Alert archive / Virginia / Loudoun County

Weather alerts in Loudoun County, Virginia, 2020

172 weather alerts in 2020, 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 2020. Tap one for its archive.

Alerts: 172
Warnings: 65
Watches: 38
Advisories: 34
Busiest month: June31 alerts
Busiest day: August 7, 20209 alerts

Over time

By month

Warning verification

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

0 of 1 tornado reports fell inside a warning.

Loudoun County, 2020

	Warnings	With a report	False alarm ratio	Reports	Inside a warning	Mean lead time
Tornado warnings	0			1	0%
Severe thunderstorm warnings	44	36	18%	49	67%	21 min
Flash flood warnings	6	5	17%	9	100%	52 min

Each office's whole area, 2020

	Warnings	With a report	False alarm ratio	Reports	Inside a warning	Mean lead time
NWS Baltimore/Washington: tornado warnings	27	6	78%	15	47%	9 min
NWS Baltimore/Washington: severe thunderstorm warnings	456	314	31%	1,047	79%	23 min
NWS Baltimore/Washington: flash flood warnings	66	34	48%	130	90%	72 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 4, 4:14 AM EST	Dense Fog Advisory	LWX	7 hr
Jan 6, 1:49 PM EST	Winter Weather Advisory	LWX	29 hr
Jan 7, 12:29 PM EST	Mesoscale Discussion	SPC	2 hr
Jan 8, 3:40 AM EST	Wind Advisory	LWX	13 hr
Jan 8, 7:56 AM EST	Snow Squall Warning	LWX	34 min
Jan 14, 10:41 PM EST	Dense Fog Advisory	LWX	10 hr
Jan 15, 9:26 AM EST	Dense Fog Advisory	LWX	34 min
Jan 17, 1:33 PM EST	Winter Weather Advisory	LWX	29 hr
Feb 6, 9:30 PM EST	Wind Advisory	LWX	20 hr
Feb 7, 4:08 AM EST	Dense Fog Advisory	LWX	3 hr
Feb 7, 7:26 AM EST	Severe Thunderstorm Warning	LWX	34 min
Feb 26, 12:54 AM EST	Dense Fog Advisory	LWX	8 hr
Feb 26, 2:49 PM EST	Mesoscale Discussion	SPC	116 min
Mar 3, 4:27 PM EST	Mesoscale Discussion	SPC	2 hr
Mar 3, 6:14 PM EST	Severe Thunderstorm Warning	LWX	18 min
Mar 3, 10:26 PM EST	Severe Thunderstorm Warning	LWX	34 min
Mar 3, 10:52 PM EST	Mesoscale Discussion	SPC	113 min
Mar 3, 10:54 PM EST	Severe Thunderstorm Warning	LWX	36 min
Mar 29, 3:32 AM EDT	Dense Fog Advisory	LWX	7 hr
Mar 29, 11:16 PM EDT	Dense Fog Advisory	LWX	5 hr
Apr 8, 3:43 AM EDT	Severe Thunderstorm Warning	LWX	47 min
Apr 8, 3:53 AM EDT	Mesoscale Discussion	SPC	97 min
Apr 8, 8:13 PM EDT	Wind Advisory	LWX	23 hr
Apr 9, 11:44 AM EDT	Severe Thunderstorm Warning	LWX	46 min
Apr 9, 7:38 PM EDT	Wind Advisory	LWX	22 hr
Apr 9, 7:47 PM EDT	Freeze Watch	LWX	19 hr
Apr 10, 2:28 PM EDT	Freeze Warning	LWX	19 hr
Apr 12, 12:35 PM EDT	Wind Advisory	LWX	29 hr
Apr 13, 10:34 AM EDT	Mesoscale Discussion	SPC	86 min
Apr 13, 11:33 AM EDT	Tornado Watch	SPC	5 hr
Apr 13, 1:20 PM EDT	Severe Thunderstorm Warning	LWX	40 min
Apr 13, 1:20 PM EDT	Mesoscale Discussion	SPC	85 min
