Alert archive / Pennsylvania / Chester County

Weather alerts in Chester County, Pennsylvania, 2010

177 weather alerts in 2010, 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 2010. Tap one for its archive.

Alerts: 177
Warnings: 57
Watches: 16
Advisories: 21
Busiest month: July35 alerts
Busiest day: July 25, 201010 alerts

Over time

By month

Warning verification

How often warnings here had a storm report inside them, and how much warning the reports had.

0 of 1 tornado warnings covering Chester County in 2010 had a tornado report inside them; 0 of 1 tornado reports fell inside a warning.

Chester County, 2010

	Warnings	With a report	False alarm ratio	Reports	Inside a warning	Mean lead time
Tornado warnings	1	0	100%	1	0%
Severe thunderstorm warnings	35	25	29%	14	86%	31 min
Flash flood warnings	2	0	100%	0

Each office's whole area, 2010

	Warnings	With a report	False alarm ratio	Reports	Inside a warning	Mean lead time
NWS Philadelphia/Mount Holly: tornado warnings	12	1	92%	4	25%	1 min
NWS Philadelphia/Mount Holly: severe thunderstorm warnings	183	107	42%	252	82%	29 min
NWS Philadelphia/Mount Holly: flash flood warnings	14	2	86%	15	60%	45 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 25, 9:42 AM EST	Severe Thunderstorm Warning	PHI	63 min
Jan 25, 9:56 AM EST	Areal Flood Advisory	PHI	4 hr
Jan 25, 10:09 AM EST	Areal Flood Warning	PHI	10 hr
Jan 25, 12:08 PM EST	Areal Flood Advisory	PHI	29 days
Jan 25, 1:50 PM EST	River Flood Warning	PHI	4 hr
Jan 25, 8:00 PM EST	Areal Flood Warning	PHI	2 hr
Feb 5, 6:58 PM EST	Mesoscale Discussion	SPC	4 hr
Feb 9, 7:04 PM EST	Mesoscale Discussion	SPC	4 hr
Feb 10, 7:27 AM EST	Mesoscale Discussion	SPC	5 hr
Feb 10, 12:20 PM EST	Mesoscale Discussion	SPC	4 hr
Mar 13, 12:16 PM EST	Areal Flood Advisory	PHI	6 hr
Mar 13, 12:40 PM EST	Areal Flood Warning	PHI	6 hr
Mar 13, 3:52 PM EST	River Flood Warning	PHI	12 hr
Mar 13, 3:52 PM EST	River Flood Warning	PHI	19 hr
Mar 13, 6:04 PM EST	Areal Flood Warning	PHI	8 hr
Mar 14, 1:47 AM EST	Areal Flood Warning	PHI	20 hr
Mar 29, 12:56 AM EDT	Areal Flood Advisory	PHI	4 hr
Mar 29, 1:28 AM EDT	Flash Flood Warning	PHI	4 hr
Mar 30, 1:51 PM EDT	Areal Flood Warning	PHI	8 hr
Apr 8, 9:25 PM EDT	Severe Thunderstorm Warning	PHI	37 min
Apr 8, 9:56 PM EDT	Severe Thunderstorm Warning	PHI	28 min
Apr 16, 6:14 PM EDT	Mesoscale Discussion	SPC	61 min
Apr 16, 7:41 PM EDT	Severe Thunderstorm Warning	PHI	34 min
May 2, 11:26 PM EDT	Areal Flood Advisory	PHI	3 hr
May 2, 11:47 PM EDT	Severe Thunderstorm Warning	PHI	43 min
May 3, 12:30 AM EDT	Areal Flood Advisory	PHI	3 hr
May 3, 1:51 AM EDT	Areal Flood Advisory	PHI	6 hr
May 14, 3:43 PM EDT	Severe Thunderstorm Watch	SPC	6 hr
May 14, 5:49 PM EDT	Severe Thunderstorm Warning	PHI	56 min
May 14, 6:25 PM EDT	Severe Thunderstorm Warning	PHI	65 min
