August 12, 2010 Severe Weather

000
NOUS41 KLWX 171346
PNSLWX
DCZ001-MDZ003>007-009>011-013-014-016>018-501-502-VAZ021-025>031-
036>040-042-050>057-501-502-WVZ050>055-501>504-180200-
DISTRICT OF COLUMBIA-WASHINGTON-FREDERICK MD-CARROLL-
NORTHERN BALTIMORE-HARFORD-MONTGOMERY-HOWARD-SOUTHERN BALTIMORE-
PRINCE GEORGES-ANNE ARUNDEL-CHARLES-ST. MARYS-CALVERT-
EXTREME WESTERN ALLEGANY-CENTRAL AND EASTERN ALLEGANY-HIGHLAND-
AUGUSTA-ROCKINGHAM-SHENANDOAH-FREDERICK VA-PAGE-WARREN-CLARKE-
NELSON-ALBEMARLE-GREENE-MADISON-RAPPAHANNOCK-LOUDOUN-ORANGE-
CULPEPER-PRINCE WILLIAM/MANASSAS/MANASSAS PARK-FAIRFAX-
ARLINGTON/FALLS CHURCH/ALEXANDRIA-STAFFORD-SPOTSYLVANIA-
KING GEORGE-NORTHERN FAUQUIER-SOUTHERN FAUQUIER-HAMPSHIRE-MORGAN-
BERKELEY-JEFFERSON-PENDLETON-HARDY-WESTERN GRANT-EASTERN GRANT-
WESTERN MINERAL-EASTERN MINERAL-

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
946 AM EDT TUE AUG 17 2010

...STORM SURVEYS CONDUCTED FOR 12 AUGUST 2010 THUNDERSTORMS...

THE NATIONAL WEATHER SERVICE BALTIMORE/WASHINGTON WEATHER
FORECAST OFFICE IN STERLING VIRGINIA DISPATCHED SURVEY TEAMS
FRIDAY MORNING TO EVALUATE DAMAGE IN FREDERICK...CARROLL AND 
MONTGOMERY COUNTIES IN MARYLAND...AND STAFFORD COUNTY VIRGINIA IN 
THE WAKE OF THUNDERSTORMS ON 12 AUGUST 2010.

THESE TEAMS DETERMINED A SMALL EF-0 TORNADO STRUCK JUST SOUTH OF 
UNIONVILLE IN FREDERICK COUNTY MARYLAND WITH PEAK WINDS OF 80 MPH... 
WHILE THE REST OF THE DAMAGE TO THE AREA WAS FROM THUNDERSTORM WIND 
GUSTS...UP TO 90 MPH IN A FEW AREAS.

&&

FREDERICK AND CARROLL COUNTIES...

...EF-0 TORNADO CONFIRMED SOUTH OF UNIONVILLE MARYLAND...

LOCATION...SOUTH OF UNIONVILLE IN FREDERICK COUNTY MARYLAND 
DATE...12 AUGUST 2010
ESTIMATED TIME...503 PM
MAXIMUM EF-SCALE RATING...EF-0
ESTIMATED MAXIMUM WIND SPEED...80 MPH 
MAXIMUM PATH WIDTH...50 YARDS 
PATH LENGTH...0.25 MILES 
BEGINNING LAT/LON...39.4403N/77.1837W 
ENDING LAT/LON...39.4377N/77.1829W 
* FATALITIES...NONE
* INJURIES...NONE

* THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO
  CHANGE PENDING FINAL REVIEW OF THE EVENT(S) AND PUBLICATION IN
  NWS STORM DATA.

...SUMMARY...

A SURVEY TEAM INSPECTED THE TRACK OF A STORM THAT MOVED THROUGH 
PORTIONS OF EASTERN FREDERICK AND WESTERN CARROLL COUNTIES IN 
MARYLAND DURING THE AFTERNOON OF 12 AUGUST. IN THE AREA FROM EAST OF 
EMMITSBURG TO NEAR UNION BRIDGE...VERY SPORADIC DAMAGE WAS FOUND 
CONSISTING MAINLY OF LEAF DEBRIS...DEAD BRANCHES OR SMALL LIVE 
BRANCHES. NEAR KEYSVILLE AND GREGG ROADS...MAIN LIMBS FROM A LARGE 
HARDWOOD TREE WERE BROKEN OFF. ADDITIONAL SPORADIC DAMAGE TO LARGE 
LIMBS WAS FOUND NEAR THE TOWN OF DETOUR. THIS DAMAGE WAS CONSISTENT 
WITH SPORADIC WIND GUSTS TO 60 MPH.

