000
FXUS63 KDMX 151427 AAB
AFDDMX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
927 AM CDT MON MAR 15 2010

.UPDATE...
SFC OBS AND WEBCAMS CONTINUE TO SHOW DENSE FOG LOCKED INTO PLACE
OVER MUCH OF CENTRAL AND WRN IA.  TRENDS HAVE BEEN STATIC OR EVEN
GETTING WORSE SO HAVE EXTENDED AND EXPANDED PREVIOUS NRN IA ADVY TIL
18Z.

&&

.SHORT TERM /TODAY/...
HAVE ALLOWED FLASH FLOOD WATCH FOR ICE JAMS TO EXPIRE. SOME ICE
ACTION STILL POSSIBLE...BUT THE TROUBLE SPOTS HAVE SETTLED DOWN IN
THE PAST 24 HOURS...AND MOST RIVERS NOW FLOWING MORE FREELY WITH NO
REPORTS OF PROBLEMS DUE TO ICE JAMMING.  WILL CONTINUE TO MONITOR
SITUATION FOR ANY CHANGES ACROSS THE REGION. /REV

LOW STRATUS REMAIN TRAPPED OVER CENTRAL AND WESTERN IOWA...THOUGH
THE BACK EDGE OF THE CLOUD DECK HAS DRIFTED BACK TOWARD NEBRASKA
OVERNIGHT. FOG DEVELOPED ONCE AGAIN AND WILL BE CONFINED TO CENTRAL
AND WESTERN SECTIONS. MUCH LIKE SUNDAY...SOME SUN EAST WILL ALLOW
FOR A NICE AFTERNOON WITH CLOUDS/SUN MIX CENTRAL AND WEST. NEXT
UPSTREAM WEAK SHORT WAVE OVER SOUTH DAKOTA WILL DROP SOUTHEAST AND
INCREASE CLOUD COVER WEST SECTIONS THIS AFTERNOON. HAVE LEFT AREA
DRY FOR NOW AS MOISTURE IS LIMITED AND FORCING REMAINS RATHER WEAK.
TEMPS TO RISE AGAIN INTO THE 50S AREA WIDE...H850 TEMPS ARE A TOUCH
LOWER EAST TODAY THAN SUNDAY...SO MID TO UPPER 50S EAST TO UPPER 40S
WEST WHERE CLOUDS WILL BE MORE PREVALENT. /REV

.LONG TERM /TONIGHT THROUGH SUNDAY/...
UPR LVL SYSTEM WILL DROP THROUGH THE AREA ABOUT AS EXPECTED ON TUE.
DO NOT THINK THERE WILL BE MORE THAN ISOLD -RN WITH THIS
FEATURE...SO NO REAL CHANGE IN THINKING FROM YDA.  CLOUDS WILL HOLD
TEMPS DOWN A BIT ON TUE...BUT EXPECTED TO SEE THINGS REBOUND INTO
THE 50S TO MID 60S FOR WED AND THU WITH HI PRES BLDG INTO THE
STATE.  NEXT WEATHER SYS WILL BE MORE SIG.  MODELS ARE NOT ALL THAT
CONSISTENT WITH THE DETAILS...BUT DO AGREE FAIRLY WELL WITH THE
MACRO DETAILS.  THE TIMING FOR FRI INTO SAT LOOKS GOOD.  SLOWED
THINGS DOWN SLGTLY FOR THE BEGINNING ON FRI...BUT OTRW NO REAL BIG
CHNGS.  PCPN WILL GRADULY CHNG OVER TO SN FM THE NW LATER FRI AND
FRI NGT.  DIFFERENCES EXIST BTWN THE OP-GFS AND THE ECMWF AND GEM
SOLNS.  GFS IS RUNNING WARMER THAN THE ENS RUNS...THOUGH
INTERESTINGLY ENUF THE MOS-ENS ACTUALLY HAS LWR SN AND RASN POPS
THAN THE OP-MOS.  AT ANY RATE...THIS WILL NEED TO BE MONITORED DURG
THE WEEK AS THERE A POTENTIAL FOR A NARROW BAND OF HEAVIER SNW ALONG
THE BACK SIDE OF THE LO/WAVE AS IT RIDES UP THE FRONT.  NO REAL COLD
AIR TO SPEAK OF BHND THE LO...SO WOULDN`T EXPECT ANYTHING THAT FELL
TO LAST LONG.

