Alert archive / Virginia / Loudoun County
Weather alerts in Loudoun County, Virginia, 2010
152 weather alerts in 2010, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered this county.
Loudoun County and its neighbors
Each county as a circle sized by its count in 2010. Tap one for its archive.
- Alerts
- 152
- Warnings
- 64
- Watches
- 19
- Advisories
- 0
- Busiest month
- June37 alerts
- Busiest day
- August 5, 201011 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
Loudoun County, 2010
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 0 | 0 | ||||
| Severe thunderstorm warnings | 42 | 34 | 19% | 43 | 91% | 20 min |
| Flash flood warnings | 10 | 9 | 10% | 1 | 100% | 5 min |
Each office's whole area, 2010
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Baltimore/Washington: tornado warnings | 31 | 2 | 94% | 4 | 50% | 17 min |
| NWS Baltimore/Washington: severe thunderstorm warnings | 257 | 198 | 23% | 762 | 86% | 21 min |
| NWS Baltimore/Washington: flash flood warnings | 64 | 35 | 45% | 139 | 92% | 166 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, 4:18 PM EST | River Flood Warning | LWX | 37 hr |
| Jan 25, 4:18 PM EST | River Flood Warning | LWX | 54 hr |
| Feb 5, 11:45 AM EST | Mesoscale Discussion | SPC | 4 hr |
| Feb 5, 6:58 PM EST | Mesoscale Discussion | SPC | 4 hr |
| Feb 6, 6:53 AM EST | Mesoscale Discussion | SPC | 4 hr |
| Mar 13, 10:25 AM EST | Areal Flood Warning | LWX | 6 hr |
| Mar 13, 11:42 AM EST | River Flood Warning | LWX | 58 hr |
| Mar 13, 11:42 AM EST | River Flood Warning | LWX | 72 hr |
| Mar 13, 4:17 PM EST | Areal Flood Warning | LWX | 8 hr |
| Mar 13, 4:38 PM EST | River Flood Warning | LWX | 18 hr |
| Mar 14, 12:24 AM EST | Areal Flood Warning | LWX | 6 hr |
| Mar 14, 7:19 AM EDT | Areal Flood Warning | LWX | 6 hr |
| Mar 22, 12:44 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Mar 22, 6:53 PM EDT | Mesoscale Discussion | SPC | 3 hr |
| Apr 8, 5:37 PM EDT | Special Weather Statement | LWX | 23 min |
| Apr 8, 6:37 PM EDT | Mesoscale Discussion | SPC | 53 min |
| Apr 16, 6:16 PM EDT | Special Weather Statement | LWX | 74 min |
| Apr 16, 6:20 PM EDT | Special Weather Statement | LWX | 70 min |
| Apr 16, 8:05 PM EDT | Special Weather Statement | LWX | 70 min |
| Apr 25, 10:56 AM EDT | Mesoscale Discussion | SPC | 2 hr |
| Apr 25, 2:26 PM EDT | Mesoscale Discussion | SPC | 94 min |
| Apr 25, 4:37 PM EDT | Severe Thunderstorm Watch | SPC | 6 hr |
| Apr 25, 6:10 PM EDT | Severe Thunderstorm Warning | LWX | 50 min |
| Apr 25, 6:16 PM EDT | Mesoscale Discussion | SPC | 89 min |
| Apr 25, 7:01 PM EDT | Flash Flood Warning | LWX | 3 hr |
| Apr 25, 7:04 PM EDT | Severe Thunderstorm Warning | LWX | 41 min |
| Apr 25, 7:19 PM EDT | Severe Thunderstorm Warning | LWX | 41 min |
| Apr 25, 7:54 PM EDT | Severe Thunderstorm Warning | LWX | 51 min |
| Apr 25, 8:28 PM EDT | Severe Thunderstorm Warning | LWX | 47 min |
| Apr 25, 8:53 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Apr 25, 9:11 PM EDT | Special Weather Statement | LWX | 34 min |
| May 2, 4:45 PM EDT | Mesoscale Discussion | SPC | 60 min |
| May 2, 5:58 PM EDT | Severe Thunderstorm Watch | SPC | 5 hr |
| May 2, 8:27 PM EDT | Mesoscale Discussion | SPC | 63 min |
| May 3, 5:11 AM EDT | Special Weather Statement | LWX | 49 min |
| May 14, 11:56 AM EDT | Mesoscale Discussion | SPC | 2 hr |
| May 14, 2:29 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| May 14, 5:47 PM EDT | Severe Thunderstorm Warning | LWX | 43 min |
| May 14, 6:35 PM EDT | Mesoscale Discussion | SPC | 55 min |
| May 23, 1:19 PM EDT | Flash Flood Warning | LWX | 3 hr |
| May 27, 1:23 PM EDT | Severe Thunderstorm Watch | SPC | 8 hr |
