Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 061746
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1246 PM CDT SUN JUL 6 2014

.SHORT TERM /TODAY/...
ISSUED AT 343 AM CDT SUN JUL 6 2014

THUNDERSTORM TRENDS WILL BE THE PRIMARY CONCERN TODAY. CURRENT
SCENARIO HAS SHORT WAVE ON NOSE OF 100KT JET DRIVING NRN PLAINS
CONVECTION. AIRMASS AHEAD OF THIS FEATURE IS VERY UNSTABLE WITH 3-4K
J/KG MUCAPES ROOTED QUITE LOW AND NEARLY SURFACE BASED EVEN AT THIS
HOUR  DUE TO PLENTY OF 70F PLUS DEWPOINTS ALONG THE MO RIVER VALLEY
INTO SD. THIS AIRMASS SHOULD PUSH SOUTH AND EAST WITH THE SYSTEM
RESULTING IN UNCAPPED MLCAPES POSSIBLY PUSHING 5K J/KG LATE BY LATE
AFTERNOON. ALTHOUGH THERE IS SOME CONCERN THAT LINGERING STRATUS AND
UPSTREAM MID/HIGH DEBRIS CLOUDS MAY LIMIT INSOLATION
SOMEWHAT...KINEMATIC AND THERMODYNAMIC FORCING ASSOCIATED WITH THE
FEATURE SHOULD BE SUFFICIENT TO DEVELOP ROBUST CONVECTION ALONG AND
AHEAD OF THE FRONT.  FORECAST SOUNDINGS SCOUR OUT THE LOW LEVEL
MOISTURE...WHICH IS ALREADY HINTED AT IN VIS/FOG SATELLITE
IMAGERY...AND ACTUALLY MIX FAIRLY WELL LATE...ESPECIALLY THE RAP.
DEEP SHEAR WILL NOT BE TOO STRONG...BUT CERTAINLY SUFFICIENT FOR
ORGANIZATION AND SUPERCELL POTENTIAL CONSIDERING THE DEGREE OF
INSTABILITY. LOW LEVEL SHEAR IS NOT IMPRESSIVE SUGGESTING LARGE HAIL
AND DAMAGING WINDS WILL BE THE PRIMARY THREATS.  POSITIVE AREA IN
-10 TO -30C ZONE IS IMPRESSIVE SO WOULD NOT BE SURPRISED TO SEE HAIL
GET QUITE LARGE.  WEAKER LOW LEVEL SHEAR/SRH WILL PRECLUDE A
SIGNIFICANT TORNADO THREAT...BUT POTENTIAL CANNOT BE RULED OUT
CONSIDERING THE MAGNITUDE OF 0-3KM CAPE AND OVERALL PARCEL
ACCELERATIONS.  CONDITIONS REMAIN FAVORABLE FOR MORE HEAVY
RAINS...BUT PROGRESSIVE NATURE OF THE SYSTEM SHOULD LIMIT THE
FLOODING POTENTIAL SOMEWHAT.

MOS SEEMS TO BE HOLDING MAXES BACK SOMEWHAT...BUT HAVE GONE JUST
ABOVE THOSE VALUES IN MOST LOCATIONS BASED ON RAW MODEL TEMPS AND
FORECAST SOUNDINGS.  THIS RESULTS IN UPPER 80S/LOW 90S HIGHS WITH
HEAT INDICES TO AROUND 100F BY AFTERNOON SOUTH HALF.

