Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 281726
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1220 PM CDT THU APR 28 2016

.SHORT TERM.../TODAY/
ISSUED AT 330 AM CDT THU APR 28 2016

THE UPPER LOW WILL SLOWLY LIFT NORTHEAST ACROSS IOWA TODAY WHILE THE
SURFACE LOW MEANDERS EAST ACROSS THE SOUTHERN PORTION OF THE STATE.
AS THE SYSTEM PROGRESSES EAST COLDER AIR WILL SPILL IN ON THE
BACKSIDE OF THE LOW.  THIS WILL OCCUR DURING THE AFTERNOON HOURS. AS
A RESULT WE WILL SEE CLOUDY SKIES TODAY AND TEMPS WILL BE QUITE
COOL. WHILE THE BULK OF THE PRECIP IS OVER FOR US...THERE WILL BE
SOME LIGHT RAIN AT TIMES OR DRIZZLE AND PATCHY LIGHT FOG AROUND
THROUGH THE DAY IN ADDITION TO LOW CLOUDS. THE COMBINATION OF ALL OF
THIS WILL MAKE FOR A PRETTY DISMAL DAY. WINDS WILL SWITCH AROUND TO
THE NORTH BY EARLY TO MID AFTERNOON AND TEMPS WILL EITHER REMAIN
STEADY OR SLOWLY FALL FROM MID AFTERNOON ONWARD.  HIGHS TODAY WILL
ONLY BE IN THE 40S ACROSS THE FAR NORTH WITH LOWER TO MID 50S
ELSEWHERE.  THE EXCEPTION WILL BE THE FAR SOUTH WHERE UPPER 50S TO
LOWER 60S WILL BE REACHED.

.LONG TERM.../TONIGHT THROUGH WEDNESDAY/
ISSUED AT 330 AM CDT THU APR 28 2016

THE OVERALL PATTERN WILL CHANGE LITTLE THROUGH THE WEEKEND WITH COOL
TEMPERATURES AND ANOTHER ROUND OF PRECIPITATION. IA WILL BE ON THE
MORE STABLE SIDE OF THE NEXT SYSTEM HOWEVER WITH LITTLE IF ANY
SEVERE WEATHER POTENTIAL. ANY EFFECTS FROM THE CURRENT SYSTEM WILL
BE ALL BUT OVER AT ONSET WITH THE UPPER LOW MOVING INTO WI. THIS
WILL LEAVE IA IN WEAK NELY SURFACE FLOW BUT AT LEAST PATCHY STRATUS.
MID AND HIGH CLOUDS WILL THEN BE ON THE INCREASE INTO FRI AHEAD OF
THE NEXT SYSTEM...WHICH IS CURRENTLY MOVING THROUGH THE SWRN
CONUS...SO STILL EXPECT PLENTY OF CLOUDS. WARM/THETA-E ADVECTION
MAY JUST PUSH SOME LIGHT SHOWERS INTO SWRN SECTIONS LATE IN THE
DAY FRI...BUT THE MAJORITY OF THE PRECIP IS EXPECTED TO OCCUR
LATER FRI NIGHT INTO SAT. THE MID LEVEL FORCING /DPVA/ PRECEDES
THE THERMODYNAMIC FORCING JUST A BIT BUT THERE WILL BE A DECENT
BAROCLINIC AND FRONTOGENETIC ZONE LIFTING THROUGH EARLY SAT AND
SHOULD PRODUCE THE MOST SIGNIFICANT RAINFALL. VARIOUS 295-310K
ISENT SURFACES SHOW THIS NICELY AND SUGGEST THAT THE THERMODYNAMIC
CONTRIBUTION WILL WANE INTO THE NIGHT AND SUN WITH THOSE WINDS
WEAKENING AND MORE IMMEDIATE MECHANICAL FORCING WITH THE PASSAGE
OF THE UPPER LOW TAKING OVER. HAVE LOWERED TEMPS A TAD FURTHER SAT
WITH PLENTY OF PRECIP AND COOL BRISK ELY WINDS.

THE PATTERN WILL TRY TO CYCLE ANOTHER ITERATION OF A SWRN CONUS
SYSTEM INTO THE PLAINS EARLY NEXT WEEK BUT IT WILL WEAKEN WITH A
WRN CONUS OMEGA BLOCK TAKING AROUND...AND IA WEATHER BECOMING
MORE DOMINATED BY THE NRN STREAM AS THE PATTERN AMPLIFIES. HAVE
SOME TOKEN PRECIP CHANCES AROUND TUE WHEN UPPER MS VALLEY SHORT
WAVES MAY BRUSH IA...BUT THE MAIN WEATHER STORY BY THEN WILL BE
MAINLY DRY WEATHER AND TEMPERATURES MODERATING BACK CLOSER TO
NORMAL.

&&

&&

.AVIATION.../FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON/
ISSUED AT 1220 PM CDT THU APR 28 2016

MVFR CIGS EXPECTED THROUGH THE TAF PERIOD...WITH SOME IFR CIGS
POSSIBLE OVERNIGHT TONIGHT. ALTHOUGH SURFACE LOW WILL CONTINUE
TRACKING EASTWARD AND DEPART IOWA LATER TODAY...MOISTURE WILL REMAIN
HIGH IN THE BOUNDARY LAYER AND CLOUDS WILL REMAIN. AFTER A BRIEF
IMPROVEMENT IN CIGS THIS AFTN...CIGS WILL AGAIN LOWER THIS EVENING.
FOG IS POSSIBLE OVERNIGHT ESPECIALLY AT THE WESTERN AND NORTHERN
TERMINALS. SOME INSTABILITY SHRA IS POSSIBLE THIS AFTN BUT WILL
DISSIPATE TOWARD SUNSET.

&&

.HYDROLOGY...
ISSUED AT 330 AM CDT THU APR 28 2016

OBSERVATIONS AND MRMS PRECIP ESTIMATES INDICATE THAT THE RACCOON
BASIN RECEIVED THE MOST SIGNIFICANT RAINS OVER THE PAST 24 HOURS
WITH MANY AMOUNTS FROM 1-1.25 INCHES. LATEST 00Z RFC
FORECASTS...WITH 24 HOURS OF QPF...STILL DEPICT WITHIN BANK RISES
WITH FLOODING NOT ANTICIPATED FROM THIS INITIAL ROUND OF PRECIP. WED
RFC 72 HOUR QPF CONTINGENCY FORECASTS SUGGESTED PRECIP FROM THE NEXT
SYSTEM WOULD BE REMOVED ENOUGH FROM THIS RUNOFF TO KEEP THE OUTLOOK
BELOW FLOOD STAGE FOR ALL FORECAST POINTS...HOWEVER IT WILL BE VERY
CLOSE IN PARTS OF THE DES MOINES AND RACCOON BASINS SO CONFIDENCE IN
NOT REACHING FLOOD STAGE HAS DIMINISHED SOMEWHAT FROM THIS TIME
YESTERDAY. CURRENT QPF FOR THESE AREAS WITH THE NEXT SYSTEM IS
ESSENTIALLY 0.75-1.25 INCHES...BUT IF THOSE EXPECTATIONS ARE
EXCEEDED A FEW SPOTS MAY ECLIPSE FLOOD STAGE.

&&

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

&&

$$

SHORT TERM...FAB
LONG TERM...SMALL
AVIATION...FAB
HYDROLOGY...SMALL



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