Alert archive / Pennsylvania / Delaware County

Weather alerts in Delaware County, Pennsylvania, 2017

177 weather alerts in 2017, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered this county.

Delaware County and its neighbors

Each county as a circle sized by its count in 2017. Tap one for its archive.

Alerts: 177
Warnings: 40
Watches: 27
Advisories: 48
Busiest month: July47 alerts
Busiest day: July 13, 20179 alerts

Over time

By month

Warning verification

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

Delaware County, 2017

	Warnings	With a report	False alarm ratio	Reports	Inside a warning	Mean lead time
Tornado warnings	0			0
Severe thunderstorm warnings	25	21	16%	6	100%	31 min
Flash flood warnings	5	2	60%	2	0%

Each office's whole area, 2017

	Warnings	With a report	False alarm ratio	Reports	Inside a warning	Mean lead time
NWS Philadelphia/Mount Holly: tornado warnings	13	1	92%	6	33%	2 min
NWS Philadelphia/Mount Holly: severe thunderstorm warnings	197	120	39%	396	79%	26 min
NWS Philadelphia/Mount Holly: flash flood warnings	52	15	71%	54	78%	91 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 1, 3:15 PM EST	Freezing Rain Advisory	PHI	23 hr
Jan 5, 11:13 AM EST	Winter Weather Advisory	PHI	18 hr
Jan 6, 4:42 PM EST	Winter Weather Advisory	PHI	25 hr
Jan 21, 8:58 AM EST	Dense Fog Advisory	PHI	2 hr
Jan 21, 3:29 PM EST	Dense Fog Advisory	PHI	22 hr
Jan 22, 3:44 AM EST	High Wind Warning	PHI	40 hr
Jan 22, 3:44 AM EST	Wind Advisory	PHI	38 hr
Jan 23, 5:44 PM EST	Wind Advisory	PHI	115 min
Jan 26, 11:15 AM EST	Wind Advisory	PHI	7 hr
Feb 7, 3:29 PM EST	Winter Storm Watch	PHI	13 hr
Feb 8, 4:01 AM EST	Winter Storm Warning	PHI	36 hr
Feb 9, 3:35 AM EST	Wind Advisory	PHI	18 hr
Feb 9, 4:55 AM EST	Mesoscale Discussion	SPC	6 hr
Feb 12, 3:55 AM EST	High Wind Watch	PHI	11 hr
Feb 12, 2:45 PM EST	Wind Advisory	PHI	27 hr
Feb 12, 11:10 PM EST	Severe Thunderstorm Warning	PHI	50 min
Feb 23, 2:58 AM EST	Dense Fog Advisory	PHI	7 hr
Feb 25, 12:16 PM EST	Mesoscale Discussion	SPC	89 min
Feb 25, 1:30 PM EST	Severe Thunderstorm Watch	SPC	6 hr
Feb 25, 4:04 PM EST	Severe Thunderstorm Warning	PHI	41 min
Feb 25, 4:17 PM EST	Severe Thunderstorm Warning	PHI	43 min
Feb 25, 4:26 PM EST	Mesoscale Discussion	SPC	94 min
Feb 25, 4:40 PM EST	Severe Thunderstorm Warning	PHI	50 min
Feb 25, 6:10 PM EST	Special Weather Statement	PHI	35 min
Mar 1, 12:50 PM EST	Mesoscale Discussion	SPC	55 min
Mar 1, 1:13 PM EST	Severe Thunderstorm Watch	SPC	4 hr
Mar 1, 2:00 PM EST	Severe Thunderstorm Warning	PHI	45 min
Mar 1, 2:46 PM EST	Special Weather Statement	PHI	29 min
Mar 1, 2:50 PM EST	Mesoscale Discussion	SPC	55 min
Mar 1, 3:09 PM EST	Wind Advisory	PHI	19 hr
Mar 2, 2:47 AM EST	High Wind Warning	PHI	7 hr
Mar 3, 3:42 PM EST	Special Weather Statement	PHI	33 min
