Alert archive / Virginia / Fairfax County
Weather alerts in Fairfax County, Virginia, 2017
125 weather alerts in 2017, from the National Weather Service and the Storm Prediction Center. An alert counts here when it covered this county.
Fairfax County and its neighbors
Each county as a circle sized by its count in 2017. Tap one for its archive.
- Alerts
- 125
- Warnings
- 51
- Watches
- 17
- Advisories
- 27
- Busiest month
- July29 alerts
- Busiest day
- March 1, 20177 alerts
Over time
By month
Warning verification
How often warnings here had a storm report inside them, and how much warning the reports had.
1 of 1 tornado warnings covering Fairfax County in 2017 had a tornado report inside them; 3 of 3 tornado reports fell inside a warning, on average 10 minutes after it went out.
Fairfax County, 2017
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| Tornado warnings | 1 | 1 | 0% | 3 | 100% | 10 min |
| Severe thunderstorm warnings | 33 | 30 | 9% | 62 | 81% | 16 min |
| Flash flood warnings | 6 | 4 | 33% | 5 | 100% | 69 min |
Each office's whole area, 2017
| Warnings | With a report | False alarm ratio | Reports | Inside a warning | Mean lead time | |
|---|---|---|---|---|---|---|
| NWS Baltimore/Washington: tornado warnings | 11 | 4 | 64% | 18 | 33% | 7 min |
| NWS Baltimore/Washington: severe thunderstorm warnings | 261 | 194 | 26% | 976 | 81% | 19 min |
| NWS Baltimore/Washington: flash flood warnings | 49 | 34 | 31% | 130 | 81% | 78 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 6, 8:48 AM EST | Winter Weather Advisory | LWX | 30 hr |
| Jan 13, 3:32 AM EST | Winter Weather Advisory | LWX | 47 hr |
| Jan 17, 9:20 PM EST | Dense Fog Advisory | LWX | 7 hr |
| Jan 22, 1:51 PM EST | Wind Advisory | LWX | 26 hr |
| Jan 26, 3:35 AM EST | Wind Advisory | LWX | 15 hr |
| Jan 29, 3:42 AM EST | Winter Weather Advisory | LWX | 33 hr |
| Feb 9, 8:57 AM EST | Wind Advisory | LWX | 9 hr |
| Feb 11, 2:22 PM EST | High Wind Watch | LWX | 13 hr |
| Feb 12, 3:36 AM EST | High Wind Warning | LWX | 32 hr |
| Feb 12, 3:36 AM EST | Wind Advisory | LWX | 37 hr |
| Feb 12, 9:49 PM EST | Special Weather Statement | LWX | 116 min |
| Feb 12, 10:38 PM EST | Severe Thunderstorm Warning | LWX | 38 min |
| Feb 12, 11:02 PM EST | Severe Thunderstorm Warning | LWX | 43 min |
| Feb 25, 12:24 PM EST | Mesoscale Discussion | SPC | 2 hr |
| Feb 25, 1:30 PM EST | Severe Thunderstorm Watch | SPC | 6 hr |
| Feb 25, 2:35 PM EST | Severe Thunderstorm Warning | LWX | 40 min |
| Mar 1, 9:44 AM EST | Mesoscale Discussion | SPC | 91 min |
| Mar 1, 10:38 AM EST | Severe Thunderstorm Watch | SPC | 4 hr |
| Mar 1, 12:25 PM EST | Mesoscale Discussion | SPC | 65 min |
| Mar 1, 1:05 PM EST | Severe Thunderstorm Warning | LWX | 40 min |
| Mar 1, 1:36 PM EST | Severe Thunderstorm Warning | LWX | 54 min |
| Mar 1, 1:40 PM EST | Severe Thunderstorm Warning | LWX | 50 min |
| Mar 1, 2:47 PM EST | Wind Advisory | LWX | 18 hr |
| Mar 11, 7:52 PM EST | Winter Storm Watch | LWX | 31 hr |
| Mar 12, 2:58 PM EDT | Winter Storm Warning | LWX | 47 hr |
| Mar 13, 4:00 AM EDT | Winter Weather Advisory | LWX | 34 hr |
| Mar 13, 10:01 PM EDT | Mesoscale Discussion | SPC | 4 hr |
| Mar 14, 3:22 AM EDT | Mesoscale Discussion | SPC | 5 hr |
| Mar 15, 3:52 AM EDT | Wind Advisory | LWX | 16 hr |
