Scattered storms developed in a warm, humid airmass to the south of a stalled frontal boundary over southern New York state during the late afternoon and early evening of August 27, 2021. A couple of these storms produced wind damage in the Lower Susquehanna Valley.
Every event with a place to put it. Tap one for its entry below.
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 CTP wrote it up.
Scattered storms developed in a warm, humid airmass to the south of a stalled frontal boundary over southern New York state during the late afternoon and early evening of August 27, 2021. A couple of these storms produced wind damage in the Lower Susquehanna Valley. Flash flooding was also reported in Tioga County near Mansfield.
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 State College, PA wrote its last area forecast discussion before the first event at Aug 27, 1:43 PM EST, 2 hours 22 minutes earlier.
Area Forecast Discussion National Weather Service State College PA 243 PM EDT Fri Aug 27 2021 .SYNOPSIS... Warm, humid, and unsettled weather is expected through the last weekend of August and into early next week. Heavy downpours may produce isolated flooding this afternoon into tonight. Isolated pockets of strong to locally damaging winds may also occur with the greatest risk in the lee of the Allegheny Mountains. We will be measuring and mapping the potential for impacts associated with Hurricane Ida by the middle of next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Slow moving upper trough tracking from the SC Mountains into the Lower Susq Valley this afternoon and evening during peak afternoon heating, helping to pool PW to 2"+ and produce slow moving downpours. Weather risks for this afternoon include potential for flooding downpours and localized strong/damaging wind gusts. Slowly south-sagging surface front along the PA/NY border this afternoon to focus isold to sct shra/tsra north of I80, but we're also concerned for the diurnal maximum of slow moving convection in areas that saw the heaviest rainfall from Henri remnants last weekend. Slow- moving, heavy downpours are possible with localized rainfall amounts of 2+ inches will place the eastern third of CWA at an elevated risk of excessive rainfall due to antecedent conditions (lower FFG, elevated streamflows, above normal soil moisture, and % of normal rainfall in the last 7 days. Radar evolution through mid afternoon confirms earlier thinking that heavy rainfall and slow moving cells would be the primary concern as aforementioned upper trough tracks across my southern counties through this evening. Cells have demonstrated some backbuilding before raining themselves out and throwing down outflow boundaries, similar to Thursday evening, and the lack of shear to maintain cells seems to be a limiting factor for severe. With heavy downpours a certainty as the trough reaches southeast PA due to the very moist and moderately unstable environment, scattered to numerous diurnal pulse t-storms with intense water-loaded downdrafts will be capable of 45-60 mph wind gusts, so we'll be watching for isold svr threat as well (SPC has indicated WW is unlikely). The severe risk should likely subside after 00Z with the loss of heating/sunset. However, heavy downpours may persist through 06Z before coverage/intensity trends decrease after midnight. Partial clearing along with nearly calm winds and plenty of residual low level moisture (especially where it rains) should result in pockets of fog/lower visibility into early Saturday morning. MinT will be +10-15F above climo in the mid 60s to lower 70s. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY/... The aforementioned frontal boundary pivots and becomes quasi- stationary over CPA on Saturday. This pattern should bring noticeably cooler temperatures (-5 to -10F d/d) to the eastern portion of the area. Hires EFS and NBM PPI are once again signaling diurnal convection along the frontal zone but it appears the axis of instability is mainly over the western part of the CWA. The q-stationary/warm front should lift to the north on Sunday and allow for slightly warmer highs and continued risk of PM storms. From a temperature departure perspective, minTs will far outpace MaxT in terms of deviation from climo means. While temperatures will trend a bit cooler on the margin, humidity levels will remain sticky high. No outlooks for severe wx or excessive rainfall through the weekend. As mentioned in the Synopsis, Hurricane Ida is expected to become a major hurricane as it nears the northern Gulf coast late this weekend. We'll be watching Ida's forecast evolution throughout the weekend as its remnants may impact central PA by midweek. