Flooding in Iowa, March 12 to 27, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
325 PM CDT SUN MAR 11 2007

.DISCUSSION...

CHALLENGES THIS FORECAST PERIOD CONTINUE TO BE HYDROLOGY WITH RIVER
FLOODING ISSUES AS WELL AS THE TIMING TO THE END OF THE WARM WEATHER
BY MID WEEK. SFC ANALYSES THIS MORNING CONTINUE TO SHOW HIGH
PRESSURE BEGINNING TO EXIT THE REGION. COLD TEMPS ACROSS THE NORTH
LAST NIGHT DUE TO STRONG RADIATIONAL COOLING OVER THE PERSISTENT
SNOW FIELD THERE. VIS SAT SHOWS SOME SNOW STILL FROM NEAR KADU TO
HIGHWAY 30 WITH THE DEEPER SNOW COVER NORTH. NEARLY A 20 DEGREE
GRADIENT FROM SOUTH TO NORTH ATTM (16Z) AS WOULD BE EXPECTED.
SOUTHERN STREAM SYSTEM CONTINUES TO MOVE EAST AS NORTHERN STREAM
TROUGH ALSO ADVANCES EAST TODAY. ALOFT CONTINUE TO SEE H500-H700
WAVE OVER THE TX PANHANDLE WITH ATTENDANT SHOWERS/TSRA THERE WITH
WEAK MID LEVEL WARMING PRODUCING SOME CLOUDS OVER SOUTHERN IA THIS
AM.

LITTLE CHANGE IN THE SHORT TERM AS WARMING CONTINUES TO INCREASE
ACROSS THE REGION THROUGH TUESDAY. FOG NOT EXPECTED TO BE AN ISSUE
TONIGHT AS THICKNESS INCREASE ALONG WITH SOUTHWEST WINDS WILL
INHIBIT FOG DEVELOPMENT...EVEN OVER SNOW COVER. MODELS CONSISTENT IN
MIXING TO 925 MB WHICH WILL CAP SOME OF THE HEATING POTENTIAL FOR
THE TWO DAY PERIOD. MODELS HAVE ALSO NOW GRAVITATED TOWARD A FASTER
PASSING OF THE COLD FRONT BY 18Z TUESDAY. THOUGH NAM/GFS TRENDING
TOWARD BRINGING THE FRONT AGAIN NORTH WED AND RESULTANT
FRONTOGENETICAL FORCING DEVELOPING OVER NORTHERN SECTIONS OF THE
STATE AND AREAS NORTH. FEEL THAT THE EURO/GEM HAVE BETTER HANDLE ON
GREAT LAKES HIGH THAT PASSES SOUTHEAST WITH THE FRONTAL PASSAGE FOR
TUESDAY. THOUGH NOT STRONG...THIS FEATURE MAY NOT MOVE EAST AS
QUICKLY AS PROGGED. VAST DIFFERENCES IN WHERE FRONT ENDS UP ON WED
AFTERNOON. GEM/EURO HAVE FRONT WELL SOUTH OF STATE WITH SECONDARY
FRONT HEADING INTO THE NORTHERN PLAINS. CONTRASTING THAT...NAM/GFS
SHOW VARIOUS DEGREES OF FRONT WAVERING BACK OVER SOUTHERN HALF OF
CWA WITH LARGE GRADIENT IN H850 PROG AND THUS TMAX. MAV ENSEMBLE
GUIDANCE LEANING TOWARD COLDEST MEMBER OF SPREAD AND FEEL MORE
CONFIDENT ABOUT FRONT REMAINING SOUTH. TEMPS HAVE BEEN TRIMMED BACK
CONSIDERABLY FOR WED WITH HIGHS LOW 40S NORTH TO NEAR 60 SOUTH.
ALONG WITH THAT...ATTM NOT MUCH JUSTIFICATION FOR POP OVER THE AREA
AND HAVE LEFT ONLY CHANCE/SLIGHT CHANCES AND ALL LIQUID. MOISTURE
TRANSPORT MAINLY SHUNTED EAST AND NORTH OF THE REGION BUT WILL HAVE
SHIFTS REEXAMINE AGAIN TONIGHT/MONDAY.

