A severe thunderstorm impacted the Laurel Highlands and localized flooding impacted the city of Altoona during the afternoon of July 1, 2023. Scattered thunderstorm developed in a modest CAPE environment (1000-1500 J/kg) and modest shear environment ahead of an approaching mid-level trough.
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The episode as NWS CTP wrote it up.
A severe thunderstorm impacted the Laurel Highlands and localized flooding impacted the city of Altoona during the afternoon of July 1, 2023. Scattered thunderstorm developed in a modest CAPE environment (1000-1500 J/kg) and modest shear environment ahead of an approaching mid-level trough.
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 Jul 1, 2:29 PM EST, 1 hour 21 minutes earlier.
Area Forecast Discussion National Weather Service State College PA 329 PM EDT Sat Jul 1 2023 .SYNOPSIS... A warm front will stall out across Central Pennsylvania this weekend. High humidity and weak forcing along this front will result in periods of unsettled weather through the weekend, with scattered showers and thunderstorms expected. Low pressure riding along this boundary is likely to track north of Pennsylvania by early Monday, dragging a cold front through the state. High pressure is then likely to build into the region Tuesday. The wildfire smoke that brought poor air quality to the region over the past few days is expected to decrease in concentration this weekend, resulting in improving air quality. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Weak shear environment with modest destablization is maintaining scattered coverage of showers and storms from the NW/NC Mountains southwestward to the Laurel Highlands at mid afternoon as shortwave aloft tracks across the region. Broken lines of shallow convection have produced mainly brief downpours, with some suggestion of pea sized hail indicated in volumetric scans and cross sections. A fairly persistent cell is yielding higher probs of hail over Clinton County at the moment, with localized shear organizing a similar cell around Renovo, so MRGL outlook for isold stronger storms is playing out as anticipated. For most cells, the vertical extent of rain cores are remaining below 10k feet with brief heavy rates, as PW surges over 1.5" ahead of upstream trough over the midwest and GLAKS, and weak mid level shortwaves pass overhead. Expanding shower chances across central and eastern sections through evening are thus expected, with greatest POPs over western and central areas. The southeast will see the least coverage of showers and storms through this evening, but may see isolated coverage late in the day before activity tends to weaken into tonight. Meanwhile upstream, a deepening trough will spawn a surface low over the midwest tonight, which is progged to run northeast across the Lower GLAKS into Sunday. We expect increasing activity once again in the predawn hours into Sunday morning as overrunning ahead of the warm front supports showers and embedded tsra. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... Main question on Sunday is how far the warm sector lifts in central PA, and although clouds are likely to linger over northern PA, breaking clouds in the warm sector could potentially result in the threat of late day severe weather across southern PA, where modest capes and a ribbon of 35-40kt mid level winds are progged. SPC maintains a SLGHT risk for now just the far southern tier of central PA but this may be subject to change. Showers and thunderstorms will last into Sunday evening before decreasing by late evening. A few discrete cells are possible over the southern half of central PA and depending upon the location of the warm sector severe storms are possible into early Sunday evening. Activity diminishes to isolated showers late Sunday night. && .LONG TERM /MONDAY THROUGH SATURDAY/... The aforementioned upper trough will move across the eastern Great Lakes on Monday, with the trough axis crossing through central PA during the PM hours Monday. The trough of colder air aloft will result in enough instability for numerous showers and storms again on Monday, although the wind field will be weaker within the trough, limiting the severe threat. Rising heights and subsidence behind the departing trough on Tuesday (Independence Day) supports the idea that the 4th of July will be mainly dry. Latest NBM shows PoPs less than 20 percent for most of the area Tuesday with some spots around 25 percent over northern PA. The ridging over the eastern US during this period will also bring warmer temps - with most spots in the mid to upper 80s on Tue and upper 80s to near 90 on Wed and Thu. Longer term guidance depicts a cold front approaching towards the end of the week or weekend, bringing increase PoPs and cooler temps. && .AVIATION /19Z SATURDAY THROUGH THURSDAY/... Low clouds are starting to dissipate over southeastern and central PA where it has been stable through the morning. These MVFR cigs will break up allowing for VFR conditions into the afternoon at LNS, MDT and IPT. Elsewhere, shra and isolated tsra have been forming over western PA and may bring brief reductions this afternoon as they expand eastward. Outlook... Sun-Mon...AM low cigs possible, esp central Mtns. Sct PM tsra impacts possible. Mon-Wed...Sct PM tsra could lead to some restrictions. Activity expected to taper off a bit later Tuesday into Wed. