A pressure trough remained over Maryland on the 12th while an upper-level disturbance passed through in a zonal flow aloft. The forcing from these two systems were responsible for the development of showers and thunderstorms.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS LWX wrote it up.
A pressure trough remained over Maryland on the 12th while an upper-level disturbance passed through in a zonal flow aloft. The forcing from these two systems were responsible for the development of showers and thunderstorms. As thunderstorms passed across the Baltimore metropolitan area during the afternoon locally heavy rainfall of 1 to 2 inches produced minor street flooding.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Baltimore/Washington wrote its last area forecast discussion before the first event at Jul 12, 2:01 PM EST, 24 minutes earlier.
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</html>SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
101 PM EDT MON JUL 12 2010
VAZ026-036-037-121730-
NELSON VA-ALBEMARLE VA-ROCKINGHAM VA-
101 PM EDT MON JUL 12 2010
...SHOWERS AND THUNDERSTORMS TO AFFECT NELSON...ALBEMARLE AND
ROCKINGHAM COUNTIES...
AT 1259 PM EDT...DOPPLER RADAR INDICATED SHOWERS AND THUNDERSTORMS
WITH RAINFALL RATES OVER ONE INCH PER HOUR ACROSS PORTIONS OF NELSON
AND ALBERMARLE COUNTIES...MOVING NORTHEAST AT 20 MPH.
HEAVY RAIN WITH THIS STORM MAY REDUCE VISIBILITIES TO BELOW ONE MILE
AND MAY CAUSE PONDING OF WATER ON ROADWAYS.
&&
LAT...LON 3769 7899 3772 7907 3777 7908 3779 7917
3790 7914 3791 7906 3789 7899 3793 7895
3795 7890 3803 7888 3808 7878 3813 7879
3818 7875 3822 7877 3824 7874 3807 7844
3755 7891
TIME...MOT...LOC 1659Z 216DEG 18KT 3795 7880
BJLSPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
231 PM EDT MON JUL 12 2010
MDZ010-013-014-121900-
HOWARD MD-ANNE ARUNDEL MD-PRINCE GEORGES MD-
231 PM EDT MON JUL 12 2010
...STRONG THUNDERSTORMS TO AFFECT HOWARD...ANNE ARUNDEL AND PRINCE
GEORGES COUNTIES...
AT 228 PM EDT...DOPPLER RADAR INDICATED A STRONG THUNDERSTORM 3 MILES
NORTHEAST OF GLENN DALE AND ANOTHER STRONG THUNDERSTORM 3 MILES
NORTHEAST OF ELLICOTT CITY...MOVING NORTH AT 25 MPH.
THESE STORMS ARE PRODUCING FREQUENT CLOUD TO GROUND LIGHTNING. MOVE
INDOORS IMMEDIATELY FOR YOUR SAFETY. IF YOU CAN HEAR THUNDER...YOU
ARE CLOSE ENOUGH TO BE STRUCK BY LIGHTNING.
HEAVY RAIN WITH THESE STORMS MAY REDUCE VISIBILITIES TO BELOW ONE
MILE AND MAY CAUSE PONDING OF WATER ON ROADWAYS.
WIND GUSTS OF 40 TO 50 MPH CAN BE EXPECTED WITH THESE STORMS.
&&
LAT...LON 3891 7666 3898 7684 3928 7678 3925 7678
3922 7673 3921 7668 3923 7666 3923 7662
3914 7646
TIME...MOT...LOC 1828Z 200DEG 23KT 3903 7675
JRKSPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
238 PM EDT MON JUL 12 2010
DCZ001-MDZ013-121915-
DISTRICT OF COLUMBIA DC-PRINCE GEORGES MD-
238 PM EDT MON JUL 12 2010
...STRONG THUNDERSTORMS TO AFFECT THE DISTRICT OF COLUMBIA...PRINCE
GEORGES COUNTY...
AT 238 PM EDT...DOPPLER RADAR INDICATED A STRONG THUNDERSTORM 2 MILES
SOUTH OF NATIONAL HARBOR...MOVING NORTH AT 15 MPH.
STORM INTENSITY IS INCREASING...AND SEVERE WEATHER MAY DEVELOP
RAPIDLY. REMAIN ALERT...AND BE PREPARED TO TAKE ACTION IF WARNINGS
ARE ISSUED.
THIS STORM IS PRODUCING FREQUENT CLOUD TO GROUND LIGHTNING. MOVE
INDOORS IMMEDIATELY FOR YOUR SAFETY. IF YOU CAN HEAR THUNDER...YOU
ARE CLOSE ENOUGH TO BE STRUCK BY LIGHTNING.
