Spring Thaw Progress for the Red River Basin - 4 April

...SPRING THAW PROGRESS FOR RED RIVER OF THE NORTH...

...SPRING THAW CONTINUES WITH GRADUAL SNOWMELT THROUGH NEXT
             WEEK AND A BIT OF EARLY WEEKEND MIXED PRECIPITATION...

...FARGO-MOORHEAD FLOOD LIKELY TO PEAK AFTER APRIL 15TH...

...NORTHERN VALLEY FLOODING STARTING MUCH LATER THAN NORMAL...

A SOUTHWARDLY DISPLACED JET STREAM IS PREVENTING WARMER SURFACE
AIR FROM INTRUDING INTO THE RED RIVER BASIN...SLOWING THE PROGRESS
OF OUR SNOW MELT. THESE FACTORS...AND THE MOSTLY INTACT BUT SLOWLY
RIPENING SNOWPACK...ARE KEEPING TEMPERATURES ABOUT 10 TO 15 DEGREES
BELOW NORMAL FOR THIS TIME OF THE YEAR. TEMPERATURES FOR THE NEXT
WEEK WILL REMAIN BELOW NORMAL WITH DAYTIME HIGHS ABOVE FREEZING
AND NIGHTTIME LOWS FALLING BELOW THE FREEZING MARK. THIS WILL PROLONG
THE MELT BUT WILL CAUSE THE SNOW PACK TO DIMINISH SLOWLY AND NOT OVERWHELM
THE RIVER CHANNELS WITH A FAST RUNOFF. HOWEVER...THIS PROLONGED GENTLE
MELT DOES INCREASE THE RISK FOR HEAVY SPRING RAINS ON TOP OF THE SNOWPACK
DURING THE FLOOD WHICH WILL ADD TO THE RUNOFF.

SIGNS OF SNOWPACK RIPENING ARE INCREASING...ESPECIALLY IN THE
SOUTHERN PART OF THE RED RIVER BASIN. SURFACE CRUSTING AND OVERALL
COMPACTION ARE TAKING PLACE WITH SNOWPACK TEMPERATURES RISING TO
NEAR THE MELTING POINT IN THE SOUTHEASTERN PART OF THE BASIN. SOME
BARE GROUND IS APPEARING AND WILL SLOWLY GROW AS THE SNOWPACK ERODES
ALONG ITS EDGES. THERE IS ALSO SOME POOLING AND PONDING OF MELT WATER
IN URBAN AREAS AND AT THE BOTTOM OF SOME DITCHES AND DRAINS ALONG RURAL
ROADS. INFILTRATION OF THIS MELT WATER WILL SERVE TO RE MOISTEN THE DRY
TOP SOIL LAYER.

AS THE SNOWPACK WARMS FROM NOW ON...THE WATER FRACTION WILL
CONTINUE TO MOVE DOWN INTO THE NEAR GROUND SURFACE LEVEL. WATER
SHOULD BEGIN TO TRICKLE INTO AREA DITCHES AND SMALL STREAMS.
HOWEVER...SNOW AND ICE IN THE DITCHES AND CULVERTS COULD DELAY
SOME OF THE RUNOFF FROM GETTING INTO THE RIVER CHANNELS. DEAD TREES
IN THE RIVER CHANNEL...FRACTURED RIVER ICE AND OTHER DEBRIS MAY CAUSE
SOME QUICK DEVELOPING ICE JAMS IN LOCATIONS PRONE TO THESE EVENTS.

IN URBANIZED AREAS AND WHERE THE SNOWPACK HAS BEGUN TO ERODE...YOU CAN
EXPECT WET OR WATER COVERED STREETS AND ROADS DEVELOPING DURING THE
DAYTIME...WITH A REFREEZE AGAIN AT NIGHT. SOME AREAS OF BARE SOIL OR
LAWN WILL BEGIN TO SHOW UP. LATE THIS WEEK...EXPECT SNOW COVER TO
DIMINISH MORE QUICKLY IN THE THINNER SNOW PACK AREAS OF EAST CENTRAL
NORTH DAKOTA AND IN SOME PARTS OF THE FORESTED UPLANDS OF NORTHWESTERN
THROUGH WEST-CENTRAL MINNESOTA. SNOW COVER EXTENT SHOULD PERSIST
LONGEST IN THE HEAVIER SNOWPACKS OF THE SOUTHERN RED RIVER VALLEY AND
FAR NORTHEASTERN NORTH DAKOTA INTO FAR NORTHERN MINNESOTA.

