Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 250846
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
346 AM CDT MON APR 25 2016

.SHORT TERM.../TODAY/
ISSUED AT 345 AM CDT MON APR 25 2016

MAIN CHALLENGES TODAY WILL BE CLOUDS AND TEMPERATURES. SYSTEM
DRIVING EAST NORTHEAST ACROSS SOUTHERN MN WITH DRY SLOT MOVING
ACROSS THE AREA DURING THE DAY TODAY.  COOLER AIR AND CLOUDS BEHIND
TRAILING COLD FRONT FROM THE LOW WILL DROP SOUTH ACROSS NORTHERN
IOWA DURING THE AFTERNOON HOURS. ACROSS CENTRAL...DAYTIME HEATING
SHOULD AID IN SOME CLOUD DEVELOPMENT BUT LIKELY TO SEE MOSTLY SUNNY
TO PARTLY SUNNY SKIES WITH MILDER TEMPERATURES. H850 TEMPERATURES
REMAIN QUITE MILD WITH READINGS IN THE 10-13C RANGE ACROSS THE DRY
SLOT WHILE NORTH OF THE COLD FRONT READINGS DROP INTO THE 7-10C
RANGE. THIS WILL AFFECT MAINLY THE FAR NORTHWEST SECTIONS OF THE
FORECAST AREA. WINDS WILL BE BRISK IN THE LATE MORNING AND AFTERNOON
AS MIXING INCREASES. BY 15Z MIXING WILL INCREASE WINDS TO 15 TO 25
MPH AND PEAK AT NEAR 30 MPH OVER THE NORTH JUST AFTER THE NOON HOUR.
BY LATE AFTERNOON WINDS WILL SLOWLY WEAKEN BUT STILL REMAIN BREEZY.
THE BREAK FROM ACTIVE WEATHER WILL BE BRIEF AS THE NEXT SYSTEM WILL
ARRIVE LATER ON TUESDAY.

.LONG TERM.../TONIGHT THROUGH SUNDAY/
ISSUED AT 345 AM CDT MON APR 25 2016

THE PATTERN IS EXPECTED TO CHANGE LITTLE THROUGH THE PERIOD WITH THE
SUB-TROPICAL JET DRIVING MULTIPLE ITERATIONS OF A WESTERN CONUS
TROUGH INTO THE MIDWEST. INITIALLY LITTLE WILL BE GOING ON WITH ANY
FORCING ASSOCIATED WITH CURRENT DAKOTAS PV TROUGH STAYING TO OUR
NORTH. ATTENTION WILL THEN QUICKLY TURN UPSTREAM TO THE PROGRESSION
OF THE CURRENT CA TROUGH. THIS WILL INDUCE LEE SIDE CYCLOGENESIS
DURING THE DAY TUE WITH A WARM FRONT ESTABLISHING ITSELF SOMEWHERE
NEAR THE KS/NE/MO BORDERS TOWARD 00Z...AND POSSIBLY A TAD NORTH...WITH
ATTENDANT DRY LINE TO THE SOUTH. THIS WILL DRIVE A NOSE OF
MODERATE-HIGH INSTABILITY BETWEEN THESE FEATURES INTO FAR SWRN IA
WITH 0-1KM MOISTURE CONVERGENCE POSSIBLY GENERATING SURFACE BASED
CONVECTION. MLCAPES MAY REACH OR EXCEED 3000 J/KG JUST SW OF THE
FORECAST AREA WITH A TIGHT GRADIENT INTO US JUST A BIT NORTH AS
INSTABILITY QUICKLY DIMINISHES. IF CONVERGENCE AND REDUCED
INHIBITION DO NOT ADEQUATELY PHASE...CRESTON FORECAST SOUNDINGS
SUGGEST PERSISTENT CONVERGENCE INTO THE EVENING MAY STILL BE
SUFFICIENT FOR FAIRLY LOW ROOTED AND EVEN POSSIBLY STILL SURFACE
BASED CONVECTION TO DEVELOP AS RELATIVELY WEAK LOW LEVEL JET
MATURES. 300K ISENT SURFACE NOTES STRONG CONVERGENCE JUST BARELY
ALOFT SO WOULD STILL EXPECT THIS LOW BASED CONVECTION TO DEVELOP
DURING THE EVENING AND LIFT SSW-NNE ACROSS IOWA THROUGH THE
NIGHT. SREF PROBS OF MUCAPE 1000 J/KG OR MORE AND EFFECTIVE SHEAR
OF 30KTS PLUS SUGGEST THE SEVERE POTENTIAL WOULD DECREASE WITH
TIME AND NERN EXTENT...BUT STILL AGREE WITH A SEVERE WEATHER
WINDOW SW AS OUTLINED IN THE SPC DAY 2 OUTLOOK.

