A cold front and its associated trough of low pressure triggered showers and thunderstorms across Maryland. A southwest flow ahead of the front ushered in plenty of moisture from the Gulf of Mexico, resulting in an unstable atmosphere.
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 cold front and its associated trough of low pressure triggered showers and thunderstorms across Maryland. A southwest flow ahead of the front ushered in plenty of moisture from the Gulf of Mexico, resulting in an unstable atmosphere. The moderate amounts of instability combined with the forcing from the front and strong winds aloft for some thunderstorms to become severe.
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 31, 10:20 AM EST, 2 hours 45 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1120 AM EDT FRI JUL 31 2009
.SYNOPSIS...
A LOW PRESSURE SYSTEM OVER WEST VIRGINIA WILL MOVE NORTHEAST ACROSS
THE REGION TODAY. AFTER THIS FEATURE MOVES OFF THE MID ATLANTIC
COAST TONIGHT...THE MOIST AIRMASS WILL REMAIN IN PLACE OVER THE
MID ATLANTIC REGION THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK...WITH A BROAD UPPER LEVEL LOW PRESSURE SYSTEM REMAINING OVER
EAST-CENTRAL CANADA. SEVERAL DISTURBANCES WILL MOVE THROUGH THE
REGION AND WILL PROMOTE DAILY DEVELOPMENT OF SHOWERS AND
THUNDERSTORMS.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A LARGE SWATH OF MAINLY STRATIFORM PRECIP STRETCHES ALONG A
FRONTAL BOUNDARY ALONG THE ENTIRE APPALACHIAN RANGE...W/ EMBEDDED
CONVECTIVE ELEMENTS IN SRN WV...AND CONVECTIVE STORMS STRETCHING SW FROM
NRN GA. AN EMBEDDED LOW ALONG THIS BOUNDARY /ANALYZED AT 15 Z TO
BE OVER NRN WV/ WILL CONTINUE TO FOCUS PRECIPITATION ALONG AND
AHEAD OF THE FEATURE /WITH NE MOTION PRECIP WILL BE CONTAINED
ACROSS FAR WRN/NWRN ZONES INTO THE EARLY AFTERNOON/.
INTO THE AFTERNOON HOURS...AMPLE LOW LEVEL MOISTURE WITH FILTERED
INSOLATION /ACROSS CENTRAL CWA/ TO FULL INSOLATION EAST OF I-95 TO
PRIME ATMOS AHEAD OF THE EASTWARD PROGRESSION OF THE FRONT. NO CU
FIELD YET...THOUGH EXPECT CONVECTION TO CREATE ISOLATED...THEN
SCATTERED CELLS WELL AHEAD OF THE FRONT EARLY THIS AFTERNOON. THE
HRRR MODEL CONTINUES TO DEPICT DISCRETE TSTM DEVELOPMENT ALONG
LEADING EDGE OF FRONT THAT QUICKLY TRANSITIONS TO SEGMENTED LINES
IN THE NEAR UNIDIRECTIONAL SW FLOW ABOVE 2 KFT.
WIND FIELD IN LOW LEVELS BECOMES SOUTHERLY WITH PERHAPS SOME
BACKING AHEAD OF THE LINE...INCREASING THE TORNADO THREAT FOR THIS
AFTERNOON...PARTICULARLY EAST OF THE BLUE RIDGE /WITH TIMING OF
FRONT/.
PREVIOUS DISCUSSION...
LAPSE RATES WILL BE FAIRLY POOR W/ THE VERY MOIST
AND ALMOST TROPICAL PROFILES ACROSS THE REGION TODAY.
HOWEVER...THE UNSEASONABLY STRONG LOW LEVEL JET WILL LIKELY AIDE
IN THE ORGANIZATION OF DIFFERENT MODES SUCH AS BOW-ECHO/MCS-TYPE
SEGMENTS CARRYING AND BRINGING DOWN WIND GUSTS OF 30-40KT PLUS.
