Alert archive / Pennsylvania / Montgomery County
Weather alerts in Montgomery County, Pennsylvania, 2009
129 weather alerts in 2009, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered this county.
Montgomery County and its neighbors
Each county as a circle sized by its count in 2009. Tap one for its archive.
- Alerts
- 129
- Warnings
- 60
- Watches
- 9
- Advisories
- 21
- Busiest month
- August33 alerts
- Busiest day
- August 2, 200910 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
Montgomery County, 2009
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 0 | 0 | ||||
| Severe thunderstorm warnings | 32 | 26 | 19% | 13 | 92% | 23 min |
| Flash flood warnings | 12 | 4 | 67% | 7 | 86% | 96 min |
Each office's whole area, 2009
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Philadelphia/Mount Holly: tornado warnings | 13 | 1 | 92% | 2 | 50% | 38 min |
| NWS Philadelphia/Mount Holly: severe thunderstorm warnings | 235 | 113 | 52% | 260 | 82% | 26 min |
| NWS Philadelphia/Mount Holly: flash flood warnings | 67 | 20 | 70% | 69 | 62% | 85 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 7, 12:10 AM EST | Mesoscale Discussion | SPC | 4 hr |
| Jan 7, 8:21 AM EST | Areal Flood Advisory | PHI | 8 hr |
| Jan 7, 8:32 AM EST | Areal Flood Advisory | PHI | 8 hr |
| Jan 10, 7:58 PM EST | Mesoscale Discussion | SPC | 4 hr |
| Jan 28, 12:31 AM EST | Mesoscale Discussion | SPC | 5 hr |
| Feb 11, 10:14 PM EST | Mesoscale Discussion | SPC | 61 min |
| Mar 2, 5:38 AM EST | Mesoscale Discussion | SPC | 3 hr |
| Mar 29, 1:49 PM EDT | Mesoscale Discussion | SPC | 116 min |
| Mar 29, 5:53 PM EDT | Mesoscale Discussion | SPC | 97 min |
| Mar 29, 5:55 PM EDT | Severe Thunderstorm Warning | PHI | 50 min |
| Mar 29, 6:11 PM EDT | Severe Thunderstorm Warning | PHI | 64 min |
| May 7, 1:08 AM EDT | Flash Flood Warning | PHI | 6 hr |
| May 7, 10:15 AM EDT | Areal Flood Warning | PHI | 3 hr |
| May 7, 1:42 PM EDT | Areal Flood Advisory | PHI | 4 hr |
| May 7, 2:34 PM EDT | Areal Flood Advisory | PHI | 3 hr |
| May 16, 6:29 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| May 16, 9:53 PM EDT | Areal Flood Advisory | PHI | 95 min |
| May 24, 7:11 PM EDT | Mesoscale Discussion | SPC | 64 min |
| May 24, 8:04 PM EDT | Severe Thunderstorm Warning | PHI | 56 min |
| May 29, 12:20 PM EDT | Mesoscale Discussion | SPC | 55 min |
| May 29, 1:26 PM EDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Jun 2, 1:58 PM EDT | Severe Thunderstorm Watch | SPC | 6 hr |
| Jun 9, 6:01 AM EDT | Mesoscale Discussion | SPC | 59 min |
| Jun 9, 7:20 AM EDT | Severe Thunderstorm Warning | PHI | 55 min |
| Jun 9, 8:20 AM EDT | Areal Flood Advisory | PHI | 3 hr |
| Jun 9, 2:24 PM EDT | Severe Thunderstorm Warning | PHI | 66 min |
| Jun 13, 2:57 PM EDT | Flash Flood Warning | PHI | 2 hr |
| Jun 13, 4:07 PM EDT | Flash Flood Warning | PHI | 6 hr |
| Jun 13, 9:38 PM EDT | Areal Flood Warning | PHI | 4 hr |
| Jun 14, 1:19 AM EDT | Areal Flood Warning | PHI | 4 hr |
| Jun 15, 4:15 PM EDT | Severe Thunderstorm Warning | PHI | 60 min |
| Jun 15, 5:13 PM EDT | Severe Thunderstorm Warning | PHI | 62 min |
| Jun 15, 5:55 PM EDT | Severe Thunderstorm Warning | PHI | 65 min |
