Severe Thunderstorm Watch 11:00 PM

Loudoun County, Virginia, United States

Last updated: 10:34 PM CDT  ·  Refresh
21°C
Feels like 22°
Overcast
▲ 29°  /  ▼ 19°
Wind
8 mph SSW
Humidity
92%
Dew Point
19°
Pressure
29.24 inHg
Visibility
10 mi
UV Index
0.0
Cloud Cover
88%
Sunrise
6:01 AM
Sunset
8:31 PM
Drag to pan · double-click to forecast a point
WeatherAI™ Analysis

WeatherAI Analysis: Loudoun County is currently overcast at 21°C. Dry conditions are expected through the next 24 hours. Atmospheric instability is elevated (CAPE up to 782 J/kg) — isolated convective development possible. Sunrise: 6:01AM · Sunset: 8:31PM.

Alerts

Severe Thunderstorm Watch
Expires 11:00 PM
33 AQI · Good Dominant: PM2.5 Air Quality
Hourly Forecast · Next 24 Hours
Now
21°
35%
12 AM
21°
39%
1 AM
21°
39%
2 AM
21°
18%
3 AM
21°
19%
4 AM
21°
25%
5 AM
19°
28%
6 AM
20°
12%
7 AM
21°
8%
8 AM
23°
8%
9 AM
23°
8%
10 AM
24°
8%
11 AM
26°
5%
12 PM
26°
5%
1 PM
28°
5%
2 PM
28°
5%
3 PM
28°
5%
4 PM
28°
5%
5 PM
28°
3%
6 PM
26°
3%
7 PM
26°
3%
8 PM
24°
3%
9 PM
23°
3%
10 PM
22°
3%
7-Day Forecast
Tonight
29° 19°
Overcast with a 35% chance of rain.
Wed
28° 18°
Mostly Clear with a 28% chance of rain.
Thu
27° 16°
Clear.
Fri
28° 14°
Mostly Cloudy with a 37% chance of rain.
Sat
27° 17°
Partly Cloudy with a 26% chance of rain.
Sun
31° 17°
Rain, 70% chance.
Mon
33° 19°
Rain, 64% chance.
TimeTempConditionsPrecipWindHumidity
Now 21° Overcast 35% 8 mph SSW 92%
12 AM 21° Mostly Cloudy 39% 7 mph SSW 93%
1 AM 21° Mostly Cloudy 39% 6 mph SSW 94%
2 AM 21° Partly Cloudy 18% 5 mph SSW 94%
3 AM 21° Partly Cloudy 19% 5 mph SW 94%
4 AM 21° Mostly Cloudy 25% 4 mph SW 95%
5 AM 19° Partly Cloudy 28% 4 mph SW 95%
6 AM 20° Partly Cloudy 12% 4 mph WSW 94%
7 AM 21° Mostly Clear 8% 5 mph WSW 91%
8 AM 23° Mostly Clear 8% 7 mph W 85%
9 AM 23° Mostly Clear 8% 8 mph W 76%
10 AM 24° Mostly Clear 8% 10 mph W 68%
11 AM 26° Mostly Clear 5% 11 mph W 61%
12 PM 26° Mostly Clear 5% 12 mph W 56%
1 PM 28° Mostly Clear 5% 12 mph W 52%
2 PM 28° Clear 5% 12 mph W 50%
3 PM 28° Clear 5% 11 mph WNW 50%
4 PM 28° Clear 5% 11 mph WNW 50%
5 PM 28° Clear 3% 10 mph WNW 53%
6 PM 26° Mostly Clear 3% 9 mph WNW 57%
7 PM 26° Mostly Clear 3% 8 mph NW 61%
8 PM 24° Mostly Clear 3% 7 mph NW 62%
9 PM 23° Partly Cloudy 3% 7 mph NW 62%
10 PM 22° Partly Cloudy 3% 8 mph NW 62%
15-Day Forecast
Today
7/21
Overcast
35%
19°
29°
Wed
7/22
Mostly Clear
28%
18°
28°
Thu
7/23
Clear
3%
16°
27°
Fri
7/24
Mostly Cloudy
37%
14°
28°
Sat
7/25
Partly Cloudy
26%
17°
27°
Sun
7/26
Rain
70%
17°
31°
Mon
7/27
Rain
64%
19°
33°
Tue
7/28
Rain
63%
18°
36°
Wed
7/29
Drizzle
69%
17°
31°
Thu
7/30
Drizzle
44%
16°
30°
Fri
7/31
Drizzle
60%
16°
29°
Sat
8/1
Drizzle
60%
17°
30°
Sun
8/2
Drizzle
60%
18°
30°
Mon
8/3
Drizzle
60%
18°
32°
Tue
8/4
Drizzle
60%
19°
33°
33
Good
U.S. Air Quality Index · Dominant: PM2.5
50 100 150 200

Air quality is satisfactory and poses little or no health risk.

Pollutant Breakdown · Today
PM2.5
Fine particulate matter
Dominant
33 AQI 5.9 µg/m³
O3
Ground-level ozone
32 AQI 36 ppb
3-Day Outlook
DayAQICategoryO₃PM2.5
Today 33 Good 32 33
Thu 38 Good 38 13
Fri 38 Good 38 22
About the Air Quality Index
0–50 Good
51–100 Moderate
101–150 Unhealthy for Sensitive Groups
151–200 Unhealthy
201–300 Very Unhealthy
301–500 Hazardous

The U.S. AQI runs 0–500. The overall value equals the highest individual pollutant sub-index, and the dominant pollutant is the one driving it. PM2.5 (fine particles) is reported in µg/m³ and ozone (O3) in ppb. Forecast source: NWS NAQFC.

1000850700500400300250200150100 -40-30-20-10010203040 0.41247101624 LCL0°C Temperature (°C) Pressure (hPa)
Temp Dewpoint Parcel (SB) CAPE CIN Dry adiabat Moist adiabat Mixing ratio
RAP
Valid Wed Jul 22, 02:00'Z' · F0 · 130 (13 km CONUS/NA)
Hodograph · kt
10 20 30 40 50 60 70 80 SM
0–1 1–3 3–6 6–9 km
Instability
SBCAPE0 J/kg
MLCAPE36 J/kg
MUCAPE143 J/kg
SBCIN-5668 J/kg
MLCIN0 J/kg
Lifted Index0.7
Kinematics
0–6 km Shear39 kt
0–1 km Shear36 kt
Eff. Shear13 kt
0–1 km SRH2
0–3 km SRH15
Eff. SRH5
Storm Motion242° @ 39 kt
0–1 km EHI0.0
Composite Parameters
Sig. Tornado0.0
STP (eff)0.0
Supercell0.0
K-Index33.7
Thermo & Levels
PWAT1.78 in
0–3 km LR4.0 °C/km
700–500 LR6.1 °C/km
Total Totals46.4
LCL971 hPa
LFC—
EL—
Freezing Lvl14,528 ft