| Mar 21, 10:00 AM EDT | Special Weather Statement | LWX | 15 min |
| Mar 27, 4:37 AM EDT | Dense Fog Advisory | LWX | 5 hr |
| Mar 31, 11:23 AM EDT | Areal Flood Warning | LWX | 6 hr |
| Apr 6, 5:59 AM EDT | Mesoscale Discussion | SPC | 91 min |
| Apr 6, 12:18 PM EDT | Mesoscale Discussion | SPC | 57 min |
| Apr 6, 12:43 PM EDT | Severe Thunderstorm Warning | LWX | 47 min |
| Apr 6, 12:45 PM EDT | Severe Thunderstorm Watch | SPC | 4 hr |
| Apr 6, 1:12 PM EDT | Severe Thunderstorm Warning | LWX | 48 min |
| Apr 6, 1:26 PM EDT | Tornado Warning | LWX | 19 min |
| Apr 8, 2:10 PM EDT | Frost Advisory | LWX | 18 hr |
| Apr 20, 8:05 PM EDT | Severe Thunderstorm Warning | LWX | 40 min |
| Apr 21, 4:00 PM EDT | Severe Thunderstorm Warning | LWX | 45 min |
| Apr 21, 4:19 PM EDT | Mesoscale Discussion | SPC | 56 min |
| Apr 30, 3:25 PM EDT | Mesoscale Discussion | SPC | 95 min |
| May 1, 5:54 PM EDT | Severe Thunderstorm Watch | SPC | 5 hr |
| May 1, 8:28 PM EDT | Mesoscale Discussion | SPC | 92 min |
| May 5, 7:49 AM EDT | Severe Thunderstorm Warning | LWX | 56 min |
| May 5, 8:35 AM EDT | Severe Thunderstorm Warning | LWX | 21 min |
| May 5, 8:45 AM EDT | Areal Flood Warning | LWX | 4 hr |
| May 5, 8:53 AM EDT | Areal Flood Warning | LWX | 3 hr |
| May 5, 6:15 PM EDT | Mesoscale Discussion | SPC | 90 min |
| May 18, 7:03 PM EDT | Severe Thunderstorm Warning | LWX | 42 min |
| May 18, 7:24 PM EDT | Severe Thunderstorm Warning | LWX | 66 min |
| May 18, 7:39 PM EDT | Severe Thunderstorm Warning | LWX | 66 min |
| May 18, 7:57 PM EDT | Severe Thunderstorm Warning | LWX | 63 min |
| May 18, 8:23 PM EDT | Severe Thunderstorm Warning | LWX | 34 min |
| May 19, 3:36 PM EDT | Mesoscale Discussion | SPC | 114 min |
| May 25, 12:59 PM EDT | Mesoscale Discussion | SPC | 61 min |
| May 25, 4:55 PM EDT | Severe Thunderstorm Warning | LWX | 50 min |
| May 25, 5:28 PM EDT | Severe Thunderstorm Warning | LWX | 17 min |
| May 31, 5:12 PM EDT | Severe Thunderstorm Warning | LWX | 26 min |
| Jun 19, 4:09 AM EDT | Flash Flood Watch | LWX | 14 hr |
| Jun 19, 12:14 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jun 19, 12:48 PM EDT | Severe Thunderstorm Watch | SPC | 8 hr |
| Jun 19, 2:21 PM EDT | Mesoscale Discussion | SPC | 114 min |
| Jun 19, 2:45 PM EDT | Severe Thunderstorm Warning | LWX | 45 min |
| Jun 19, 3:19 PM EDT | Severe Thunderstorm Warning | LWX | 41 min |
| Jul 1, 12:54 PM EDT | Mesoscale Discussion | SPC | 66 min |
| Jul 1, 1:34 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Jul 1, 2:38 PM EDT | Severe Thunderstorm Warning | LWX | 41 min |
| Jul 1, 3:00 PM EDT | Severe Thunderstorm Warning | LWX | 45 min |
| Jul 1, 4:10 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Jul 6, 6:20 AM EDT | Flash Flood Watch | LWX | 20 hr |
| Jul 6, 10:07 AM EDT | Areal Flood Warning | LWX | 8 hr |
| Jul 7, 7:40 PM EDT | Severe Thunderstorm Warning | LWX | 35 min |
| Jul 12, 3:05 PM EDT | Heat Advisory | LWX | 28 hr |
| Jul 14, 12:12 PM EDT | Heat Advisory | LWX | 6 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, 4:14 PM EDT | Severe Thunderstorm Warning | LWX | 27 min |
| Jul 14, 4:23 PM EDT | Mesoscale Discussion | SPC | 67 min |
| Jul 14, 4:24 PM EDT | Severe Thunderstorm Warning | LWX | 51 min |
