Alert archive / Maryland / Montgomery County
Weather alerts in Montgomery County, Maryland, 2011
215 weather alerts in 2011, 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 2011. Tap one for its archive.
- Alerts
- 215
- Warnings
- 92
- Watches
- 24
- Advisories
- 0
- Busiest month
- April48 alerts
- Busiest day
- April 16, 201112 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
3 of 6 tornado warnings covering Montgomery County in 2011 had a tornado report inside them; 1 of 1 tornado reports fell inside a warning, on average 8 minutes after it went out.
Montgomery County, 2011
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 6 | 3 | 50% | 1 | 100% | 8 min |
| Severe thunderstorm warnings | 44 | 36 | 18% | 27 | 78% | 18 min |
| Flash flood warnings | 22 | 18 | 18% | 12 | 67% | 172 min |
Each office's whole area, 2011
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Baltimore/Washington: tornado warnings | 96 | 27 | 72% | 45 | 67% | 11 min |
| NWS Baltimore/Washington: severe thunderstorm warnings | 440 | 335 | 24% | 963 | 78% | 18 min |
| NWS Baltimore/Washington: flash flood warnings | 170 | 99 | 42% | 341 | 84% | 121 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 17, 7:44 PM EST | Mesoscale Discussion | SPC | 6 hr |
| Jan 26, 2:19 PM EST | Mesoscale Discussion | SPC | 6 hr |
| Feb 21, 6:33 PM EST | Mesoscale Discussion | SPC | 5 hr |
| Feb 25, 12:19 PM EST | Severe Thunderstorm Watch | SPC | 3 hr |
| Feb 25, 1:25 PM EST | Severe Thunderstorm Warning | LWX | 33 min |
| Feb 28, 8:36 AM EST | Mesoscale Discussion | SPC | 24 min |
| Feb 28, 8:57 AM EST | Tornado Watch | SPC | 9 hr |
| Mar 6, 2:26 PM EST | Special Weather Statement | LWX | 64 min |
| Mar 6, 3:48 PM EST | Areal Flood Warning | LWX | 6 hr |
| Mar 6, 10:44 PM EST | River Flood Warning | LWX | 9 hr |
| Mar 10, 1:25 PM EST | Severe Thunderstorm Watch | SPC | 7 hr |
| Mar 10, 2:46 PM EST | River Flood Warning | LWX | 13 hr |
| Mar 10, 4:06 PM EST | Areal Flood Warning | LWX | 4 hr |
| Mar 10, 5:48 PM EST | Flash Flood Warning | LWX | 4 hr |
| Mar 10, 6:29 PM EST | Flash Flood Warning | LWX | 4 hr |
| Mar 10, 6:58 PM EST | Tornado Warning | LWX | 32 min |
| Mar 10, 7:20 PM EST | Special Weather Statement | LWX | 25 min |
| Mar 10, 7:32 PM EST | River Flood Warning | LWX | 55 hr |
| Mar 21, 6:18 AM EDT | Special Weather Statement | LWX | 27 min |
| Mar 23, 4:13 PM EDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Mar 23, 8:13 PM EDT | Mesoscale Discussion | SPC | 92 min |
| Apr 2, 2:14 PM EDT | Special Weather Statement | LWX | 31 min |
| Apr 3, 9:46 PM EDT | Special Weather Statement | LWX | 44 min |
| Apr 5, 2:13 AM EDT | Mesoscale Discussion | SPC | 32 min |
| Apr 5, 2:18 AM EDT | Tornado Watch | SPC | 8 hr |
| Apr 5, 3:34 AM EDT | Mesoscale Discussion | SPC | 116 min |
| Apr 5, 3:56 AM EDT | Special Weather Statement | LWX | 64 min |
| Apr 5, 4:29 AM EDT | Severe Thunderstorm Warning | LWX | 51 min |
| Apr 5, 4:40 AM EDT | Severe Thunderstorm Warning | LWX | 53 min |
| Apr 16, 12:52 PM EDT | Mesoscale Discussion | SPC | 113 min |