HELICAL VALUES IMPRESSIVE ON FORECAST
SOUNDING/HODOGRAPHS...ESPECIALLY IN TERMS OF LOW LEVEL SPEED
SHEAR. DIRECTIONAL SHEAR WILL BE THE BEST AS THE COLD FRONT PUSHES
E OF THE BLUE RIDGE. LOCAL GUIDANCE POINTING TO A PRE-FRONTAL
INDIVIDUAL CELLS POPPING UP ACROSS THE I-95 CORRIDOR...ANY ONE
COULD DEVELOP SUPERCELLULAR CHARACTERISTICS GIVEN THE WIND FIELD
LATER THIS AFTN/EVNG. ISOLATED TORNADOES AND ISOLATED ENHANCED
DOWNBURST FEATURES WILL BE POSSIBLE IN THIS ENVIRONMENT...EVEN W/
LOW REFLECTIVITY STORMS...LIKE WED AFTN/EVNG.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
AS THE SFC COLD FRONT TRUDGES EWD ACROSS THE MID ATLC LATER THIS
EVNG...THE CONVECTIVE LINES AND INDIVIDUAL STORMS WILL BE USHERED E
ACROSS DELMARVA AND OFF THE MID ATLC COAST. MUCH OF THE ACTIVITY
WILL HAVE DECREASED AFT 00Z...W/ LINGERING SHOWERS/STORMS MOVING
ACROSS THE BAY INTO THE LATE NIGHT HRS. SFC WINDS WILL TURN BACK TO
THE W-WNW INTO THE OVERNIGHT HRS.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
POPULATED SAT THROUGH SUN NIGHT WITH ADJMAV GUIDANCE. SATURDAY MAV
GIVING SINGLE DIGIT POPS TO ENTIRE REGION SO XPCTNG PLEASANT SUMMER
DAY WITH LIGHT WIND.
MEX GUIDANCE IS ESSENTIALLY FORECASTING VERY SEASONABLE CONDITIONS
DURING THE LONG TERM...WITH HIGHS IN THE BALT/WASH METRO AREAS NEAR
90...LOWS NEAR 70 AND 30 POPS EACH DAY FOR AFTERNOON/EVENGS TSTMS
WITH AFT CAPES AOA 1500 J/KG. WIND FIELD IS VERY LIGHT...BUT WITH
1500 J/KG...PULSE SVR TSTMS CANT BE RULED OUT EACH DAY.
DID NOT ALTER LONG TERM BEYOND DAY 3.
&&
.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
A LOW PRESSURE SYSTEM WILL WORK ITS WAY ACROSS THE REGION
TODAY...W/ THE BIGGEST THREATS FOR THE MID ATLC BEING THE STRONG
SLY WINDS AHEAD OF THE SYSTEM /15-25KT GUSTS/ AND SCATTERED TSTMS
DEVELOPING BY EARLY THIS AFTN ACROSS THE REGION. A COLD FRONT WILL
PUSH ANY RA/TS ACTIVITY OVER THE I-95 CRDR LATER THIS
EVNG...POSSIBLY AFFECTING EACH AREA TAF SITE FOR A SHORT PERIOD
/1-2 HRS OR SO/. STRONG GUSTY WINDS THE MAIN CONCERN ALONG W/
PERIODS OF HEAVY RAIN. THE FRONT WILL MOVE E OVERNIGHT AND WINDS
WILL SHIFT TO W-WNWLY AND DECREASE OVERNIGHT.
VFR CONDS EXPECTED FOR THE WEEKEND AND INTO EARLY NEXT
WEEK...OUTSIDE OF ANY CONVECTIVE ELEMENTS THAT MAY DEVELOP UNDER
AFTN HEATING FOR THE EARLY PART OF NEXT WEEK.
&&
.MARINE...
A GALE WARNING IS POSTED FOR THE MD CHESAPEAKE BAY SOUTH OF SANDY
POINT AND EXTREME LOWER TIDAL PTMC FOR MUCH OF THE AFTN/EVNG HRS
TODAY. A STRONG LOW LEVEL JET WILL DEVELOP OVER THE COURSE OF THE
MRNG/AFTN. A THREAT FOR GALE GUSTS FROM MIXING DOWN THE LOW LEVEL
JET EXISTS...PARTICULARLY WITH CLEARER SKIES THAN ANTICIPATED.
A COLD FRONT WILL MOVE ACROSS THE REGION LATER THIS EVNG... ANY
INDIVIDUAL CELL WILL HAVE THE POTENTIAL TO PUSH +35KT GUSTS. W/
SLY WINDS AHEAD OF THE BOUNDARY ALSO GUSTING INTO THE 20-30KT
RANGE W/ INTERMITTENT GUSTS ABOVE 35KT POSSIBLE. THE FRONT WILL
CLEAR THE WATERS DURING THE EARLY MRNG HRS...W/ LIGHTER CONDITIONS
EXPECTED INTO SAT.
