Alert archive / Pennsylvania / Chester County
Weather alerts in Chester County, Pennsylvania, 2012
182 weather alerts in 2012, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered this county.
Chester County and its neighbors
Each county as a circle sized by its count in 2012. Tap one for its archive.
- Alerts
- 182
- Warnings
- 37
- Watches
- 15
- Advisories
- 40
- Busiest month
- July35 alerts
- Busiest day
- September 18, 201212 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
Chester County, 2012
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 0 | 0 | ||||
| Severe thunderstorm warnings | 21 | 19 | 10% | 13 | 92% | 24 min |
| Flash flood warnings | 4 | 2 | 50% | 2 | 100% | 37 min |
Each office's whole area, 2012
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Philadelphia/Mount Holly: tornado warnings | 8 | 1 | 88% | 3 | 33% | 1 min |
| NWS Philadelphia/Mount Holly: severe thunderstorm warnings | 238 | 159 | 33% | 410 | 90% | 28 min |
| NWS Philadelphia/Mount Holly: flash flood warnings | 57 | 25 | 56% | 49 | 73% | 55 min |
An office's figures cover every county it serves, including across state lines.
Verified by the Iowa Environmental Mesonet's Cow, which matches each storm-based warning with the local storm reports inside its polygon while it was in force, within 15 km of its edge: a tornado warning counts as verified on a tornado report, a severe thunderstorm warning on hail of 1 inch or more, a gust of 58 mph or more, or wind damage, a flash flood warning on a flash flood report. The false alarm ratio is the share of warnings with no such report; "inside a warning" is the probability of detection, the share of reports that fell inside one; lead time runs from the warning's issue to each report inside it, counting zero for a report that came first. A warning with no report is not proof nothing happened: reports come from spotters, the public and damage surveys, and are thin where few people live.
The alerts
Every alert, in the order issued. Times are local, Eastern Time. Each opens its own page with the text, the map, the radar and the sounding.
| Issued | Product | Office | Lasted |
|---|---|---|---|
| Jan 15, 4:32 AM EST | Special Weather Statement | PHI | 43 min |
| Jan 21, 7:07 AM EST | Mesoscale Discussion | SPC | 3 hr |
| Jan 27, 8:27 AM EST | Special Weather Statement | PHI | 93 min |
| Feb 11, 3:19 PM EST | Special Weather Statement | PHI | 3 hr |
| Feb 11, 5:49 PM EST | Special Weather Statement | PHI | 86 min |
| Feb 25, 10:35 AM EST | Special Weather Statement | PHI | 55 min |
| Feb 29, 6:44 PM EST | Special Weather Statement | PHI | 61 min |
| Feb 29, 7:45 PM EST | Special Weather Statement | PHI | 2 hr |
| Mar 9, 12:01 AM EST | Special Weather Statement | PHI | 59 min |
| Apr 21, 7:19 PM EDT | Special Weather Statement | PHI | 116 min |
| Apr 21, 8:41 PM EDT | Special Weather Statement | PHI | 109 min |
| Apr 21, 8:45 PM EDT | Severe Thunderstorm Warning | PHI | 30 min |
| Apr 22, 9:00 PM EDT | Areal Flood Advisory | PHI | 6 hr |