MORE SIGNIFICANT DAMAGE WAS ENCOUNTERED FROM NEAR UNIONVILLE SOUTH 
TO THE WOODVILLE AREA OF MOUNT AIRY. ALONG THIS PATH...NUMEROUS 
TREES WERE UPROOTED AND LARGE LIMBS WERE SNAPPED. SEVERAL SOFTWOOD 
TREES LOST UPPER SECTIONS OF THEIR MAIN TRUNKS. DAMAGE WAS 
ESPECIALLY CONCENTRATED NEAR HARRISVILLE ROAD AND WOODVILLE ROAD. 
ALONG WESTVALE COURT...A CLUSTER OF SOFTWOOD TREES WAS SNAPPED 20 TO 
30 FEET ABOVE GROUND. HERE AND ALONG STREETS TO THE SOUTH...SEVERAL 
OTHER TREES WERE UPROOTED. MANY LARGE LIMBS ALSO WERE SNAPPED OFF. 
DAMAGE BECAME MORE SPORADIC SOUTH OF GLISSANS MILL ROAD. SEVERAL 
BROKEN BRANCHES AND LIMBS WERE FOUND ALONG BOTTOM ROAD...AND SEVERAL 
TOPPED TREES WERE REPORTED OFF OF OLD ANNAPOLIS ROAD. THROUGHOUT 
THIS TRACK...NO DAMAGE TO STRUCTURES WAS OBSERVED.

FALLEN TREES AND LIMBS GENERALLY WERE ORIENTED TOWARD THE 
SOUTH-SOUTHWEST...CONSISTENT WITH STRONG STRAIGHT-LINE WINDS IN THE 
REAR FLANK DOWNDRAFT ON THE WESTERN PERIPHERY OF THE STORM 
CIRCULATION. HOWEVER...SEVERAL OF THE TREES ALONG WESTVALE COURT 
WERE FELLED TOWARD THE SOUTH-SOUTHEAST. ADDITIONALLY...THE DEBRIS 
FIELD FROM NORTH OF WESTVALE COURT SOUTHWARD ACROSS HARRISVILLE ROAD 
SHOWED A CONVERGENT AND WEAKLY ROTATIONAL PATTERN.

DAMAGE ALONG THIS PATH IS CONSISTENT WITH WIDESPREAD STRAIGHTLINE 
WIND GUSTS OF 70 TO 80 MPH. HOWEVER...BASED UPON THE CONVERGENT AND 
ROTATIONAL DEBRIS FIELD ALONG AND SOUTH OF WESTVALE COURT...IT 
APPEARS A SHORT-LIVED TORNADO OCCURRED. IT IS LIKELY THAT STRUCTURES 
WERE SHELTERED SUFFICIENTLY BY THE TREES TO PREVENT VISIBLE DAMAGE 
FROM OCCURRING. DAMAGE WAS CONSISTENT WITH WIND SPEEDS OF 80 MPH... 
WHICH CLASSIFIES THE TORNADO AS EF0 ON THE ENHANCED FUJITA SCALE.

&& 

MONTGOMERY COUNTY...

...THUNDERSTORMS HEAVILY DAMAGE SILVER SPRING AND GAITHERSBURG...

A SEVERE THUNDERSTORM MOVED THROUGH THE SILVER SPRING AREA OF 
MONTGOMERY COUNTY MARYLAND DURING THE EARLY MORNING OF 12 AUGUST. 
A SECOND TEAM FOUND WIDESPREAD TREE DAMAGE WITHIN A 200-300 YARD 
STRETCH OF US-29 BETWEEN NORTHWEST DRIVE AND PRELUDE DRIVE NEAR 
WHITE OAK. IN THIS AREA...NUMEROUS TREES OF 18 TO 24 INCH DIAMETER 
WERE SNAPPED AROUND 30 FEET ABOVE THE GROUND. WIND DAMAGE WAS CAUSED 
BY THUNDERSTORM OUTFLOW WIND AND WAS CONSISTENT WITH A LOCALIZED 
SWATH OF 80 TO 90 MPH GUSTS.

