Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 200453
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1153 PM CDT SAT JUL 19 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 329 PM CDT SAT JUL 19 2014

EARLIER CONVECTION CLOSE TO NORTHWEST IOWA HAS DISSIPATED INTO THE
EARLY AFTERNOON. THE STORMS WERE ALONG AND AREA OF CONVERGENCE
THAT HAS WEAKENED AS SHORTWAVE ENERGY LIFTS NORTHEAST INTO CANADA.
DO NOT ANTICIPATE MUCH THREAT OF CONVECTION FROM THIS WAVE AS
CONVERGENCE DIMINISHES ALONG BOUNDARY TO THE NORTHWEST OF IOWA AND
BEST FORCING REMAINS NORTH OF THE STATE. OTHERWISE...EXTENSIVE CU
FIELD WILL DISSIPATE THIS EVENING WITH SOME LINGERING HIGH
CLOUDINESS OVERNIGHT. TEMPERATURES WILL CONTINUE TO GAIN A FEW
DEGREES EACH NIGHT AS WARM ADVECTION PERSISTS AND DEWPOINTS CLIMB
AND READINGS WILL BE CLOSE TO NORMAL BY SUNDAY MORNING.

.LONG TERM /SUNDAY THROUGH SATURDAY/...
ISSUED AT 329 PM CDT SAT JUL 19 2014

NO SIGNIFICANT CHANGES IN FORECAST THINKING TODAY. FROM SUNDAY
INTO TUESDAY THE WEATHER WILL BECOME INCREASINGLY HOT AND HUMID
WITH VERY LITTLE CHANCE FOR ANY RAIN. LATE SUNDAY NIGHT THERE ARE
INDICATIONS THAT A WEAK SURFACE TROUGH OR EFFECTIVE WARM FRONT MAY
LIFT NORTHWARD ACROSS THE AREA AND HAVE MAINTAINED SLIGHT CHANCE
POPS DURING THAT TIME...OTHERWISE DO NOT SEE ANY MECHANISM FOR
SHOWER/STORM DEVELOPMENT UNTIL AT LEAST TUESDAY MORNING.
TEMPERATURES WILL RISE INTO THE 90S IN MANY AREAS ON MONDAY...AND
PROBABLY AGAIN ON TUESDAY DEPENDING ON THE TIMING OF A COOL FRONT
THAT WILL BE ADVANCING TOWARD/ACROSS THE AREA. WITH DEWPOINTS
SURGING WELL INTO THE 70S ON BOTH DAYS...CURRENTLY FORECAST HEAT
INDEX VALUES TOP OUT IN THE 98 TO 103 RANGE ON MONDAY AFTERNOON
AND OVER 100...POSSIBLY APPROACHING 110 FROM I-80 SOUTH...ON
TUESDAY AFTERNOON. AT THIS TIME NO HEAT HEADLINES ARE IN
EFFECT...BUT THIS WILL BEAR WATCHING AS WE HEAD THROUGH THE NEXT
COUPLE OF DAYS ESPECIALLY IF THE FRONT DOES NOT MOVE ACROSS THE
AREA UNTIL LATE ON TUESDAY.

REGARDING THE AFOREMENTIONED COOL FRONT...IT WILL SHARPEN ACROSS
SOUTH DAKOTA AND NEBRASKA ON MONDAY NIGHT AS THE PARENT SURFACE
LOW PRESSURE SYSTEM MOVES ACROSS THE UPPER MIDWEST. THE FRONT
SHOULD LIE SOMEWHERE AROUND THE NORTHWEST CORNER OF IOWA BY MID
MORNING TUESDAY...AND PROGRESS SOUTHEASTERLY THEREAFTER AS IT IS
PUSHED BY A MID LEVEL SHORTWAVE RIDING AROUND THE LARGE WESTERN
U.S. 500 MB HIGH. THIS WILL BRING SOME RELIEF FROM THE HOT
TEMPERATURES EARLIER IN THE WEEK...AND WILL ALSO LIKELY GENERATE
SOME THUNDERSTORMS AND POSSIBLY SEVERE WEATHER ACROSS OUR FORECAST
AREA. HOWEVER...THE EXTENT OF ANY SUCH STORMS WILL DEPEND ON
FRONTAL TIMING AS WE ARE LIKELY TO REMAIN CAPPED FOR MUCH OF THE
DAY ON TUESDAY. AT THIS TIME THE MOST LIKELY SCENARIO IS THAT THE
FRONT ACTIVATES WITH STORMS DEVELOPING AROUND TUESDAY
EVENING...POSSIBLY FROM SOUTHWESTERN INTO NORTHEASTERN IOWA...THEN
STORMS WILL PERSIST INTO TUESDAY NIGHT AS THE FRONT MOVES INTO
SOUTHEASTERN IOWA BEFORE CLEARING OUT AROUND WEDNESDAY MORNING.
THESE TRENDS IN RAINFALL CHANCES AND TIMING WILL BE BETTER REFINED
IN THE NEXT COUPLE OF DAYS.

FROM WEDNESDAY THROUGH THURSDAY THE WEATHER WILL BE COOLER AND
QUIET IN WAKE OF THE TUESDAY COOL FRONT. BY THURSDAY NIGHT MID
LEVEL RIDGING WILL BUILD IN ONCE AGAIN WITH A RETURN OF SOUTH
SOUTHEAST SURFACE FLOW LEADING TO MILDER CONDITIONS ON FRIDAY.
HOWEVER...THIS WILL BE SHORT LIVED AS ANOTHER SYSTEM APPROACHES
FROM THE WEST LATE IN THE DAY. THIS SYSTEM WILL COME IN THE FORM
OF A 500 MB SHORTWAVE TROUGH CROSSING THE NORTHERN HIGH PLAINS THAT
WILL SHUNT THE LARGER 500 MB HIGH SOUTHWARD INTO THE SOUTHERN
PLAINS AND SOUTHWESTERN U.S. FOR NEXT WEEKEND. AS THIS TROUGH
APPROACHES IOWA LATE ON FRIDAY NIGHT IT IS LIKELY TO TRIGGER
ANOTHER ROUND OF THUNDERSTORMS...SOMETIME AROUND FRIDAY NIGHT OR
SATURDAY...BUT BEHIND IT COOLER WEATHER WILL PREVAIL AGAIN FOR
THE THE LATTER PART OF THE WEEKEND.

&&

.AVIATION...20/06Z
ISSUED AT 1151 PM CDT SAT JUL 19 2014

SOUTHERLY WINDS GENERALLY AT 10 KTS OR LESS TONIGHT WILL BECOME
BREEZY AGAIN BY MID TO LATE SUNDAY AFTERNOON. BKN CIGS TO NEAR
3500 FT HAVE MOVED ACROSS PORTIONS OF NORTH CENTRAL IA THIS
EVENING HOWEVER THESE CIGS ARE NOT EXPECTED TO LOWER AND CONDITIONS
WILL TO REMAIN VFR AT ALL LOCATIONS.

&&

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

$$

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



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