| Apr 23, 2:49 AM EDT | Areal Flood Advisory | PHI | 116 min |
| May 2, 5:58 AM EDT | Special Weather Statement | PHI | 92 min |
| May 4, 1:26 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| May 4, 9:54 PM EDT | Special Weather Statement | PHI | 66 min |
| May 15, 6:40 AM EDT | Special Weather Statement | PHI | 50 min |
| May 15, 7:30 AM EDT | Special Weather Statement | PHI | 2 hr |
| May 15, 9:49 PM EDT | Special Weather Statement | PHI | 86 min |
| May 15, 10:45 PM EDT | Areal Flood Advisory | PHI | 57 min |
| May 15, 11:05 PM EDT | Special Weather Statement | PHI | 55 min |
| May 15, 11:24 PM EDT | Areal Flood Advisory | PHI | 116 min |
| May 15, 11:38 PM EDT | Areal Flood Warning | PHI | 4 hr |
| May 16, 12:12 AM EDT | Areal Flood Advisory | PHI | 3 hr |
| May 16, 12:34 AM EDT | Flash Flood Warning | PHI | 4 hr |
| May 24, 2:01 PM EDT | Areal Flood Advisory | PHI | 83 min |
| May 26, 7:20 PM EDT | Areal Flood Advisory | PHI | 59 min |
| May 29, 2:13 PM EDT | Mesoscale Discussion | SPC | 62 min |
| May 29, 4:40 PM EDT | Mesoscale Discussion | SPC | 65 min |
| May 29, 5:54 PM EDT | Severe Thunderstorm Watch | SPC | 3 hr |
| May 29, 6:46 PM EDT | Special Weather Statement | PHI | 89 min |
| May 29, 6:52 PM EDT | Severe Thunderstorm Warning | PHI | 53 min |
| May 29, 7:35 PM EDT | Areal Flood Advisory | PHI | 115 min |
| Jun 1, 3:49 PM EDT | Mesoscale Discussion | SPC | 56 min |
| Jun 1, 4:25 PM EDT | Mesoscale Discussion | SPC | 65 min |
| Jun 1, 6:17 PM EDT | Severe Thunderstorm Warning | PHI | 44 min |
| Jun 1, 6:54 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jun 1, 8:01 PM EDT | Tornado Watch | SPC | 4 hr |
| Jun 1, 8:46 PM EDT | Areal Flood Advisory | PHI | 5 hr |
| Jun 3, 1:32 PM EDT | Special Weather Statement | PHI | 118 min |
| Jun 3, 1:37 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jun 3, 6:05 PM EDT | Special Weather Statement | PHI | 85 min |
| Jun 3, 7:20 PM EDT | Special Weather Statement | PHI | 85 min |
| Jun 12, 10:17 PM EDT | Areal Flood Advisory | PHI | 106 min |
| Jun 22, 12:18 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jun 22, 1:41 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 22, 4:33 PM EDT | Mesoscale Discussion | SPC | 87 min |
| Jun 22, 6:42 PM EDT | Mesoscale Discussion | SPC | 63 min |
| Jun 25, 3:44 AM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jun 25, 6:39 AM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 29, 3:41 AM EDT | Mesoscale Discussion | SPC | 94 min |
| Jun 29, 3:51 AM EDT | Special Weather Statement | PHI | 54 min |
| Jun 29, 4:14 AM EDT | Severe Thunderstorm Warning | PHI | 76 min |
| Jun 29, 4:34 AM EDT | Severe Thunderstorm Watch | SPC | 3 hr |
| Jun 29, 4:46 AM EDT | Severe Thunderstorm Warning | PHI | 48 min |
| Jun 29, 5:00 AM EDT | Severe Thunderstorm Warning | PHI | 75 min |
| Jun 29, 10:54 PM EDT | Special Weather Statement | PHI | 51 min |
| Jul 1, 12:11 PM EDT | Mesoscale Discussion | SPC | 64 min |
