…SECOND SPRING HYDROLOGIC SUMMARY AND OUTLOOK…

THE FOLLOWING INFORMATION IS THE SECOND PLANNED FLOOD OUTLOOK
PROVIDING FLOOD POTENTIAL AND CLIMATOLOGICAL INFORMATION FOR THIS
COMING SPRING. THIS OUTLOOK CONTAINS INFORMATION WHICH WAS COLLECTED
FROM A NUMBER OF SOURCES…INCLUDING THE UNITED STATES GEOLOGICALSURVEY /USGS/…
US ARMY CORPS OF ENGINEERS /USACE/…MIDWESTREGIONAL CLIMATE CENTER /MRCC/…
CLIMATE PREDICTION CENTER /CPC/…US DROUGHT MONITOR…AND THE
NATIONAL OPERATIONAL REMOTE SENSING CENTER /NOHRSC/.

THE FOLLOWING OUTLOOK IS A SUMMARY OF THE PAST AND PRESENT BASIN
CONDITIONS FOR PORTIONS OF NORTHEAST IOWA…SOUTHEAST MINNESOTA…
AND SOUTHWEST INTO CENTRAL WISCONSIN.

*** FLOOD POTENTIAL HIGHLIGHTS ***

IN SHORT…THE FLOODING POTENTIAL FOR THIS SPRING HAS INCREASED
SLIGHTLY FROM THE OUTLOOK ISSUED 2 WEEKS AGO ON FEBRUARY 21ST. THE
OVERALL THREAT IS NOW ABOUT NORMAL WHEN COMPARED TO A TYPICAL YEAR.

THE GREATEST INCREASE IN FLOOD RISK IS FOR OUR TRIBUTARY CREEKS AND
RIVERS. RECENT SNOWFALL AND THE CURRENT FROZEN SOILS MAY LEAD TO
MORE RAPID RUNOFF ONCE THE WARMER WEATHER FINALLY ARRIVES. THE
OVERALL FLOOD RISK FOR THE MISSISSIPPI RIVER ITSELF IS STILL VERY
SIMILAR TO THE PREVIOUS OUTLOOK…WITH ONLY A SMALL CHANCE FOR MINOR
FLOODING.

THERE ARE SOME FACTORS THAT COULD STILL CONTRIBUTE TO AN INCREASE IN
THE FLOODING POTENTIAL AS WE MOVE INTO SPRING.

THE FROST CONDITION IS OF MOST CONCERN. THE FROST DEPTH IS QUITE
DEEP…FROM 1.5 TO 3 FEET DEEP ACROSS THE REGION. IN ADDITION…THE
TOP SEVERAL INCHES OF SOIL ARE COMPLETELY FROZEN…AS RAINFALL AND
THE SNOW MELT FROM EARLY JANUARY WAS LOCKED INTO THE SOIL PRIOR TO
GETTING ANY APPRECIABLE SNOW COVER. THIS ICY SOIL CONDITION…
SOMETIMES REFERRED TO AS CONCRETE FROST…SHOULD LEAD TO INCREASED
RUNOFF INTO CREEKS AND RIVERS AS THE SNOWMELT PERIOD BEGINS. ANY
MELT WATER WILL BE UNABLE TO PENETRATE THE FROZEN GROUND…AND WILL
DIRECTLY RUN OFF INTO RIVERS AND CREEKS…EVEN MORESO THAN IN A
NORMAL SPRING.

IN ADDITION…THERE IS ANOTHER STORM SYSTEM THAT LOOKS TO IMPACT THE
AREA OVER THE WEEKEND…BRINGING RAIN AND SNOW TO THE REGION. THIS
WILL LIKELY ADD TO THE AVAILABLE MOISTURE FOR FUTURE RUNOFF.

AND FINALLY…THE OUTLOOK FOR THE NEXT FEW WEEKS IS FOR BELOW
AVERAGE TEMPERATURES. THE LONGER THE FROZEN GROUND AND SNOW COVER
LASTS INTO THE SPRING SEASON…THE GREATER THE RISK THAT
TEMPERATURES WILL RAPIDLY WARM UP AND ALLOW THE SNOW TO QUICKLY
MELT. A FAST MELT…OR A MELT COMBINED WITH SIGNIFICANT
RAINFALL…WILL BE A RECIPE FOR MORE SEVERE FLOODING. THIS
SITUATION WILL NEED TO BE MONITORED FOR THE REMAINDER OF MARCH.

*** CLIMATE OVERVIEW ***

MUCH OF THE REGION CONTINUES TO BE IMPACTED BY A MODERATE /D1/ TO
EXTREME /D3/ DROUGHT. THIS DROUGHT DEVELOPED RAPIDLY IN JUNE AND
JULY OF 2012. TEMPERATURES DURING THIS TIME PERIOD AVERAGED 4 TO
5 DEGREES ABOVE NORMAL AND PRECIPITATION DEFICITS RANGED FROM 3 TO
8 INCHES ALONG AND SOUTH OF THE INTERSTATE 90 CORRIDOR. THIS DROUGHT
THEN EXPANDED INTO NORTH-CENTRAL WISCONSIN AS 3 TO 9 INCH
PRECIPITATION DEFICITS DEVELOPED ACROSS THAT AREA. BASED ON THE
PALMER DROUGHT SEVERITY INDEX…THIS DROUGHT RANKS AS THE 15TH WORST
SINCE 1890 FOR THE LA CROSSE HYDROLOGICAL SERVICE AREA. IT WAS THE
MOST SEVERE SINCE THE 1987-89 DROUGHT /WHICH RANKS AS THE MOST
SEVERE FOR THE AREA/.