| Jul 18, 2:31 PM EDT | Mesoscale Discussion | SPC | 59 min |
| Jul 20, 3:21 AM EDT | Heat Advisory | LWX | 16 hr |
| Jul 20, 8:30 PM EDT | Heat Advisory | LWX | 23 hr |
| Jul 22, 3:09 AM EDT | Heat Advisory | LWX | 16 hr |
| Jul 22, 1:12 PM EDT | Mesoscale Discussion | SPC | 3 hr |
| Jul 23, 11:39 PM EDT | Areal Flood Warning | LWX | 6 hr |
| Jul 24, 5:02 PM EDT | Severe Thunderstorm Warning | LWX | 43 min |
| Jul 24, 6:09 PM EDT | Mesoscale Discussion | SPC | 3 hr |
| Jul 27, 1:47 PM EDT | Flash Flood Watch | LWX | 48 hr |
| Jul 28, 10:25 AM EDT | Flash Flood Warning | LWX | 4 hr |
| Jul 28, 3:18 PM EDT | Flash Flood Warning | LWX | 3 hr |
| Jul 28, 6:05 PM EDT | Areal Flood Warning | LWX | 12 hr |
| Jul 29, 12:09 AM EDT | Flash Flood Warning | LWX | 3 hr |
| Jul 29, 5:50 AM EDT | Areal Flood Warning | LWX | 6 hr |
| Aug 2, 1:30 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Aug 3, 6:13 PM EDT | Severe Thunderstorm Warning | LWX | 47 min |
| Aug 3, 6:28 PM EDT | Mesoscale Discussion | SPC | 62 min |
| Aug 3, 6:47 PM EDT | Severe Thunderstorm Warning | LWX | 24 min |
| Aug 6, 5:29 PM EDT | Flash Flood Watch | LWX | 23 hr |
| Aug 11, 3:48 PM EDT | Mesoscale Discussion | SPC | 87 min |
| Aug 11, 7:00 PM EDT | Severe Thunderstorm Warning | LWX | 45 min |
| Aug 11, 7:40 PM EDT | Severe Thunderstorm Warning | LWX | 65 min |
| Aug 11, 8:47 PM EDT | Flash Flood Warning | LWX | 3 hr |
| Aug 11, 10:18 PM EDT | Areal Flood Warning | LWX | 6 hr |
| Aug 12, 4:11 PM EDT | Severe Thunderstorm Watch | SPC | 7 hr |
| Aug 12, 7:32 PM EDT | Severe Thunderstorm Warning | LWX | 43 min |
| Aug 15, 11:15 AM EDT | Flash Flood Warning | LWX | 3 hr |
| Aug 15, 10:31 PM EDT | Dense Fog Advisory | LWX | 11 hr |
| Aug 18, 3:42 AM EDT | Heat Advisory | LWX | 15 hr |
| Aug 18, 12:35 PM EDT | Flash Flood Watch | LWX | 8 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, 6:34 PM EDT | Flash Flood Warning | LWX | 3 hr |
| Aug 21, 2:53 PM EDT | Mesoscale Discussion | SPC | 2 hr |
| Oct 17, 1:39 PM EDT | Frost Advisory | LWX | 19 hr |
| Oct 23, 6:31 PM EDT | Wind Advisory | LWX | 10 hr |
| Oct 26, 3:53 AM EDT | Frost Advisory | LWX | 29 hr |
| Oct 29, 3:44 AM EDT | Wind Advisory | LWX | 30 hr |
| Nov 9, 2:17 AM EST | Freeze Watch | LWX | 24 hr |
| Nov 10, 2:41 AM EST | Freeze Warning | LWX | 31 hr |
| Nov 18, 3:40 AM EST | Wind Advisory | LWX | 33 hr |
| Dec 8, 5:50 AM EST | Winter Weather Advisory | LWX | 51 hr |
| Dec 24, 10:35 AM EST | Wind Advisory | LWX | 26 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 | 33 |
| Tornado Warning | 1 |
| Severe Thunderstorm Watch | 9 |
| Mesoscale Discussion | 28 |
| Special Weather Statement | 2 |
| Flooding | |
| Areal Flood Warning | 8 |
| Flash Flood Warning | 6 |
| Flash Flood Watch | 5 |
| Winter | |
| Winter Storm Warning | 1 |
| Winter Storm Watch | 1 |
| Winter Weather Advisory | 5 |
| Heat | |
| Heat Advisory | 6 |
| Cold | |
| Freeze Warning | 1 |
| Freeze Watch | 1 |
| Frost Advisory | 3 |
| Wind and dust | |
| High Wind Warning | 1 |
| High Wind Watch | 1 |
| Wind Advisory | 10 |
| Fog and smoke | |
| Dense Fog Advisory | 3 |
The busiest days
Days with the most alerts issued, by UTC date.
Nearby
Alerts in force nowTornadoes on recordForecastThe radar archive20162018
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.