251345- Northern Oxford-Northern Franklin-Central Somerset-Southern Oxford- Southern Franklin-Southern Somerset-Interior York- Central Interior Cumberland-Androscoggin-Kennebec-Interior Waldo- Coastal York-Coastal Cumberland-Sagadahoc-Lincoln-Knox-Coastal Waldo- Interior Cumberland Highlands-Northern Coos-Southern Coos- Northern Grafton-Northern Carroll-Southern Grafton-Southern Carroll- Sullivan-Merrimack-Belknap-Strafford-Cheshire-Eastern Hillsborough- Interior Rockingham-Coastal Rockingham- Western And Central Hillsborough- 945 AM EDT Mon Aug 24 2020 This Hazardous Weather Outlook is for Maine, south central Maine, southwest Maine, west central Maine, western Maine, New Hampshire, central New Hampshire, northern New Hampshire and southern New Hampshire. .DAY ONE...Today and Tonight. Scattered strong thunderstorms will develop today. A few storms may develop damaging winds, hail, and heavy rainfall. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. Tuesday a cold front will cross the region with a final round of strong to severe thunderstorms. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. ANZ150>154-251345- 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- 945 AM EDT Mon Aug 24 2020 This Hazardous Weather Outlook is for Atlantic coastal waters. .DAY ONE...Today and Tonight. Scattered thunderstorms with gusty winds are expected this afternoon. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. Scattered thunderstorms with gusty winds are expected Tuesday afternoon. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
Special Weather Statement National Weather Service Gray ME 120 PM EDT Mon Aug 24 2020 MEZ009-014-021-241745- Southern Somerset-Kennebec-Central Somerset- 120 PM EDT Mon Aug 24 2020 ...A STRONG THUNDERSTORM WILL AFFECT SOUTHEASTERN SOMERSET COUNTY... At 120 PM EDT, a strong thunderstorm was located near Madison, or 12 miles northwest of Skowhegan, moving east at 40 mph. Winds in excess of 40 mph and pea size hail are possible with this storm. Locations impacted include... Skowhegan, Madison, Anson, Canaan, Hartland, Cornville, Athens, Embden, Harmony, Solon, New Portland, Concord and Lexington. LAT...LON 4487 7005 4497 7000 4496 6946 4471 6955 TIME...MOT...LOC 1720Z 283DEG 36KT 4489 6990 Watson
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</html>The Boston radar (KBOX), 136 km away, was scanning. The volume nearest the first event began at 18:50 UTC.
5 hail, 4 thunderstorm wind. Local standard time, as filed.
Damaging outflow winds associated with a severe thunderstorm downed multiple trees near Burt Hill Road.
Damaging outflow winds associated with a severe thunderstorm downed multiple trees just east of Goffstown.
Trees down near the Everett Turnpike in Litchfield.
Quarter size hail reported in Hudson.
Quarter size hail was reported near Hudson New Hampshire.
Half dollar size hail reported just south of Auburn.
Half dollar size hail in Derry.
Quarter size hail in Derry.
Damaging outflow winds associated with a severe thunderstorm downed multiple trees near Bow Center Road.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in New Hampshire in 2020Every state in 2020This day in weather historyWarnings in New Hampshire, 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 2026-09-30. Each event’s entry at NCEI: 919115, 919114, 919111, 919112, 919113, 919109, 919108, 919106, 919116.