Severe Thunderstorm Watch 9:00 PM

Chester County, Pennsylvania, United States

Last updated: 7:33 PM CDT  ·  Refresh
22°C
Feels like 24°
Rain
▲ 28°  /  ▼ 20°
Wind
7 mph SSW
Humidity
95%
Dew Point
21°
Pressure
29.19 inHg
Visibility
10 mi
UV Index
0.0
Cloud Cover
92%
Sunrise
5:51 AM
Sunset
8:26 PM
Drag to pan · double-click to forecast a point
WeatherAI™ Analysis

WeatherAI Analysis: Chester County is currently rain at 22°C. Precipitation is likely — peak probability 73% around 9 PM. Atmospheric instability is elevated (CAPE up to 955 J/kg) — isolated convective development possible. Sunrise: 5:51AM · Sunset: 8:26PM.

Alerts

Severe Thunderstorm Watch
Expires 9:00 PM
69 AQI · Moderate Dominant: PM2.5 Air Quality
Hourly Forecast · Next 24 Hours
Now
22°
67%
9 PM
22°
73%
10 PM
22°
60%
11 PM
22°
61%
12 AM
22°
41%
1 AM
21°
46%
2 AM
21°
36%
3 AM
21°
36%
4 AM
21°
40%
5 AM
20°
38%
6 AM
21°
38%
7 AM
21°
31%
8 AM
22°
39%
9 AM
23°
42%
10 AM
24°
30%
11 AM
24°
27%
12 PM
25°
30%
1 PM
26°
26%
2 PM
27°
24%
3 PM
27°
24%
4 PM
27°
21%
5 PM
26°
19%
6 PM
26°
20%
7 PM
24°
20%
7-Day Forecast
Tonight
28° 20°
Rain, 67% chance.
Wed
27° 18°
Rain, 39% chance.
Thu
27° 16°
Clear.
Fri
27° 16°
Partly Cloudy.
Sat
28° 16°
Partly Cloudy.
Sun
29° 17°
Rain, 62% chance.
Mon
30° 18°
Rain, 66% chance.
TimeTempConditionsPrecipWindHumidity
Now 22° Rain 67% 7 mph SSW 95%
9 PM 22° Rain 73% 9 mph SSW 94%
10 PM 22° Rain 60% 8 mph SSW 94%
11 PM 22° Mostly Cloudy 61% 8 mph SSW 95%
12 AM 22° Mostly Cloudy 41% 8 mph SSW 94%
1 AM 21° Partly Cloudy 46% 9 mph SW 94%
2 AM 21° Partly Cloudy 36% 10 mph SW 94%
3 AM 21° Mostly Cloudy 36% 8 mph SW 94%
4 AM 21° Mostly Cloudy 40% 8 mph SW 94%
5 AM 20° Mostly Cloudy 38% 8 mph SW 94%
6 AM 21° Mostly Cloudy 38% 8 mph SW 92%
7 AM 21° Partly Cloudy 31% 8 mph WSW 89%
8 AM 22° Rain 39% 10 mph WSW 85%
9 AM 23° Mostly Clear 42% 10 mph W 79%
10 AM 24° Mostly Clear 30% 10 mph W 74%
11 AM 24° Mostly Clear 27% 11 mph W 70%
12 PM 25° Mostly Clear 30% 11 mph W 67%
1 PM 26° Mostly Clear 26% 11 mph WNW 64%
2 PM 27° Mostly Clear 24% 10 mph WNW 62%
3 PM 27° Mostly Clear 24% 10 mph W 60%
4 PM 27° Mostly Clear 21% 10 mph W 58%
5 PM 26° Mostly Clear 19% 10 mph W 58%
6 PM 26° Clear 20% 9 mph W 59%
7 PM 24° Clear 20% 9 mph WNW 60%
15-Day Forecast
Today
7/21
Rain
67%
20°
28°
Wed
7/22
Rain
39%
18°
27°
Thu
7/23
Clear
3%
16°
27°
Fri
7/24
Partly Cloudy
14%
16°
27°
Sat
7/25
Partly Cloudy
19%
16°
28°
Sun
7/26
Rain
62%
17°
29°
Mon
7/27
Rain
66%
18°
30°
Tue
7/28
Thunderstorm
66%
19°
28°
Wed
7/29
Drizzle
54%
18°
28°
Thu
7/30
Drizzle
54%
17°
28°
Fri
7/31
Drizzle
60%
18°
28°
Sat
8/1
Drizzle
60%
18°
28°
Sun
8/2
Drizzle
60%
18°
29°
Mon
8/3
Drizzle
60%
19°
29°
Tue
8/4
Drizzle
90%
19°
30°
69
Moderate
U.S. Air Quality Index · Dominant: PM2.5
50 100 150 200

Air quality is acceptable. Unusually sensitive people should consider limiting prolonged outdoor exertion.

Pollutant Breakdown · Today
PM2.5
Fine particulate matter
Dominant
69 AQI 18.9 µg/m³
O3
Ground-level ozone
35 AQI 39 ppb
3-Day Outlook
DayAQICategoryO₃PM2.5
Today 69 Moderate 35 69
Thu 50 Good 40 50
Fri 52 Moderate 43 52
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 Tue Jul 21, 23:00'Z' · F0 · 130 (13 km CONUS/NA)
Hodograph · kt
10 20 30 40 50 60 SM
0–1 1–3 3–6 6–9 km
Instability
SBCAPE274 J/kg
MLCAPE946 J/kg
MUCAPE1416 J/kg
SBCIN-286 J/kg
MLCIN0 J/kg
Lifted Index-1.8
Kinematics
0–6 km Shear43 kt
0–1 km Shear31 kt
Eff. Shear41 kt
0–1 km SRH196
0–3 km SRH151
Eff. SRH53
Storm Motion229° @ 39 kt
0–1 km EHI0.3
Composite Parameters
Sig. Tornado0.5
STP (eff)0.0
Supercell1.6
K-Index33.5
Thermo & Levels
PWAT2.02 in
0–3 km LR4.2 °C/km
700–500 LR6.4 °C/km
Total Totals48.4
LCL972 hPa
LFC676 hPa
EL322 hPa
Freezing Lvl13,707 ft