Apr 13, 1:48 PM EDT	Severe Thunderstorm Warning	LWX	42 min
Apr 15, 1:09 PM EDT	Freeze Watch	LWX	24 hr
Apr 16, 1:19 PM EDT	Freeze Warning	LWX	20 hr
Apr 17, 7:20 PM EDT	Freeze Watch	LWX	18 hr
Apr 18, 1:19 PM EDT	Frost Advisory	LWX	20 hr
Apr 21, 4:04 AM EDT	Freeze Warning	LWX	27 hr
Apr 29, 4:24 AM EDT	Flood Watch	LWX	39 hr
May 1, 4:30 AM EDT	River Flood Watch	LWX	11 hr
May 1, 3:39 PM EDT	River Flood Warning	LWX	25 hr
May 3, 7:35 PM EDT	Flash Flood Watch	LWX	5 hr
May 7, 2:16 PM EDT	Freeze Watch	LWX	24 hr
May 7, 2:16 PM EDT	Freeze Warning	LWX	43 hr
May 8, 3:30 AM EDT	Freeze Watch	LWX	24 hr
May 9, 3:36 AM EDT	Freeze Warning	LWX	28 hr
May 11, 3:43 AM EDT	Frost Advisory	LWX	26 hr
May 12, 2:41 PM EDT	Frost Advisory	LWX	18 hr
May 29, 12:27 PM EDT	Mesoscale Discussion	SPC	63 min
May 29, 2:25 PM EDT	Severe Thunderstorm Watch	SPC	7 hr
May 29, 2:53 PM EDT	Severe Thunderstorm Warning	LWX	25 min
Jun 3, 3:10 PM EDT	Mesoscale Discussion	SPC	2 hr
Jun 4, 2:02 PM EDT	Mesoscale Discussion	SPC	118 min
Jun 4, 2:29 PM EDT	Severe Thunderstorm Watch	SPC	8 hr
Jun 4, 4:41 PM EDT	Mesoscale Discussion	SPC	94 min
Jun 4, 6:41 PM EDT	Severe Thunderstorm Warning	LWX	34 min
Jun 4, 6:55 PM EDT	Severe Thunderstorm Warning	LWX	35 min
Jun 4, 7:02 PM EDT	Severe Thunderstorm Warning	LWX	43 min
Jun 4, 7:07 PM EDT	Severe Thunderstorm Warning	LWX	26 min
Jun 4, 7:28 PM EDT	Severe Thunderstorm Warning	LWX	47 min
Jun 4, 10:10 PM EDT	Severe Thunderstorm Warning	LWX	25 min
Jun 4, 10:51 PM EDT	Flash Flood Watch	LWX	4 hr
Jun 5, 3:40 AM EDT	Flash Flood Watch	LWX	17 hr
Jun 5, 1:15 PM EDT	Mesoscale Discussion	SPC	2 hr
Jun 5, 2:20 PM EDT	Severe Thunderstorm Warning	LWX	27 min
Jun 10, 7:02 PM EDT	Severe Thunderstorm Warning	LWX	43 min
Jun 10, 7:23 PM EDT	Severe Thunderstorm Warning	LWX	37 min
Jun 11, 12:53 AM EDT	Areal Flood Warning	LWX	4 hr
Jun 20, 10:45 AM EDT	Flash Flood Watch	LWX	10 hr
Jun 22, 1:58 PM EDT	Mesoscale Discussion	SPC	3 hr
Jun 22, 3:30 PM EDT	Severe Thunderstorm Warning	LWX	45 min
Jun 22, 3:44 PM EDT	Severe Thunderstorm Warning	LWX	46 min
Jun 22, 3:45 PM EDT	Severe Thunderstorm Warning	LWX	24 min
Jun 22, 5:12 PM EDT	Severe Thunderstorm Warning	LWX	35 min
Jun 22, 5:23 PM EDT	Flash Flood Watch	LWX	116 min
Jun 22, 5:40 PM EDT	Severe Thunderstorm Warning	LWX	35 min
Jun 22, 5:58 PM EDT	Severe Thunderstorm Warning	LWX	47 min
Jun 23, 3:08 AM EDT	Dense Fog Advisory	LWX	6 hr
Jun 23, 9:50 PM EDT	Flash Flood Warning	LWX	2 hr
Jun 25, 1:48 PM EDT	Mesoscale Discussion	SPC	117 min
Jun 25, 5:26 PM EDT	Severe Thunderstorm Warning	LWX	29 min
Jun 25, 6:09 PM EDT	Mesoscale Discussion	SPC	96 min
Jul 5, 1:50 PM EDT	Mesoscale Discussion	SPC	115 min
