Spring Snowmelt Progression Outlook

HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE GRAND FORKS ND
236 PM CST FRI MAR 15 2013
 
...2013 SPRING SNOWMELT PROGRESSION OUTLOOK...

THE FOLLOWING IS THE PRELIMINARY SNOWMELT PROGRESSION OUTLOOK FOR
THE 2013 RED RIVER VALLEY SPRING FLOOD. THIS OUTLOOK WILL BE
UPDATED ON ROUGHLY A WEEKLY BASIS...FROM NOW THROUGH THE END OF THE
SPRING RUNOFF PERIOD.

THIS OUTLOOK DESCRIBES THE EXISTING SNOW PACK CONDITIONS AND
PROJECTS ANY SIGNIFICANT CHANGES EXPECTED OVER THE NEXT 14 DAYS.

SINCE THE LAST HYDROLOGIC OUTLOOKS ISSUED ON MARCH 7TH AND 8TH THE
PATTERN OF ABOVE NORMAL SNOWFALL AND BELOW NORMAL TEMPERATURES
ACROSS THE NORTHERN PLAINS HAS CONTINUED. AS OF THIS FRIDAY
AFTERNOON...WEEKLY SNOWFALL AMOUNTS WITHIN THE DEVILS LAKE AND RED
RIVER BASINS HAVE RANGED FROM 1 TO 8 INCHES. LIQUID EQUIVALENTS HAVE
RANGED FROM 0.15 TO 0.25 INCHES NORTH AND WEST OF THE FARGO/MOORHEAD
AREA AND FROM 0.25 TO 0.50 INCHES TO THE SOUTH AND EAST...INCLUDING
SOME FREEZING RAIN WITH THE SNOW. PORTIONS OF THE LAKE TRAVERSE AND
UPPER OTTER TAIL RIVER DRAINAGE AREAS FROM NORTHEAST SOUTH DAKOTA
INTO WEST CENTRAL MINNESOTA RECEIVED IN EXCESS OF 0.75 INCHES OF
LIQUID EQUIVALENT...IN A COMBINATION OF RAIN...FREEZING RAIN AND
SNOW FROM EVENTS ENDING ON MARCH 9...10 AND 14.

AS OF THIS AFTERNOON...SNOW DEPTHS STILL RANGED FROM 6 TO 12 INCHES
IN THE CENTRAL RED RIVER AND MID TO UPPER SHEYENNE TO AROUND TWO
FEET IN THE FAR NORTH AND FAR SOUTHERN RED RIVER BASINS. SNOW PACK
IN THE DEVILS LAKE BASIN RANGES FROM AROUND A FOOT IN THE SOUTH TO
AROUND 30 INCHES IN THE NORTHERN CHAIN OF LAKES TO FAR NORTH. RECENT
SNOWFALLS HAVE GENERALLY ACTED TO MAINTAIN EXISTING SNOWDEPTHS WHILE
INCREASING THE OVERALL SNOW WATER AMOUNTS.

SNOW PACK MOISTURE IS AT LEAST 3 INCHES BASIN WIDE...WITH THE FAR
NORTHERN BASIN AVERAGING NEARLY 5 INCHES OF SNOW WATER. THE SOUTHERN
BASIN IS HOLDING 4 TO 5 INCHES WITH 5 TO 6 INCH AMOUNTS FOUND IN
ISOLATED AREAS. THESE CONDITIONS RANGE FROM NEAR NORMAL IN THE
CENTRAL RED RIVER AND MID/UPPER SHEYENNE BASINS TO MUCH ABOVE NORMAL
IN THE FAR NORTH AND FAR SOUTHERN RED RIVER BASINS AND PORTIONS OF
THE SHEYENNE HEADWATERS AND THE DEVILS LAKE BASIN.

EXPECTATIONS FOR PRECIPITATION THROUGH THE END OF MARCH...

IN THE NEAR TERM...LIGHT SNOW WILL PUSH ACROSS MUCH OF THE BASIN
THROUGH TONIGHT WITH AN ADDITIONAL 2 TO 4 INCHES OF SNOW EXPECTED.

EARLY IN COMING WEEK...ANOTHER ROUND OF MODERATE TO HEAVY SNOWFALL
IS EXPECTED TO AFFECT PORTIONS THE BASIN...WITH AN OVERALL ACTIVE
PATTERN EXPECTED TO PERSIST FOR THE NEXT COUPLE OF WEEKS.

RIGHT NOW...THE ENTIRE BASIN IS QUITE SNOW COVERED...AND WITH RECENT
FRESH SNOW OUR SNOWPACK SURFACES ARE GENERALLY QUITE WHITE /OUTSIDE
OF FORESTED AREAS/ MEANING THEY HAVE A HIGH REFLECTIVITY TO SUNLIGHT
/ALBEDO/. THE NET RESULT OF THESE ADDITIONAL SNOW EPISODES OVER THE
COMING WEEK WILL BE TO KEEP THE SNOWPACK BOTH FRESH AND
REFLECTIVE...AND REDUCE THE AMOUNT OF SNOWPACK WARMING /RIPENING/ TO
MUCH BELOW SEASONALLY NORMAL RANGES.

EXPECTATIONS FOR TEMPERATURES THROUGH THE END OF MARCH...

TEMPERATURES THROUGH MARCH TO DATE HAVE GENERALLY BEEN FROM 3 TO 5
DEGREES FAHRENHEIT BELOW SEASONAL NORMALS. THIS PATTERN OF MUCH
BELOW NORMAL TEMPERATURES IS EXPECTED TO PERSIST THROUGH THE NEXT
WEEK TO TWO WEEK PERIOD.

NORMAL TEMPERATURES FOR THIS PERIOD IN MID TO LATE MARCH WOULD
EXPECT TO SEE DAYTIME HIGHS WELL INTO THE MIDDLE 30S OR HIGHER...
WITH NIGHTTIME LOWS DROPPING WELL BELOW FREEZING. THE CURRENT
FORECAST HAS TEMPERATURES ACROSS THE DEVILS LAKE AND RED RIVER BASIN
REMAINING BELOW THE FREEZING MARK THROUGH THE END OF NEXT WEEK...
AND WITH LITTLE RECOVERY EXPECTED THROUGH THE LAST WEEK IN MARCH.

SO WHEN WILL THIS MELT... AND WHAT MIGHT THIS MEAN FOR A FLOOD?

AT THIS TIME...LARGE SCALE SNOWMELT AND RUNOFF CONDITIONS LOOK TO BE
DELAYED UNTIL THE EARLY OR MIDDLE PART OF APRIL. SUCH A DELAYED
ONSET GENERALLY MEANS AN INCREASED RISK FOR A MORE RAPID THAW /IN
APRIL/ AND AN INCREASED RISK FOR ISOLATED HEAVY RAIN EVENTS TO OCCUR
WHILE SNOWMELT FLOODING IS UNDERWAY.

THE NEXT PROBABILISTIC HYDROLOGIC OUTLOOK WILL BE ISSUED ON
THURSDAY...MARCH 21ST... AND WILL ADDRESS WHAT THESE RISKS MIGHT
BE.


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