Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 230916
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
416 AM CDT SAT AUG 23 2014

.SHORT TERM /TODAY/...
ISSUED AT 415 AM CDT SAT AUG 23 2014

YET ANOTHER ACTIVE OVERNIGHT/EARLY MORNING TODAY WITH A LARGE AREA
OF THUNDERSTORMS MOVING ACROSS WEST/SOUTHWEST IOWA AT THE CURRENT
HOUR. THIS ACTIVITY IS ASSOCIATED WITH THE NOSE OF THE NOCTURNAL LOW
LEVEL JET AND A SURGE OF WARM AIR ADVECTION ALOFT COMING OUT OF THE
SOUTHERN PLAINS. EXPECT THE STORMS TO MOVE SLOWLY ACROSS MUCH OF THE
FORECAST AREA THIS MORNING AND HAVE INCLUDED HIGH POPS ACCORDINGLY.
WHILE LOCALLY HEAVY RAINFALL WILL OCCUR...THE BAR FOR FLASH FLOODING
IS SET HIGH DUE TO ANTECEDENT AND VEGETATIVE CONDITIONS.

AS THE WARM AIR ADVECTION SURGE CONTINUES NORTHWARD AND THE JET
WEAKENS AFTER SUNRISE...EXPECT THE SWATH OF THUNDERSTORMS TO SHIFT
TOWARD THE NORTH AND NORTHEAST AND GRADUALLY DIMINISH...LIKELY
ENDING IN OUR NORTHEASTERN COUNTIES IN THE EARLY AFTERNOON.
MEANWHILE...BEHIND THIS PUSH HOTTER CONDITIONS WILL MOVE INTO
PARTICULARLY SOUTH/SOUTHWEST IOWA IN THE AFTERNOON. HEATING WILL BE
MITIGATED BY MORNING CONVECTIVE DEBRIS CLOUDS...SOUTHEASTERLY LOW
LEVEL WIND TRAJECTORIES...AND PERSISTENTLY HIGH DEWPOINTS...BUT
BELIEVE TEMPERATURES SHOULD STILL EXCEED YESTERDAYS LEVELS IN THESE
AREAS WITH LOWER 90S TYPICAL. HEAT INDEX VALUES WILL LIKELY TOP OUT
IN THE 100 TO 105 DEGREE RANGE ONCE AGAIN...JUST BELOW ADVISORY
CRITERIA AND PRECLUDING A HEADLINE ISSUANCE AT THIS TIME.

.LONG TERM /TONIGHT THROUGH FRIDAY/...
ISSUED AT 415 AM CDT SAT AUG 23 2014

UPPER LOW MOVING ACROSS IDAHO THIS MORNING...WILL CONTINUE TO
SHIFT EAST/NORTHEAST INTO WESTERN NORTH DAKOTA BY MID DAY SUNDAY.
STRONG PV ANOMALY OVER COLORADO AND NEW MEXICO WILL LIFT QUICKLY
NORTH AND BE INGESTED IN THE UPPER LOW OVERNIGHT. THIS WILL HELP
PUSH THE FRONTAL BOUNDARY WILL NORTH OF THE STATE AND PLACING THE
AREA INTO THE WARM SECTOR. MUCH DRIER MID LEVELS WILL HELP LOWER
PWATS DOWN TO NEAR 1.25 INCHES...WHICH WILL HELP STABILIZE THE
ATMOSPHERE. THE SUB TROPICAL HIGH WILL REMAIN ENTRENCHED OVER THE
SOUTHEAST CONUS AND WILL KEEP SOUTHWEST FLOW OVER THE STATE
THROUGH THE EARLY PORTION OF THE WEEK. TEMPERATURES SHOULD BE
QUITE WARM ON SUNDAY WITH THE THERMAL RIDGE IN PLACE WITH HIGHS
IN THE UPPER 80S TO MID 90S.

ANOTHER STRONG UPPER LOW WILL MOVE THROUGH THE INTERMOUNTAIN WEST
MID NEXT WEEK AND WILL HELP THE FRONTAL BOUNDARY DROP INTO IOWA
AND BECOME NEARLY STATIONARY ONCE AGAIN. THIS WILL RESULT INTO
SEVERAL CHANCES FOR THUNDERSTORMS TUESDAY AND WEDNESDAY WITH SOME
SEVERE WEATHER AND THE POTENTIAL FOR LOCALLY HEAVY RAINFALL. THE
UPPER LEVEL SYSTEM WILL EVENTUALLY PUSH THE SFC BOUNDARY TO THE
EAST OF THE STATE THOUGH THIS MAY NOT OCCUR UNTIL THURSDAY. A
NEARLY 20 DEGREE DIFFERENCE IN TEMPERATURES NORTH AND SOUTH OF THE
BOUNDARY WHILE IT IS STALLED OVER THE AREA WITH 70S NORTH TO NEAR
90 SOUTH. COOLER FOR THE ENTIRE AREA BY FRIDAY.

&&

.AVIATION...23/06Z
ISSUED AT 1150 PM CDT FRI AUG 22 2014

DELAYED CONVECTION UNTIL PAST 12Z SATURDAY FOR ALL TAF SITES AS
THE 23/00Z HOPWRF AND HRRR ARE IN GOOD AGREEMENT WITH CONVECTION
SPREADING ACROSS SOUTH-CENTRAL IOWA WITH THE HRRR MORE WIDESPREAD
FURTHER NORTH. HAVE MENTION OF VCTS AT FOD/DSM/OTM WITH A LITTLE
HIGHER CONFIDENCE SITES WILL SEE STORMS. HAVE MVFR TO IFR VIS WRT
TO FOG PAST 08Z TONIGHT. MIXING DEVELOPS LATE SATURDAY MORNING AND
KEPT MENTION OF GUSTS THROUGH THE AFTERNOON HOURS.


&&

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

$$

SHORT TERM...LEE
LONG TERM...DONAVON
AVIATION...PODRAZIK



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