Jul 5, 5:12 PM EDT	Severe Thunderstorm Warning	LWX	48 min
Jul 5, 5:38 PM EDT	Severe Thunderstorm Warning	LWX	30 min
Jul 6, 12:33 PM EDT	Mesoscale Discussion	SPC	3 hr
Jul 6, 1:38 PM EDT	Severe Thunderstorm Watch	SPC	9 hr
Jul 6, 4:33 PM EDT	Mesoscale Discussion	SPC	117 min
Jul 7, 2:11 AM EDT	Flash Flood Warning	LWX	3 hr
Jul 18, 2:59 PM EDT	Heat Advisory	LWX	29 hr
Jul 19, 2:47 PM EDT	Heat Advisory	LWX	29 hr
Jul 21, 2:01 PM EDT	Mesoscale Discussion	SPC	59 min
Jul 22, 12:07 AM EDT	Heat Advisory	LWX	18 hr
Jul 22, 10:48 AM EDT	Mesoscale Discussion	SPC	117 min
Jul 22, 12:01 PM EDT	Severe Thunderstorm Watch	SPC	7 hr
Jul 22, 1:32 PM EDT	Severe Thunderstorm Warning	LWX	43 min
Jul 22, 1:36 PM EDT	Flash Flood Watch	LWX	4 hr
Jul 22, 2:03 PM EDT	Severe Thunderstorm Warning	LWX	42 min
Jul 22, 2:36 PM EDT	Severe Thunderstorm Warning	LWX	39 min
Jul 22, 3:18 PM EDT	Mesoscale Discussion	SPC	87 min
Jul 28, 3:19 PM EDT	Mesoscale Discussion	SPC	116 min
Jul 30, 10:01 PM EDT	Flash Flood Watch	LWX	20 hr
Aug 1, 4:00 PM EDT	Mesoscale Discussion	SPC	2 hr
Aug 1, 6:53 PM EDT	Flash Flood Watch	LWX	7 hr
Aug 1, 7:05 PM EDT	Mesoscale Discussion	SPC	115 min
Aug 2, 3:28 PM EDT	Flash Flood Watch	LWX	45 hr
Aug 5, 10:51 PM EDT	Flash Flood Watch	LWX	25 hr
Aug 6, 8:54 PM EDT	Areal Flood Warning	LWX	6 hr
Aug 6, 8:56 PM EDT	Severe Thunderstorm Warning	LWX	49 min
Aug 6, 9:06 PM EDT	Flash Flood Warning Considerable damage threat	LWX	3 hr
Aug 6, 10:09 PM EDT	Flash Flood Warning Considerable damage threat	LWX	4 hr
Aug 6, 10:13 PM EDT	Flash Flood Warning EmergencyCatastrophic damage threat	LWX	96 min
Aug 7, 2:04 AM EDT	Areal Flood Warning	LWX	3 hr
Aug 7, 2:21 AM EDT	Areal Flood Warning	LWX	5 hr
Aug 7, 3:46 AM EDT	Flash Flood Watch	LWX	21 hr
Aug 7, 1:30 PM EDT	Mesoscale Discussion	SPC	3 hr
Aug 11, 3:19 PM EDT	Flash Flood Watch	LWX	52 hr
Aug 12, 1:15 PM EDT	Mesoscale Discussion	SPC	2 hr
Aug 12, 6:54 PM EDT	Flash Flood Warning Considerable damage threat	LWX	2 hr
Aug 12, 7:53 PM EDT	Areal Flood Warning	LWX	2 hr
Aug 23, 3:57 PM EDT	Mesoscale Discussion	SPC	2 hr
Aug 24, 12:44 PM EDT	Mesoscale Discussion	SPC	2 hr
Aug 25, 11:27 AM EDT	Severe Thunderstorm Warning	LWX	33 min
Aug 25, 3:10 PM EDT	Mesoscale Discussion	SPC	95 min
Aug 25, 3:34 PM EDT	Severe Thunderstorm Watch	SPC	7 hr
Aug 25, 6:06 PM EDT	Severe Thunderstorm Warning	LWX	39 min
Aug 25, 6:27 PM EDT	Severe Thunderstorm Warning	LWX	48 min
Aug 25, 6:42 PM EDT	Severe Thunderstorm Warning	LWX	48 min
Aug 25, 7:07 PM EDT	Mesoscale Discussion	SPC	113 min
Aug 28, 1:37 PM EDT	Severe Thunderstorm Watch	SPC	8 hr
Aug 28, 4:59 PM EDT	Flash Flood Watch	LWX	11 hr
Aug 28, 5:29 PM EDT	Severe Thunderstorm Warning	LWX	46 min