| Jul 7, 11:19 AM EDT | Mesoscale Discussion | SPC | 86 min |
| Jul 7, 5:43 PM EDT | Mesoscale Discussion | SPC | 62 min |
| Jul 7, 5:57 PM EDT | Severe Thunderstorm Warning | PHI | 63 min |
| Jul 7, 6:14 PM EDT | Severe Thunderstorm Watch | SPC | 3 hr |
| Jul 7, 6:58 PM EDT | Severe Thunderstorm Warning | PHI | 48 min |
| Jul 7, 8:45 PM EDT | Special Weather Statement | PHI | 60 min |
| Jul 7, 9:05 PM EDT | Severe Thunderstorm Warning | PHI | 32 min |
| Jul 15, 8:27 PM EDT | Special Weather Statement | PHI | 63 min |
| Jul 15, 8:30 PM EDT | Severe Thunderstorm Warning | PHI | 45 min |
| Jul 15, 9:16 PM EDT | Special Weather Statement | PHI | 59 min |
| Jul 18, 10:25 AM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jul 18, 12:41 PM EDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Jul 18, 3:44 PM EDT | Mesoscale Discussion | SPC | 91 min |
| Jul 18, 3:51 PM EDT | Severe Thunderstorm Warning | PHI | 28 min |
| Jul 19, 6:53 PM EDT | Mesoscale Discussion | SPC | 97 min |
| Jul 23, 1:24 PM EDT | Severe Thunderstorm Watch | SPC | 10 hr |
| Jul 23, 5:09 PM EDT | Severe Thunderstorm Warning | PHI | 51 min |
| Jul 23, 5:56 PM EDT | Special Weather Statement | PHI | 64 min |
| Jul 24, 1:08 PM EDT | Severe Thunderstorm Watch | SPC | 6 hr |
| Jul 24, 2:30 PM EDT | Special Weather Statement | PHI | 90 min |
| Jul 26, 3:37 PM EDT | Mesoscale Discussion | SPC | 113 min |
| Jul 26, 3:57 PM EDT | Severe Thunderstorm Watch | SPC | 6 hr |
| Jul 26, 6:04 PM EDT | Mesoscale Discussion | SPC | 86 min |
| Jul 26, 6:46 PM EDT | Severe Thunderstorm Warning | PHI | 89 min |
| Jul 26, 7:28 PM EDT | Mesoscale Discussion | SPC | 92 min |
| Jul 26, 10:19 PM EDT | Areal Flood Advisory | PHI | 3 hr |
| Jul 28, 12:26 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jul 28, 1:36 PM EDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Jul 28, 2:33 PM EDT | Special Weather Statement | PHI | 57 min |
| Jul 28, 4:18 PM EDT | Mesoscale Discussion | SPC | 87 min |
| Jul 28, 7:37 PM EDT | Special Weather Statement | PHI | 53 min |
| Jul 28, 7:57 PM EDT | Severe Thunderstorm Warning | PHI | 48 min |
| Jul 28, 8:00 PM EDT | Mesoscale Discussion | SPC | 30 min |
| Jul 29, 3:40 PM EDT | Areal Flood Advisory | PHI | 74 min |
| Aug 1, 1:02 AM EDT | Special Weather Statement | PHI | 58 min |
| Aug 1, 2:03 PM EDT | Special Weather Statement | PHI | 57 min |
| Aug 1, 6:08 PM EDT | Flash Flood Warning | PHI | 2 hr |
| Aug 1, 6:30 PM EDT | Areal Flood Advisory | PHI | 64 min |
| Aug 1, 7:32 PM EDT | Special Weather Statement | PHI | 58 min |
| Aug 1, 7:49 PM EDT | Areal Flood Advisory | PHI | 52 min |
| Aug 3, 2:39 PM EDT | Special Weather Statement | PHI | 66 min |
| Aug 5, 2:49 PM EDT | Mesoscale Discussion | SPC | 86 min |
| Aug 5, 3:36 PM EDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Aug 5, 4:23 PM EDT | Severe Thunderstorm Warning | PHI | 67 min |
| Aug 5, 5:22 PM EDT | Severe Thunderstorm Warning | PHI | 68 min |
| Aug 9, 3:05 PM EDT | Special Weather Statement | PHI | 85 min |
