Severe Thunderstorm Watch 12:00 AM

Loudoun County, Virginia, United States

Last updated: 11:47 PM CDT  ·  Refresh
21°C
Feels like 22°
Mostly Cloudy
▲ 29°  /  ▼ 16°
Wind
7 mph SSW
Humidity
94%
Dew Point
20°
Pressure
29.24 inHg
Visibility
9 mi
UV Index
0.0
Cloud Cover
74%
Sunrise
6:02 AM
Sunset
8:31 PM
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WeatherAI™ Analysis

WeatherAI Analysis: Loudoun County is currently mostly cloudy at 21°C. Dry conditions are expected through the next 24 hours. Atmospheric instability is elevated (CAPE up to 778 J/kg) — isolated convective development possible. Sunrise: 6:02AM · Sunset: 8:31PM.

Alerts

Severe Thunderstorm Watch
Expires 12:00 AM
33 AQI · Good Dominant: PM2.5 Air Quality
Hourly Forecast · Next 24 Hours
Now
21°
41%
1 AM
21°
35%
2 AM
21°
18%
3 AM
21°
21%
4 AM
21°
25%
5 AM
19°
28%
6 AM
20°
12%
7 AM
21°
7%
8 AM
23°
8%
9 AM
24°
8%
10 AM
25°
8%
11 AM
26°
5%
12 PM
27°
5%
1 PM
28°
5%
2 PM
28°
5%
3 PM
28°
5%
4 PM
28°
5%
5 PM
28°
3%
6 PM
27°
3%
7 PM
25°
3%
8 PM
24°
3%
9 PM
23°
3%
10 PM
22°
3%
11 PM
22°
3%
7-Day Forecast
Today
29° 16°
Mostly Clear with a 41% chance of rain.
Thu
27° 16°
Clear.
Fri
28° 14°
Mostly Cloudy with a 32% chance of rain.
Sat
27° 17°
Partly Cloudy with a 37% chance of rain.
Sun
31° 17°
Rain, 70% chance.
Mon
33° 19°
Rain, 64% chance.
Tue
36° 18°
Rain, 63% chance.
TimeTempConditionsPrecipWindHumidity
Now 21° Mostly Cloudy 41% 7 mph SSW 94%
1 AM 21° Partly Cloudy 35% 5 mph SSW 95%
2 AM 21° Partly Cloudy 18% 5 mph SW 94%
3 AM 21° Partly Cloudy 21% 4 mph SW 95%
4 AM 21° Partly Cloudy 25% 4 mph SW 95%
5 AM 19° Partly Cloudy 28% 4 mph SW 94%
6 AM 20° Mostly Clear 12% 4 mph SW 93%
7 AM 21° Mostly Clear 7% 6 mph WSW 90%
8 AM 23° Mostly Clear 8% 7 mph W 83%
9 AM 24° Mostly Clear 8% 9 mph W 74%
10 AM 25° Mostly Clear 8% 11 mph W 66%
11 AM 26° Mostly Clear 5% 11 mph W 60%
12 PM 27° Mostly Clear 5% 11 mph W 55%
1 PM 28° Clear 5% 11 mph W 51%
2 PM 28° Clear 5% 11 mph WNW 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 54%
6 PM 27° Mostly Clear 3% 8 mph WNW 58%
7 PM 25° Mostly Clear 3% 7 mph NW 62%
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 61%
11 PM 22° Partly Cloudy 3% 8 mph NNW 62%
15-Day Forecast
Today
7/22
Mostly Clear
41%
16°
29°
Thu
7/23
Clear
3%
16°
27°
Fri
7/24
Mostly Cloudy
32%
14°
28°
Sat
7/25
Partly Cloudy
37%
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
Rain
69%
17°
32°
Thu
7/30
Drizzle
44%
16°
30°
Fri
7/31
Drizzle
51%
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°
Wed
8/5
Drizzle
60%
20°
32°
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 LCLLFCEL0°C Temperature (°C) Pressure (hPa)
Temp Dewpoint Parcel (SB) CAPE CIN Dry adiabat Moist adiabat Mixing ratio
RAP
Valid Wed Jul 22, 03:00'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
MLCAPE25 J/kg
MUCAPE1 J/kg
SBCIN-328 J/kg
MLCIN0 J/kg
Lifted Index0.4
Kinematics
0–6 km Shear40 kt
0–1 km Shear30 kt
Eff. Shear—
0–1 km SRH4
0–3 km SRH6
Eff. SRH—
Storm Motion231° @ 34 kt
0–1 km EHI0.0
Composite Parameters
Sig. Tornado0.0
STP (eff)—
Supercell—
K-Index35.6
Thermo & Levels
PWAT1.70 in
0–3 km LR4.4 °C/km
700–500 LR5.6 °C/km
Total Totals44.7
LCL977 hPa
LFC655 hPa
EL639 hPa
Freezing Lvl14,344 ft