| May 27, 4:13 PM EDT | Mesoscale Discussion | SPC | 62 min |
| May 27, 8:08 PM EDT | Mesoscale Discussion | SPC | 97 min |
| May 27, 8:59 PM EDT | Severe Thunderstorm Warning | LWX | 46 min |
| May 27, 9:22 PM EDT | Severe Thunderstorm Warning | LWX | 38 min |
| May 27, 9:59 PM EDT | Special Weather Statement | LWX | 31 min |
| May 27, 10:01 PM EDT | Severe Thunderstorm Warning | LWX | 44 min |
| May 27, 10:10 PM EDT | Severe Thunderstorm Warning | LWX | 50 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, 3:41 PM EDT | Severe Thunderstorm Warning | LWX | 49 min |
| Jun 3, 4:19 PM EDT | Severe Thunderstorm Warning | LWX | 41 min |
| Jun 3, 4:23 PM EDT | Severe Thunderstorm Warning | LWX | 52 min |
| Jun 3, 6:28 PM EDT | Mesoscale Discussion | SPC | 62 min |
| Jun 4, 1:09 PM EDT | Mesoscale Discussion | SPC | 66 min |
| Jun 4, 2:39 PM EDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Jun 4, 3:38 PM EDT | Severe Thunderstorm Warning | LWX | 52 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, 11:42 AM EDT | Mesoscale Discussion | SPC | 63 min |
| Jun 6, 12:40 PM EDT | Tornado Watch | SPC | 6 hr |
| Jun 6, 1:18 PM EDT | Severe Thunderstorm Warning | LWX | 27 min |
| Jun 6, 1:43 PM EDT | Severe Thunderstorm Warning | LWX | 47 min |
| Jun 12, 2:47 PM EDT | Mesoscale Discussion | SPC | 88 min |
| Jun 12, 4:03 PM EDT | Severe Thunderstorm Warning | LWX | 42 min |
| Jun 12, 4:16 PM EDT | Mesoscale Discussion | SPC | 89 min |
| Jun 12, 4:36 PM EDT | Special Weather Statement | LWX | 24 min |
| Jun 12, 4:51 PM EDT | Special Weather Statement | LWX | 24 min |
| Jun 12, 5:02 PM EDT | Special Weather Statement | LWX | 28 min |
| Jun 12, 5:11 PM EDT | Severe Thunderstorm Warning | LWX | 28 min |
| Jun 22, 11:35 AM EDT | Mesoscale Discussion | SPC | 25 min |
| Jun 22, 3:48 PM EDT | Mesoscale Discussion | SPC | 27 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, 2:34 PM EDT | Mesoscale Discussion | SPC | 116 min |
| Jun 24, 3:00 PM EDT | Severe Thunderstorm Warning | LWX | 49 min |
| Jun 27, 4:55 PM EDT | Severe Thunderstorm Warning | LWX | 23 min |
| Jun 28, 12:26 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jun 28, 12:49 PM EDT | Special Weather Statement | LWX | 26 min |
| Jun 28, 1:12 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jun 28, 1:35 PM EDT | Special Weather Statement | LWX | 25 min |
| Jun 28, 1:55 PM EDT | Severe Thunderstorm Warning | LWX | 50 min |
| Jun 28, 2:18 PM EDT | Severe Thunderstorm Warning | LWX | 42 min |
| Jun 28, 3:53 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jul 8, 8:00 PM EDT | Special Weather Statement | LWX | 60 min |
| Jul 12, 2:42 PM EDT | Special Weather Statement | LWX | 48 min |
| Jul 19, 5:05 PM EDT | Special Weather Statement | LWX | 25 min |
| Jul 19, 5:44 PM EDT | Severe Thunderstorm Warning | LWX | 33 min |
| Jul 25, 10:48 AM EDT | Mesoscale Discussion | SPC | 27 min |
| Jul 25, 12:50 PM EDT | Mesoscale Discussion | SPC | 55 min |
| Jul 25, 1:21 PM EDT | Mesoscale Discussion | SPC | 54 min |
| Jul 25, 1:46 PM EDT | Severe Thunderstorm Watch | SPC | 6 hr |
| Jul 25, 2:36 PM EDT | Severe Thunderstorm Warning | LWX | 54 min |
| Jul 25, 3:07 PM EDT | Severe Thunderstorm Warning | LWX | 38 min |
| Jul 25, 3:25 PM EDT | Mesoscale Discussion | SPC | 65 min |
| Jul 29, 11:36 AM EDT | Mesoscale Discussion | SPC | 54 min |
| Jul 29, 11:54 AM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jul 29, 12:31 PM EDT | Severe Thunderstorm Warning | LWX | 44 min |
| Aug 4, 5:30 PM EDT | Mesoscale Discussion | SPC | 30 min |
| Aug 4, 5:52 PM EDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Aug 4, 6:59 PM EDT | Severe Thunderstorm Warning | LWX | 61 min |