| Apr 16, 1:29 PM EDT | Tornado Watch | SPC | 8 hr |
| Apr 16, 4:13 PM EDT | Special Weather Statement | LWX | 92 min |
| Apr 16, 4:21 PM EDT | Severe Thunderstorm Warning | LWX | 39 min |
| Apr 16, 4:29 PM EDT | Mesoscale Discussion | SPC | 31 min |
| Apr 16, 4:59 PM EDT | Severe Thunderstorm Warning | LWX | 46 min |
| Apr 16, 5:09 PM EDT | Special Weather Statement | LWX | 66 min |
| Apr 16, 6:15 PM EDT | Special Weather Statement | LWX | 60 min |
| Apr 16, 6:38 PM EDT | Mesoscale Discussion | SPC | 97 min |
| Apr 16, 7:01 PM EDT | Severe Thunderstorm Warning | LWX | 44 min |
| Apr 16, 7:14 PM EDT | Tornado Warning | LWX | 31 min |
| Apr 16, 7:38 PM EDT | Severe Thunderstorm Warning | LWX | 52 min |
| Apr 16, 8:12 PM EDT | Mesoscale Discussion | SPC | 63 min |
| Apr 16, 10:14 PM EDT | River Flood Warning | LWX | 58 hr |
| Apr 24, 2:12 PM EDT | Mesoscale Discussion | SPC | 93 min |
| Apr 24, 3:36 PM EDT | Severe Thunderstorm Warning | LWX | 39 min |
| Apr 24, 3:40 PM EDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Apr 24, 4:03 PM EDT | Tornado Warning | LWX | 27 min |
| Apr 24, 4:07 PM EDT | Severe Thunderstorm Warning | LWX | 38 min |
| Apr 24, 4:30 PM EDT | Severe Thunderstorm Warning | LWX | 45 min |
| Apr 24, 6:10 PM EDT | Mesoscale Discussion | SPC | 65 min |
| Apr 24, 8:24 PM EDT | Severe Thunderstorm Warning | LWX | 34 min |
| Apr 24, 9:02 PM EDT | Mesoscale Discussion | SPC | 58 min |
| Apr 27, 1:23 PM EDT | Tornado Watch | SPC | 5 hr |
| Apr 27, 4:39 PM EDT | Mesoscale Discussion | SPC | 66 min |
| Apr 27, 6:00 PM EDT | Mesoscale Discussion | SPC | 60 min |
| Apr 27, 6:15 PM EDT | Tornado Watch | SPC | 6 hr |
| Apr 27, 7:55 PM EDT | Mesoscale Discussion | SPC | 65 min |
| Apr 27, 8:19 PM EDT | Severe Thunderstorm Warning | LWX | 36 min |
| Apr 28, 12:27 AM EDT | Mesoscale Discussion | SPC | 63 min |
| Apr 28, 12:41 AM EDT | Tornado Watch | SPC | 7 hr |
| Apr 28, 6:37 AM EDT | Tornado Warning | LWX | 38 min |
| Apr 28, 7:05 AM EDT | Tornado Warning | LWX | 25 min |
| Apr 28, 7:27 AM EDT | Flash Flood Warning | LWX | 5 hr |
| Apr 28, 7:38 AM EDT | Tornado Watch | SPC | 7 hr |
| Apr 28, 9:14 AM EDT | Tornado Warning | LWX | 31 min |
| Apr 28, 9:39 AM EDT | Severe Thunderstorm Warning | LWX | 36 min |
| Apr 28, 9:45 AM EDT | Flash Flood Warning | LWX | 101 min |
| Apr 28, 10:44 AM EDT | Mesoscale Discussion | SPC | 61 min |
| Apr 28, 12:15 PM EDT | Areal Flood Warning | LWX | 3 hr |
| May 4, 5:13 PM EDT | Special Weather Statement | LWX | 32 min |
| May 17, 6:27 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| May 18, 9:47 AM EDT | River Flood Warning | LWX | 58 hr |
| May 18, 11:55 AM EDT | Mesoscale Discussion | SPC | 65 min |
| May 18, 12:55 PM EDT | Severe Thunderstorm Watch | SPC | 8 hr |
| May 18, 3:08 PM EDT | Mesoscale Discussion | SPC | 67 min |
| May 18, 6:01 PM EDT | Mesoscale Discussion | SPC | 89 min |
| May 19, 7:15 PM EDT | Special Weather Statement | LWX | 30 min |
| May 19, 7:22 PM EDT | Severe Thunderstorm Warning | LWX | 38 min |
| May 23, 2:00 AM EDT | Special Weather Statement | LWX | 30 min |
