Widely scattered thunderstorms formed in an unseasonably warm and humid airmass over western Pennsylvania, while southeasterly flow and a cooler, more stable airmass was situated across eastern Pennsylvania. After an overcast morning, the warmer air made it into the south-central mountains of Pennsylvania.
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.
Widely scattered thunderstorms formed in an unseasonably warm and humid airmass over western Pennsylvania, while southeasterly flow and a cooler, more stable airmass was situated across eastern Pennsylvania. After an overcast morning, the warmer air made it into the south-central mountains of Pennsylvania. One of the storms developed over Cambria County and became severe as it descended the Allegheny Front into Altoona, producing wind damage and hail across central Blair County.
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 Apr 30, 4:50 PM EST, 11 minutes earlier.
Area Forecast Discussion National Weather Service State College PA 550 PM EDT Sun Apr 30 2017 .SYNOPSIS... A nearly stationary front will remain just south of PA today. A strong cold front will move across the region on Monday followed by brisk west to northwest winds and cooler air for Tuesday. Fair weather with milder temperatures will occur Wednesday under a weak ridge of high pressure. Deep moisture will flow north into the state Thursday afternoon through Friday bringing a return to inclement weather. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... The strong late April sun has effectively led to the western periphery of the low cloud shield eroding as the warm air tries to chew away at the cool air damming pattern. Eastern areas remain relatively cool with more clouds than sun, but even there satellite indicates there are a lot of thin areas and breaks. Latest radar shows that convection has fired in the unstable air over western PA where the sun has been out all day. These popcorn cells are streaking NNE over my western and NWRN zones, and will likely continue into the late afternoon before lowering sun angles lead to a weakening trend. QPF is expected to be generally a few hundredths to around one tenth of an inch on average with the usual isolated heavier amounts in the stronger convection. After the usual melting away of the convection when the sun goes down, the remainder of the overnight should stay dry in most locations. It will be very mild in the mid to upper 50s. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... Monday represent the most active day in the forecast period. A potent cold front is expected to pass through the region during the afternoon and early evening Monday. Strong deep layer shear and respectable instability are generated by all the near term deterministic models. SPC has elevated the RISK to ENHANCED with EHI's forecast in the 2-3 range (anything above 1.0 is considered significant). The mitigating factor to be aware of (as always) will be the amount of cloud cover in the warm air ahead of the cold front. The cool air damming as defined by low level stability is forecast to mix out rapidly early in the day. With the cold front and upper flow strongly aligned, I would expect the warm sector to mix out and at least a healthy mix of sun and clouds to develop by mid to late morning. Temps should return/rise to very very warm levels on Monday. A narrow north/south ribbon of +3-4 sigma PWAT air along and just ahead of the cold front will support some locally heavy downpours and QPF up over one inch in some spots. WPC highlights a small portion of my NERN zones with a MARGINAL risk of heavy rain/flooding. It's too soon to get into watches at this point. