Flood Potential Outlook
Issued by NWS Sterling, VA

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WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
230 PM EDT THU MAR 20 2014

...2014 WINTER/SPRING FLOOD POTENTIAL OUTLOOK...NUMBER 6

...RIVER FLOOD POTENTIAL OUTLOOK THROUGH APRIL 3RD...

INTRODUCTION...
EACH WINTER AND EARLY SPRING...THE NATIONAL WEATHER SERVICE OFFICE
SERVING THE BALTIMORE/WASHINGTON AREA ISSUES A SERIES OF ROUTINE
FLOOD POTENTIAL OUTLOOKS. THESE OUTLOOKS ESTIMATE THE POTENTIAL FOR
RIVER FLOODING /NOT FLASH FLOODING/ ACROSS THE BALTIMORE/WASHINGTON
HYDROLOGIC SERVICE AREA /HSA/. THIS AREA INCLUDES THE ENTIRE
POTOMAC...SHENANDOAH...AND RAPPAHANNOCK RIVER BASINS...AS WELL AS
DRAINAGE BASINS WEST OF BUT NOT INCLUDING THE SUSQUEHANNA IN THE
UPPER CHESAPEAKE BAY.

DURING THIS TIME OF YEAR...CONTRIBUTING FACTORS TO RIVER FLOODING
COME FROM RECENT PRECIPITATION...SOIL MOISTURE CONDITIONS...SNOW
COVER AND SNOW WATER EQUIVALENT...RIVER ICE...ANTECEDENT
STREAMFLOW...EXPECTED WEATHER CONDITIONS...AND OTHER FACTORS. THIS
OUTLOOK IS VALID FOR THE PERIOD THROUGH APRIL 3RD 2014.

IN THE MID-ATLANTIC REGION...HEAVY RAINFALL IS THE PRIMARY FACTOR
WHICH LEADS TO RIVER FLOODING. HEAVY RAIN CAN RAPIDLY CAUSE RIVER
FLOODING AT ANY TIME OF THE YEAR...EVEN WHEN RIVER FLOOD POTENTIAL
IS CONSIDERED TO BE LOW OR BELOW AVERAGE.

TWO WEEK RIVER FLOOD POTENTIAL OUTLOOK...
IN THE BALTIMORE/WASHINGTON HSA...THE RIVER FLOOD POTENTIAL IS BELOW
AVERAGE THROUGH MARCH 27TH...THEN NEAR AVERAGE THROUGH APRIL 3RD.

CURRENT FLOODING...
NONE CURRENTLY ACROSS THE MID-ATLANTIC REGION.

RECENT PRECIPITATION...
A SIGNIFICANT SNOWFALL OCCURRED ACROSS THE AREA ON MONDAY...MARCH
17TH. HOWEVER...VIRTUALLY ALL OF THAT SNOW HAS MELTED ALREADY. SOME
MINOR STREAMFLOW RISES OCCURRED AS A RESULT OF THE SNOWMELT AND
LATER LIGHT RAIN...BUT NO FLOODING WAS OBSERVED.

PRECIPITATION OVER THE LAST 14 DAYS...AND IN FACT...SINCE
MID-FEBRUARY...HAS ACTUALLY BEEN BELOW NORMAL AREAWIDE.
PRECIPITATION ON LONGER TIME SCALES IS ABOVE NORMAL DUE TO A
GENERALLY WET WINTER.

SNOW CONDITIONS...
ONLY TRACES OF SNOW REMAIN ON THE GROUND ACROSS THE AREA.

RIVER ICE...
RIVER ICE IS NO LONGER A CONCERN FOR THE SEASON.

STREAMFLOW CONDITIONS...
RIVERS IN THE STERLING HSA ARE GENERALLY NEAR NORMAL FOR THIS TIME
OF YEAR.

SOIL MOISTURE...
SOIL MOISTURE IS NEAR NORMAL ACROSS MOST OF THE MID-ATLANTIC
REGION...BUT STARTING TO SLIP BELOW NORMAL ACROSS NORTH CENTRAL
MARYLAND.

GROUNDWATER CONDITIONS...
GROUNDWATER CONDITIONS ARE NEAR TO ABOVE NORMAL ACROSS THE ENTIRE
HYDROLOGIC SERVICE AREA.

EXPECTED WEATHER...
DRY CONDITIONS ARE EXPECTED THROUGH MOST...IF NOT ALL...OF THE
UPCOMING WEEKEND. A MORE UNSETTLED PATTERN TAKES SHAPE AFTER
THAT...BUT AT THIS TIME ALL POTENTIAL PRECIPITATION APPEARS TO BE
LIGHT...WITH TOTALS THROUGH WEDNESDAY MARCH 26TH EXPECTED TO BE LESS
THAN HALF AN INCH.

THE OUTLOOK FOR WEEK TWO...MARCH 27 THROUGH APRIL 2...STILL FAVORS
BELOW NORMAL TEMPERATURES...AND ALSO FAVORS ABOVE NORMAL
PRECIPITATION. IT IS FOR THIS REASON THAT THE FLOOD POTENTIAL IS
HIGHER IN THE SECOND WEEK OF THE OUTLOOK.

PROBABILISTIC/ENSEMBLE RIVER FORECASTS...
THE ENSEMBLE RIVER FORECASTS USING THE EXPERIMENTAL SHORT-TERM
HYDROLOGIC ENSEMBLE FORECAST INDICATE VIRTUALLY NO FLOOD POTENTIAL
THROUGH MARCH 26TH.

THE LONGER-TERM PROBABILISTIC FORECASTS ON THE ADVANCED HYDROLOGIC
PREDICTION SERVICE INDICATE NEAR NORMAL CHANCE OF REACHING FLOOD
STAGES THROUGH MID APRIL. TYPICALLY...THE CHANCE OF REACHING FLOOD
STAGE AT OUR RIVER FORECAST POINTS DURING THIS TIME OF YEAR IS 30
PERCENT OR LESS AT ALL RIVER FORECAST POINTS.

SUMMARY...
THE RIVER FLOOD POTENTIAL IS BELOW AVERAGE THROUGH MARCH 27TH...THEN
NEAR AVERAGE UNTIL APRIL 3RD.

WATER SUPPLY OUTLOOK...
ASSUMING NEAR NORMAL PRECIPITATION DURING THE NEXT FEW MONTHS...
WATER SUPPLY IS EXPECTED TO REMAIN NORMAL THROUGH THE SPRING. NO
DROUGHT CONDITIONS CURRENTLY EXIST IN THE REGION. DEVELOPMENT OF
DROUGHT CONDITIONS IS NOT EXPECTED.

NEXT ISSUANCE...
THIS IS THE FINAL REGULARLY SCHEDULED ISSUANCE OF THE SEASONAL FLOOD
OUTLOOK UNTIL JANUARY 2015. HOWEVER...SHOULD CONDITIONS WARRANT...
THIS PRODUCT COULD BE UPDATED ON THURSDAY...APRIL 3RD 2014.

FOR ADDITIONAL HYDROLOGIC OR WEATHER INFORMATION...VISIT OUR
WEBSITE AT WWW.WEATHER.GOV/BALTIMORE OR WEATHER.GOV/WASHINGTON.

$$

ELLIOTT






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