LOOKING INTO WED A LARGE SWATH OF MID LEVEL FORCING SHOULD FOLLOW
WITH THETA-E ADVECTION ALSO CONTINUING TO AID LIFT AND AT LEAST
WEAK CONVECTION. NEARLY ALL SOLUTIONS SUGGEST IA WILL STAY OUT OF
THE WARM SECTOR...HOWEVER THE FARTHER NORTH ECMWF WILL NEED TO BE
MONITORED AND ACTUALLY BRINGS THE WARM FRONT INTO FAR SRN IA
DURING THE EVENING. THE FAIRLY DEEP FORCING CHANGES LITTLE INTO
THE NIGHT...ONLY OOZING SLIGHTLY NORTHWARD WITH TIME. THIS WILL
KEEP THE MIDDLE OF THE WEEK QUITE WET WITH CHANCES OF PRECIP NOT
DIMINISHING APPRECIABLY UNTIL THU. TOTAL QPF BY THU RESULTS IN
WIDESPREAD INCH PLUS AMOUNTS WITH IN EXCESS OF TWO INCHES SOUTH
AND WEST OF DES MOINES. ALTHOUGH THE HIGH END OF QPF FORECASTS
COULD PUSH A FEW BASINS JUST ABOVE FLOOD STAGE...THE VAST MAJORITY
OF EXTENDED RFC SIMULATIONS SUGGEST WITHIN BANK RISES AS THIS
PRECIP WOULD BE DRAWN OUT OVER AN EXTENDED TIME.

AFTER THIS BRIEF BREAK WE ESSENTIALLY REPEAT THE PROCESS AGAIN WITH
WARM ADVECTION LATE FRI FOLLOWED BY LARGE SCALE MID LEVEL FORCING
INTO THE WEEKEND. THE GFS/GEFS SUITE KEEPS IA ON THE COOL SIDE OF
THE SURFACE TRACK WITH GENERALLY WEAKER CONVECTION AND COOLER TEMPS.
HOWEVER THE ECMWF AND ITS ENSEMBLES NUDGE THE WARM SECTOR INTO SERN
IA LATE SUN WITH A WARMER AND POTENTIALLY MORE SEVERE SOLUTION.
WILL HAVE TO MONITOR TEMPS THROUGH THE ENTIRE PERIOD. WITH
SEVERAL EPISODES OF WET...CLOUDY ELY FLOW...TEMPS MAY BE TOO
WARM...ESPECIALLY MAXES. MOS MAY BE GETTING TUGGED TOO HIGH BY
CLIMATOLOGY...ALTHOUGH THE OFTEN FARTHER NORTH ECMWF TRACKS MAY
OFFSET THIS CONCERN AS WELL.

&&

.AVIATION.../FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT/
ISSUED AT 1153 PM CDT SUN APR 24 2016

PRIMARILY VFR FORECAST ALTHOUGH AREAS OF MVFR OVERNIGHT WHERE
THUNDERSTORMS ARE OCCURRING. ANY MVFR CEILINGS ON MONDAY WILL BE
ACROSS NORTHERN IOWA CLOSER TO THE UPPER LOW WITH VFR CONDITIONS
ELSEWHERE. WINDS OVERNIGHT WILL BECOME SOUTHWEST TO WEST BY MONDAY
AND INCREASE.

&&

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

&&

$$

SHORT TERM...REV
LONG TERM...SMALL
AVIATION...COGIL



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