| Jun 18, 11:40 AM EDT | Mesoscale Discussion | SPC | 95 min |
| Jun 26, 2:19 PM EDT | Mesoscale Discussion | SPC | 56 min |
| Jun 26, 2:42 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 26, 6:01 PM EDT | Severe Thunderstorm Warning | PHI | 59 min |
| Jun 26, 6:23 PM EDT | Severe Thunderstorm Warning | PHI | 52 min |
| Jun 26, 6:57 PM EDT | Severe Thunderstorm Warning | PHI | 48 min |
| Jun 26, 7:10 PM EDT | Severe Thunderstorm Warning | PHI | 50 min |
| Jun 26, 7:15 PM EDT | Severe Thunderstorm Warning | PHI | 60 min |
| Jun 26, 7:28 PM EDT | Severe Thunderstorm Warning | PHI | 92 min |
| Jun 26, 7:33 PM EDT | Mesoscale Discussion | SPC | 57 min |
| Jun 26, 9:11 PM EDT | Mesoscale Discussion | SPC | 64 min |
| Jun 30, 11:37 AM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 30, 2:18 PM EDT | Mesoscale Discussion | SPC | 57 min |
| Jun 30, 2:31 PM EDT | Severe Thunderstorm Warning | PHI | 44 min |
| Jun 30, 2:51 PM EDT | Severe Thunderstorm Warning | PHI | 54 min |
| Jun 30, 3:13 PM EDT | Flash Flood Warning | PHI | 114 min |
| Jul 1, 12:03 PM EDT | Mesoscale Discussion | SPC | 87 min |
| Jul 1, 11:55 PM EDT | Areal Flood Advisory | PHI | 3 hr |
| Jul 16, 4:04 PM EDT | Mesoscale Discussion | SPC | 86 min |
| Jul 16, 6:42 PM EDT | Severe Thunderstorm Warning | PHI | 63 min |
| Jul 16, 7:05 PM EDT | Severe Thunderstorm Warning | PHI | 70 min |
| Jul 17, 6:18 PM EDT | Mesoscale Discussion | SPC | 57 min |
| Jul 17, 7:07 PM EDT | Severe Thunderstorm Warning | PHI | 53 min |
| Jul 17, 7:22 PM EDT | Severe Thunderstorm Warning | PHI | 53 min |
| Jul 17, 7:33 PM EDT | Areal Flood Advisory | PHI | 86 min |
| Jul 17, 8:12 PM EDT | Areal Flood Advisory | PHI | 96 min |
| Jul 21, 8:24 AM EDT | Areal Flood Advisory | PHI | 3 hr |
| Jul 24, 3:34 PM EDT | Mesoscale Discussion | SPC | 86 min |
| Jul 26, 3:14 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jul 26, 3:51 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jul 26, 6:37 PM EDT | Mesoscale Discussion | SPC | 113 min |
| Jul 27, 9:05 PM EDT | Severe Thunderstorm Warning | PHI | 55 min |
| Jul 28, 7:18 AM EDT | Areal Flood Warning | PHI | 2 hr |
| Jul 29, 11:48 AM EDT | Severe Thunderstorm Warning | PHI | 72 min |
| Jul 29, 12:22 PM EDT | Mesoscale Discussion | SPC | 23 min |
| Jul 29, 12:49 PM EDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Jul 29, 5:05 PM EDT | Mesoscale Discussion | SPC | 55 min |
| Jul 29, 5:55 PM EDT | Areal Flood Advisory | PHI | 4 hr |
| Jul 29, 7:14 PM EDT | Mesoscale Discussion | SPC | 61 min |
| Jul 31, 10:20 AM EDT | Mesoscale Discussion | SPC | 85 min |
| Jul 31, 12:06 PM EDT | Mesoscale Discussion | SPC | 84 min |
| Jul 31, 1:18 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jul 31, 3:04 PM EDT | Flash Flood Warning | PHI | 3 hr |
| Jul 31, 3:05 PM EDT | Mesoscale Discussion | SPC | 85 min |
| Jul 31, 4:08 PM EDT | Flash Flood Warning | PHI | 3 hr |
| Jul 31, 4:31 PM EDT | Severe Thunderstorm Warning | PHI | 59 min |
| Aug 2, 7:34 AM EDT | Areal Flood Advisory | PHI | 3 hr |
| Aug 2, 9:04 AM EDT | Areal Flood Warning | PHI | 4 hr |
| Aug 2, 10:01 AM EDT | Mesoscale Discussion | SPC | 119 min |
| Aug 2, 10:08 AM EDT | Flash Flood Warning | PHI | 9 hr |
| Aug 2, 10:24 AM EDT | Severe Thunderstorm Warning | PHI | 66 min |
