Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 011738
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1238 PM CDT TUE SEP 1 2015

.SHORT TERM /TODAY/...
ISSUED AT 352 AM CDT TUE SEP 1 2015

AS EXPECTED SOME PATCHY DENSE FOG HAS DEVELOPED EARLY THIS
MORNING...BUT IS NOT NEARLY WIDESPREAD ENOUGH TO WARRANT AN ADVISORY
AT THIS TIME. WILL MONITOR OBSERVATIONAL TRENDS BUT EXPECT THAT
COVERAGE WILL REMAIN PRETTY ISOLATED EXCEPT POSSIBLY FOR A BRIEF
TIME RIGHT AROUND SUNRISE. ONCE DAYTIME HEATING BEGINS THE FOG
SHOULD BURN OFF QUICKLY YIELDING TO ANOTHER MOSTLY SUNNY...HOT AND
HUMID LATE SUMMER DAY. WARM AIR ADVECTION WILL CONTINUE WITH SOUTH
SOUTHWESTERLY LOW LEVEL WINDS AND THE PERIPHERY OF THE LARGE
SOUTHERN U.S. RIDGE OVERHEAD. HAVE BUMPED UP HIGH TEMPERATURES JUST
A DEGREE OR TWO MAINLY ACROSS OUR SOUTHEAST HALF AS THE HEAT SHOULD
BE ABLE TO BUILD ON YESTERDAYS START PARTICULARLY GIVEN THE
RELATIVELY WARM TEMPERATURES IN PLACE AT THE CURRENT HOUR. WITH
HIGHS AROUND 88 TO 90 IN THESE AREAS AND DEWPOINTS AROUND 70 IT WILL
FEEL PRETTY MUGGY...HOWEVER FORECAST HEAT INDEX VALUES ONLY PEAK
AROUND 95 AND THERE WILL BE MODEST BREEZES OF AROUND 10 MPH.

.LONG TERM /TONIGHT THROUGH MONDAY/...
ISSUED AT 352 AM CDT TUE SEP 1 2015

UPPER LOW OVER THE OHIO VALLEY WILL FINALLY DEPART THE OHIO VALLEY
AND SHIFT EAST LATE TONIGHT WILL ALLOW MORE PROGRESSIVE FLOW
ACROSS THE STATE WEDNESDAY AND WEDNESDAY NIGHT THAT WILL BRING A
COUPLE LOW AMPLITUDE IMPULSES ACROSS THE MIDWEST. THE PRIMARY
REGION FOR INSTABILITY WILL BE OVER THE NORTHWEST HALF OF IOWA
WHILE DRIER AIR FROM SFC HIGH PRESSURE WILL KEEP MUCH OF THE
SOUTHEAST DRY. THE MID LEVEL RIDGE WILL AMPLIFY ACROSS THE CENTRAL
AND NORTHERN PLAINS LATE WEDNESDAY NIGHT INTO THURSDAY AS AN UPPER
LOW MOVES INTO THE PACIFIC NORTHWEST.

THE BUILDING RIDGE WILL BE THE PRIMARY INFLUENCE ON THE REGION
THROUGH SATURDAY NIGHT BEFORE THE PACIFIC NW UPPER LOW BEGINS TO
SHIFT EAST AND SUPPRESSES THE RIDGE AND ALLOWING A BOUNDARY TO
DROP SOUTH. THE 850 MB TEMPERATURES OF LOW TO MID 20S C WILL BE
COMMON THROUGH THE PERIOD ALONG WITH GOOD SOUTH TO SOUTHWEST
WINDS. HIGH TEMPERATURES IN THE MID 80S TO LOWER 90S THROUGH
SATURDAY FOLLOWED BY A COOLING TREND SUNDAY THROUGH TUESDAY AS THE
BOUNDARY ARRIVES ALONG WITH THE NEXT CHANCE FOR THUNDERSTORMS. DEW
POINTS IN THE MID 60S TO LOWER 70S WILL KEEP CONDITIONS HUMID AND
HEAT INDEX VALUES IN THE 90S THIS WEEK. THE THREAT FOR FOG WILL
DECREASE WITH A STRONGER PRESSURE GRADIENT IN PLACE AND THE
SATURATED GROUND GETTING A CHANCE TO DRY. ANY QPF MID WEEK WILL
GENERALLY BE ONE QUARTER INCH OR LESS.

&&

.AVIATION...01/18Z
ISSUED AT 1238 PM CDT TUE SEP 1 2015

MAINLY VFR CONDITIONS IN THE CRITICAL TAF PERIOD...SOME MVFR VSBYS
POSSIBLE IN LIGHT FOG AT A FEW LOCATIONS LATE TONIGHT INTO EARLY
WEDNESDAY. WEAK ENERGY TO MOVE THROUGH ALOFT MAY TRIGGER SOME
SHOWERS AND THUNDERSTORMS...HOWEVER COVERAGE IS UNCERTAIN SO HAVE
LEFT MENTION OUT OF THE TAFS AT THIS TIME. SOUTHERLY TO
SOUTHWESTERLY WINDS EXPECTED THROUGH THE PERIOD WITH INCREASING
HIGH CLOUDS.

&&

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

&&

$$

SHORT TERM...LEE
LONG TERM...DONAVON
AVIATION...BEERENDS


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