SCA CONDITIONS NOT EXPECTED INTO MID NEXT WEEK.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EDT SATURDAY FOR ANZ530-531-
535-538-539.
SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 4 AM EDT
SATURDAY FOR ANZ532>534-537-540>543.
GALE WARNING UNTIL MIDNIGHT EDT TONIGHT FOR ANZ532>534-537-
540>543.
SMALL CRAFT ADVISORY UNTIL 4 AM EDT SATURDAY FOR ANZ536.
&&
SYNOPSIS...BAJ/GMS
NEAR TERM...BAJ/GMS
SHORT TERM...GMS
LONG TERM...JEL
AVIATION...BAJ/JEL/GMS
MARINE...BAJ/JEL/GMSHAZARDOUS WEATHER OUTLOOK...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 148 PM EDT FRI JUL 31 2009 ANZ530>543-DCZ001-MDZ006-007-011-013-014-016>018-VAZ052>057- 011000- CHESAPEAKE BAY NORTH OF POOLES ISLAND MD- CHESAPEAKE BAY FROM POOLES ISLAND TO SANDY POINT MD- CHESAPEAKE BAY FROM SANDY POINT TO NORTH BEACH MD- CHESAPEAKE BAY FROM NORTH BEACH TO DRUM POINT MD- CHESAPEAKE BAY FROM DRUM POINT MD TO SMITH POINT VA- TIDAL POTOMAC FROM KEY BRIDGE TO INDIAN HEAD MD- TIDAL POTOMAC FROM INDIAN HEAD TO COBB ISLAND MD- TIDAL POTOMAC FROM COBB ISLAND MD TO SMITH POINT VA- PATAPSCO RIVER INCLUDING BALTIMORE HARBOR- CHESTER RIVER TO QUEENSTOWN MD-EASTERN BAY- CHOPTANK RIVER TO CAMBRIDGE MD AND THE LITTLE CHOPTANK RIVER- PATUXENT RIVER TO BROOMES ISLAND MD- TANGIER SOUND AND THE INLAND WATERS SURROUNDING BLOODSWORTH ISLAND-DISTRICT OF COLUMBIA-NORTHERN BALTIMORE-HARFORD- SOUTHERN BALTIMORE-PRINCE GEORGES-ANNE ARUNDEL-CHARLES-ST. MARYS- CALVERT-PRINCE WILLIAM/MANASSAS/MANASSAS PARK-FAIRFAX- ARLINGTON/FALLS CHURCH/ALEXANDRIA-STAFFORD-SPOTSYLVANIA- KING GEORGE- 148 PM EDT FRI JUL 31 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE MARYLAND PORTION OF THE CHESAPEAKE BAY...TIDAL POTOMAC RIVER...AND ADJACENT COUNTIES IN CENTRAL MARYLAND AND NORTHERN VIRGINIA AS WELL AS THE DISTRICT OF COLUMBIA. .DAY ONE...THIS AFTERNOON AND TONIGHT NUMEROUS SHOWERS AND THUNDERSTORMS WILL MOVE ACROSS THE AREA THIS AFTERNOON AND EVENING. SOME OF THE STORMS MAY BE SEVERE...PRODUCING DAMAGING WIND GUSTS...HEAVY RAIN AND POSSIBLE ISOLATED TORNADOES. A SEVERE THUNDERSTORM WATCH IS IN EFFECT FOR THE OUTLOOK AREA UNTIL 9 PM. A GALE WARNING IS IN EFFECT FOR THE MARYLAND CHESAPEAKE BAY FROM SANDY POINT TO SMITH POINT...AND THE TIDAL POTOMAC RIVER FROM COBB ISLAND TO SMITH POINT...UNTIL MIDNIGHT TONIGHT. A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE TIDAL POTOMAC RIVER ABOVE COBB ISLAND...AND MARYLAND CHESAPEAKE BAY...NORTH OF SANDY POINT...FROM THIS AFTERNOON THROUGH LATE TONIGHT. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED LATER THIS AFTERNOON AND EVENING. MDZ003>005-009-010-501-502-VAZ021-025>031-036>042-050-051- WVZ050>055-501>504-011000- WASHINGTON-FREDERICK MD-CARROLL-MONTGOMERY-HOWARD- EXTREME WESTERN ALLEGANY-CENTRAL AND EASTERN ALLEGANY-HIGHLAND- AUGUSTA-ROCKINGHAM-SHENANDOAH-FREDERICK VA-PAGE-WARREN-CLARKE- NELSON-ALBEMARLE-GREENE-MADISON-RAPPAHANNOCK-FAUQUIER-LOUDOUN- ORANGE-CULPEPER-HAMPSHIRE-MORGAN-BERKELEY-JEFFERSON-PENDLETON- HARDY-WESTERN GRANT-EASTERN GRANT-WESTERN MINERAL-EASTERN MINERAL- 148 PM EDT FRI JUL 31 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR EASTERN WEST VIRGINIA... NORTHERN AND