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.
$$
COGIL
WINTER STORM WATCH
Warning Issue Date: 418 AM CST TUE DEC 22 2009
...WINTER STORM WATCH REMAINS IN EFFECT FROM WEDNESDAY MORNING
THROUGH FRIDAY AFTERNOON...
A WINTER STORM WATCH REMAINS IN EFFECT FROM WEDNESDAY MORNING
THROUGH FRIDAY AFTERNOON.
* TIMING...ALTHOUGH FREEZING DRIZZLE MAY OCCUR LATER TODAY AND
TONIGHT...THE MOST SIGNIFICANT IMPACTS WITH THIS STORM SHOULD
OCCUR WEDNESDAY MORNING THROUGH LATE FRIDAY AFTERNOON.
* STORM TOTAL ICE ACCUMULATIONS...ICING OF UP TO ONE QUARTER OF AN
INCH IS EXPECTED FROM THE HIGHWAY 30 TO HIGHWAY 20 CORRIDORS
THROUGH THURSDAY WITH LESSER AMOUNTS EITHER SIDE OF THOSE AREAS.
* STORM TOTAL SNOW ACCUMULATIONS...THE PRECIPITATION SHOULD BECOME
PRIMARILY SNOW LATE THURSDAY WITH TOTAL ACCUMULATIONS FROM 2 TO
4 INCHES FROM ATLANTIC...DES MOINES AND GRINNELL...UP TO OVER A
FOOT ALONG AND WEST OF A DENISON...TO FORT DODGE...TO MASON CITY
LINE.
* WINDS...BRISK EAST WINDS OF 15 TO 25 MPH WILL BE IN PLACE
THROUGH MUCH OF WEDNESDAY AND THURSDAY BEE FORE INCREASING EVEN
FURTHER BY FRIDAY. WINDS BY THAT TIME MAY BE SUSTAINED AT 25 TO
35 MPH WITH GUSTS EVEN HIGHER.
* VISIBILITY...DURING THE PERIODS OF HEAVY SNOW THURSDAY INTO
FRIDAY...VISIBILITIES WILL GENERALLY BE LESS THAN ONE MILE AND
EVEN DOWN TO A QUARTER MILE DURING THE HEAVIEST SNOWS. WITH
INCREASING WINDS AND SNOW COINCIDENT BY FRIDAY...BLOWING SNOW
AND GREATLY REDUCED VISIBILITIES NEAR BLIZZARD CONDITIONS ARE
EXPECTED BY THAT TIME.
* IMPACTS...TRAVEL WILL BECOME INCREASINGLY DIFFICULT IN THE WATCH
AREA ON WEDNESDAY DURING THE WINTRY MIX OF PRECIPITATION AND
CONTINUE TO BE DIFFICULT INTO THURSDAY AND FRIDAY AS SNOW
ACCUMULATES AND WINDS INCREASE. IN THE HEAVIEST SNOW
AREAS...TRAVEL MAY BECOME NEARLY IMPOSSIBLE DUE TO BLOWING AND
DRIFTING SNOW THURSDAY NIGHT INTO FRIDAY.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT
SNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL.
CONTINUE TO MONITOR THE LATEST FORECASTS.
$$
SMALL
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