| Aug 9, 3:20 PM EDT | Severe Thunderstorm Warning | PHI | 55 min |
| Aug 9, 3:57 PM EDT | Areal Flood Advisory | PHI | 104 min |
| Aug 10, 7:40 AM EDT | Areal Flood Advisory | PHI | 3 hr |
| Aug 10, 8:21 AM EDT | Mesoscale Discussion | SPC | 2 hr |
| Aug 10, 9:08 AM EDT | Areal Flood Advisory | PHI | 3 hr |
| Aug 10, 7:31 PM EDT | Mesoscale Discussion | SPC | 119 min |
| Aug 11, 6:11 PM EDT | Special Weather Statement | PHI | 49 min |
| Aug 11, 7:52 PM EDT | Special Weather Statement | PHI | 23 min |
| Aug 11, 8:16 PM EDT | Special Weather Statement | PHI | 29 min |
| Aug 11, 8:39 PM EDT | Areal Flood Advisory | PHI | 57 min |
| Aug 14, 8:06 AM EDT | Special Weather Statement | PHI | 84 min |
| Aug 14, 8:39 AM EDT | Areal Flood Advisory | PHI | 2 hr |
| Aug 14, 9:56 AM EDT | Areal Flood Advisory | PHI | 108 min |
| Aug 14, 9:57 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Aug 14, 11:40 PM EDT | Special Weather Statement | PHI | 95 min |
| Aug 15, 12:49 AM EDT | Areal Flood Advisory | PHI | 3 hr |
| Aug 27, 5:08 AM EDT | Special Weather Statement | PHI | 52 min |
| Aug 27, 6:41 AM EDT | Special Weather Statement | PHI | 49 min |
| Sep 3, 12:24 AM EDT | Areal Flood Advisory | PHI | 3 hr |
| Sep 3, 12:58 AM EDT | Flash Flood Warning | PHI | 5 hr |
| Sep 3, 4:44 AM EDT | Areal Flood Advisory | PHI | 3 hr |
| Sep 3, 6:24 AM EDT | Areal Flood Warning | PHI | 4 hr |
| Sep 3, 8:05 AM EDT | Areal Flood Advisory | PHI | 3 hr |
| Sep 3, 9:15 AM EDT | Flash Flood Warning | PHI | 3 hr |
| Sep 3, 12:04 PM EDT | Areal Flood Warning | PHI | 4 hr |
| Sep 3, 2:44 PM EDT | Areal Flood Advisory | PHI | 119 min |
| Sep 4, 12:13 AM EDT | Areal Flood Advisory | PHI | 111 min |
| Sep 4, 12:15 PM EDT | Areal Flood Warning | PHI | 106 min |
| Sep 4, 2:22 PM EDT | Areal Flood Advisory | PHI | 4 hr |
| Sep 4, 4:37 PM EDT | Areal Flood Advisory | PHI | 3 hr |
| Sep 8, 12:15 PM EDT | Severe Thunderstorm Watch | SPC | 9 hr |
| Sep 8, 2:12 PM EDT | Mesoscale Discussion | SPC | 93 min |
| Sep 8, 2:40 PM EDT | Severe Thunderstorm Warning | PHI | 65 min |
| Sep 18, 11:14 AM EDT | Mesoscale Discussion | SPC | 91 min |
| Sep 18, 11:19 AM EDT | Mesoscale Discussion | SPC | 86 min |
| Sep 18, 12:10 PM EDT | Tornado Watch | SPC | 9 hr |
| Sep 18, 1:56 PM EDT | Mesoscale Discussion | SPC | 64 min |
| Sep 18, 2:00 PM EDT | Special Weather Statement | PHI | 60 min |
| Sep 18, 2:23 PM EDT | Severe Thunderstorm Warning | PHI | 30 min |
| Sep 18, 3:52 PM EDT | Special Weather Statement | PHI | 53 min |
| Sep 18, 4:19 PM EDT | Severe Thunderstorm Warning | PHI | 56 min |
| Sep 18, 4:21 PM EDT | Mesoscale Discussion | SPC | 114 min |
| Sep 18, 4:35 PM EDT | Areal Flood Advisory | PHI | 55 min |
| Sep 18, 5:01 PM EDT | Severe Thunderstorm Warning | PHI | 59 min |
| Sep 18, 5:12 PM EDT | Areal Flood Advisory | PHI | 63 min |
| Sep 22, 3:09 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Sep 22, 5:11 PM EDT | Special Weather Statement | PHI | 64 min |