SOME LOCALIZED RUNOFF IS ALREADY REACHING THE RIVERS AND STREAMS
IN THE BASIN WITH SOME SLIGHT BUT STEADY RIVER STAGE INCREASES AT
GAGED LOCATIONS AROUND THE BASIN. HOWEVER...GAGES ALONG THE SHEYENNE
RIVER ARE DROPPING DUE TO THE SHUTDOWN OF RESERVOIR RELEASES FROM
BALDHILL DAM ON LAKE ASHTABULA. MOST OF THE RIVERS REMAIN ICE
COVERED...WITH SOME OPEN WATER REMAINING DOWNSTREAM OF AREA RESERVOIRS
AND DAMS.

NEAR TERM FORECAST. A MIX OF LIGHT RAIN TURNING TO SNOW IS POSSIBLE
ACROSS MUCH OF THE BASIN FROM LATE FRIDAY INTO SATURDAY...AND AGAIN
FROM LATE SUNDAY INTO MONDAY. PRECIPITATION AMOUNTS FROM ONE QUARTER TO
ONE HALF INCH OF LIQUID FROM THIS COMBINATION ARE POSSIBLE THROUGH
MONDAY EVENING. A SLOW AND STEADY COOL RAIN COULD HELP TO THAW THE
SNOW AND SOIL. HOWEVER...IT SHOULD NOT ADD MUCH TO THE OVERALL SPRING
RUNOFF. HEAVY RAINFALL AMOUNTS OF ONE INCH OR MORE WOULD STILL BE A
PROBLEM IF THEY OCCUR.

TEMPERATURES ARE EXPECTED TO CONTINUE A SLOW BUT STEADY WARM UP
THROUGH THE NEXT TWO WEEKS WITH THE OVERALL TREND OF BELOW NORMAL
TEMPERATURES PERSISTING INTO MID APRIL. AS WE GET INTO THE SECOND HALF
OF APRIL THERE ARE SIGNS OF A CHANGE IN WEATHER PATTERNS. SHOULD THE
PATTERN CHANGE OCCUR IT MAY RESULT IN AN INCREASED RISK OF SIGNIFICANT
RAINFALL. IT IS NOT POSSIBLE TO PREDICT PRECIPITATION AMOUNTS THAT FAR
INTO THE FUTURE...BUT RAIN AMOUNTS GREAT THAN 2 INCHES ARE NOT
UNCOMMON IN THE LAST HALF OF APRIL.

AS IT GETS LATER INTO THE SPRING SNOWMELT SEASON...THE NATIONAL
WEATHER SERVICE OFFICE IN GRAND FORKS WILL BE CLOSELY MONITORING
WEATHER AND RIVER CONDITIONS. FLOOD WARNINGS AND STATEMENTS...AS
WELL AS 7 DAY RIVER FORECASTS...WILL BE ISSUED WHEN RIVER FORECAST
POINTS ARE EXPECTED TO REACH OR EXCEED FLOOD STAGE WITHIN THAT PERIOD.

THE 7 DAY FORECASTS ARE PRESENTED AS TEXT PRODUCTS OF DAILY RIVER
STAGES AT ESTABLISHED RIVER FORECAST LOCATIONS AND HYDROGRAPHS OF
6 HOUR RIVER STAGES FOR THE PREVIOUS 3 DAYS AND FOR THE NEXT 7 DAYS.
THESE GRAPHS AND TEXT PRODUCTS ARE AVAILABLE FROM THE NWS GRAND FORKS
AHPS WEB PAGE ON THE INTERNET AT:

                  WWW.WEATHER.GOV/GRANDFORKS

THEN CLICK ON THE "RIVERS AND LAKES AHPS" TAB ABOVE THE MAP OR THE
LINK IN THE MENU ON THE LEFT SIDE OF THE WEB PAGE.

IF YOU HAVE ANY QUESTIONS...CONTACT THE NWS AT 701-772-0720.

WE WILL BE UPDATING THE SPRING THAW PROGRESS REPORTS PERIODICALLY
DURING THE NEXT FEW WEEKS AS WE SEE CONDITIONS CHANGING OR UNTIL THE
SNOWPACK MELTS.



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