CENTRAL VIRGINIA...AND CENTRAL AND WESTERN MARYLAND WITH THE EXCEPTION OF GARRETT COUNTY. .DAY ONE...THIS AFTERNOON AND TONIGHT NUMEROUS SHOWERS AND THUNDERSTORMS WILL MOVE ACROSS THE AREA THIS AFTERNOON AND EVENING. SOME OF THE STORMS MAY BE SEVERE...PARTICULARLY ALONG AND EAST OF THE BLUE RIDGE...PRODUCING DAMAGING WIND GUSTS...HEAVY RAIN...AND POSSIBLE ISOLATED TORNADOES. A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL 9 PM FOR MOST COUNTIES EAST OF THE BLUE RIDGE. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED LATER THIS AFTERNOON AND EVENING. KRAMAR
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
832 AM EDT FRI JUL 31 2009
..TIME.. ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE.. ....MAG.... ..COUNTY LOCATION.. ST.. ...SOURCE....
..REMARKS..
0451 PM HAIL 1 WNW LUCKETTS 39.22N 77.55W
07/26/2009 E1.00 INCH LOUDOUN VA PUBLIC
STORM SPOTTER RELAYED REPORT BY NEIGHBOR
&&
EVENT NUMBER LWX0900385
KRAMARSPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 100 PM EDT FRI JUL 31 2009 MDZ003-004-VAZ028-031-042-WVZ052-053-311800- WASHINGTON MD-FREDERICK MD-CLARKE VA-LOUDOUN VA-JEFFERSON WV- BERKELEY WV-FREDERICK VA- 100 PM EDT FRI JUL 31 2009 ...SHOWERS AND THUNDERSTORMS TO AFFECT WASHINGTON...FREDERICK MARYLAND... CLARKE...LOUDOUN ...JEFFERSON...BERKELEY AND FREDERICK VIRGINIA COUNTIES... AT 1257 PM EDT...DOPPLER RADAR INDICATED SHOWERS WITH GUSTY WINDS ALONG A LINE EXTENDING FROM 2 MILES SOUTHEAST OF TOMAHAWK TO 2 MILES SOUTH OF HAYFIELD...MOVING EAST AT 40 MPH. LOCATIONS THAT WILL LIKELY BE AFFECTED BY THESE STORMS INCLUDE CEDAR HILL...ALBIN...MARTINSBURG...INWOOD...STEPHENSON...CLEAR BROOK... BUNKER HILL...VANVILLE...BRUCETOWN AND WADESVILLE. WIND GUSTS OF 40 TO 50 MPH AND OCCASIONAL THUNDER CAN BE EXPECTED WITH THESE STORMS. BAJ
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 110 PM EDT FRI JUL 31 2009 MDZ009-VAZ042-052-053-311800- MONTGOMERY MD-LOUDOUN VA-PRINCE WILLIAM/MANASSAS/MANASSAS PARK VA- FAIRFAX VA- 110 PM EDT FRI JUL 31 2009 ...STRONG STORM TO AFFECT MONTGOMERY...LOUDOUN...PRINCE WILLIAM/MANASSAS/MANASSAS PARK AND FAIRFAX COUNTIES... AT 110 PM EDT...DOPPLER RADAR INDICATED A STRONG STORM 3 MILES SOUTHWEST OF BULL RUN...MOVING NORTHEAST AT 40 MPH. LOCATIONS THAT WILL LIKELY BE AFFECTED BY THIS STORM INCLUDE SUDLEY...MANASSAS PARK...CENTREVILLE...CHANTILLY...OAKTON...WOLF TRAP...VIENNA...RESTON...BELLEVIEW AND TYSONS CORNER. WIND GUSTS OF 40 TO 50 MPH CAN BE EXPECTED WITH THIS STORM. KRAMAR
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 135 PM EDT FRI JUL 31 2009 VAZ026-027-029-030-039>041-051-311830- MADISON VA-CULPEPER VA-PAGE VA-RAPPAHANNOCK VA-FAUQUIER VA-WARREN VA- SHENANDOAH VA-ROCKINGHAM VA- 135 PM EDT FRI JUL 31 2009 ...STRONG SHOWERS TO AFFECT MADISON...CULPEPER...PAGE... RAPPAHANNOCK...FAUQUIER...WARREN...SHENANDOAH AND ROCKINGHAM COUNTIES... AT 134 PM EDT...DOPPLER RADAR INDICATED A LINE OF STRONG SHOWERS ALONG A LINE EXTENDING FROM 2 MILES EAST OF TOMS BROOK TO 4 MILES NORTHWEST OF SHENANDOAH...MOVING EAST AT 30 MPH. LOCATIONS THAT WILL LIKELY BE AFFECTED BY THESE STORMS INCLUDE STANLEY...LURAY...FRONT ROYAL...BIG MEADOWS...SPERRYVILLE...HUME AND DELAPLANE. WIND GUSTS OF 40 TO 50 MPH CAN BE EXPECTED WITH THIS STORM. BAJ