| Sep 22, 6:02 PM EDT | Special Weather Statement | PHI | 88 min |
| Oct 15, 2:02 PM EDT | Special Weather Statement | PHI | 88 min |
| Oct 15, 3:25 PM EDT | Special Weather Statement | PHI | 80 min |
| Oct 19, 4:48 PM EDT | Mesoscale Discussion | SPC | 87 min |
| Oct 19, 9:24 PM EDT | Special Weather Statement | PHI | 96 min |
| Oct 19, 10:00 PM EDT | Areal Flood Advisory | PHI | 63 min |
| Oct 29, 7:40 AM EDT | Areal Flood Warning | PHI | 23 hr |
| Oct 29, 11:15 AM EDT | River Flood Warning | PHI | 33 hr |
| Oct 29, 11:21 AM EDT | River Flood Warning | PHI | 21 hr |
| Oct 29, 4:28 PM EDT | Special Weather Statement | PHI | 2 hr |
| Oct 30, 4:51 AM EDT | River Flood Warning | PHI | 5 hr |
| Oct 30, 5:42 AM EDT | Areal Flood Warning | PHI | 5 hr |
| Nov 13, 12:01 AM EST | Special Weather Statement | PHI | 89 min |
| Nov 13, 1:17 AM EST | Special Weather Statement | PHI | 88 min |
| Dec 9, 7:23 PM EST | Dense Fog Advisory | PHI | 14 hr |
| Dec 16, 8:41 PM EST | Dense Fog Advisory | PHI | 16 hr |
| Dec 17, 3:27 PM EST | Dense Fog Advisory | PHI | 12 hr |
| Dec 18, 1:19 PM EST | Special Weather Statement | PHI | 56 min |
| Dec 18, 2:15 PM EST | Special Weather Statement | PHI | 60 min |
| Dec 21, 4:44 AM EST | Areal Flood Warning | PHI | 14 hr |
| Dec 21, 12:08 PM EST | River Flood Warning | PHI | 5 hr |
| Dec 21, 3:16 PM EST | Wind Advisory | PHI | 27 hr |
| Dec 24, 4:02 AM EST | Winter Weather Advisory | PHI | 29 hr |
| Dec 25, 3:03 PM EST | Flood Watch | PHI | 36 hr |
| Dec 25, 9:21 PM EST | Winter Weather Advisory | PHI | 37 hr |
| Dec 26, 12:48 PM EST | Mesoscale Discussion | SPC | 6 hr |
| Dec 26, 7:55 PM EST | Areal Flood Advisory | PHI | 6 hr |
| Dec 26, 9:29 PM EST | Areal Flood Warning | PHI | 118 min |
| Dec 28, 3:49 AM EST | Winter Weather Advisory | PHI | 39 hr |
| Dec 30, 9:53 AM EST | Wind Advisory | PHI | 6 hr |
By product
Every kind of product issued here, grouped by hazard. Each opens the same place narrowed to that product.
| Product | Alerts |
|---|---|
| Severe storms | |
| Severe Thunderstorm Warning | 21 |
| Severe Thunderstorm Watch | 12 |
| Tornado Watch | 2 |
| Mesoscale Discussion | 37 |
| Special Weather Statement | 53 |
| Flooding | |
| Areal Flood Warning | 8 |
| Flash Flood Warning | 4 |
| River Flood Warning | 4 |
| Flood Watch | 1 |
| Areal Flood Advisory | 32 |
| Winter | |
| Winter Weather Advisory | 3 |
| Wind and dust | |
| Wind Advisory | 2 |
| Fog and smoke | |
| Dense Fog Advisory | 3 |
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordForecastThe radar archive20112013
Sources
National Weather Service watches, warnings, advisories and statements from the Iowa Environmental Mesonet's VTEC archive, which reconstructs tornado, severe thunderstorm, flash flood and marine warnings back to 1986 from the NWS text archive. Storm Prediction Center watches and mesoscale discussions from SPC's archive through the Mesonet. County centers from the US Census Bureau. Warning verification from the Mesonet's Cow. Rebuilt daily.