URGENT – WINTER WEATHER MESSAGE NATIONAL WEATHER SERVICE DES MOINES IA

409 AM CST SAT FEB 4 2012

…HEAVY SNOW EXPECTED TO EXPAND ACROSS CENTRAL AND SOUTHWEST IOWA TODAY…

A POWERFUL WINTER STORM WILL AFFECT THE AREA TODAY AND BRING MODERATE TO HEAVY SNOWFALL TO THE REGION. A PERIOD OF SNOW WITH THUNDER IS POSSIBLE THIS MORNING. IF THE THUNDER SNOW OCCURS…SNOWFALL RATES WILL APPROACH 2 INCHES PER HOUR. THE SNOWFALL WILL GRADUALLY DIMINISH FROM NORTH TO SOUTH THIS AFTERNOON.

CRAWFORD-CARROLL-GREENE-BOONE-STORY-AUDUBON-GUTHRIE-DALLAS-POLK-

CASS-ADAIR-MADISON-ADAMS & UNION COUNTIES, INCLUDING THE CITIES OF…DENISON…CARROLL…JEFFERSON…BOONE…AMES…AUDUBON…GUTHRIE CENTER…ADEL…DES MOINES…ATLANTIC…GREENFIELD…WINTERSET…CORNING…CRESTON

…WINTER STORM WARNING REMAINS IN EFFECT UNTIL 6 AM CST SUNDAY…

* SHORT TERM TRENDS...PRECIPITATION WILL CONTINUE TO EXPAND AND TRANSITION TO ALL SNOW EARLY THIS MORNING. EXPECT THE HEAVIEST SNOW TO OCCUR BETWEEN 6 AM AND NOON TODAY.

* STORM TOTAL SNOW…SNOWFALL AMOUNTS FROM 4 TO 8 INCHES ARE FORECAST FOR THE AREA. LOCALLY HEAVIER AMOUNTS ARE POSSIBLE OVER THE WESTERN PORTION OF THE WARNED AREA. A SHARP CUTOFF IS EXPECTED ALONG A WEST TO EAST LINE FROM NORTHERN CRAWFORD THROUGH NORTHERN STORY COUNTIES.

* WINDS/VISIBILITY…NORTHEAST WINDS OF 20 TO 30 MPH WITH A FEW HIGHER GUSTS WILL CAUSE VISIBILITY RESTRICTIONS AND DRIFTING OF SNOW TODAY AND TONIGHT.

* IMPACTS…HEAVY SNOW WILL MAKE TRAVEL DANGEROUS DURING THE PERIOD. THE FALLING SNOW…COMBINED WITH STRONG WINDS… WILL LEAD TO REDUCED VISIBILITIES. UNTREATED SURFACES WILL BECOME ICY AS THE SNOW FREEZES TO THE PAVEMENT.

PRECAUTIONARY/PREPAREDNESS ACTIONS…

A WINTER STORM WARNING FOR HEAVY SNOW MEANS SEVERE WINTER WEATHER CONDITIONS ARE EXPECTED OR OCCURRING. SIGNIFICANT AMOUNTS OF SNOW ARE FORECAST THAT WILL MAKE TRAVEL DANGEROUS. ONLY TRAVEL IN AN EMERGENCY. IF YOU MUST TRAVEL…KEEP AN EXTRA FLASHLIGHT… FOOD…AND WATER IN YOUR VEHICLE IN CASE YOU BECOME STRANDED.

(Source: Severe Storms Predication Center/Norman, OK 3:28-A.M. cst)

AREAS AFFECTED…Eastern NE & Western IA

CONCERNING…HEAVY SNOW….

INCH AN HOUR SNOWFALL RATES /GREATER IN THUNDERSNOW/ WILL GRADUALLY TAPER OFF LATER THIS MORNING. CESSATION OF HEAVIER RATES IS ALREADY ONGOING ACROSS CENTRAL NEB.  HEAVY SNOWFALL HAS DEVELOPED IN THE FAVORED LEFT EXIT REGION OF A MID-UPPER LEVEL JET…NOW QUICKLY PROGRESSING NORTHEASTWARD.

WITH THE LESSENING OF MORE SUPPORTIVE VERTICAL MOTION…RATES SHOULD GRADUALLY BEGIN TO TAPER OFF THIS MORNING. UNTIL THEN…WEAK MID-LEVEL INSTABILITY HAS SUPPORTED THE OCCASIONAL LIGHTNING STRIKE ACROSS SOUTHERN NEB. THIS AREA OF ENHANCED CONVECTIVE SNOWFALL POTENTIAL WILL SHIFT INTO SOUTHERN IA OVER THE NEXT FEW HOURS. BRIEF BURSTS OF HEAVIER SNOW REMAIN POSSIBLE IN THUNDERSNOW.

A Winter Weather Advisory remains in effect until Midnight for Fremont & Page Counties, where 1-3 inches of snow are expected.

WINTER STORM WARNING…

MONONA-HARRISON-SHELBY-POTTAWATTAMIE-MILLS-MONTGOMERY COUNTIES...

…WINTER STORM WARNING REMAINS IN EFFECT UNTIL MIDNIGHT CST TONIGHT…

* TIMING…SNOW WILL CONTINUE THROUGH MUCH OF DAY. THE HEAVIEST SNOWFALL WILL OCCUR THROUGH THE LATE MORNING HOURS WITH SNOW TAPERING OFF BY LATE AFTERNOON. * ACCUMULATIONS…A BAND OF SNOW ACCUMULATIONS OF 6 TO 11 INCHES IS EXPECTED TO EXTEND FROM SOUTH CENTRAL NEBRASKA ROUGHLY ALONG AND NORTH OF THE INTERSTATE 80 CORRIDOR AND INTO WEST CENTRAL IOWA. LOCALLY HIGHER AMOUNTS UP TO OVER A FOOT ARE POSSIBLE WITHIN THAT BAND OF HEAVY SNOW. * IMPACTS…TRAVEL WILL BE VERY DIFFICULT THROUGH THE DAY DUE TO HEAVY WET SNOW AND SOME BLOWING SNOW IS POSSIBLE. THE COMBINATION OF SNOWFALL AND WINDS OF 15 TO 30 MPH WILL REDUCE VISIBILITIES TO A HALF MILE OR LESS AT TIMES.