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Monday and early Tuesday will see a chance for showers and thunderstorms during the afternoon. Temperatures at the beginning of the week will start warmer than normal, before they trend to about normal for the middle and end of the week. By the end of the week, daytime temperatures and nighttime low temperatures will feel refreshingly cool. Later Tuesday and into Wednesday, models are hinting that there will be a surge of moisture from the remnants of tropical storm Ida that is currently in the gulf. High pressure centered over the Atlantic will guide the moisture to Pennsylvania. The GFS and the Euro are disagreeing on how far northward to bring the moisture. There is complex interaction between the front moving into the area from the northwest Tuesday-Wednesday and the remnants of Ida. The GFS is progressive in bringing moisture as far north at New York, while the Euro keeps the bulk of the moisture just south of Pennsylvania. Recent model trends still hint that moisture will still advect into Pennsylvania, from a combination of Ida moisture and the cold front moving through the region. Will need to continue to watch as the frontal setup will determine just how much moisture makes it into the region. Regardless, showers and thunderstorms likely Tuesday through Wednesday. Tropical moisture appears to leave the region on Thursday as a Canadian High develops and helps to push that moisture to the southeast. That Canadian high pressure and northwest flow will also usher in more seasonal (less hot) temperatures for the start of September. The end of the week and the weekend are looking pleasant at the moment with cooler daytime temperatures and dry weather. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... Showers and storms later today may be a bit more widespread than Thursday, especially across the southeast sites, MDT and LNS. Activity should die down by Midnight. Not much change over the next few days. Outlook... Sat-Tue...AM valley fog. Sct afternoon and evening showers and storms, impacts possible. && .CLIMATE... Meteorological Summer (June-July-August) is tracking in the top 10 at both Harrisburg and Williamsport with very warm nights (avg. minT) contributing more than hot days (avg. maxT). More to come into month-end. && .CTP WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch until 1 AM EDT Saturday for PAZ057-059-065- 066. && SYNOPSIS...DeVoir/Steinbugl NEAR TERM...DeVoir/Steinbugl SHORT TERM...DeVoir/Steinbugl LONG TERM...Gutierrez AVIATION...Gutierrez CLIMATE...
Hazardous Weather Outlook National Weather Service State College PA 445 AM EDT Fri Aug 27 2021 PAZ004>006-010-011-017-024-033-037-280845- Warren-McKean-Potter-Elk-Cameron-Clearfield-Cambria-Somerset-Tioga- 445 AM EDT Fri Aug 27 2021 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...Today and tonight. Locally heavy downpours could lead to isolated flooding this afternoon and evening. .DAYS TWO THROUGH SEVEN...Saturday through Thursday. The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotters are encouraged to report significant hazardous weather. PAZ012-018-019-025>028-034>036-041-042-045-046-049>053-056-058-063- 064-280845- Northern Clinton-Northern Centre-Southern Centre-Blair-Huntingdon- Mifflin-Juniata-Bedford-Fulton-Franklin-Northern Lycoming-Sullivan- Southern Clinton-Southern Lycoming-Union-Snyder-Montour- Northumberland-Columbia-Perry-Schuylkill-Cumberland-Adams- 445 AM EDT Fri Aug 27 2021 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...Today and tonight. Locally heavy downpours could lead to isolated flooding this afternoon and evening. An isolated strong to locally damaging thunderstorm wind gust is possible this afternoon and early evening. .DAYS TWO THROUGH SEVEN...Saturday through Thursday. The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotters are encouraged to report significant hazardous weather. PAZ057-059-065-066-280845- Dauphin-Lebanon-York-Lancaster- 445 AM EDT Fri Aug 27 2021 ...FLASH FLOOD WATCH IN EFFECT FROM 1 PM EDT THIS AFTERNOON THROUGH LATE TONIGHT... This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...Today and tonight. Please listen to NOAA Weather Radio or go to weather.gov/StateCollege on the internet for more information about the following hazards. Flash Flood Watch. In addition to the flash flood threat, an isolated strong to locally damaging thunderstorm wind gust is possible this afternoon and early evening. .DAYS TWO THROUGH SEVEN...Saturday through Thursday. The probability for widespread hazardous weather is low. .SPOTTER INFORMATION STATEMENT... Spotters are encouraged to report significant hazardous weather. MRS
Special Weather Statement
National Weather Service State College PA
310 PM EDT Fri Aug 27 2021
PAZ065-066-271945-
Lancaster PA-York PA-
310 PM EDT Fri Aug 27 2021
...A strong thunderstorm will impact portions of west central
Lancaster and central York Counties through 345 PM EDT...
At 309 PM EDT, Doppler radar was tracking a strong thunderstorm over
Hallam, moving northeast at 10 mph.