Mar 9, 3:35 AM EST	Winter Weather Advisory	PHI	34 hr
Mar 10, 10:46 AM EST	Special Weather Statement	PHI	74 min
Mar 10, 3:46 PM EST	Special Weather Statement	PHI	29 min
Mar 10, 4:15 PM EST	Special Weather Statement	PHI	45 min
Mar 10, 4:28 PM EST	Special Weather Statement	PHI	32 min
Mar 10, 4:49 PM EST	Special Weather Statement	PHI	41 min
Mar 11, 3:52 PM EST	Winter Storm Watch	PHI	35 hr
Mar 12, 3:08 PM EDT	Winter Storm Warning	PHI	48 hr
Mar 13, 10:01 PM EDT	Mesoscale Discussion	SPC	4 hr
Mar 14, 3:22 AM EDT	Mesoscale Discussion	SPC	5 hr
Mar 14, 9:02 AM EDT	Areal Flood Advisory	PHI	3 hr
Mar 14, 9:04 AM EDT	Mesoscale Discussion	SPC	4 hr
Mar 15, 3:41 AM EDT	Wind Advisory	PHI	16 hr
Mar 27, 3:30 AM EDT	Dense Fog Advisory	PHI	6 hr
Mar 31, 3:41 AM EDT	Flood Watch	PHI	20 hr
Mar 31, 4:50 PM EDT	Areal Flood Advisory	PHI	9 hr
Apr 4, 3:09 PM EDT	Flood Watch	PHI	54 hr
Apr 6, 12:18 PM EDT	Mesoscale Discussion	SPC	57 min
Apr 6, 12:45 PM EDT	Severe Thunderstorm Watch	SPC	4 hr
Apr 6, 2:07 PM EDT	Special Weather Statement	PHI	53 min
Apr 6, 2:29 PM EDT	Areal Flood Advisory	PHI	4 hr
Apr 6, 2:56 PM EDT	Special Weather Statement	PHI	64 min
Apr 6, 3:12 PM EDT	Mesoscale Discussion	SPC	63 min
Apr 29, 3:51 AM EDT	Special Weather Statement	PHI	39 min
Apr 29, 4:22 AM EDT	Special Weather Statement	PHI	38 min
May 1, 7:16 PM EDT	Mesoscale Discussion	SPC	2 hr
May 5, 9:12 AM EDT	Special Weather Statement	PHI	33 min
May 5, 11:14 AM EDT	Areal Flood Advisory	PHI	4 hr
May 19, 3:36 PM EDT	Mesoscale Discussion	SPC	114 min
May 25, 5:29 PM EDT	Areal Flood Advisory	PHI	2 hr
May 25, 8:39 PM EDT	Special Weather Statement	PHI	51 min
Jun 12, 2:06 PM EDT	Heat Advisory	PHI	29 hr
Jun 18, 3:30 AM EDT	Flash Flood Watch	PHI	39 hr
Jun 19, 11:13 AM EDT	Severe Thunderstorm Watch	SPC	9 hr
Jun 19, 2:21 PM EDT	Mesoscale Discussion	SPC	114 min
Jun 19, 3:35 PM EDT	Areal Flood Advisory	PHI	3 hr
Jun 19, 4:07 PM EDT	Severe Thunderstorm Warning	PHI	38 min
Jun 19, 4:07 PM EDT	Severe Thunderstorm Warning	PHI	38 min
Jun 19, 4:34 PM EDT	Severe Thunderstorm Warning	PHI	41 min
Jun 21, 2:38 PM EDT	Mesoscale Discussion	SPC	3 hr
Jun 21, 4:28 PM EDT	Severe Thunderstorm Warning	PHI	47 min
Jun 21, 5:28 PM EDT	Special Weather Statement	PHI	32 min
Jun 23, 3:35 PM EDT	Mesoscale Discussion	SPC	115 min
Jun 23, 5:09 PM EDT	Severe Thunderstorm Watch	SPC	4 hr
Jun 23, 8:25 PM EDT	Mesoscale Discussion	SPC	65 min
Jul 1, 1:34 PM EDT	Severe Thunderstorm Watch	SPC	7 hr
Jul 1, 5:01 PM EDT	Severe Thunderstorm Warning	PHI	44 min
Jul 1, 5:30 PM EDT	Areal Flood Advisory	PHI	4 hr
Jul 1, 5:35 PM EDT	Severe Thunderstorm Warning	PHI	40 min
Jul 6, 4:16 PM EDT	Flash Flood Watch	PHI	3 hr
Jul 7, 7:30 PM EDT	Special Weather Statement	PHI	30 min
Jul 11, 2:52 PM EDT	Excessive Heat Watch	PHI	19 hr
Jul 12, 9:37 AM EDT	Excessive Heat Warning	PHI	34 hr