| May 23, 10:33 AM EDT | Mesoscale Discussion | SPC | 87 min |
| May 23, 10:48 AM EDT | Severe Thunderstorm Watch | SPC | 9 hr |
| May 23, 2:33 PM EDT | Mesoscale Discussion | SPC | 87 min |
| May 23, 4:40 PM EDT | Mesoscale Discussion | SPC | 95 min |
| May 23, 5:12 PM EDT | Severe Thunderstorm Warning | LWX | 48 min |
| May 23, 5:57 PM EDT | Special Weather Statement | LWX | 48 min |
| May 23, 6:13 PM EDT | Severe Thunderstorm Warning | LWX | 47 min |
| May 24, 3:26 PM EDT | Special Weather Statement | LWX | 34 min |
| May 27, 12:24 PM EDT | Mesoscale Discussion | SPC | 96 min |
| May 27, 12:57 PM EDT | Severe Thunderstorm Watch | SPC | 9 hr |
| May 27, 6:14 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| May 27, 7:21 PM EDT | Severe Thunderstorm Warning | LWX | 39 min |
| May 27, 7:29 PM EDT | Severe Thunderstorm Warning | LWX | 46 min |
| May 27, 7:55 PM EDT | Severe Thunderstorm Warning | LWX | 50 min |
| Jun 1, 1:37 PM EDT | Mesoscale Discussion | SPC | 83 min |
| Jun 1, 2:24 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 9, 12:53 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 9, 1:45 PM EDT | Mesoscale Discussion | SPC | 90 min |
| Jun 9, 6:17 PM EDT | Mesoscale Discussion | SPC | 58 min |
| Jun 9, 6:44 PM EDT | Severe Thunderstorm Warning | LWX | 46 min |
| Jun 9, 7:15 PM EDT | Special Weather Statement | LWX | 30 min |
| Jun 10, 5:28 PM EDT | Mesoscale Discussion | SPC | 92 min |
| Jun 11, 12:44 PM EDT | Mesoscale Discussion | SPC | 91 min |
| Jun 12, 12:03 PM EDT | Mesoscale Discussion | SPC | 87 min |
| Jun 12, 1:48 PM EDT | Severe Thunderstorm Watch | SPC | 6 hr |
| Jun 12, 3:16 PM EDT | Severe Thunderstorm Warning | LWX | 44 min |
| Jun 12, 3:39 PM EDT | Mesoscale Discussion | SPC | 96 min |
| Jun 16, 6:01 PM EDT | Mesoscale Discussion | SPC | 89 min |
| Jun 17, 4:29 PM EDT | Severe Thunderstorm Warning | LWX | 33 min |
| Jun 17, 7:59 PM EDT | Special Weather Statement | LWX | 31 min |
| Jun 22, 2:03 PM EDT | Mesoscale Discussion | SPC | 117 min |
| Jun 24, 1:05 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jun 28, 7:21 PM EDT | Special Weather Statement | LWX | 24 min |
| Jul 3, 3:22 PM EDT | Mesoscale Discussion | SPC | 53 min |
| Jul 3, 4:21 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jul 3, 5:10 PM EDT | Special Weather Statement | LWX | 50 min |
| Jul 3, 5:27 PM EDT | Severe Thunderstorm Warning | LWX | 48 min |
| Jul 3, 5:35 PM EDT | Severe Thunderstorm Warning | LWX | 35 min |
| Jul 3, 5:58 PM EDT | Severe Thunderstorm Warning | LWX | 62 min |
| Jul 3, 6:03 PM EDT | Severe Thunderstorm Warning | LWX | 72 min |
| Jul 3, 7:00 PM EDT | Special Weather Statement | LWX | 60 min |
| Jul 7, 9:57 PM EDT | Special Weather Statement | LWX | 33 min |
| Jul 7, 10:01 PM EDT | Severe Thunderstorm Warning | LWX | 29 min |
| Jul 8, 11:44 AM EDT | Mesoscale Discussion | SPC | 61 min |
| Jul 8, 1:51 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jul 8, 3:01 PM EDT | Special Weather Statement | LWX | 89 min |
| Jul 8, 3:33 PM EDT | Flash Flood Warning | LWX | 3 hr |