| Aug 2, 10:53 AM EDT | Severe Thunderstorm Warning | PHI | 67 min |
| Aug 2, 11:14 AM EDT | Severe Thunderstorm Warning | PHI | 61 min |
| Aug 2, 11:25 AM EDT | Severe Thunderstorm Warning | PHI | 65 min |
| Aug 2, 1:25 PM EDT | Areal Flood Warning | PHI | 6 hr |
| Aug 2, 6:15 PM EDT | Areal Flood Warning | PHI | 4 hr |
| Aug 9, 9:23 AM EDT | Areal Flood Advisory | PHI | 83 min |
| Aug 9, 2:45 PM EDT | Mesoscale Discussion | SPC | 60 min |
| Aug 9, 3:18 PM EDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Aug 9, 5:17 PM EDT | Severe Thunderstorm Warning | PHI | 76 min |
| Aug 9, 6:03 PM EDT | Areal Flood Advisory | PHI | 117 min |
| Aug 9, 6:10 PM EDT | Severe Thunderstorm Warning | PHI | 80 min |
| Aug 9, 7:11 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Aug 12, 1:01 PM EDT | Mesoscale Discussion | SPC | 89 min |
| Aug 12, 5:18 PM EDT | Flash Flood Warning | PHI | 2 hr |
| Aug 18, 7:37 PM EDT | Severe Thunderstorm Warning | PHI | 68 min |
| Aug 18, 8:35 PM EDT | Severe Thunderstorm Warning | PHI | 70 min |
| Aug 19, 6:05 PM EDT | Mesoscale Discussion | SPC | 55 min |
| Aug 21, 10:01 AM EDT | Mesoscale Discussion | SPC | 119 min |
| Aug 21, 11:28 AM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Aug 21, 1:58 PM EDT | Mesoscale Discussion | SPC | 92 min |
| Aug 22, 1:40 AM EDT | Areal Flood Advisory | PHI | 3 hr |
| Aug 22, 1:51 AM EDT | Flash Flood Warning | PHI | 77 min |
| Aug 22, 6:03 AM EDT | Flash Flood Warning | PHI | 3 hr |
| Aug 22, 7:00 PM EDT | Flash Flood Warning | PHI | 4 hr |
| Aug 28, 9:42 AM EDT | Areal Flood Advisory | PHI | 2 hr |
| Aug 28, 3:13 PM EDT | Areal Flood Advisory | PHI | 4 hr |
| Aug 28, 9:28 PM EDT | Areal Flood Advisory | PHI | 3 hr |
| Aug 29, 10:33 PM EDT | Areal Flood Warning | PHI | 2 hr |
| Sep 11, 8:41 AM EDT | Areal Flood Advisory | PHI | 3 hr |
| Oct 24, 12:19 PM EDT | Mesoscale Discussion | SPC | 116 min |
| Oct 24, 4:49 PM EDT | Areal Flood Advisory | PHI | 4 hr |
| Oct 24, 4:55 PM EDT | Areal Flood Advisory | PHI | 4 hr |
| Oct 24, 6:02 PM EDT | Flash Flood Warning | PHI | 3 hr |
| Oct 24, 9:01 PM EDT | Areal Flood Warning | PHI | 9 hr |
| Oct 24, 9:58 PM EDT | Areal Flood Warning | PHI | 4 hr |
| Dec 3, 5:41 AM EST | Severe Thunderstorm Warning | PHI | 49 min |
| Dec 3, 6:29 AM EST | Areal Flood Warning | PHI | 106 min |
| Dec 9, 6:53 AM EST | Areal Flood Warning | PHI | 8 hr |
| Dec 9, 7:47 AM EST | Areal Flood Warning | PHI | 7 hr |
| Dec 9, 11:36 AM EST | River Flood Warning | PHI | 5 hr |
| Dec 9, 2:55 PM EST | Areal Flood Warning | PHI | 7 hr |
| Dec 19, 6:57 AM EST | Mesoscale Discussion | SPC | 6 hr |
| Dec 19, 12:27 PM EST | Mesoscale Discussion | SPC | 6 hr |
| Dec 19, 7:25 PM EST | Mesoscale Discussion | SPC | 5 hr |
| Dec 26, 10:28 AM EST | Areal Flood Warning | PHI | 20 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 | 32 |
| Severe Thunderstorm Watch | 9 |
| Mesoscale Discussion | 39 |
| Flooding | |
| Areal Flood Warning | 15 |
| Flash Flood Warning | 12 |
| River Flood Warning | 1 |
| Areal Flood Advisory | 21 |
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordForecastThe radar archive20082010
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.