May 14, 6:35 PM EDT	Severe Thunderstorm Warning	PHI	55 min
May 14, 6:35 PM EDT	Mesoscale Discussion	SPC	55 min
May 27, 11:28 AM EDT	Mesoscale Discussion	SPC	92 min
May 27, 1:23 PM EDT	Severe Thunderstorm Watch	SPC	8 hr
May 27, 2:45 PM EDT	Special Weather Statement	PHI	60 min
May 27, 4:13 PM EDT	Mesoscale Discussion	SPC	62 min
May 27, 5:53 PM EDT	Severe Thunderstorm Warning	PHI	37 min
May 27, 6:20 PM EDT	Severe Thunderstorm Warning	PHI	55 min
May 27, 7:12 PM EDT	Severe Thunderstorm Warning	PHI	48 min
May 27, 7:44 PM EDT	Areal Flood Advisory	PHI	3 hr
May 27, 7:56 PM EDT	Severe Thunderstorm Warning	PHI	34 min
May 27, 8:08 PM EDT	Mesoscale Discussion	SPC	97 min
May 27, 9:55 PM EDT	Areal Flood Advisory	PHI	118 min
May 27, 10:13 PM EDT	Severe Thunderstorm Warning	PHI	47 min
May 27, 10:30 PM EDT	Severe Thunderstorm Warning	PHI	60 min
May 31, 3:02 PM EDT	Special Weather Statement	PHI	43 min
Jun 3, 11:27 AM EDT	Mesoscale Discussion	SPC	93 min
Jun 3, 1:32 PM EDT	Severe Thunderstorm Watch	SPC	7 hr
Jun 3, 3:36 PM EDT	Mesoscale Discussion	SPC	54 min
Jun 3, 6:28 PM EDT	Mesoscale Discussion	SPC	62 min
Jun 3, 8:51 PM EDT	Special Weather Statement	PHI	54 min
Jun 4, 1:45 PM EDT	Special Weather Statement	PHI	90 min
Jun 4, 2:39 PM EDT	Severe Thunderstorm Watch	SPC	8 hr
Jun 4, 2:59 PM EDT	Special Weather Statement	PHI	91 min
Jun 4, 3:14 PM EDT	Severe Thunderstorm Warning	PHI	76 min
Jun 4, 4:24 PM EDT	Mesoscale Discussion	SPC	66 min
Jun 4, 7:03 PM EDT	Mesoscale Discussion	SPC	57 min
Jun 6, 10:25 AM EDT	Mesoscale Discussion	SPC	65 min
Jun 6, 11:08 AM EDT	Tornado Watch	SPC	8 hr
Jun 6, 2:38 PM EDT	Mesoscale Discussion	SPC	67 min
Jun 12, 7:28 PM EDT	Special Weather Statement	PHI	92 min
Jun 13, 12:58 PM EDT	Mesoscale Discussion	SPC	2 hr
Jun 22, 4:38 PM EDT	Special Weather Statement	PHI	52 min
Jun 22, 4:56 PM EDT	Severe Thunderstorm Warning	PHI	34 min
Jun 22, 5:00 PM EDT	Special Weather Statement	PHI	60 min
Jun 22, 5:06 PM EDT	Severe Thunderstorm Watch	SPC	4 hr
Jun 22, 5:15 PM EDT	Special Weather Statement	PHI	60 min
Jun 22, 5:29 PM EDT	Special Weather Statement	PHI	46 min
Jun 22, 5:41 PM EDT	Severe Thunderstorm Warning	PHI	49 min
Jun 22, 6:29 PM EDT	Severe Thunderstorm Warning	PHI	46 min
Jun 24, 12:16 PM EDT	Mesoscale Discussion	SPC	89 min
Jun 24, 12:28 PM EDT	Severe Thunderstorm Watch	SPC	8 hr
Jun 24, 2:31 PM EDT	Severe Thunderstorm Warning	PHI	59 min
Jun 24, 2:56 PM EDT	Severe Thunderstorm Warning	PHI	64 min
Jun 24, 3:07 PM EDT	Mesoscale Discussion	SPC	53 min
Jun 24, 3:29 PM EDT	Severe Thunderstorm Warning	PHI	61 min
Jun 27, 9:08 PM EDT	Special Weather Statement	PHI	52 min
Jun 28, 12:49 PM EDT	Mesoscale Discussion	SPC	56 min
Jun 28, 1:12 PM EDT	Severe Thunderstorm Watch	SPC	7 hr
Jun 28, 3:53 PM EDT	Mesoscale Discussion	SPC	2 hr
Jul 10, 7:06 AM EDT	Areal Flood Advisory	PHI	5 hr
Jul 10, 7:30 AM EDT	Areal Flood Advisory	PHI	6 hr
