000
FGUS71 KBUF 051456
ESFBUF
NYC003-009-011-013-029-037-045-049-051-055-063-069-073-075-117-
121-191500-

WINTER/SPRING FLOOD POTENTIAL OUTLOOK
NATIONAL WEATHER SERVICE BUFFALO NY
1056 AM EDT FRI APR 5 2013

...NEAR NORMAL FLOOD RISK THROUGH MID-APRIL... 
...ABOVE NORMAL FLOOD RISK FOR THE BLACK RIVER BASIN LATE NEXT
WEEK...

UPDATED TO INCLUDE NEW MEASUREMENTS FROM THE BLACK RIVER BASIN.

THIS IS THE SEVENTH WINTER / SPRING FLOOD POTENTIAL OUTLOOK OF
THE 2013 SEASON. FLOOD OUTLOOKS WILL BE ISSUED EVERY TWO WEEKS
INTO EARLY SPRING TO SUMMARIZE BASIN HYDROMETEOROLOGICAL
CONDITIONS AND TO ASSESS THE POTENTIAL FOR FLOODING. THE OUTLOOKS
ARE BASED ON CURRENT AND FORECAST HYDROMETEOROLOGICAL CONDITIONS.
THIS INCLUDES SNOW COVER AND SNOW WATER EQUIVALENT...CREEK AND
RIVER LEVELS AND THE AMOUNT OF ICE COVER ON THEM...ALONG WITH THE
EXPECTED PRECIPITATION OVER THE NEXT TWO WEEKS.

...CURRENT CONDITIONS SUMMARY...

WHILE TEMPERATURES HAVE GENERALLY AVERAGED BELOW NORMAL OVER THE 
PAST TWO WEEKS...THE INCREASING SUN ANGLE AND WARMER CLIMATOLOGY 
HAS REDUCED THE SNOWPACK IN MANY LOCATIONS. TEMPERATURES CLIMBED 
INTO THE 50S ON THE LAST DAY OF MARCH...WHICH FINISHED OFF MOST
OF THE SNOWPACK IN ALL AREAS EXCEPT THE TUG HILL.

ANOTHER SHOT OF COLDER AIR POURED INTO WESTERN NEW YORK THE FIRST
SEVERAL DAYS OF APRIL. THIS AIR MASS WAS COLD ENOUGH TO BRING
SOME LIGHT LAKE EFFECT SNOWS TO THE TUG HILL. WATER CONTENT IN THE
SNOW PACK ON THE TUG HILL IS RUNNING ABOUT 25 PERCENT ABOVE NORMAL
FOR THIS DATE...WITH UP TO 8 INCHES WATER EQUIVALENT STILL IN
PLACE. THIS SNOW PACK IS BECOMING QUITE RIPE...WITH ABOUT A 3 TO 1
RATIO BETWEEN SNOW DEPTH AND WATER CONTENT.

ELSEWHERE...WATER EQUIVALENT AMOUNTS OF SNOW ARE FAIRLY 
INSIGNIFICANT. THIS FINAL BIT OF SNOW MELT DID RAISE CREEK AND
RIVER FLOWS A BIT...BUT THESE FLOWS ARE STILL RUNNING A BIT BELOW
NORMAL FOR THIS TIME OF YEAR. ALSO...NEARLY ALL THE LINGERING
RIVER AND CREEK ICE HAS MELTED...WITH ANYTHING LEFT LIKELY TO BE
TOO BRITTLE TO RESULT IN ICE JAMS.

THE FOLLOWING IS A SUMMARY OF CONDITIONS AND OUTLOOK BY BASIN AS
OF THURSDAY MORNING ON APRIL 4TH:

...BUFFALO AREA CREEKS / LAKE ERIE BASIN...
.SNOW COVER..........TRACE...LESS THAN 3 INCHES IN THE HEADWATERS.
.WATER EQUIVALENT....TRACE...LESS THAN A HALF INCH IN THE HEADWATERS.
.CREEK FLOWS.........BELOW NORMAL.
.CREEK ICE...........NONE.
.GROUND FROST........NONE.
.GROUND STATE........SATURATED.

