Flood Potential Outlook
Issued by NWS Jacksonville, FL

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HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE JACKSONVILLE FL
200 PM EST THU MAR 5 2015

...SPRING FLOOD POTENTIAL OUTLOOK FOR SOUTHEAST GEORGIA AND
NORTHEAST FLORIDA...

...ABOVE NORMAL POTENTIAL FOR RIVER FLOODING THIS SPRING...

...EXISTING CONDITIONS...

IN THE ALTAMAHA...SATILLA AND ALAPAHA BASINS...

RAINFALL SINCE OCTOBER 1ST 2014 ACROSS INLAND SOUTHEAST GEORGIA HAS
BEEN ABOVE NORMAL WITH RAINFALL SURPLUSES OF 2 TO 6 INCHES AND THIS
HAS LED TO MULTIPLE MINOR FLOOD EVENTS ALREADY THIS PAST WINTER.
STREAM FLOWS REMAIN WELL ABOVE NORMAL AND MINOR FLOODING IS ALREADY
ONGOING DURING THE FIRST WEEK OF MARCH.

IN THE UPPER SUWANNEE AND ST. MARYS BASINS...

RAINFALL OVER THE LAST FEW MONTHS HAS BEEN GENERALLY ABOVE NORMAL
WITH RAINFALL SURPLUSES OF 2 TO 6 INCHES...MAINLY LOCATED IN THE
HEADWATERS OF THESE BASINS OVER THE OKEFENOKEE SWAMP. THIS HAS LED
TO ABOVE NORMAL STREAM FLOWS FOR THIS TIME OF YEAR AND NEAR BANKFULL
CONDITIONS DURING SEVERAL OCCASIONS THIS PAST WINTER.

IN THE SANTA FE BASIN...

RAINFALL OVER THE LAST FEW MONTHS HAS GENERALLY BEEN BELOW NORMAL
WITH RAINFALL DEFICITS UP TO 2 TO 4 INCHES BELOW NORMAL AND THIS HAS
KEPT CURRENT STREAM FLOWS NEAR NORMAL AFTER A LONG PERIOD OF WET
CONDITIONS DURING THE FIRST HALF OF 2014. ANY SIGNIFICANT FLOODING
WILL LIKELY DEPEND ON HOW HIGH THE SUWANNEE BASIN WOULD GET TO
CREATE BACKWATER PROBLEMS IN THE LOWER PORTIONS OF THE SANTA FE
BASIN.

IN THE BLACK CREEK BASIN...

RAINFALL OVER THE LAST FEW MONTHS HAS GENERALLY BEEN NORMAL TO BELOW
NORMAL WITH RAINFALL DEFICITS UP TO 2 TO 4 INCHES BELOW NORMAL AND
THIS HAS KEPT CURRENT STREAM FLOWS NEAR NORMAL AFTER A LONG PERIOD
OF WET CONDITIONS DURING THE FIRST HALF OF 2014.

...LONG TERM PRECIPITATION OUTLOOK...

THE ONE MONTH PRECIPITATION OUTLOOK FOR MARCH INDICATES A GREATER
THAN 40 PERCENT CHANCE OF ABOVE NORMAL PRECIPITATION. THIS IS
SUPPORTED BY NUMERICAL MODEL FORECASTS WHICH SUGGESTS THE MORE
ENERGETIC PATTERN EXPERIENCED IN LATE FEBRUARY WILL CONTINUE INTO
MUCH OF THE MONTH OF MARCH. THE LONGER RANGE PRECIPITATION OUTLOOK
FEATURES NEAR NORMAL PRECIPITATION FOR THE MONTHS OF APRIL AND MAY.
THE POTENTIAL FOR HEAVY RAINFALL TYPICALLY DECREASES AFTER EARLY
APRIL AS THE REGION TRANSITIONS INTO MORE OF A DRIER PATTERN AS
INFLUENCES FROM FRONTAL SYSTEMS DIMINISH.

...SPRING FLOOD OUTLOOK SUMMARY...

TAKING INTO ACCOUNT LONG TERM ENSEMBLE PROBABILITIES FOR
PRECIPITATION...RECENT RAINFALL AND CURRENT STREAM FLOWS...THERE IS
AN ABOVE NORMAL POTENTIAL FOR RIVER FLOODING ACROSS THE REGION THIS
SPRING. THIS RISK IS MAXIMIZED ACROSS SOUTHEAST GEORGIA AND INLAND
NORTH FLORIDA...WHICH INCLUDES THE ALTAMAHA...SATILLA...ALAPAHA...
ST. MARYS AND UPPER SUWANNEE BASINS. IN THESE SPECIFIC
BASINS...THERE IS POTENTIAL FOR A HIGH IMPACT BASIN-WIDE FLOOD EVENT
THIS SPRING SHOULD HEAVIER THAN NORMAL RAINFALL OCCUR...AS STORAGE
CAPACITY IN THE HEADWATER PORTION OF THESE BASINS IS ESPECIALLY LOW.

SHOULD NORMAL TO ABOVE NORMAL SPRING RAINFALL AMOUNTS MATERIALIZE
THE CONTINUED WET CONDITIONS WILL KEEP AN INCREASED FLOOD RISK FOR
OUR AREA RIVERS MOVING INTO HURRICANE SEASON IN JUNE.

&&

$$

HESS/GODSEY



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