Back-to-back powerful Pacific storm systems to impact the Pacific Northwest and northern California through the end of this week with heavy rain, flooding, strong winds, and higher elevation mountain snow. A strong, long-duration atmospheric river will accompany the Pacific storms, bringing excessive rainfall and flash flooding to southwest Oregon and northwest California through the week. Read More >
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. $$