Jul 10, 9:30 AM EDT	Areal Flood Advisory	PHI	4 hr
Jul 10, 11:56 AM EDT	River Flood Warning	PHI	2 hr
Jul 12, 5:27 PM EDT	Special Weather Statement	PHI	63 min
Jul 12, 8:12 PM EDT	Special Weather Statement	PHI	63 min
Jul 13, 1:06 AM EDT	Areal Flood Advisory	PHI	3 hr
Jul 13, 6:07 AM EDT	Areal Flood Advisory	PHI	113 min
Jul 13, 7:42 AM EDT	Areal Flood Advisory	PHI	4 hr
Jul 14, 1:44 AM EDT	Special Weather Statement	PHI	61 min
Jul 14, 2:32 AM EDT	Flash Flood Warning	PHI	3 hr
Jul 14, 12:52 PM EDT	Areal Flood Advisory	PHI	3 hr
Jul 14, 4:03 PM EDT	Areal Flood Warning	PHI	79 min
Jul 19, 7:46 AM EDT	Special Weather Statement	PHI	59 min
Jul 19, 1:17 PM EDT	Mesoscale Discussion	SPC	58 min
Jul 19, 5:25 PM EDT	Special Weather Statement	PHI	65 min
Jul 19, 5:39 PM EDT	Severe Thunderstorm Warning	PHI	66 min
Jul 19, 6:22 PM EDT	Severe Thunderstorm Warning	PHI	53 min
Jul 21, 12:38 PM EDT	Mesoscale Discussion	SPC	67 min
Jul 21, 1:32 PM EDT	Severe Thunderstorm Watch	SPC	9 hr
Jul 21, 3:41 PM EDT	Mesoscale Discussion	SPC	64 min
Jul 21, 7:00 PM EDT	Mesoscale Discussion	SPC	90 min
Jul 21, 10:10 PM EDT	Severe Thunderstorm Warning	PHI	65 min
Jul 21, 10:41 PM EDT	Special Weather Statement	PHI	94 min
Jul 23, 6:23 PM EDT	Mesoscale Discussion	SPC	67 min
Jul 24, 11:26 PM EDT	Special Weather Statement	PHI	49 min
Jul 25, 10:48 AM EDT	Mesoscale Discussion	SPC	27 min
Jul 25, 11:29 AM EDT	Severe Thunderstorm Watch	SPC	8 hr
Jul 25, 12:50 PM EDT	Mesoscale Discussion	SPC	55 min
Jul 25, 12:53 PM EDT	Special Weather Statement	PHI	112 min
Jul 25, 1:30 PM EDT	Severe Thunderstorm Warning	PHI	75 min
Jul 25, 2:25 PM EDT	Severe Thunderstorm Warning	PHI	80 min
Jul 25, 2:45 PM EDT	Tornado Warning	PHI	30 min
Jul 25, 3:18 PM EDT	Severe Thunderstorm Warning	PHI	57 min
Jul 25, 3:25 PM EDT	Mesoscale Discussion	SPC	65 min
Aug 4, 9:25 PM EDT	Special Weather Statement	PHI	65 min
Aug 4, 9:36 PM EDT	Special Weather Statement	PHI	54 min
Aug 4, 9:52 PM EDT	Special Weather Statement	PHI	23 min
Aug 12, 2:40 PM EDT	Areal Flood Advisory	PHI	96 min
Aug 12, 3:10 PM EDT	Areal Flood Advisory	PHI	3 hr
Aug 16, 12:05 PM EDT	Severe Thunderstorm Watch	SPC	9 hr
Aug 16, 2:17 PM EDT	Mesoscale Discussion	SPC	88 min
Aug 16, 5:01 PM EDT	Severe Thunderstorm Warning	PHI	74 min
Aug 16, 5:50 PM EDT	Severe Thunderstorm Warning	PHI	55 min
Aug 16, 6:44 PM EDT	Severe Thunderstorm Warning	PHI	61 min
Aug 16, 7:16 PM EDT	Mesoscale Discussion	SPC	59 min
Aug 16, 9:52 PM EDT	Special Weather Statement	PHI	113 min
Sep 22, 3:10 PM EDT	Mesoscale Discussion	SPC	65 min
Sep 22, 3:43 PM EDT	Severe Thunderstorm Watch	SPC	7 hr
Sep 22, 4:23 PM EDT	Special Weather Statement	PHI	52 min
Sep 22, 4:46 PM EDT	Mesoscale Discussion	SPC	59 min
Sep 22, 4:49 PM EDT	Special Weather Statement	PHI	56 min
Sep 22, 7:14 PM EDT	Mesoscale Discussion	SPC	61 min
