400
FXUS63 KDMX 291828
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
128 PM CDT THU JUL 29 2021
..UPDATED FOR 18Z AVIATION DISCUSSION
DISCUSSION
/TODAY THROUGH WEDNESDAY/
ISSUED AT 345 AM CDT THU JUL 29 2021
FORECAST HIGHLIGHTS
-HOT/HUMID SOUTH TODAY
-STORM POTENTIAL LATE TONIGHT INTO EARLY SATURDAY
-COOLER TEMPS AND DRY WEATHER SUNDAY INTO NEXT WEEK
TODAY INTO TONIGHT...EARLY THIS MORNING, WEAK CONVECTION HAS
DEVELOPED ALONG A BOUNDARY SAGGING SOUTHWARD IN NORTHERN PARTS OF
THE FORECAST AREA. COVERAGE REMAINS FAIRLY ISOLATED AND
SUSTAINABILITY LOOKS TO BE ONLY A FEW HOURS THIS MORNING AS DEEP
SHEAR IS LOW IN THE VICINITY OF THIS CONVECTION AT ABOUT 25 KT.
ENOUGH MOISTURE CONVERGENCE AND CERTAINLY PLENTY OF INSTABILITY
PRESENT, BUT THERE IS ALSO PLENTY OF CIN. STILL, WITH DCAPE
VALUES AT ~1500 J/KG AND HIGH LCLS, IF A STORM DOES BREAK THROUGH
THE CAP, COULD PRODUCE SOME ISOLATED STRONG WIND GUSTS. MOST OF
THE HIRES MODELS DISSIPATE THIS WEAK CONVECTION BY 15Z AT THE
LATEST, IF IT DOES SUGGEST CONVECTION. HRRR IS THE MOST
AGGRESSIVE, BUT CONFIDENT ENOUGH TO KEEP SOME POPS GOING THROUGH
THE AFOREMENTIONED TIME.
HEAT AND HUMIDITY REMAIN A FACTOR ACROSS THE SOUTH TODAY WITH THE
BOUNDARY GRADUALLY STALLING OR SLOWING DOWN OVER CENTRAL IOWA.
SHOULD BE ENOUGH TIME FOR HIGHS TO REACH THE LOWER 90S, ESPECIALLY
WITH TEMPERATURES REMAINING IN THE MIDDLE 70S OVERNIGHT. PLUS,
DEWPOINTS CONTINUE TO BE SULTRY AS THEY RANGE IN THE LOWER TO
MIDDLE 70S AND THUS EXPANDED THE HEAT ADVISORY A ROW OF COUNTIES
NORTH TODAY WITH HEAT INDEX VALUES NEARING 105. WITH THE BOUNDARY
IN THIS VICINITY, THIS WILL BRING SOME CONVECTION POTENTIAL LATE
THIS AFTERNOON INTO TONIGHT BUT SHOULD BE SHORT-LIVED AS MOST
HIRES MODELS QUICKLY PUSH THE CONVECTION INTO NORTHERN MISSOURI.
FRIDAY INTO SATURDAY...SURFACE LOW PRESSURE OVER EASTERN ROCKIES
DEEPENS A BIT THROUGH THE DAY FRIDAY INTO FRIDAY NIGHT AND PUSHES
EAST INTO WESTERN KANSAS. MID-LEVEL SHORTWAVE CUTS ACROSS SD/NE
ALONG THE PRESSURE GRADIENT B/T THE SURFACE LOW OVER CO AND THE HIGH
PRESSURE TO THE NORTHEAST. HEAVY RAIN THREAT SEEMS VIABLE WITH
PRECIPITABLE WATER VALUES OVER 2 INCHES, WARM-LAYER CLOUD DEPTHS OF
4000 METERS, AND CORFIDI VECTORS LINING UP WITH THE MEAN STORM
MOTION. THE GREATEST THREAT LOOKS TO BE CENTRAL TO SOUTHWEST
PORTIONS OF THE IOWA FRIDAY AFTERNOON INTO EARLY SATURDAY MORNING
AND THE WPC DY2 EXCESSIVE RAINFALL OUTLOOK HIGHLIGHTS THIS SETUP
WELL.
SUNDAY INTO NEXT WEEK...SURFACE HIGH PRESSURE BUILDS INTO THE STATE
SUNDAY AND REMAINS THE STALWART THROUGH AT LEAST WEDNESDAY. THERE
ARE SIGNS OF THE RIDGE BREAKING DOWN BY THURSDAY INTO FRIDAY OF NEXT
WEEK, BUT CONFIDENT TO KEEP FORECAST DRY ATTM WITH MODELS IN
DISARRAY.
AVIATION
/FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON/
ISSUED AT 128 PM CDT THU JUL 29 2021
MAIN CONCERN THIS PERIOD ARE CEILINGS THIS AFTERNOON AND SURFACE
VISIBILITY REDUCTION DUE TO SMOKE FROM CANADIAN WILDFIRES LATER
THIS AFTERNOON THROUGH THE END OF THE PERIOD. SITES HAVE BEEN
BOUNCING BETWEEN VFR AND MVFR WITH SCT/BKN DECK AND SHOULD GO TO
PREVAILING VFR AS BOUNDARY LAYER DEPTH GROWS THIS AFTERNOON.
HOWEVER, SMOKE FROM CANADIAN WILDFIRES WILL SINK SOUTHWARD THIS
AFTERNOON INTO TONIGHT AND BEGIN TO IMPACT VISIBILITY. CONFIDENCE
IS HIGH IN SMOKE, BUT TO WHAT DEGREE THE VISIBILITY IS REDUCED IS
LOWER CONFIDENCE. FOR NOW, HAVE SMOKE ARRIVING TO THE NORTHERN
TERMINALS THIS AFTERNOON OR EARLY EVENING WITH 5SM FU, WHICH
CONTINUES INTO TONIGHT. BASED ON UPSTREAM OBS, RESTRICTIONS COULD
FALL INTO IFR, BUT WAS NOT CONFIDENT TO INCLUDE ANYTHING BEYOND
HIGH END MVFR AT THIS TIME. FU OR HZ MAY EXPAND INTO DSM AND OTM
LATER IN THIS PERIOD, BUT WILL ALLOW FUTURE TAFS TO EVALUATE.
DMX WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR IAZ070>075-081>086-
092>097.
DISCUSSION...PODRAZIK
AVIATION...ANSORGE
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page