Jul 13, 11:09 AM EDT	Mesoscale Discussion	SPC	2 hr
Jul 13, 2:33 PM EDT	Mesoscale Discussion	SPC	57 min
Jul 13, 2:57 PM EDT	Severe Thunderstorm Watch	SPC	6 hr
Jul 13, 4:43 PM EDT	Mesoscale Discussion	SPC	62 min
Jul 13, 5:07 PM EDT	Areal Flood Advisory	PHI	7 hr
Jul 13, 5:08 PM EDT	Severe Thunderstorm Warning	PHI	35 min
Jul 13, 5:30 PM EDT	Special Weather Statement	PHI	45 min
Jul 13, 6:23 PM EDT	Mesoscale Discussion	SPC	97 min
Jul 13, 6:34 PM EDT	Special Weather Statement	PHI	41 min
Jul 14, 11:40 AM EDT	Flash Flood Watch	PHI	11 hr
Jul 14, 1:09 PM EDT	Mesoscale Discussion	SPC	2 hr
Jul 14, 1:40 PM EDT	Severe Thunderstorm Watch	SPC	7 hr
Jul 14, 2:14 PM EDT	Areal Flood Advisory	PHI	3 hr
Jul 14, 2:31 PM EDT	Severe Thunderstorm Warning	PHI	59 min
Jul 14, 2:53 PM EDT	Flash Flood Warning	PHI	3 hr
Jul 14, 3:18 PM EDT	Severe Thunderstorm Warning	PHI	12 min
Jul 14, 3:23 PM EDT	Severe Thunderstorm Warning	PHI	67 min
Jul 14, 4:23 PM EDT	Mesoscale Discussion	SPC	67 min
Jul 17, 4:44 PM EDT	Areal Flood Advisory	PHI	3 hr
Jul 19, 2:58 PM EDT	Excessive Heat Warning	PHI	53 hr
Jul 22, 5:18 PM EDT	Severe Thunderstorm Warning	PHI	42 min
Jul 22, 5:50 PM EDT	Severe Thunderstorm Warning	PHI	55 min
Jul 22, 6:00 PM EDT	Areal Flood Advisory	PHI	3 hr
Jul 23, 3:16 PM EDT	Flash Flood Watch	PHI	15 hr
Jul 23, 3:44 PM EDT	Mesoscale Discussion	SPC	3 hr
Jul 23, 4:48 PM EDT	Areal Flood Advisory	PHI	4 hr
Jul 23, 5:22 PM EDT	Special Weather Statement	PHI	23 min
Jul 23, 6:08 PM EDT	Special Weather Statement	PHI	37 min
Jul 23, 6:53 PM EDT	Flash Flood Warning	PHI	14 hr
Jul 23, 7:41 PM EDT	Flash Flood Warning	PHI	6 hr
Jul 24, 12:41 AM EDT	Mesoscale Discussion	SPC	2 hr
Jul 24, 1:33 AM EDT	Areal Flood Advisory	PHI	5 hr
Jul 24, 2:34 AM EDT	Severe Thunderstorm Warning	PHI	41 min
Jul 24, 3:00 AM EDT	Flash Flood Warning	PHI	4 hr
Jul 24, 2:17 PM EDT	Mesoscale Discussion	SPC	118 min
Jul 24, 6:09 PM EDT	Mesoscale Discussion	SPC	3 hr
Jul 24, 8:08 PM EDT	Severe Thunderstorm Warning	PHI	52 min
Jul 24, 8:59 PM EDT	Areal Flood Advisory	PHI	2 hr
Jul 27, 3:08 PM EDT	Flash Flood Watch	PHI	42 hr
Aug 2, 12:28 PM EDT	Areal Flood Advisory	PHI	4 hr
Aug 2, 12:55 PM EDT	Special Weather Statement	PHI	35 min
Aug 2, 1:26 PM EDT	Special Weather Statement	PHI	34 min
Aug 2, 1:30 PM EDT	Severe Thunderstorm Warning	PHI	30 min
Aug 2, 1:30 PM EDT	Mesoscale Discussion	SPC	2 hr
Aug 2, 4:27 PM EDT	Areal Flood Advisory	PHI	4 hr
Aug 3, 5:57 PM EDT	Special Weather Statement	PHI	33 min
Aug 3, 6:28 PM EDT	Mesoscale Discussion	SPC	62 min
Aug 6, 3:12 PM EDT	Flash Flood Watch	PHI	26 hr
Aug 12, 2:44 PM EDT	Severe Thunderstorm Watch	SPC	5 hr
Aug 12, 5:17 PM EDT	Mesoscale Discussion	SPC	88 min
Aug 16, 3:11 AM EDT	Dense Fog Advisory	PHI	5 hr
Aug 18, 3:39 AM EDT	Flash Flood Watch	PHI	18 hr
Aug 18, 1:54 PM EDT	Mesoscale Discussion	SPC	2 hr
