Flood Potential Outlook
Issued by NWS Grand Rapids, MI

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HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
1024 AM EST TUE FEB 18 2014

...FLOOD POTENTIAL INCREASES ACROSS SOUTHWEST LOWER MICHIGAN...

SEVERAL FACTORS ARE COMBINING TO CREATE AN INCREASED FLOOD RISK
STARTING LATE THIS WEEK AND CONTINUING IN TO EARLY MARCH. THE
INCREASED FLOOD RISK IS DUE TO THE FOLLOWING FACTORS WHICH ARE
SIGNIFICANTLY ABOVE NORMAL...PRECIPITATION...SNOW DEPTH...WATER IN
THE SNOWPACK... ICE ON RIVERS...AND SOIL MOISTURE. THE WEATHER
PATTERN IS CHANGING AND WARMER WEATHER...WITH THE POSSIBILITY FOR
RAIN...IS ON THE WAY FOR LATER THIS WEEK.

THE BIGGEST THREAT FROM THIS BRIEF WARM UP ON THURSDAY WILL BE
LOCALIZED DRAINAGE ISSUES DUE TO CLOGGED STORM DRAINS AND INCREASED
WEIGHT ON ROOFS WITH SIGNIFICANT SNOWDEPTH.

CURRENTLY THE MODELS ARE INDICATING A BRIEF WARM UP...WITH A HALF TO
AN INCH OF RAIN...FOLLOWED BY TEMPERATURES FALLING BACK BELOW
FREEZING.  THE DEEP SNOWPACK WILL ABSORB MOST OF THE RAIN ON THURSDAY
AND THE RETURN TO BELOW FREEZING TEMPERATURES WILL REDUCE THE AMOUNT
OF RUNOFF THAT WOULD NORMALLY OCCUR WITH A RAIN EVENT. THE NET RESULT
WILL BE MORE WATER IN THE SNOWPACK WAITING TO BE RELEASED DURING THE
NEXT WARM UP EVENT...WHICH AT THIS TIME IS NOT LIKELY UNTIL EARLY
MARCH.

PRECIPITATION FOR THE FALL OF 2013 AND WINTER OF 2014 WAS ABOVE
NORMAL.

THE SNOWPACK IS SIGNIFICANTLY ABOVE NORMAL FOR THIS TIME OF YEAR AND
CONTAINS A LARGE QUANTITY OF STORED WATER...GENERALLY 3 TO 5.5 INCHES
ACROSS SOUTHWEST LOWER MICHIGAN. THE RAIN FORECAST FOR THURSDAY WILL
ONLY ADD TO THE WATER CONTENT IN THE SNOWPACK.

WHILE AREA RIVERS ARE FLOWING AT NEAR NORMAL LEVELS...THE AMOUNT AND
THICKNESS OF ICE ON AREA RIVERS IS ABOVE NORMAL.  THE POTENTIAL FOR
BREAK UP AND DOWNSTREAM MOVEMENT OF THICK ICE ON RIVERS WOULD
INCREASE THE RISK FOR ICE JAMS TO DEVELOP AND FURTHER EXACERBATE THE
FLOODING RISK. ICE JAMS IN RIVERS TEND TO FORM NEAR SHARP BENDS...IN
SHALLOW AREAS...AND NEAR OBSTRUCTIONS...LIKE BRIDGES AND ISLANDS. ICE
BREAKUP ON RIVERS CAN OCCUR WHENEVER THE RIVER STAGE RISES 1.5 TO 3
TIMES THE RIVER ICE THICKNESS.  ICE JAMS ON RIVERS CAN RESULT IN
UNPREDICTABLE RAPID RISES ON RIVERS.

THE THREAT FOR FLOODING IS INCREASING WITH TIME DUE TO THE HIGH
WATER CONTENT IN THE SNOWPACK AND INCREASED PROBABILITY OF A
SIGNIFICANT WARM UP WITH RAIN AS WE HEAD INTO SPRING. IF YOU LIVE IN
A FLOOD PRONE AREA...NOW IS THE TIME TO PREPARE FOR POSSIBLE
FLOODING. STAY ALERT TO THE LATEST FORECAST TRENDS OVER THE NEXT
SEVERAL DAYS BY VISITING WEATHER.GOV/GRR.

ADDITIONAL FLOOD AWARENESS INFORMATION IS AVAILABLE AT
WEATHER.GOV/FLOODSAFETY...FLOODSMART.GOV AND READY.GOV/FLOODS

$$

WALTON/SEKELSKY




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