| Aug 4, 7:48 PM EDT | Mesoscale Discussion | SPC | 87 min |
| Aug 5, 12:37 PM EDT | Mesoscale Discussion | SPC | 53 min |
| Aug 5, 1:19 PM EDT | Severe Thunderstorm Watch | SPC | 9 hr |
| Aug 5, 2:20 PM EDT | Special Weather Statement | LWX | 25 min |
| Aug 5, 2:26 PM EDT | Severe Thunderstorm Warning | LWX | 49 min |
| Aug 5, 3:01 PM EDT | Severe Thunderstorm Warning | LWX | 44 min |
| Aug 5, 3:53 PM EDT | Severe Thunderstorm Warning | LWX | 52 min |
| Aug 5, 3:56 PM EDT | Mesoscale Discussion | SPC | 64 min |
| Aug 5, 4:29 PM EDT | Severe Thunderstorm Warning | LWX | 46 min |
| Aug 5, 4:54 PM EDT | Flash Flood Warning | LWX | 105 min |
| Aug 5, 5:29 PM EDT | Severe Thunderstorm Warning | LWX | 46 min |
| Aug 5, 6:23 PM EDT | Mesoscale Discussion | SPC | 97 min |
| Aug 12, 1:52 PM EDT | Mesoscale Discussion | SPC | 83 min |
| Aug 12, 2:12 PM EDT | Special Weather Statement | LWX | 33 min |
| Aug 12, 2:45 PM EDT | Severe Thunderstorm Warning | LWX | 45 min |
| Aug 12, 2:51 PM EDT | Severe Thunderstorm Watch | SPC | 5 hr |
| Aug 12, 5:13 PM EDT | Severe Thunderstorm Warning | LWX | 62 min |
| Aug 12, 5:39 PM EDT | Special Weather Statement | LWX | 36 min |
| Aug 16, 2:01 PM EDT | Mesoscale Discussion | SPC | 89 min |
| Aug 16, 2:13 PM EDT | Severe Thunderstorm Watch | SPC | 6 hr |
| Aug 18, 7:54 AM EDT | Areal Flood Warning | LWX | 3 hr |
| Sep 16, 11:24 PM EDT | Special Weather Statement | LWX | 51 min |
| Sep 16, 11:58 PM EDT | Special Weather Statement | LWX | 32 min |
| Sep 22, 2:04 PM EDT | Special Weather Statement | LWX | 41 min |
| Sep 22, 2:15 PM EDT | Severe Thunderstorm Warning | LWX | 45 min |
| Sep 22, 2:31 PM EDT | Mesoscale Discussion | SPC | 59 min |
| Sep 22, 2:45 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Sep 22, 2:49 PM EDT | Severe Thunderstorm Warning | LWX | 41 min |
| Sep 22, 3:24 PM EDT | Severe Thunderstorm Warning | LWX | 32 min |
| Sep 30, 4:57 AM EDT | Flash Flood Warning | LWX | 6 hr |
| Sep 30, 6:39 AM EDT | Flash Flood Warning | LWX | 6 hr |
| Sep 30, 10:29 AM EDT | Flash Flood Warning | LWX | 4 hr |
| Sep 30, 10:38 AM EDT | Flash Flood Warning | LWX | 6 hr |
| Sep 30, 11:12 AM EDT | River Flood Warning | LWX | 5 hr |
| Sep 30, 11:12 AM EDT | River Flood Warning | LWX | 5 hr |
| Sep 30, 12:22 PM EDT | Flash Flood Warning | LWX | 6 hr |
| Sep 30, 4:40 PM EDT | Flash Flood Warning | LWX | 11 hr |
| Sep 30, 10:56 PM EDT | Flash Flood Warning | LWX | 4 hr |
| Oct 26, 7:19 PM EDT | Tornado Watch | SPC | 12 hr |
| Oct 26, 11:05 PM EDT | Mesoscale Discussion | SPC | 55 min |
| Oct 27, 12:24 AM EDT | Mesoscale Discussion | SPC | 66 min |
| Nov 16, 11:52 PM EST | Special Weather Statement | LWX | 23 min |
| Nov 16, 11:59 PM EST | Severe Thunderstorm Warning | LWX | 46 min |
| Nov 17, 12:06 AM EST | Severe Thunderstorm Watch | SPC | 4 hr |
| Nov 17, 12:35 AM EST | Severe Thunderstorm Warning | LWX | 17 min |
| Dec 1, 3:48 AM EST | Tornado Watch | SPC | 7 hr |
| Dec 1, 4:58 AM EST | Severe Thunderstorm Warning | LWX | 47 min |
| Dec 1, 5:44 AM EST | Severe Thunderstorm Warning | LWX | 26 min |
| Dec 1, 6:01 AM EST | Special Weather Statement | LWX | 119 min |
| Dec 1, 7:25 AM EST | Severe Thunderstorm Warning | LWX | 35 min |
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 | 42 |
| Severe Thunderstorm Watch | 16 |
| Tornado Watch | 3 |
| Mesoscale Discussion | 46 |
| Special Weather Statement | 23 |
| Flooding | |
| Areal Flood Warning | 5 |
| Flash Flood Warning | 10 |
| River Flood Warning | 7 |
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordForecastThe radar archive20092011
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.