Sep 22, 8:50 PM EDT	Special Weather Statement	PHI	40 min
Sep 27, 1:03 PM EDT	Mesoscale Discussion	SPC	87 min
Sep 28, 8:00 AM EDT	Mesoscale Discussion	SPC	2 hr
Sep 28, 9:26 AM EDT	Special Weather Statement	PHI	64 min
Sep 28, 9:59 AM EDT	Special Weather Statement	PHI	61 min
Sep 28, 10:05 AM EDT	Severe Thunderstorm Warning	PHI	55 min
Sep 28, 10:17 AM EDT	Special Weather Statement	PHI	58 min
Sep 28, 10:58 AM EDT	Tornado Watch	SPC	7 hr
Sep 28, 11:15 AM EDT	Severe Thunderstorm Warning	PHI	45 min
Sep 28, 1:50 PM EDT	Mesoscale Discussion	SPC	55 min
Sep 30, 6:06 AM EDT	Areal Flood Warning	PHI	4 hr
Sep 30, 7:33 AM EDT	Special Weather Statement	PHI	117 min
Sep 30, 8:03 AM EDT	Areal Flood Warning	PHI	4 hr
Sep 30, 10:49 AM EDT	Mesoscale Discussion	SPC	116 min
Sep 30, 12:39 PM EDT	Tornado Watch	SPC	6 hr
Sep 30, 1:48 PM EDT	Areal Flood Warning	PHI	6 hr
Sep 30, 3:16 PM EDT	Mesoscale Discussion	SPC	119 min
Sep 30, 6:55 PM EDT	River Flood Warning	PHI	30 hr
Sep 30, 7:37 PM EDT	Special Weather Statement	PHI	113 min
Sep 30, 7:50 PM EDT	Areal Flood Warning	PHI	16 hr
Sep 30, 8:29 PM EDT	Mesoscale Discussion	SPC	91 min
Oct 1, 12:01 AM EDT	Mesoscale Discussion	SPC	89 min
Oct 1, 2:01 AM EDT	River Flood Warning	PHI	13 hr
Oct 1, 2:35 AM EDT	River Flood Warning	PHI	13 hr
Oct 11, 3:38 PM EDT	Severe Thunderstorm Watch	SPC	6 hr
Oct 11, 6:07 PM EDT	Mesoscale Discussion	SPC	83 min
Oct 11, 9:51 PM EDT	Special Weather Statement	PHI	114 min
Nov 17, 12:06 AM EST	Severe Thunderstorm Watch	SPC	4 hr
Nov 17, 1:44 AM EST	Special Weather Statement	PHI	61 min
Nov 17, 2:16 AM EST	Special Weather Statement	PHI	59 min
Nov 17, 2:35 AM EST	Severe Thunderstorm Warning	PHI	55 min
Nov 17, 2:40 AM EST	Severe Thunderstorm Warning	PHI	65 min
Dec 1, 6:35 AM EST	Special Weather Statement	PHI	55 min
Dec 1, 6:55 AM EST	Mesoscale Discussion	SPC	65 min
Dec 1, 7:01 AM EST	Areal Flood Advisory	PHI	8 hr
Dec 1, 7:43 AM EST	Special Weather Statement	PHI	47 min
Dec 1, 8:36 AM EST	Special Weather Statement	PHI	54 min
Dec 1, 8:58 AM EST	Areal Flood Advisory	PHI	6 hr
Dec 1, 9:31 AM EST	Special Weather Statement	PHI	59 min
Dec 1, 10:49 AM EST	Special Weather Statement	PHI	56 min
Dec 1, 11:35 AM EST	Severe Thunderstorm Warning	PHI	40 min
Dec 1, 12:45 PM EST	Areal Flood Warning	PHI	7 hr
Dec 12, 2:12 PM EST	Areal Flood Advisory	PHI	4 hr
Dec 27, 2:49 AM EST	Mesoscale Discussion	SPC	4 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	35
Tornado Warning	1
Severe Thunderstorm Watch	13
Tornado Watch	3
Mesoscale Discussion	44
Special Weather Statement	39
Flooding
Areal Flood Warning	12
Flash Flood Warning	2
River Flood Warning	7
Areal Flood Advisory	21

The busiest days

Days with the most alerts issued, by UTC date.

Nearby

Alerts in force now Tornadoes on record Forecast The radar archive 2009 2011

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.