FXUS63 KDMX 131726 AAC
AFDDMX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
1125 AM CST SAT MAR 13 2010

.UPDATED AVIATION DISCUSSION 13/18Z...

.SHORT TERM /TODAY/...
STRONGER UPPER LEVEL SYSTEM AND SFC WAVE NOW BACKING INTO STATE FROM
EAST TODAY. MODELS CONTINUE TO INCREASE FORCING FARTHER WEST WITH
TIME AND HAVE INCREASED POPS BACK INTO CENTRAL IOWA TODAY. BEST
CHANCES APPEAR THIS MORNING WITH FORCING WEAKENING DURING THE
AFTERNOON HOURS. TEMPS TO BE HELD IN CHECK WITH EXPECTED RAINFALL
OVER THE AREA AND THICK CLOUD COVER. CURRENT TRENDS ON RADAR STILL
SUGGEST A MORE SOUTHERLY TRACK WITH THE SYSTEM TODAY...THOUGH GFS IS
BACK A BIT FARTHER NORTHWEST COMPARED TO THE NAM12/GEM. THE EURO IS
ALSO CLOSER TO THE GFS...BUT PREFER THE MORE SOUTHERN SOLNS TODAY.
TEMPS WILL HOLD IN THE 40S OVER THE REGION...CONTINUING SNOW MELT
AND RIVER ISSUES FOR TODAY.

.LONG TERM /TONIGHT THROUGH FRIDAY/...
UPPER LOW WILL MOVE OUT OF THE REGION SLOWLY WITH CLOUDS BEGINNING
TO THIN SUN INTO ERY NEXT WEEK. WITH ALL THE LOW LVL
MOISTURE...CAN'T GET TOO EXCITED ABOUT IT CLEARING OUT ALL THAT MUCH
AS THERE IS NO REAL PUSH OF DRY AIR. ANOTHER S/WV WILL DROP SOUTH
THROUGH THE UPPER MIDWEST TUE NGT INTO WED. ATTM...THINKING IS THAT
IT WILL HAVE LITTLE OR NO WX ASSOCD WITH IT OTHER THAN AN INCREASE
IN CLOUDS. OVERALL MILDER WX WILL PERSIST THROUGH THE WEEK AS UPR
RDG BUILDS INTO THE CENTRAL U.S. FOR THE END OF THE WEEK. THE NEXT
CHANCE FOR ANY SIG WX WILL ARRIVE LATE IN THE FCST PD AND INTO NXT
WEEKEND AS A STRONGER SYSTEM SWEEPS THROUGH. THE BEGINNINGS OF THIS
SHOULD BE FELT BY FRI.

&&

.AVIATION...
13/18Z...SURFACE LOW STILL MEANDERING ABOUT THE WESTERN OHIO VALLEY
BRINGING PRECIP OVER CWA ALONG AND EAST OF INTERSTATE 35. SURFACE
OBS OVER EASTERN IOWA SHOW SOME IMPROVEMENT IN CIGS WHICH MAY RAISE
ALO...DSM AND OTM CIGS ABOVE 1000 FT LATER TODAY...BUT WILL DROP
AGAIN LATER THIS EVENING. BY 00Z...MAX ISENTROPIC LIFT SHIFTS
WESTWARD AND MOST SHOWERS SHOULD END OVER TERMINALS. SOUNDINGS AND
SREF PROBABILISTIC FORECASTS INDICATE DRY AIR TO MOVE IN FROM EAST BY
MID MORNING TOMORROW AND CIGS SHOULD IMPROVE...BUT WILL LIKELY
REMAIN MAINLY IFR UNTIL THEN.

&&

.HYDROLOGY...
WIDESPREAD MODERATE TO MAJOR FLOOD EVENT CONTINUES TO UNFOLD ACROSS
THE ENTIRE CWA. WE/RE NOT LOOKING AT ANOTHER 2008 EVENT HOWEVER.
THIS FLOOD EVENT WAS EXPECTED TO OCCUR...THOUGH...PER OUR FIRST
SPRING FLOOD OUTLOOK FROM LATE JANUARY WHICH HIGHLIGHTED A HIGH RISK
OF SIGNIFICANT FLOODING. THE FLOOD THREAT IS MIGRATING FROM SOUTH TO
NORTH WITH TIME. BASINS OF MOST CONCERN ARE FIRST THE DES
MOINES/RACCOON...FOLLOWED BY THE CEDAR/IOWA THEN SKUNK. MODERATE TO
MAJOR FLOODING EXPECTED AT MANY LOCATIONS IN THE DES MOINES/RACCOON
RIVER BASINS.

ICE JAMS CONTINUE TO BE PROBLEMATIC...WITH THE LEADING EDGE OF THE
ACTIVITY MIGRATING FROM SOUTH TO NORTH AHEAD OF THE OVERALL FLOOD
THREAT. THE ICE JAM ACTIVITY HAS BEEN RATHER PREDICTABLE FOR THIS
EVENT...WITH THE MAJORITY OF THE EVENTS OCCURRING WITHIN 12 TO 24
HRS AFTER STREAMS BEGIN TO RISE. THE ICE JAM ACTIVITY HAS BEEN MORE
PROLIFIC THAN NORMAL...WHICH WAS EXPECTED. THE ICE HAS BECOME
THICKER THAN NORMAL...DUE TO OUR COLDER THAN NORMAL WINTER...WITH
THICKNESSES EXCEEDING 12 TO 18 INCHES IN SOME LOCATIONS. THE ICE JAM
HOT SPOTS TODAY HAVE INCLUDED BUT ARE NOT LIMITED TO THE FORT DODGE
AREA...AS WELL AS VARIOUS LOCATIONS IN THE CEDAR RIVER BASIN
UPSTREAM OF WATERLOO. DUE TO THE WIDESPREAD POTENTIAL FOR FLASH
FLOODING FROM THE JAMS...A FLASH FLOOD WATCH WILL BE EXTENDED
THROUGH AT LEAST SUNDAY AFTERNOON FOR COUNTIES ALONG AND NORTH OF
U.S. HWY 20. IT IS VERY POSSIBLE THAT THE WATCH WILL BE EXTENDED FOR
LONGER IN TIME FOR A GROUPING OF COUNTIES IN THE FAR NORTHWEST WHERE
SIGNIFICANT RISES IN RIVERS WILL NOT HAVE OCCURRED UNTIL LATE THIS
WEEKEND AND EARLY NEXT WEEK.

REGARDLESS OF HOW MUCH RAIN FALLS THIS WEEKEND...HOWEVER...MANY
STREAMS WILL BE SLOWER THAN NORMAL TO RECEDE POST-CREST AND FALL
BELOW STAGE...AS THE RUNOFF FROM SNOW MELT AS WELL AS EXCESS SOIL
MOISTURE TAKES A WHILE TO FINDS THEIR WAY INTO THE STREAMS.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...

FLASH FLOOD WATCH THROUGH SUNDAY FOR NORTH CENTRAL IOWA.

&&

$$

SHORT TERM...REV
AVIATION...HINSBERGER
LONG TERM...MS MAR 10
HYDROLOGY...ZOGG/REV



















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