MODELS COMING IN AGREEMENT ON COLDER WEEKEND AHEAD. NORTHWEST FLOW
TO BE REESTABLISHED WITH COOLING HTS AND H850 TEMPS. MODELS DIFFER
ON WESTWARD EXTENT OF COLD POOL AND ALSO THE STRENGTH OF THE
NORTHWEST SYSTEM PASSING OVER THE GREAT LAKES. GFS STRONGEST RIGHT
NOW AND ALSO FARTHER WEST. THERMAL FIELDS ON GFS LOOK SUSPECT AND
MAY BE LEADING TO RAPID H500 LOW INTENSIFICATION. WITH STRONG
AMPLIFICATION ALONG THE EAST COAST...GFS DEEPENS H500 TROUGH AND
SLOWER TO MOVE ENTIRE SYSTEM EAST. ATTM...WILL LEAN TOWARD THE
GEM/EURO SOLN WHICH FAVOR A SLIGHTLY QUICKER WARM UP AND POSSIBILITY
OF SOME PRECIP OVER THE WEEKEND.

&&

.HYDROLOGY...
STILL CONSIDERABLE UNCERTAINLY REGARDING SNOWMELT AND ASSOCIATED
RELEASE INTO SKUNK...IOWA AND CEDAR RIVER BASINS.  LATEST NOHRSC
SNOW WATER EQUIVALENT ESTIMATES BEFORE MELTING TODAY SHOWED ANYWHERE
FROM 1 TO POSSIBLY IN EXCESS OF 5 INCHES STILL IN THE SNOW
THROUGHOUT THESE AREAS.  HAVE ISSUED SEVERAL MINOR FLOOD ADVISORIES
FOR POINTS ALONG THE SOUTH SKUNK RIVER AND SQUAW CREEK FROM AMES
AREA DOWNSTREAM TOWARD OSKALOOSA...AND THE IOWA RIVER NEAR
MARSHALLTOWN WHERE RESPONSE MAY OCCUR WITHIN THE NEXT FEW DAYS..OR
EVEN SOONER.  STAYED WITH ESF OUTLOOK IN CEDAR BASIN WHERE RESPONSE
MAY NOT OCCUR UNTIL LATER THIS WEEK.  SOME OF THESE POINTS MAY
EVENTUALLY NEED RIVER FLOOD WARNINGS IF EXPECTED TRENDS CONTINUE.
HOWEVER FORECASTS ARE NOT THE HIGHEST CONFIDENCE JUST YET BECAUSE OF
UNCERTAIN RUNOFF AND COMPLICATIONS FROM NUMEROUS FREEZE THAW
CYCLES...NOT TO MENTION ICE JAMS.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

REV

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
1058 AM CDT SUN MAR 11 2007

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-121100-
EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO-
POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-SAC-CALHOUN-
WEBSTER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK-CRAWFORD-CARROLL-GREENE-
BOONE-STORY-MARSHALL-TAMA-AUDUBON-GUTHRIE-DALLAS-POLK-JASPER-
POWESHIEK-CASS-ADAIR-MADISON-WARREN-MARION-MAHASKA-ADAMS-UNION-
CLARKE-LUCAS-MONROE-WAPELLO-TAYLOR-RINGGOLD-DECATUR-WAYNE-
APPANOOSE-DAVIS-
1058 AM CDT SUN MAR 11 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...TODAY AND TONIGHT

MINOR SNOWMELT FLOODING WILL CONTINUE OR DEVELOP ALONG PORTIONS OF
THE SOUTH SKUNK AND IOWA RIVERS...AS WELL AS THEIR SMALLER
TRIBUTARIES.

ADDITIONAL INFORMATION ON FLOODING CAN BE FOUND IN THE RIVERS AND
HYDROLOGY SECTION OF OUR WEBSITE AT WEATHER.GOV/DESMOINES.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

MINOR SNOWMELT FLOODING WILL CONTINUE OR DEVELOP FROM MONDAY INTO
WEDNESDAY ALONG PORTIONS OF THE SOUTH SKUNK AND IOWA RIVERS...AS
WELL AS THEIR SMALLER TRIBUTARIES.  SNOWMELT AND MINOR FLOODING MAY
ALSO BECOME A PROBLEM LATER THIS WEEK OVER NORTHERN PORTIONS OF THE
STATE THROUGH THE CEDAR RIVER BASIN AND A FEW OF ITS SMALLER
TRIBUTARIES...AS WELL AS UPPER REACHES OF THE EAST FORK OF THE DES
MOINES RIVER.  IN CENTRAL IOWA...LOWER PORTIONS OF THE RACCOON RIVER
NEAR VAN METER AND BEAVER CREEK NEAR GRIMES MAY ALSO EXPERIENCE
MINOR FLOODING LATER IN THE WEEK.

ADDITIONAL INFORMATION ON FLOODING CAN BE FOUND IN THE RIVERS AND
HYDROLOGY SECTION OF OUR WEBSITE AT WEATHER.GOV/DESMOINES.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED.

SMALL