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... Expect significant convection to be ongoing/near to exiting the CWA at the start of the period Monday night. Cold front forcing the convection will move east through the state overnight into Tuesday morning, advecting much chillier air into the state Cyclonic flow with a gusty NW wind and unsettled light showery weather will persisting mainly for the northern part of the state right into Wednesday. A chance for a more widespread (potentially MDT to HVY) rain arrives Thu into Fri as latest 00Z Operational GFS/EC run and their EFSs are coming into decent/converging agreement with an area of low pressure progged to develop along the southern Appalachians and the lift north-northeastward. Although this event shows some pretty strong signals (even at this long time range) for a potential, widespread 1-2 inch rainfall late in the upcoming week, A wide and varying array of models solutions has been present prior to the latest model run or two to throw some uncertainty into the mix w/respect to the specific timing and amount of showers across the CWA. Fri night and Saturday will turn windy and quite cool with isolated rain showers falling across the central mtns, while the Alleghenies experiences more numerous rain showers (and yes, maybe even the last gasp of show showers until later this fall). && .AVIATION /22Z SUNDAY THROUGH FRIDAY/... Adjusted 21Z TAFS for ongoing convection. Earlier discussion below. Cool, stable air with MVFR stratus covers the eastern half of central Pennsylvania, while the western half is solidly in the warm, humid air with -SHRA and TSRA developing. The eastern airfields of KIPT, KMDT and KLNS currently have an MVFR status layer that is eroding rapidly as evidenced by satellite. These areas will slowly break into good VFR up through sunset. Patchy fog is possible overnight with low level moisture and stable air in place. An area of showers and thunderstorms are developing over western Pennsylvania and will gradually move toward KBFD and KJST where VCTS and VCSH have been added to the forecast. However, these storms are pulsing up and down and as they move into the stable air where stratus was slow to lift, expect them to diminish in coverage before reaching KAOO and KUNV. A cold front will approach the region tomorrow but precipitation will hold off until after this forecast period. Outlook... Mon...Breezy. Showers/thunderstorms likely with periods of sub-VFR. A few strong-severe storms possible wrn 1/2 Monday afternoon/evening. FROPA Monday night. Tue-Wed...Breezy with a chance of showers NW. Thu...Widespread sub-VFR with rain likely. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...La Corte LONG TERM...Lambert/Gartner AVIATION...La Corte/Martin
Hazardous Weather Outlook National Weather Service State College PA 917 AM EDT Sun Apr 30 2017 PAZ004-005-010-017-024-033>036-064-011330- Warren-McKean-Elk-Clearfield-Cambria-Somerset-Bedford-Fulton- Franklin-Adams- 917 AM EDT Sun Apr 30 2017 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...Today and Tonight. There is a Marginal risk of a severe thunderstorm this afternoon and evening. .DAYS TWO THROUGH SEVEN...Monday through Saturday. Scattered severe thunderstorms with damaging winds 60 mph or greater and large hail exceeding 1 inch in diameter are possible Monday afternoon and evening. The greatest risk area for severe storms is west of Interstate 81. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. PAZ006-011-012-018-019-025>028-037-041-042-045-046-049>053-056>059- 063-065-066-011330- Potter-Cameron-Northern Clinton-Northern Centre-Southern Centre- Blair-Huntingdon-Mifflin-Juniata-Tioga-Northern Lycoming-Sullivan- Southern Clinton-Southern Lycoming-Union-Snyder-Montour- Northumberland-Columbia-Perry-Dauphin-Schuylkill-Lebanon-Cumberland- York-Lancaster- 917 AM EDT Sun Apr 30 2017 This Hazardous Weather Outlook is for central Pennsylvania. .DAY ONE...Today and Tonight. The probability for widespread hazardous weather is low. .DAYS TWO THROUGH SEVEN...Monday through Saturday. Scattered severe thunderstorms with damaging winds 60 mph or greater and large hail exceeding 1 inch in diameter are possible Monday afternoon and evening. The greatest risk area for severe storms is west of Interstate 81. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
Special Weather Statement
National Weather Service State College PA
446 PM EDT SUN APR 30 2017
PAZ018-024-025-302115-
Northern Centre PA-Blair PA-Cambria PA-
446 PM EDT SUN APR 30 2017
...SPECIAL WEATHER STATEMENT...
At 444 PM EDT, Doppler radar indicated a strong thunderstorm near
Loretto, moving northeast at 30 mph. Another strong storm has formed
behind this storm.
Pea size hail and winds in excess of 30 mph are possible.
Locations impacted include...
