HYDROLOGIC OUTLOOK
Warning Issue Date: 259 PM CST TUE DEC 22 2009
SIGNIFICANT RAINFALL AND SNOW MELT POSSIBLE WEDNESDAY AND THURSDAY...
AN UNSEASONABLY STRONG SURGE OF MOISTURE IS EXPECTED INTO THE
STATE ON WEDNESDAY AND THURSDAY. THIS IS FORECAST TO PUSH
TEMPERATURES ABOVE FREEZING BY WEDNESDAY AFTERNOON...PRIMARILY
ALONG AND SOUTH OF INTERSTATE 80. THEREFORE...RAIN IS THE PRIMARY
PRECIPITATION TYPE EXPECTED ACROSS THE SOUTHERN THIRD TO HALF OF
CENTRAL IOWA WEDNESDAY AFTERNOON INTO THURSDAY. BETWEEN THREE-
QUARTERS AND AN INCH AND A HALF OF RAIN IS FORECAST DURING THIS
TIME. IN ADDITION...THE SNOW ON THE GROUND CONTAINS AROUND AN INCH
TO INCH AND A HALF OF WATER. THE COMBINATION OF THE RAINFALL AND
SNOW MELT WILL LEAD TO LARGE AMOUNTS OF RUNOFF.
TEMPERATURES WILL BE THE BIG FACTOR IN THE EFFICIENCY OF THE
RUNOFF FROM SNOW MELT. SHOULD READING STAY JUST ABOVE
FREEZING...SNOW MELT WILL NOT BE AS QUICK AND RUNOFF WILL BE
MUTED. HOWEVER...SHOULD TEMPERATURES REACH 40 OR HIGHER...THEN
SNOW MELT WILL BE MUCH FASTER WITH A BIGGER RESPONSE IN RUNOFF.
AREA STREAMS AND RIVERS ACROSS THE SOUTHERN HALF OF IOWA WILL
LIKELY EXPERIENCE LARGE RISES DUE TO THE COMBINATION OF RAINFALL
AND SNOW MELT BY THURSDAY AND RIVER FLOODING MAY BECOME
PROBLEMATIC. BASINS WHICH APPEAR MOST LIKELY TO BE AFFECTED
INCLUDE THE CHARITON...LOWER DES MOINES...SOUTH SKUNK...CEDAR
CREEK...AND THE THOMPSON RIVERS ACROSS THE SOUTHERN HALF OF
CENTRAL IOWA.
$$
COGIL
WINTER STORM WATCH
Warning Issue Date: 646 PM CST MON DEC 21 2009
...WINTER STORM WATCH REMAINS IN EFFECT FROM WEDNESDAY MORNING
THROUGH FRIDAY AFTERNOON...
A WINTER STORM WATCH REMAINS IN EFFECT FROM WEDNESDAY MORNING
THROUGH FRIDAY AFTERNOON.
* TIMING...WEDNESDAY MORNING THROUGH LATE FRIDAY AFTERNOON.
* STORM TOTAL ICE ACCUMULATIONS...UP TO ONE QUARTER INCH FROM
THE HIGHWAY 30 TO HIGHWAY 20 CORRIDORS WITH LESSER AMOUNTS
FARTHER NORTH.
* STORM TOTAL SNOW ACCUMULATIONS...4 TO 6 INCHES ALONG THE
SOUTHERN EDGE OF THE WATCH AREA UP TO OVER A FOOT ALONG AND
WEST OF A CARROLL TO MASON CITY LINE.
* WINDS...EASTERLY WINDS AT 10 TO 20 MPH ON WEDNESDAY INTO
THURSDAY BECOMING NORTHERLY AT 20 TO 30 MPH WITH HIGHER GUSTS
ON FRIDAY.
* VISIBILITY...SNOW AREAS WILL SEE VISIBILITIES GENERALLY LESS
THAN ONE MILE FOR THE DURATION OF THE STORM WITH FREQUENT
VISIBILITIES OF ONE HALF TO ONE QUARTER OF A MILE IN THE
HEAVIER SNOWS. WITH INCREASING WINDS THURSDAY NIGHT AND
FRIDAY...BLOWING SNOW AND REDUCED VISIBILITIES ARE EXPECTED IN
THE WATCH AREA.
* IMPACTS...TRAVEL WILL BECOME INCREASINGLY DIFFICULT IN THE
WATCH AREA ON WEDNESDAY AND CONTINUE TO BE DIFFICULT INTO
THURSDAY AND FRIDAY AS SNOW ACCUMULATES AND WINDS INCREASE. IN
THE HEAVIEST SNOW AREAS...TRAVEL MAY BECOME NEARLY IMPOSSIBLE
DUE TO BLOWING AND DRIFTING SNOW THURSDAY NIGHT INTO FRIDAY.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT
SNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL.
CONTINUE TO MONITOR THE LATEST FORECASTS.
$$
COGIL/DONAVON
|