WIDESPREAD DAMAGE WAS ALSO REPORTED IN GAITHERSBURG...WHERE NUMEROUS 
HARDWOOD TREES WERE UPROOTED AND LARGE LIMBS THROUGHOUT TOWN WERE 
SNAPPED. THE MAIN TRUNKS OF SEVERAL SOFTWOOD TREES WERE SNAPPED. 
MANY STRUCTURES WERE DAMAGED BY FALLEN TREES. ON SEVERAL 
BUILDINGS...TIN ROOF PANELS WERE REMOVED AND WRAPPED AROUND POWER 
POLES. ON OTHER BUILDINGS...SECTIONS OF SHINGLES WERE REMOVED AND 
WINDOWS WERE BLOWN OUT. A LARGE...2.5 TON FOOD SERVICE TRAILER WAS 
DISPLACED SLIGHTLY BY THE WIND. SECURITY VIDEO AT A GAITHERSBURG 
RESTAURANT SHOWED A BRIEF TWO-MINUTE DURATION EPISODE OF EXTREME 
WIND AND WIND-BLOWN HAIL OCCURRING AT ROUGHLY 700 AM. THIS TIME IS 
COINCIDENT WITH A SWATH OF STRONG RADAR-DETECTED WIND CAUSED BY 
THUNDERSTORM OUTFLOW. DAMAGE TO TREES AND STRUCTURES IS CONSISTENT 
WITH A FOCUSED PERIOD OF GUSTS OF 80 TO 90 MPH.

&&

STAFFORD COUNTY...

...THUNDERSTORM PRODUCES DAMAGE PATH JUST EAST OF FREDERICKSBURG...

A THIRD TEAM INSPECTED STORM DAMAGE FROM A SEVERE THUNDERSTORM THAT 
MOVED SOUTH THROUGH STAFFORD COUNTY VIRGINIA. A TRACK OF DAMAGE WAS 
NOTED ALONG A SIX MILE CORRIDOR ABOUT THREE MILES EAST OF THE CITY 
OF FREDERICKSBURG THROUGH MOSTLY UNINHABITED SWAMP LAND AND FOREST.

LEAF AND TWIG DEBRIS BEGAN ON THE SOUTHERN EDGE OF THE STAFFORD 
COUNTY LANDFILL PROPERTY. SEVEN TREES WERE FOUND UPROOTED OR SNAPPED 
ALONG A PATH THAT PROCEEDED SOUTH ACROSS POTOMAC RUN ROAD...BROOKE 
ROAD...NEW HOPE CHURCH ROAD AND NEWTON ROAD. AT THE END OF THE TRACK 
WAS THE MOST NOTABLE DAMAGE...OFF DESHAZO LANE. A HOME WAS PARTIALLY 
DESHINGLED AT THE INTERSECTION WITH ROUTE 218...AND 3 TWO FOOT 
DIAMETER PINE TREES IN A ROW WERE SNAPPED DOWN.

THE DAMAGE WAS ESTIMATED TO HAVE STARTED AT 357 PM NEAR THE 
LANDFILL...AND ENDED AT 410 PM ON DESHAZO LANE. PEAK WIND GUSTS 
ALONG MOST OF THE DAMAGE CORRIDOR WERE ESTIMATED TO HAVE BEEN 60 
MPH. DAMAGE OFF OF DESHAZO LANE WAS ESTIMATED TO HAVE BEEN CAUSED BY 
A 70 MPH WIND GUST.

&&

PARTNER APPRECIATION...

THE NATIONAL WEATHER SERVICE THANKS EMERGENCY MANAGEMENT IN 
FREDERICK AND CARROLL COUNTIES...THE DEPUTY FIRE CHIEF OF STAFFORD 
COUNTY...THE GAITHERSBURG CITY COUNCIL AND THE PUBLIC FOR ITS 
COOPERATION THROUGHOUT THE STORM SURVEYS.

$$