DESPITE HEAVY RAINS ON OCTOBER 13-14…OCTOBER 24-25…AND NOVEMBER
11 /MAINLY SOUTHEAST OF A CHARLES CITY IA TO WAUSAU WISCONSIN
LINE/…PRECIPITATION DEFICITS GREW ANOTHER 1 TO 4 INCHES DURING THE
AUTUMN. BY THE END OF NOVEMBER…THE JUNE TO NOVEMBER PRECIPITATION
DEFICITS RANGED FROM 8 TO 13 INCHES ACROSS NORTHEAST IOWA…FROM
4 TO 12 INCHES ACROSS SOUTHEAST MINNESOTA…AND FROM 3 TO 11 INCHES
ACROSS WESTERN WISCONSIN.

DURING THE WINTER OF 2012-13…ABOVE-NORMAL PRECIPITATION FELL
ACROSS THE AREA. THE PRECIPITATION SURPLUSES WERE UP TO AN INCH
ACROSS SOUTHEAST MINNESOTA AND MUCH OF NORTHEAST IOWA…AND 1 TO
3 INCHES ACROSS CLAYTON…FAYETTE…AND ALLAMAKEE COUNTIES IN
NORTHEAST IOWA AND ACROSS WESTERN WISCONSIN. DESPITE THESE ABOVE
NORMAL PRECIPITATION TOTALS…ONLY A SMALL FRACTION OF THIS MOISTURE
HAS ACTUALLY MADE IT INTO THE SOILS DUE TO THE WAY THAT THE FROST
DEVELOPED THIS WINTER.

SO FAR THIS MARCH…PRECIPITATION TOTALS HAVE RANGED FROM 0.20
INCHES TO 0.60 INCHES. THESE PRECIPITATION TOTALS ARE NEAR NORMAL
FOR EARLY MARCH…SO THIS PRECIPITATION DID NOT CAUSE ANY
IMPROVEMENT IN THE DROUGHT. HOWEVER THIS PRECIPITATION DID ADD A
LITTLE BIT MORE TO THE WATER TO OUR SNOW PACK.

A FEW EARLY WINTER RAINS…ICE AND SNOWMELT CYCLES COMBINED WITH
COLD TEMPERATURES ACROSS THE AREA…HAVE CONTRIBUTED TO DEEP FROZEN
SOILS. THIS FROST MAY ACTUALLY INTERFERE WITH THE INFILTRATION AND
ABSORPTION OF SNOWMELT RUNOFF INTO THE SOILS. FROST DEPTHS ARE QUITE
DEEP RUNNING AN AVERAGE OF 1.5 TO 3 FEET ACROSS THE AREA AND THIS
FROZEN GROUND WILL BE A FACTOR IN THE MAGNITUDE AND TIMING OF SPRING
RUNOFF. THE TOP LAYER OF THE SOIL HAS A “CONCRETE FROST” WITH THE
TOP SEVERAL INCHES OF THE SOIL COMPLETELY FROZEN WITH ICE.

THE LATE FEBRUARY AND EARLY MARCH STORMS HAVE BROUGHT MOST OF
WISCONSIN BACK UP TO NEAR HISTORICAL NORMAL CHANCES FOR FLOODING.
SOUTHERN WISCONSIN IS ONE POCKET WHERE ABOVE NORMAL SNOW HAS
SOMEWHAT ELEVATED THE CHANCES OF FLOODING. IOWA AND SOUTHERN
MINNESOTA BOTH RECEIVED THE LOWEST AMOUNTS OF NEW SNOW IN THE PAST
2 WEEKS. CHANCES OF FLOODING ARE STILL NEAR OR SLIGHTLY BELOW NORMAL
FOR THESE LOCATIONS.

A FAIRLY WET LATE JANUARY THROUGH EARLY MARCH PERIOD ACROSS THE
UPPER MISSISSIPPI RIVER BASIN AND ITS TRIBUTARIES HAS THE RIVERS
RUNNING AT FAIRLY NORMAL LEVELS. HOWEVER THE LONG-TERM DROUGHT
REMAINS IN PLACE AND AND RIVER CONDITIONS COULD RECEDE QUICKLY BACK
TO LOW CONDITIONS AFTER THE SNOWMELT RUNOFF SEASON. IT REMAINS TO BE
SEEN IF THE SNOW WE HAVE RECEIVED WILL HELP WITH THE LONG-TERM
DROUGHT. THE FROST IS STILL SIGNIFICANT AND MAY IMPEDE INFILTRATION
OF MELT OR RAIN.

RECENT STORMS HAVE INCREASED THE SNOW COVER ACROSS THE AREA. CURRENT
SNOW DEPTH IS LOWEST IN PARTS OF SOUTHEAST MINNESOTA…AND HIGHEST
OVER NORTH CENTRAL WISCONSIN. SNOW DEPTH RANGES FROM 4 TO 6 INCHES
OVER THE CEDAR RIVER BASIN OF MINNESOTA AND IOWA…TO OVER 12 INCHES
IN THE BLACK RIVER BASIN IN WISCONSIN. ELSEWHERE DEPTHS A GENERALLY
IN THE 7 TO 12 INCH RANGE.

SNOW WATER EQUIVALENT IN THIS SNOW PACK IS GENERALLY IN THE 1 TO 2
INCH RANGE ACROSS MOST OF THE REGION. THE LOWEST AMOUNTS ARE IN THE
CEDAR RIVER BASIN…AROUND AN INCH OR LESS. THE HIGHEST AMOUNTS ARE
IN THE BLACK RIVER BASIN…WHERE SNOW WATER AMOUNTS OF UP TO 3
INCHES ARE FOUND.

AS ALWAYS…ICE JAM FLOODING IS POSSIBLE DURING THE SPRING MELT
PERIOD.