...GENESEE RIVER BASIN / FINGER LAKES / ROCHESTER AREA...
.SNOW COVER..........NONE.
.WATER EQUIVALENT....NONE.
.RIVER/CREEK FLOWS...BELOW NORMAL.
.RIVER/CREEK ICE.....NONE.
.GROUND FROST........NONE.
.GROUND STATE........SATURATED.

...ALLEGHENY RIVER BASIN...
.SNOW COVER..........LESS THAN 6 INCHES.
.WATER EQUIVALENT....LESS THAN AN INCH.
.RIVER/CREEK FLOWS...BELOW NORMAL.
.RIVER CREEK ICE.....NONE.
.GROUND FROST........LESS THAN 6 INCHES.
.GROUND STATE........PARTIALLY FROZEN.

...BLACK RIVER BASINS / TUG HILL...
.SNOW COVER..........LESS THAN 6 INCHES...1 TO 2 FEET ON TUG HILL.
.WATER EQUIVALENT....LESS THAN AN INCH...4 TO 8 INCHES ON TUG HILL.
.RIVER/CREEK FLOWS...BELOW NORMAL.
.RIVER/CREEK ICE.....VERY LITTLE.
.GROUND FROST........LESS THAN 12 INCHES.
.GROUND STATE........MAINLY FROZEN.

...TEMPERATURE AND PRECIPITATION OUTLOOK...
THE PERIOD WILL START OFF WITH SEASONABLY WARMER TEMPERATURES AND
FAIRLY DRY WEATHER THROUGH SATURDAY. THEN A WEAK AREA OF LOW
PRESSURE WILL TRACK TO THE NORTH WHICH RESULT IN SOME LIGHT RAIN
SHOWERS ON SUNDAY.

LOOKING INTO NEXT WEEK...A FRONTAL BOUNDARY EXTENDING FROM WEST
TO EAST WILL STALL SOMEWHERE NEAR THE REGION. THIS FRONT WILL
DIVIDE COLDER AIR TO THE NORTH FROM SIGNIFICANTLY WARMER AIR IN
THE 60S AND 70S TO THE SOUTH OF THE BOUNDARY. THE BOUNDARY WILL
BRING A CHANCE FOR SOME RAIN FOR THE FIRST HALF OF NEXT WEEK...AND
THE POSSIBILITY OF MUCH WARMER TEMPERATURES. THEN LATE NEXT
WEEK...MODEL GUIDANCE SUGGESTS THAT THIS FRONT MAY BECOME MORE
SOUTH TO NORTH ORIENTED AS A TROUGH IN THE UPPER LEVELS IS
FORECAST TO DEVELOP ACROSS THE MID-WESTERN STATES. THIS PATTERN
WOULD RESULT IN A WARM AND MOIST FLOW FROM THE GULF...WHICH IS
CONDUCIVE FOR HEAVY RAINFALL SOMEWHERE IN THE EASTERN STATES.
WHILE THERE IS MODERATE CONFIDENCE THAT THIS GENERAL PATTERN WILL
DEVELOP...IT IS STILL QUITE UNCERTAIN EXACTLY WHERE HEAVY RAIN
WILL DEVELOP. SO WHILE THIS PATTERN CERTAINLY HAS THE POTENTIAL
FOR HEAVY RAINFALL LATE NEXT WEEK...THE PROBABILITY OF HEAVY RAIN
IN OUR REGION IS STILL JUST MODEST.

...FLOOD POTENTIAL OUTLOOK...
THE PATTERN FORECAST TO DEVELOP IS SIGNIFICANTLY DIFFERENT FROM
THE PAST COUPLE MONTHS. THE GREATEST RISK FOR FLOODING IS LATE
NEXT WEEK WHEN A WARM AND MOIST SOUTHWESTERLY FLOW IS FORECAST TO
SET UP ACROSS THE EASTERN STATES. THIS PATTERN HAS THE POTENTIAL
TO PRODUCE SIGNIFICANT RAINFALL...ESPECIALLY ALONG WHAT IS
EXPECTED TO BE A SLOW MOVING FRONTAL BOUNDARY.