&&

.AVIATION...
15/12Z...LIFR/IFR VIS AND CIGS DUE TO FOG WILL CONTINUE ACROSS THE
WESTERN SECTIONS OF THE AREA THROUGH THE MID MORNING HOURS AS
MOISTURE TRAPPED BETWEEN HIGH PRESSURE OVER THE NORTHERN ROCKIES AND
SURFACE LOW ACROSS THE EASTERN CONUS REMAINS IN PLACE. IMPROVEMENT
IS EXPECTED LATE THIS MORNING AND AFTERNOON WITH SOME DRY AIR TRYING
TO ADVECT INTO THE STATE FROM IL AND WI. BY AFTERNOON VFR/MVFR CIGS
WILL PREVAIL.  MVFR CIGS AND BR WILL REFORM TNT AS NIGHT FALLS ONCE
AGAIN AFT 00Z.

&&

.HYDROLOGY...
WIDESPREAD MODERATE TO MAJOR FLOOD EVENT CONTINUES. 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 JAM PROBLEMS CONTINUE TO DIMINISH. THERE STILL ARE ICE
JAM PROBLEMS ON THE DES MOINES RIVER IN THE FORT DODGE AREA. RIVER
ICE ACTION MAY CONTINUE NORTH OF U.S. HWY 20...BUT AGAIN NOT AS
PROBLEMATIC AS THE PAST COUPLE DAYS. OVERNIGHT...SOME ICE ACTION WAS
NOTED AT ALGONA...BUT MOST OF THE HYDROGRAPHS ARE SHOWING A STEADY
RISE ON NORTHERN RIVERS. WITH THIS IN MIND...WE HAVE LET THE
FLASH FLOOD WATCH EXPIRE THIS MORNING.  THERE MAY BE AN ICE JAM YET
NORTH...BUT NO WIDESPREAD ISSUES ARE EXPECTED AT THIS TIME. THE
WARMING OVER THE WEEKEND HAS HELPED DIMINISH THE THREAT.

CRESTS ON ALL RIVERS ARE EXPECTED BY MID TO LATE PARTS OF THIS WORK
WEEK. GFS IS NOW HINTING AT MODERATE TO HEAVY RAINFALL IN OUR CWA IN
THE FRI-SAT TIME FRAME. 12Z NORTH AMERICAN ENSEMBLE FORECAST SYSTEM
/NAEFS/ PROBABILITIES OF EXCEEDING 1 INCH OF ACCUMULATION THROUGH
NEXT WEEKEND ARE 20 TO 30 PERCENT ACROSS MUCH OF OUR CWA. THIS IS AN
INCREASE FROM THE PREVIOUS NAEFS RUN WHICH SHOWED 10 TO 20 PERCENT.
LOOKING ON THE POSITIVE SIDE...IF THIS RAIN DOES MATERIALIZE THEN IT
WILL HAVE FALLEN AFTER THE CRESTS OCCUR...WHICH MEANS IT WOULD
HAPPEN DURING THE HYDROGRAPH RECESSIONS. ONCE THE HYDROGRAPHS GO
INTO RECESSION...IT TAKES A LOT OF EXTRA WATER TO TURN THEM AROUND.
WE WILL HAVE TO KEEP AN EYE ON THINGS.

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 FIND ITS WAY INTO THE STREAMS.

&&

.DMX WATCHES/WARNINGS/ADVISORIES..DENSE FOG ADVISORY FOR PORTIONS OF
NORTHERN...CENTRAL AND WESTERN IA TIL 18Z.

&&

$$

SHORT TERM/AVIATION....REV/BSS
LONG TERM...MS MAR 10
HYDROLOGY...JAZ/REV

NWS DMX Office Area Forecast Discussion