Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 060446
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1146 PM CDT SUN JUL 5 2015

.SHORT TERM /TONIGHT/...
ISSUED AT 327 PM CDT SUN JUL 5 2015

STRENGTHENING SOUTH WINDS INTO THE STATE TODAY HAS LED TO WARMER
TEMPERATURES AND INCREASING MOISTURE ADVECTION. DEWPOINTS HAVE
CLIMBED BACK TO AROUND 70 WITH RAPID DESTABILIZATION THROUGH THE
DAY. SURFACE FRONT HAS DROPPED INTO SOUTH DAKOTA AND NORTHERN
MINNESOTA WHERE BULK OF MOISTURE CONVERGENCE WILL LEAD TO
THUNDERSTORMS DEVELOPMENT LATER THIS AFTERNOON AND TONIGHT.
INDICATIONS ARE FOR THUNDERSTORMS TO MERGE INTO A LARGE MCS IN
SOUTH DAKOTA AS LOW LEVEL JET INTENSIFIES OVERNIGHT AND MOVE INTO
MINNESOTA DURING THE EARLY MORNING HOURS NEAR SURFACE LOW TRACK.
THE SOUTHERN EDGE WILL DROP INTO NORTHERN IOWA LATE IN THE NIGHT
WITH ANY SEVERE POTENTIAL COMING FROM LARGE HAIL AND DAMAGING
WINDS. HOWEVER...WITH THE BULK OF QG FORCING AND SURFACE LOW
MOVING NORTH OF THE STATE...THE BEST COVERAGE OF THUNDERSTORMS
WILL REMAIN NORTH OF IOWA FOR MUCH OF THE NIGHT. WITH GOOD LOW
LEVEL SOUTH WINDS OVERNIGHT AND HIGHER DEWPOINTS...TEMPERATURES
SHOULD REMAIN QUITE WARM DURING THE NIGHT WITH READINGS REMAINING
IN THE 70S IN MOST LOCATIONS.

.LONG TERM /MONDAY THROUGH SUNDAY/...
ISSUED AT 327 PM CDT SUN JUL 5 2015

THERE HAS BEEN LITTLE CHANGE IN EXPECTATIONS FOR THE OVERALL
FORECAST SCENARIO THIS WEEK. IT WILL START ACTIVE ON MONDAY AS A
MID LEVEL TROUGH SWINGS ACROSS THE UPPER MIDWEST AND CASTS OFF A
SURFACE FRONT THAT WILL PUSH SOUTHEAST ACROSS IOWA DURING THE DAY.
GIVEN THE BROAD REGION OF ASCENT ON THE SOUTHERN FLANK OF THE
UPPER TROUGH ALONG WITH A DESTABILIZING ATMOSPHERE AND LOW LEVEL
CONVERGENCE ALONG THE BOUNDARY...IT IS EXPECTED THAT THERE WILL BE
WIDESPREAD COVERAGE OF SHOWERS AND THUNDERSTORMS ALONG THE FRONTAL
ZONE PROGRESSING FROM NORTHWEST TO SOUTHEAST...THUS CATEGORICAL
POPS HAVE BEEN MAINTAINED. THE SEVERE WEATHER THREAT REMAINS
MITIGATED BY THE FACT THAT THE SUPPORTING UPPER DYNAMICS WILL BE
DISPLACED FROM THE SURFACE SYSTEM ACROSS OUR AREA...AND THAT
INSTABILITY MAY BE LIMITED DEPENDING ON THE AMOUNT OF CONVECTIVE
DEBRIS LINGERING FROM MONDAY MORNING STORMS. NEVERTHELESS...THERE
IS SOME SEVERE POTENTIAL PARTICULARLY ACROSS ABOUT THE SOUTHEAST
HALF OF OUR FORECAST AREA WHERE DESTABILIZATION IS MOST LIKELY.