.LONG TERM /TONIGHT THROUGH SATURDAY/...
ISSUED AT 343 AM CDT SUN JUL 6 2014

ANY STORMS THAT DEVELOP ALONG THE ADVANCING COOL FRONT TODAY...AS
DISCUSSED IN THE SHORT TERM SECTION ABOVE...WILL LINGER IN OUR
SOUTHEASTERN COUNTIES AFTER SUNSET BEFORE CLEARING OUT. FROM LATE
TONIGHT THROUGH MONDAY MORNING IT WILL BE DRY AND A BIT COOLER
WITH A WEAK SURFACE HIGH PRESSURE AREA SCOOTING ACROSS THE REGION.
THIS RESPITE WILL BE SHORT LIVED HOWEVER AS AN EVEN STRONGER COLD
FRONT AND ATTENDANT SHORTWAVE ALOFT APPROACH THE AREA BY MONDAY
AFTERNOON. THIS SYSTEM SHOULD PRODUCE EVEN MORE ROBUST AND
WIDESPREAD CONVECTION ACROSS THE FORECAST AREA FROM LATE MONDAY
AFTERNOON INTO MONDAY NIGHT. LARGE SCALE FORCING AND MID LEVEL
SUPPORT WILL BE STRONGER WITH THIS SYSTEM BUT INSTABILITY...WHILE
STILL MORE THAN SUFFICIENT FOR SEVERE WEATHER...NOT QUITE AS
EXTREME AS ON SUNDAY AFTERNOON/EVENING. IN ANY EVENT SEVERE
WEATHER AND LOCALLY HEAVY RAIN WILL CERTAINLY BE POSSIBLE LATE
MONDAY AND ARE HIGHLIGHTED IN OUR PRODUCTS AS WELL AS THOSE OF THE
STORM PREDICTION CENTER.

AFTER THE COLD FRONT BLOWS THROUGH ON MONDAY NIGHT COOL AND DRY
CONDITIONS WILL PREVAIL FOR SEVERAL DAYS. JUST A FEW SHOWERS AND
STORMS MAY BE POSSIBLE AT TIMES WITH SECONDARY IMPULSES ROUNDING
THE CYCLONIC FLOW OVERHEAD...BUT WITH SUCH LIMITED INSTABILITY DO
NOT EXPECT ANY PRECIPITATION OF CONSEQUENCE DURING THIS TIME. A
RETURN OF MEANINGFUL RAIN CHANCES WILL HAVE TO WAIT UNTIL LOW
LEVEL FLOW TURNS BACK TOWARD THE SOUTH AND WARM AIR/MOISTURE
ADVECTION ENSUES...PROBABLY AROUND THURSDAY NIGHT...AND BOTH THE
ECMWF AND GFS BRING A 500 MB SHORTWAVE OVER JUST AFTER THIS LATE
THURSDAY NIGHT/FRIDAY WHICH SHOULD PROVIDE AN IMPETUS FOR
SCATTERED CONVECTION AND APPROPRIATE POPS. LOOKING TOWARD NEXT
WEEKEND THE LONG RANGE MODEL SOLUTIONS DIVERGE QUICKLY...BUT
OVERALL IT APPEARS THAT A FRONTAL BOUNDARY WILL WAFFLE NEARBY WITH
VARIABLE TEMPERATURES AND AT LEAST SOME CHANCES FOR ADDITIONAL
THUNDERSTORMS.

&&

.AVIATION...06/18Z
ISSUED AT 1238 PM CDT SUN JUL 6 2014

MAIN CONCERNS REMAIN THE LOW CLOUDS NORTH AND POTENTIAL FOR
CONVECTION THIS AFTERNOON AND EVENING. OVERNIGHT MCS ACROSS MN
CREATED A LARGE CI SHIELD WHICH HAS KEPT LOW ST FROM BURNING OFF
THROUGH THE MORNING OVER THE NORTH. MVFR ST ALSO FORMED IN AREA
OF MODEST LOW LEVEL MOISTURE ADVECTION OVER THE SOUTH CENTRAL.
CIGS WILL LIFT MORE RAPIDLY THIS AFTERNOON...WITH INSTABILITY
BUILDING WEST. OVER THE NORTHEAST CONVERGENCE ALONG THE BOUNDARY
WOULD FAVOR SOME CONVECTION FOR KMCW...KALO THROUGH 00Z.
ELSEWHERE...SOME CONCERNS THAT STRONG CAP SHOWING UP IN BUFR
SOUNDINGS WILL HOLD FOR KDSM AND KOTM EVEN THIS AFTERNOON AND
EVENING. CURRENT CONVECTION REMAINS WELL NORTH OF AREA ALONG
BOUNDARY FROM WEST CENTRAL WI TO KMSP. WILL MONITOR FOR ANY
EXPANSION INTO CENTRAL IOWA BUT FOR NOW...TRENDS SUGGEST NORTHEAST
SECTIONS MOST AT RISK FOR DEVELOPMENT THIS AFTERNOON/EVENING. /REV

&&

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

$$

SHORT TERM...SMALL
LONG TERM...LEE
AVIATION...REV



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