Aug 18, 2:27 PM EDT	Severe Thunderstorm Watch	SPC	9 hr
Aug 18, 4:34 PM EDT	Mesoscale Discussion	SPC	86 min
Aug 18, 5:11 PM EDT	Severe Thunderstorm Warning	PHI	49 min
Aug 18, 5:20 PM EDT	Areal Flood Advisory	PHI	3 hr
Aug 18, 5:39 PM EDT	Severe Thunderstorm Warning	PHI	66 min
Aug 18, 6:38 PM EDT	Special Weather Statement	PHI	37 min
Aug 19, 9:35 PM EDT	Special Weather Statement	PHI	25 min
Aug 21, 3:14 PM EDT	Heat Advisory	PHI	29 hr
Aug 22, 3:08 PM EDT	Mesoscale Discussion	SPC	67 min
Aug 22, 4:19 PM EDT	Severe Thunderstorm Watch	SPC	8 hr
Aug 22, 7:07 PM EDT	Mesoscale Discussion	SPC	113 min
Aug 22, 10:07 PM EDT	Severe Thunderstorm Warning	PHI	53 min
Aug 22, 10:40 PM EDT	Areal Flood Advisory	PHI	4 hr
Aug 22, 10:53 PM EDT	Mesoscale Discussion	SPC	97 min
Aug 22, 10:58 PM EDT	Severe Thunderstorm Warning	PHI	62 min
Aug 22, 11:46 PM EDT	Severe Thunderstorm Warning	PHI	44 min
Aug 23, 12:06 AM EDT	Flash Flood Warning	PHI	4 hr
Aug 23, 4:02 AM EDT	Areal Flood Warning	PHI	4 hr
Aug 29, 2:14 PM EDT	Areal Flood Advisory	PHI	4 hr
Sep 5, 3:26 PM EDT	Severe Thunderstorm Watch	SPC	5 hr
Sep 5, 5:00 PM EDT	Mesoscale Discussion	SPC	90 min
Sep 5, 6:19 PM EDT	Special Weather Statement	PHI	41 min
Sep 16, 7:27 PM EDT	Areal Flood Advisory	PHI	3 hr
Oct 23, 3:04 PM EDT	Wind Advisory	PHI	24 hr
Oct 24, 8:28 AM EDT	Special Weather Statement	PHI	32 min
Oct 28, 3:52 AM EDT	Flash Flood Watch	PHI	48 hr
Oct 29, 3:23 AM EDT	Wind Advisory	PHI	32 hr
Oct 29, 4:40 PM EDT	Areal Flood Advisory	PHI	5 hr
Oct 29, 6:11 PM EDT	Areal Flood Advisory	PHI	5 hr
Oct 29, 8:11 PM EDT	Areal Flood Warning	PHI	6 hr
Oct 29, 10:01 PM EDT	Areal Flood Warning	PHI	6 hr
Nov 9, 3:34 AM EST	Freeze Watch	PHI	11 hr
Nov 9, 2:15 PM EST	Freeze Warning	PHI	44 hr
Nov 18, 2:46 PM EST	Wind Advisory	PHI	24 hr
Dec 8, 3:04 AM EST	Winter Weather Advisory	PHI	45 hr
Dec 13, 3:28 PM EST	Winter Weather Advisory	PHI	16 hr
Dec 15, 3:26 AM EST	Winter Weather Advisory	PHI	18 hr
Dec 24, 3:18 AM EST	Wind Advisory	PHI	35 hr
Dec 29, 11:52 PM EST	Winter Weather Advisory	PHI	14 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	25
Severe Thunderstorm Watch	12
Mesoscale Discussion	35
Special Weather Statement	27
Flooding
Areal Flood Warning	3
Flash Flood Warning	5
Flash Flood Watch	8
Flood Watch	2
Areal Flood Advisory	22
Winter
Winter Storm Warning	2
Winter Storm Watch	2
Freezing Rain Advisory	1
Winter Weather Advisory	7
Heat
Excessive Heat Warning	2
Excessive Heat Watch	1
Heat Advisory	2
Cold
Freeze Warning	1
Freeze Watch	1
Wind and dust
High Wind Warning	2
High Wind Watch	1
Wind Advisory	11
Fog and smoke
Dense Fog Advisory	5

The busiest days

Days with the most alerts issued, by UTC date.

Nearby

Alerts in force now Tornadoes on record Forecast The radar archive 2016 2018

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.