THROUGH EARLY NEXT WEEK...SEVERAL DAYS OF SEASONABLY WARM WEATHER
WILL RESULT IN SIGNIFICANT SNOW MELT. THIS SHOULD NOT RESULT IN
FLOODING...BUT SHOULD CAUSE RIVER FLOWS TO RISE TO NEAR OR ABOVE
NORMAL IN THE BLACK RIVER BASIN. THIS WOULD LEAVE THIS BASIN IN
VULNERABLE TO FLOODING IF THERE IS HEAVY RAIN LATE NEXT WEEK.

IN ADDITION TO UNCERTAINLY IN THE RAINFALL FORECAST...IT IS ALSO
UNCLEAR HOW MUCH SNOW WILL REMAIN ON THE TUG HILL LATE NEXT
WEEK...WHEN THE POTENTIAL IS GREATEST FOR HEAVY RAIN. FOR
NOW...SNOW PACK IS RUNNING ABOVE NORMAL FOR THIS TIME OF YEAR ON
THE TUG HILL. NEARLY A WEEK OF WARM WEATHER SHOULD RESULT IN
PERSISTENT SNOW MELT...WHICH WOULD HELP MITIGATE FLOOD POTENTIAL
LATER IN THE WEEK. HOWEVER...WHATEVER SNOW PACK DOES REMAIN COULD
EXACERBATE FLOWS LATER IN THE WEEK IF HEAVY RAIN DOES DEVELOP.

THE MAIN CONCERN IS THE BLACK RIVER BASIN WHERE SIGNIFICANT
SNOWPACK IS IN PLACE. EVEN IN BASINS WHERE NO SNOW REMAINS...
RAINFALL IN EXCESS OF TWO INCHES COULD CAUSE FLOODING WITHOUT ANY
CONTRIBUTION FROM SNOW MELT. OVERALL...THE PATTERN CHANGE SUPPORTS
NEAR NORMAL FLOOD POTENTIAL DESPITE THE BELOW NORMAL SNOW PACK.
THE GREATEST RISK APPEARS TO BE ON THE BLACK RIVER BASIN LATE NEXT
WEEK...GIVEN BOTH THE SNOW PACK AND THE POTENTIAL FOR HEAVY RAIN.

AFTER THIS...IT APPEARS THERE WILL NO SNOW LEFT. GIVEN A FAIRLY
BENIGN FORECAST...EXPECT A DIMINISHED FLOOD RISK AFTER MID-APRIL.

...ADDITIONAL INFORMATION...

REAL TIME RIVER INFORMATION AND PROBABILISTIC FORECASTS FOR
SPECIFIC LOCATIONS ALONG RIVERS ACROSS WESTERN NEW YORK CAN BE
FOUND ON THE INTERNET AT WWW.WEATHER.GOV/BUF BY CLICKING ON THE
RIVERS AND LAKES AHPS LINK ON THE LEFT SIDE OF THE PAGE. SINCE
CONDITIONS CAN CHANGE PLEASE REFER TO THE LATEST FLOOD
WARNINGS...WATCHES...AND STATEMENTS FOR ADDITIONAL INFORMATION.

THE NEXT OUTLOOK MAY BE ISSUED BY THURSDAY APRIL 18TH IF SNOWPACK
REMAINS. BASED ON THE FORECAST...IT IS FAIRLY LIKELY THAT MOST 
OF THE SNOW WILL BE MELTED BY THEN...AND THAT THIS WILL PROBABLY
BE THE LAST HYDROLOGIC OUTLOOK OF THE SEASON. THANKS TO ALL THE
OBSERVERS AND AGENCIES WHICH HAVE HELPED GATHER DATA IN SUPPORT OF
THIS OUTLOOK.

$$

APFFEL