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && SYNOPSIS...DeVoir NEAR TERM...DeVoir/Fitzgerald SHORT TERM...DeVoir/Fitzgerald LONG TERM...Colbert/Travis AVIATION...Martin/Travis
Hazardous Weather Outlook National Weather Service State College PA 438 AM EDT Sat Jul 1 2023 PAZ004>006-010>012-017>019-037-041-042-045-046-049>053-058-020845- Warren-McKean-Potter-Elk-Cameron-Northern Clinton-Clearfield- Northern Centre-Southern Centre-Tioga-Northern Lycoming-Sullivan- Southern Clinton-Southern Lycoming-Union-Snyder-Montour- Northumberland-Columbia-Schuylkill- 438 AM EDT Sat Jul 1 2023 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...Today and tonight. Strong to severe thunderstorms with gusty winds and small hail are possible in a few locations late this afternoon or evening. .DAYS TWO THROUGH SEVEN...Sunday through Friday. Heavy showers and thunderstorms are possible in some locations Sunday, which could result in isolated flooding. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. PAZ024>028-033>036-056-057-059-063>066-020845- Cambria-Blair-Huntingdon-Mifflin-Juniata-Somerset-Bedford-Fulton- Franklin-Perry-Dauphin-Lebanon-Cumberland-Adams-York-Lancaster- 438 AM EDT Sat Jul 1 2023 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...Today and tonight. Strong to severe thunderstorms with gusty winds and small hail are possible in a few locations late this afternoon or evening. .DAYS TWO THROUGH SEVEN...Sunday through Friday. Severe thunderstorms with damaging wind gusts, torrential downpours and large hail exceeding 1 inch in diameter are possible in a few locations Sunday afternoon or evening. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
Special Weather Statement National Weather Service State College PA 1259 PM EDT Sat Jul 1 2023 PAZ033-034-011730- Bedford PA-Somerset PA- 1259 PM EDT Sat Jul 1 2023 ...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN BEDFORD AND EAST CENTRAL SOMERSET COUNTIES THROUGH 130 PM EDT... At 1259 PM EDT, Doppler radar was tracking a strong thunderstorm 13 miles south of Windber, moving east at 15 mph. HAZARD...Pea size hail. SOURCE...Radar indicated. IMPACT...Minor hail damage to vegetation possible. Locations impacted include... Central City, Indian Lake, Schellsburg, Manns Choice and New Paris. PRECAUTIONARY/PREPAREDNESS ACTIONS... If outdoors, consider seeking shelter inside a building. && LAT...LON 3999 7883 4006 7888 4023 7864 4002 7852 TIME...MOT...LOC 1659Z 248DEG 12KT 4004 7882 MAX HAIL SIZE...0.25 IN MAX WIND GUST...<30 MPH DeVoir
Special Weather Statement
National Weather Service State College PA
305 PM EDT Sat Jul 1 2023
PAZ012-041-045-046-011930-
Southern Lycoming PA-Southern Clinton PA-Northern Clinton PA-
Northern Lycoming PA-
305 PM EDT Sat Jul 1 2023
...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN LYCOMING AND EAST
CENTRAL CLINTON COUNTIES THROUGH 330 PM EDT...
At 304 PM EDT, Doppler radar was tracking a strong thunderstorm
north of Lock Haven, moving east at 20 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 hail damage to vegetation
possible.
Locations impacted include...
Lock Haven, Jersey Shore, Avis, Dunnstown, McElhattan, Salladasburg
and Lock Haven University.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4115 7756 4124 7758 4133 7722 4111 7719
TIME...MOT...LOC 1904Z 261DEG 17KT 4120 7748
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH
TravisThe State College radar (KCCX), 58 km away, was scanning. The volume nearest the first event began at 20:51 UTC.
1 flood, 1 thunderstorm wind. Local standard time, as filed.
A thunderstorm produced heavy rain over the city of Altoona, leading to 1 to 2 feet of ponded water on some city streets in and around 6th Avenue.
A severe thunderstorm producing winds estimated near 60 mph blew off a section of metal roof and knocked down power lines. Debris was blown across Route 281 near Friedens.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2023Every state in 2023This day in weather historyWarnings in Pennsylvania, July 2023
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: 1100775, 1099972.