HEAVY RAIN WITH THIS STORM MAY REDUCE VISIBILITIES TO BELOW ONE MILE
AND MAY CAUSE PONDING OF WATER ON ROADWAYS.
WIND GUSTS IN EXCESS OF 50 MPH ARE EXPECTED WITH THIS STORM. WINDS
THIS STRONG CAN BRING DOWN LARGE TREE BRANCHES. TAKE SHELTER UNTIL
THE STORM HAS PASSED.
&&
LAT...LON 3890 7677 3867 7694 3869 7704 3879 7704
3893 7699
TIME...MOT...LOC 1838Z 202DEG 13KT 3878 7701
JRKSPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
242 PM EDT MON JUL 12 2010
MDZ004-009-VAZ042-052-053-501-121930-
FREDERICK MD-MONTGOMERY MD-NORTHERN FAUQUIER VA-LOUDOUN VA-
PRINCE WILLIAM/MANASSAS/MANASSAS PARK VA-FAIRFAX VA-
242 PM EDT MON JUL 12 2010
...STRONG THUNDERSTORMS TO AFFECT FREDERICK...MONTGOMERY...NORTHERN
FAUQUIER...LOUDOUN...PRINCE WILLIAM/MANASSAS/MANASSAS PARK AND
FAIRFAX COUNTIES...
AT 242 PM EDT...DOPPLER RADAR INDICATED SHOWERS AND ISOLATED STRONG
THUNDERSTORMS ALONG A LINE EXTENDING FROM 3 MILES NORTHEAST OF
HALFWAY TO ARCOLA TO 3 MILES NORTHEAST OF CHANTILLY TO OAKTON...
MOVING NORTH AT 20 TO 25 MPH.
HEAVY RAIN WITH THIS STORM MAY REDUCE VISIBILITIES TO BELOW ONE MILE
AND MAY CAUSE PONDING OF WATER ON ROADWAYS.
WIND GUSTS OF 40 TO 50 MPH AND SMALL HAIL CAN BE EXPECTED WITH THIS
STORM.
&&
LAT...LON 3923 7766 3925 7739 3923 7720 3914 7701
3882 7729 3884 7741 3886 7757 3890 7778
TIME...MOT...LOC 1842Z 201DEG 21KT 3896 7768 3895 7753
3893 7737 3890 7729
SMZSPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
245 PM EDT MON JUL 12 2010
MDZ006-011-121915-
NORTHERN BALTIMORE MD-SOUTHERN BALTIMORE MD-
245 PM EDT MON JUL 12 2010
...STRONG THUNDERSTORMS TO AFFECT NORTHERN BALTIMORE AND SOUTHERN
BALTIMORE COUNTIES...
AT 245 PM EDT...DOPPLER RADAR INDICATED A STRONG THUNDERSTORM OVER
LOCHEARN...MOVING NORTHEAST AT 20 MPH.
STORM INTENSITY IS INCREASING...AND SEVERE WEATHER MAY DEVELOP
RAPIDLY. REMAIN ALERT...AND BE PREPARED TO TAKE ACTION IF WARNINGS
ARE ISSUED.
THIS STORM IS PRODUCING FREQUENT CLOUD TO GROUND LIGHTNING. MOVE
INDOORS IMMEDIATELY FOR YOUR SAFETY. IF YOU CAN HEAR THUNDER...YOU
ARE CLOSE ENOUGH TO BE STRUCK BY LIGHTNING.
HEAVY RAIN WITH THIS STORM MAY REDUCE VISIBILITIES TO BELOW ONE MILE
AND MAY CAUSE PONDING OF WATER ON ROADWAYS.
WIND GUSTS IN EXCESS OF 50 MPH ARE EXPECTED WITH THIS STORM. WINDS
THIS STRONG CAN BRING DOWN LARGE TREE BRANCHES. TAKE SHELTER UNTIL
THE STORM HAS PASSED.
&&
LAT...LON 3955 7653 3953 7651 3953 7650 3951 7646
3929 7669 3935 7684 3963 7671
TIME...MOT...LOC 1845Z 210DEG 16KT 3936 7674
JRK<!doctype html>
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</html>The national radar mosaic for the moment the first event began.
5 flood. Local standard time, as filed.
Flooding was reported along parts of Fulton Avenue.
Flooding was reported along portions of Uplands Parkway.
Flooding was reported along parts of Frederick Avenue.
Flooding was reported along parts of Hickory Avenue. A spotter in the area observed 2.25 inches of rain.
Flooding was reported along parts of Gwynns Falls Parkway.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Maryland in 2010Every state in 2010This day in weather historyWarnings in Maryland, July 2010
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-10-01. Each event’s entry at NCEI: 248582, 248584, 248586, 248587, 248588.