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NOUS41 KLWX 141332
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DCZ001-MDZ003>007-009>011-013-014-016>018-501-502-VAZ025>031-036>040-
042-050>057-501>504-WVZ050>053-055-501>506-150000-

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
932 AM EDT WED SEP 14 2011

...RECENT HEAVY RAINFALL WAS A RARE EVENT...

THE MID-ATLANTIC REGION...ESPECIALLY FROM WASHINGTON AND BALTIMORE
EASTWARD...HAVE RECENTLY BEEN AFFECTED BY BOTH HURRICANE IRENE AND
A WET PERIOD CAUSED LARGELY BY THE REMNANTS OF TROPICAL STORM LEE.

SOME OF THE HIGHEST RAINFALL TOTALS OVER THE LAST 30 DAYS INCLUDE...
TRUMAN DRIVE IN LARGO        24.13
CABIN BRANCH - FORESTVILLE   23.98
LEELAND ROAD IFLOWS          23.62
HERRING ROUTE 40 BALTIMORE   23.11
BRISTOL                      23.04
BOWIE                        22.90
PRINCE GEORGES JUSTICE CTR   22.87
LAKE ARBOR - LARGO           22.52
DISTRICT HEIGHTS             21.49
KINGSTOWNE - FAIRFAX         20.34
FORT MCHENRY                 19.83
FORT BELVOIR                 18.61
BWI AIRPORT                  17.43

ADDITIONALLY...THE REMNANTS OF LEE BROUGHT TWO INTENSE BANDS OF
RAINFALL TO THE REGION...ONE STRETCHING FROM CHARLES COUNTY
NORTHWARD INTO BALTIMORE COUNTY...AND ANOTHER FROM KING GEORGE
COUNTY NORTHWARD INTO MONTGOMERY COUNTY. THESE RAINBANDS LED TO
RAINFALL THAT IS EXTREMELY UNUSUAL.

ON WEDNESDAY...SEPTEMBER 7TH...THE IFLOWS GAUGE IN BOWIE RECORDED
4.57 INCHES IN THREE HOURS...WHICH HAS APPROXIMATELY A 0.5 PERCENT
CHANCE OF OCCURRING IN ANY GIVEN YEAR /SOMETIMES CALLED A 200-YEAR
RAINFALL/.

FOR ELLICOTT CITY...WHERE SEVERE FLASH FLOODING OCCURRED...THE
RAINS WERE ACTUALLY LESS RARE...ROUGHLY A 1 TO 2 PERCENT CHANCE OF
OCCURRING IN ANY GIVEN YEAR.

THE HEAVY RAINS ON THURSDAY...SEPTEMBER 8TH...WERE EVEN MORE RARE.
THE KINGSTOWNE IFLOWS GAUGE NEAR FRANCONIA IN FAIRFAX COUNTY
RECORDED 5.47 INCHES IN JUST THREE HOURS...WHICH HAS APPROXIMATELY
A 0.2 PERCENT CHANCE OF OCCURRING IN ANY GIVEN YEAR /SOMETIMES
CALLED A 500-YEAR RAINFALL/. THE SAME IS TRUE FOR RAINS IN
RESTON...WHERE 6.57 INCHES WAS RECORDED IN SIX HOURS.

AT FORT BELVOIR...THE AUTOMATED WEATHER STATION THERE RECORDED AN
INCREDIBLE 7.03 INCHES IN JUST THREE HOURS. THIS HAS LESS THAN A
0.1 PERCENT CHANCE OF OCCURRING IN ANY GIVEN YEAR /SOMETIMES
CALLED A 1000-YEAR RAINFALL/.

THESE VALUES ARE PRELIMINARY AND BASED ON PRECIPITATION FREQUENCY
CALCULATIONS FROM THE NEAREST AVAILABLE STATION. THE VALUES ARE
SUBJECT TO CORRECTION.

$$

JE