Aug 28, 5:52 PM EDT	Severe Thunderstorm Warning	LWX	38 min
Sep 2, 3:37 PM EDT	Mesoscale Discussion	SPC	53 min
Sep 2, 6:32 PM EDT	Severe Thunderstorm Warning	LWX	43 min
Sep 2, 6:43 PM EDT	Severe Thunderstorm Watch	SPC	5 hr
Sep 2, 7:06 PM EDT	Severe Thunderstorm Warning	LWX	39 min
Sep 3, 3:06 PM EDT	Mesoscale Discussion	SPC	114 min
Sep 3, 3:30 PM EDT	Severe Thunderstorm Warning	LWX	45 min
Sep 3, 3:42 PM EDT	Tornado Watch	SPC	6 hr
Sep 3, 4:07 PM EDT	Severe Thunderstorm Warning	LWX	38 min
Sep 3, 4:36 PM EDT	Severe Thunderstorm Warning	LWX	54 min
Sep 20, 1:43 PM EDT	Frost Advisory	LWX	19 hr
Sep 21, 1:31 PM EDT	Frost Advisory	LWX	19 hr
Oct 2, 8:23 AM EDT	Dense Fog Advisory	LWX	46 min
Oct 17, 2:25 PM EDT	Frost Advisory	LWX	20 hr
Oct 21, 1:51 AM EDT	Dense Fog Advisory	LWX	9 hr
Oct 22, 1:01 AM EDT	Dense Fog Advisory	LWX	9 hr
Oct 22, 10:21 AM EDT	Dense Fog Advisory	LWX	99 min
Oct 23, 3:26 AM EDT	Dense Fog Advisory	LWX	8 hr
Oct 28, 3:05 PM EDT	Flood Watch	LWX	25 hr
Oct 29, 3:24 AM EDT	Freeze Watch	LWX	13 hr
Oct 29, 4:14 PM EDT	Freeze Warning	LWX	41 hr
Oct 29, 8:44 PM EDT	Frost Advisory	LWX	36 hr
Oct 31, 6:59 PM EDT	Wind Advisory	LWX	44 hr
Nov 1, 8:45 PM EST	Wind Advisory	LWX	3 hr
Nov 9, 4:44 AM EST	Dense Fog Advisory	LWX	5 hr
Nov 11, 10:46 AM EST	Flash Flood Watch	LWX	16 hr
Nov 15, 3:33 PM EST	Mesoscale Discussion	SPC	2 hr
Nov 15, 5:35 PM EST	Severe Thunderstorm Watch	SPC	5 hr
Nov 15, 5:44 PM EST	Severe Thunderstorm Warning	LWX	46 min
Nov 15, 6:22 PM EST	Severe Thunderstorm Warning	LWX	53 min
Nov 15, 6:52 PM EST	Mesoscale Discussion	SPC	113 min
Dec 14, 4:43 AM EST	Winter Storm Watch	LWX	35 hr
Dec 15, 4:09 AM EST	Winter Storm Warning	LWX	46 hr
Dec 16, 1:57 PM EST	Mesoscale Discussion	SPC	5 hr
Dec 21, 4:21 AM EST	Dense Fog Advisory	LWX	8 hr
Dec 23, 4:27 AM EST	Flash Flood Watch	LWX	47 hr
Dec 24, 4:41 AM EST	River Flood Watch	LWX	30 hr
Dec 24, 11:47 AM EST	River Flood Watch	LWX	37 hr
Dec 24, 11:47 AM EST	River Flood Watch	LWX	31 hr
Dec 26, 1:07 AM EST	River Flood Warning	LWX	15 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
Severe Thunderstorm Watch	8
Tornado Watch	2
Mesoscale Discussion	35
Flooding
Areal Flood Warning	5
Flash Flood Warning	6
River Flood Warning	2
Flash Flood Watch	15
Flood Watch	2
River Flood Watch	4
Winter
Snow Squall Warning	1
Winter Storm Warning	1
Winter Storm Watch	1
Winter Weather Advisory	2
Heat
Heat Advisory	3
Cold
Freeze Warning	6
Freeze Watch	6
Frost Advisory	7
Wind and dust
Wind Advisory	7
Fog and smoke
Dense Fog Advisory	15

The busiest days

Days with the most alerts issued, by UTC date.

Nearby

Alerts in force now Tornadoes on record Forecast The radar archive 2019 2021

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.