The Sterling radar (KLWX), 35 km away, was scanning. The volume nearest the first event began at 18:03 UTC.
16 thunderstorm wind, 4 tornado. Local standard time, as filed.
Several trees were uprooted along with large tree limbs near Park Mills.
A wind gust of 56 knots was estimated at Crestwood Middle School.
Sporadic tree damage was noted along Tabler Road, where large branches were broken from hardwood trees. The circulation impacted several residences along Ball Road between Tabler Road and Ijamsville Road. One residence suffered roof structure damage and broken windows. In this location the roof was uplifted and shifted northward. An air conditioner unit on the north side of the home was lifted and transported fifteen feet to the east.
Many trees were snapped along Mussetter Road. A large home suffered roof damage and structural damage and a barn was destroyed.
|A second residence also experienced an uplift of roofing. Several metal-sided barns were also destroyed.
Several trees were snapped or uprooted along Ijamsville Road and Price Distillery Road. Several hundred hardwood and softwood trees were snapped or uprooted along Whiskey Road and Whiskey Court. One home bearing specialty shingles to withstand winds up to 100 mph suffered some dislodging of its shingles. A clubhouse on the golf Course also lost many shingles from its roof.
A wind gust of 52 knots was measured at Interstate 270 and Maryland Route 109.
Several one inch limbs were down from thunderstorm winds near Clarksburg.
Nine large hardwood trees were down near Mount Airy.
Trees and power lines were down at Salem Bottom Road and Bloom Road.
Multiple trees were down along Route 97 including at the intersection of Cattail Creek Drive.
Trees and power lines were down on Klee Mill Road near Sykesville Road.
Numerous trees were down near Alpha.
A large tree limb was down just west of Deer Park Road. Two pine trees were down on the westernmost portion of Constellation Way. Two residents suffered a significant loss of roof covering material. Several pine trees were uprooted at several locations along with numerous tree limbs broken. A portion of a corn field was blown over along Kays Mill Road.
Damage was reported to mobile homes near Finksburg.
Numerous trees were down.
Numerous trees were down across the northern portion of Baltimore.
Trees were down along Pulaski Highway near Oakington Road.
Boats were damaged due thunderstorm winds.
A tree top fell into the driveway and large branches were down along Cypress Creek.
Trees were down in Arnold due to thunderstorm winds.
Trees were down at 20 Swan Street.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Maryland in 2009Every state in 2009This day in weather historyThe tornado archive for Maryland, 2009Warnings in Maryland, July 2009
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 2026-09-24. Each event’s entry at NCEI: 188149, 188154, 189031, 189032, 188155, 188156, 188158, 188172, 188161, 188165, 189000, 189030, 189010, 189029, 189001, 189003, 189004, 189005, 189002, 188177.