| Jul 8, 4:10 PM EDT | Flash Flood Warning | LWX | 3 hr |
| Jul 8, 5:52 PM EDT | Mesoscale Discussion | SPC | 83 min |
| Jul 11, 5:47 PM EDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Jul 11, 7:10 PM EDT | Severe Thunderstorm Warning | LWX | 35 min |
| Jul 11, 7:42 PM EDT | Severe Thunderstorm Warning | LWX | 48 min |
| Jul 11, 7:44 PM EDT | Mesoscale Discussion | SPC | 61 min |
| Jul 11, 8:06 PM EDT | Severe Thunderstorm Warning | LWX | 39 min |
| Jul 11, 8:15 PM EDT | Severe Thunderstorm Warning | LWX | 45 min |
| Jul 11, 8:46 PM EDT | Severe Thunderstorm Warning | LWX | 44 min |
| Jul 13, 2:00 PM EDT | Special Weather Statement | LWX | 30 min |
| Jul 13, 2:16 PM EDT | Special Weather Statement | LWX | 29 min |
| Jul 13, 2:21 PM EDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Jul 22, 3:17 PM EDT | Mesoscale Discussion | SPC | 58 min |
| Jul 22, 4:26 PM EDT | Special Weather Statement | LWX | 19 min |
| Jul 22, 4:30 PM EDT | Severe Thunderstorm Warning | LWX | 45 min |
| Jul 25, 1:12 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jul 25, 3:16 PM EDT | Flash Flood Warning | LWX | 97 min |
| Aug 1, 3:22 PM EDT | Mesoscale Discussion | SPC | 83 min |
| Aug 1, 5:24 PM EDT | Severe Thunderstorm Warning | LWX | 51 min |
| Aug 1, 6:07 PM EDT | Severe Thunderstorm Warning | LWX | 38 min |
| Aug 7, 12:52 PM EDT | Mesoscale Discussion | SPC | 53 min |
| Aug 9, 3:21 PM EDT | Special Weather Statement | LWX | 24 min |
| Aug 13, 1:56 PM EDT | Special Weather Statement | LWX | 34 min |
| Aug 13, 2:07 PM EDT | Mesoscale Discussion | SPC | 113 min |
| Aug 14, 8:29 PM EDT | Special Weather Statement | LWX | 31 min |
| Aug 14, 9:02 PM EDT | Special Weather Statement | LWX | 28 min |
| Aug 14, 9:15 PM EDT | Severe Thunderstorm Warning | LWX | 22 min |
| Aug 14, 9:23 PM EDT | Flash Flood Warning | LWX | 3 hr |
| Aug 14, 9:36 PM EDT | Special Weather Statement | LWX | 54 min |
| Aug 14, 9:54 PM EDT | Flash Flood Warning | LWX | 3 hr |
| Aug 18, 5:21 PM EDT | Severe Thunderstorm Warning | LWX | 39 min |
| Aug 18, 5:44 PM EDT | Flash Flood Warning | LWX | 3 hr |
| Aug 18, 5:55 PM EDT | Severe Thunderstorm Warning | LWX | 50 min |
| Aug 18, 6:21 PM EDT | Severe Thunderstorm Warning | LWX | 39 min |
| Aug 18, 6:34 PM EDT | Special Weather Statement | LWX | 26 min |
| Aug 18, 6:39 PM EDT | Mesoscale Discussion | SPC | 96 min |
| Aug 18, 11:16 PM EDT | Special Weather Statement | LWX | 29 min |
| Aug 18, 11:58 PM EDT | Special Weather Statement | LWX | 32 min |
| Aug 19, 3:13 PM EDT | Mesoscale Discussion | SPC | 62 min |
| Aug 21, 11:54 AM EDT | Mesoscale Discussion | SPC | 2 hr |
| Aug 21, 12:52 PM EDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Aug 21, 1:28 PM EDT | Severe Thunderstorm Warning | LWX | 47 min |
| Aug 21, 1:40 PM EDT | Severe Thunderstorm Warning | LWX | 50 min |
| Aug 21, 3:11 PM EDT | Severe Thunderstorm Warning | LWX | 49 min |
| Aug 21, 3:12 PM EDT | Severe Thunderstorm Warning | LWX | 48 min |
| Aug 21, 7:12 PM EDT | Mesoscale Discussion | SPC | 63 min |
| Aug 21, 7:53 PM EDT | Special Weather Statement | LWX | 7 min |