Altoona, Portage, Ebensburg, Tyrone, Bellwood, Horseshoe Curve,
Prince Gallitzin State Park, Lilly, Loretto, Patton, South Fork,
Ehrenfeld, Tipton, Birmingham, Gallitzin, Blandburg, Sinking Valley,
Carrolltown, Sandy Ridge and Cresson.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
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 4063 7876 4073 7852 4073 7836 4074 7836
4076 7837 4080 7834 4088 7813 4080 7814
4074 7823 4074 7815 4072 7815 4068 7822
4062 7817 4056 7820 4054 7818 4033 7882
TIME...MOT...LOC 2044Z 190DEG 26KT 4056 7862
MartinSpecial Weather Statement National Weather Service State College PA 515 PM EDT SUN APR 30 2017 PAZ017>019-024-025-302215- Northern Centre PA-Clearfield PA-Blair PA-Cambria PA- Southern Centre PA- 515 PM EDT SUN APR 30 2017 ...SPECIAL WEATHER STATEMENT... At 514 PM EDT, Doppler radar indicated a strong thunderstorm near Blandburg, moving northeast at 30 mph. Other strong storms are just to the south of this storm. Pea size hail and winds in excess of 30 mph are possible. Locations impacted include... Jeffries, North Philipsburg, Osceola Mills, Woodland, South Philipsburg, Blandburg, Philipsburg, Sandy Ridge, Houtzdale, Chester Hill, Port Matilda, Prince Gallitzin State Park, West Decatur, Ramey, Glen Hope, Brisbin, Wallaceton, Coalport, Irvona and Morrisdale. PRECAUTIONARY/PREPAREDNESS ACTIONS... 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 4061 7840 4072 7862 4103 7835 4084 7798 TIME...MOT...LOC 2114Z 215DEG 28KT 4073 7844 Martin
Special Weather Statement National Weather Service State College PA 528 PM EDT SUN APR 30 2017 PAZ024-025-302230- Blair PA-Cambria PA- 528 PM EDT SUN APR 30 2017 ...SPECIAL WEATHER STATEMENT... At 527 PM EDT, Doppler radar indicated a strong thunderstorm over Cresson, moving northeast at 30 mph. Pea size hail and winds in excess of 30 mph are possible. Locations impacted include... Altoona, Hollidaysburg, Loretto, Bellwood, Gallitzin, Horseshoe Curve, Sinking Valley, Lakemont, Canoe Creek State Park, Cresson, Duncansville, Williamsburg, Sankertown, Lilly, Tipton, Tunnelhill, Ashville, Peoples Natural Gas Field, Allegheny Portage Railroad National Historic Site and Penn State Altoona. PRECAUTIONARY/PREPAREDNESS ACTIONS... 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 4052 7868 4064 7827 4047 7816 4039 7863 TIME...MOT...LOC 2127Z 258DEG 9KT 4045 7857 Martin
Special Weather Statement
National Weather Service State College PA
550 PM EDT SUN APR 30 2017
PAZ004-302215-
Warren PA-
550 PM EDT SUN APR 30 2017
...A STRONG THUNDERSTORM WILL AFFECT PARTS OF WARREN COUNTY UNTIL 615
PM EDT...
At 550 PM EDT, Doppler radar indicated a strong thunderstorm 11 miles
northeast of Tionesta, moving northeast at 40 mph.
Dime size hail and wind gusts up to 50 mph are possible.
Locations impacted include...
Warren, Sheffield, Warren South, Kinzua Dam, Chapman State Park and
Clarendon.
LAT...LON 4183 7892 4183 7895 4162 7896 4163 7937
4188 7914 4192 7892
TIME...MOT...LOC 2150Z 227DEG 35KT 4161 7930
EvanegoThe State College radar (KCCX), 57 km away, was scanning. The volume nearest the first event began at 22:03 UTC.
5 thunderstorm wind. Local standard time, as filed.
A severe thunderstorm producing winds estimated near 60 mph knocked down trees and wires across Altoona.
A severe thunderstorm produced a microburst with winds estimated near 70 mph, knocking down approximately 40 trees in the vicinity of Goodman Road and Fox Run Road in Blair County.
A severe thunderstorm producing winds estimated near 60 mph knocked down trees and wires along Route 26 north of Huntingdon.
A severe thunderstorm producing winds estimated near 60 mph knocked down trees and wires in Smethport.
A severe thunderstorm producing winds estimated near 60 mph knocked down trees and wires, blocking Whitney Run Road.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2017Every state in 2017This day in weather historyWarnings in Pennsylvania, April 2017
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: 683261, 683263, 683264, 683265, 683266.