HAZARD...Wind gusts up to 50 mph and pea size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
Locations impacted include...
Elizabethtown, Columbia, Mount Joy, East York, Stonybrook-Wilshire,
Salunga-Landisville, Maytown, Hallam, Marietta, Wrightsville,
Yorklyn, Rheems, Mount Wolf, Bainbridge, Yorkana and Elizabethtown
College.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Very heavy rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.
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.
This storm 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 4000 7672 4015 7668 4017 7666 4017 7664
4019 7661 4019 7658 4011 7636 3995 7660
TIME...MOT...LOC 1909Z 207DEG 9KT 4002 7663
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH
Gutierrez/EvanegoSpecial Weather Statement
National Weather Service State College PA
337 PM EDT Fri Aug 27 2021
PAZ028-056-272015-
Perry PA-Juniata PA-
337 PM EDT Fri Aug 27 2021
...A strong thunderstorm will impact portions of west central Juniata
and west central Perry Counties through 415 PM EDT...
At 337 PM EDT, Doppler radar was tracking a strong thunderstorm near
Colonel Denning State Park, moving east at 10 mph.
HAZARD...Wind gusts up to 50 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
Honey Grove, Spruce Hill, Loysville, Walnut, Blain and Landisburg.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Very heavy rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.
&&
LAT...LON 4031 7749 4041 7757 4055 7747 4035 7724
TIME...MOT...LOC 1937Z 265DEG 7KT 4035 7747
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH
EvanegoSpecial Weather Statement
National Weather Service State College PA
413 PM EDT Fri Aug 27 2021
PAZ037-272045-
Tioga PA-
413 PM EDT Fri Aug 27 2021
...A strong thunderstorm will impact portions of east central Tioga
County through 445 PM EDT...
At 412 PM EDT, Doppler radar was tracking a strong thunderstorm over
Covington, moving southeast at 10 mph.
HAZARD...Wind gusts up to 50 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
Mansfield, Wellsboro, Blossburg, Covington, Arnot, Roseville and
Mansfield University.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Very heavy rainfall is also occurring with this slow moving storm
and may lead to localized flooding. Do not drive your vehicle
through flooded roadways.
&&
LAT...LON 4185 7690 4165 7689 4166 7728 4171 7742
4178 7741 4187 7726 4188 7710
TIME...MOT...LOC 2012Z 301DEG 8KT 4175 7712
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH
ColbertSpecial Weather Statement
National Weather Service State College PA
502 PM EDT Fri Aug 27 2021
PAZ064-065-272130-
York PA-Adams PA-
502 PM EDT Fri Aug 27 2021
...A strong thunderstorm will impact portions of southeastern Adams
and southwestern York Counties through 530 PM EDT...
At 502 PM EDT, Doppler radar was tracking a strong thunderstorm near
Parkville, moving northeast at 30 mph.
HAZARD...Wind gusts up to 50 mph.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
York, Hanover, Weigelstown, Parkville, Spry, Dallastown, Shiloh, West
York, Codorus, Grantley, Tyler Run-Queens Gate, McSherrystown, Spring
Grove, Glen Rock, Pennville, Jacobus, East Berlin, Yoe, York Airport
and Loganville.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Very heavy rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.
&&
LAT...LON 4001 7696 3992 7661 3972 7681 3972 7706
TIME...MOT...LOC 2102Z 205DEG 24KT 3981 7690
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH
ColbertThe Binghamton radar (KBGM), 102 km away, was scanning. The volume nearest the first event began at 21:02 UTC.
4 thunderstorm wind, 1 flash flood. Local standard time, as filed.
Water was reported over the road near US 6 and Roseville Road.
A severe thunderstorm producing winds estimated near 60 mph knocked down several trees, severely damaged several outbuildings, and produced roof damage to two barns along Devonshire Heights Road in West Hanover Township.
A severe thunderstorm producing winds estimated near 60 mph knocked down a tree onto wires south of Willow Street.
A severe thunderstorm producing winds estimated near 60 mph knocked down trees onto wires near Leacock.
A severe thunderstorm producing winds estimated near 60 mph knocked down a tree onto wires east of Lancaster.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2021Every state in 2021This day in weather historyWarnings in Pennsylvania, August 2021
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: 976354, 973678, 973674, 973675, 973676.