| Aug 27, 5:26 PM EDT | Flash Flood Warning | LWX | 9 hr |
| Aug 27, 8:54 PM EDT | River Flood Warning | LWX | 7 hr |
| Aug 27, 9:38 PM EDT | Flash Flood Warning | LWX | 6 hr |
| Aug 28, 1:58 AM EDT | Areal Flood Warning | LWX | 6 hr |
| Sep 3, 9:21 AM EDT | Special Weather Statement | LWX | 24 min |
| Sep 3, 9:44 AM EDT | Severe Thunderstorm Warning | LWX | 46 min |
| Sep 3, 10:29 AM EDT | Special Weather Statement | LWX | 31 min |
| Sep 5, 9:58 PM EDT | Special Weather Statement | LWX | 62 min |
| Sep 5, 10:04 PM EDT | Flash Flood Warning | LWX | 4 hr |
| Sep 6, 12:26 PM EDT | River Flood Watch | LWX | 29 hr |
| Sep 6, 10:17 PM EDT | River Flood Warning | LWX | 19 hr |
| Sep 7, 1:03 PM EDT | Special Weather Statement | LWX | 27 min |
| Sep 7, 1:14 PM EDT | Flash Flood Warning | LWX | 3 hr |
| Sep 7, 9:09 PM EDT | Flash Flood Warning | LWX | 3 hr |
| Sep 7, 10:03 PM EDT | Flash Flood Warning | LWX | 6 hr |
| Sep 8, 3:55 AM EDT | Areal Flood Warning | LWX | 14 hr |
| Sep 8, 4:02 AM EDT | Areal Flood Warning | LWX | 20 hr |
| Sep 8, 9:41 AM EDT | River Flood Warning | LWX | 32 hr |
| Sep 8, 10:28 AM EDT | Flash Flood Warning | LWX | 9 hr |
| Sep 8, 1:00 PM EDT | Flash Flood Warning | LWX | 6 hr |
| Sep 8, 2:31 PM EDT | Flash Flood Warning | LWX | 5 hr |
| Sep 8, 5:27 PM EDT | Flash Flood Warning | LWX | 3 hr |
| Sep 8, 6:21 PM EDT | Mesoscale Discussion | SPC | 114 min |
| Sep 8, 7:01 PM EDT | Flash Flood Warning | LWX | 4 hr |
| Sep 8, 8:32 PM EDT | Flash Flood Warning | LWX | 4 hr |
| Sep 8, 9:50 PM EDT | Areal Flood Warning | LWX | 4 hr |
| Sep 9, 1:47 AM EDT | Areal Flood Warning | LWX | 8 hr |
| Sep 11, 3:24 PM EDT | Special Weather Statement | LWX | 21 min |
| Sep 11, 4:08 PM EDT | Special Weather Statement | LWX | 37 min |
| Sep 11, 6:38 PM EDT | Mesoscale Discussion | SPC | 97 min |
| Sep 14, 3:22 PM EDT | Mesoscale Discussion | SPC | 53 min |
| Sep 14, 7:13 PM EDT | Special Weather Statement | LWX | 47 min |
| Sep 14, 8:01 PM EDT | Special Weather Statement | LWX | 44 min |
| Sep 14, 10:11 PM EDT | Special Weather Statement | LWX | 34 min |
| Sep 29, 2:14 PM EDT | Special Weather Statement | LWX | 31 min |
| Oct 13, 4:28 PM EDT | Tornado Watch | SPC | 4 hr |
| Oct 13, 6:02 PM EDT | Special Weather Statement | LWX | 28 min |
| Oct 13, 6:53 PM EDT | Mesoscale Discussion | SPC | 97 min |
| Oct 13, 11:23 PM EDT | River Flood Warning | LWX | 4 hr |
| Dec 7, 2:08 PM EST | Areal Flood Warning | LWX | 14 hr |
| Dec 7, 9:36 PM EST | Areal Flood Warning | LWX | 4 hr |
| Dec 7, 10:11 PM EST | River Flood Warning | LWX | 7 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 | 44 |
| Tornado Warning | 6 |
| Severe Thunderstorm Watch | 15 |
| Tornado Watch | 8 |
| Mesoscale Discussion | 55 |
| Special Weather Statement | 44 |
| Flooding | |
| Areal Flood Warning | 10 |
| Flash Flood Warning | 22 |
| River Flood Warning | 10 |
| River Flood Watch | 1 |
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordForecastThe radar archive20102012
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.