THE COLD FRONT AND ITS ATTENDANT STORMS WILL PUSH SOUTH AND
SOUTHEAST OF OUR AREA BY TUESDAY MORNING...STALLING ACROSS
MISSOURI WHILE A COOL HIGH PRESSURE AREA SLIDES ACROSS MINNESOTA
AND WISCONSIN AND PROVIDES US WITH MOSTLY SUNNY WEATHER AND
TEMPERATURES BELOW NORMAL ON TUESDAY AND WEDNESDAY. A 500 MB
SHORTWAVE WILL THEN MOVE SLOWLY OVERHEAD BETWEEN WEDNESDAY AND
THURSDAY NIGHT...POSSIBLY GENERATING WIDELY SCATTERED SHOWERS AND
STORMS AND/OR BRINGING THE OLD FRONTAL ZONE ACROSS MISSOURI BACK
UP ACROSS IOWA. EITHER WAY...CHANCE POPS HAVE BEEN MAINTAINED
DURING THIS TIME FRAME THOUGH THE SEVERE WEATHER THREAT SHOULD BE
LOW.

BY FRIDAY MORNING A LARGE 500 MB TROUGH WILL HAVE MOVED ASHORE
OVER THE PACIFIC U.S. COAST...WHILE OVER THE SOUTHEASTERN U.S. A
HIGH PRESSURE RIDGE WILL BE BUILDING. THE BATTLE BETWEEN THESE TWO
SYSTEMS WILL DOMINATE THE FORECAST FOR OUR REGION NEXT
WEEKEND...AS THE SOUTHEAST HIGH SHOULD SLIDE WESTWARD INTO THE
TEXARKANA AREA BY SATURDAY KEEPING THE WESTERN TROUGH FROM MAKING
ANY PROGRESS. THIS WILL HAVE THE EFFECT OF PLACING US WITHIN OR
NEAR THE INFAMOUS RING OF FIRE...AS SHORTWAVE IMPULSES EJECTED
FROM THE TROUGH OVER TOP THE RIDGE AND GENERATE THUNDERSTORM
COMPLEXES PERIODICALLY MOVING ACROSS THE MIDWEST. THE ABILITY OF
THE PROGNOSTIC MODELS TO DEPICT THE DETAILS OF THIS RESOLUTION
NEARLY A WEEK OUT IS DUBIOUS...BUT CERTAINLY THERE WILL BE CHANCES
FOR THUNDERSTORMS AND SEVERE WEATHER EITHER ACROSS OUR FORECAST
AREA OR NEARBY...THUS GENERAL 20 TO 40 POPS HAVE BEEN MAINTAINED
UNTIL THESE DETAILS BECOME CLEAR. WHAT CAN BE SAID WITH A
REASONABLE DEGREE OF CONFIDENCE IS THAT BY THE END OF THIS WEEK
TEMPERATURES SHOULD BE NOTICEABLY WARMER AS THE DEEP LAYER RIDGE
BUILDS TO THE SOUTH AND WE SEE A RETURN OF SOUTH TO SOUTHWEST LOW
LEVEL FLOW...THOUGH THIS WARM UP MAY BE PERIODICALLY INTERRUPTED
BY THUNDERSTORM DEVELOPMENT.

&&

.AVIATION...06/06Z
ISSUED AT 1146 PM CDT SUN JUL 5 2015

CONVECTIVE TRENDS ARE THE PRIMARY AVIATION CONCERN THROUGH THE
PERIOD. SCT THUNDERSTORMS OVER WESTERN IA AND SOUTHEAST SOUTH
DAKOTA LIKELY WILL IMPACT KDSM/KFOD/KMCW LATER TONIGHT. ANOTHER
ROUND OF STORMS LIKELY BY MONDAY AFTERNOON INTO MONDAY EVENING AS
A BOUNDARY SHIFTS SOUTHEAST THROUGH THE AREA. THE BOUNDARY WILL
ALSO BRING A SWITCH TO NORTHWEST WINDS. EXPECT GUSTY WINDS IN
VICINITY OF STORMS.

&&

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

$$

SHORT TERM...COGIL
LONG TERM...LEE
AVIATION...DONAVON


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