Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 211726
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1226 PM CDT MON JUL 21 2014

.SYNOPSIS...
ISSUED AT 559 AM CDT MON JUL 21 2014

LOW PRESSURE WILL MOVE FROM WESTERN SOUTH DAKOTA TODAY...TOO LAKE
SUPERIOR TUESDAY. A COLD FRONT EXTENDING SOUTHWEST FROM THE THE
LOW WILL MOVE INTO IOWA TUESDAY AND PASS TO THE SOUTH TUESDAY
NIGHT. HIGH PRESSURE WILL BUILD INTO THE REGION WEDNESDAY AND
THURSDAY. NEXT WEATHER SYSTEM WILL MOVE INTO IOWA FRIDAY AND
SATURDAY.

&&

.SHORT TERM /TODAY/...
ISSUED AT 345 AM CDT MON JUL 21 2014

WARMER AND MORE HUMID AIR WILL OVERSPREAD THE CWA TODAY PUSHING
HEAT INDICES ABOVE 105 OVER THE WEST AND AROUND 100 IN THE EAST.
NAM AND GFS BOTH BREAK OUT A SMALL AREA OF THUNDERSTORMS THIS
MORNING AROUND SUNRISE. FEEL THIS IS UNLIKELY GIVEN GIVEN THE AND
THE LACK OF ANY AC PRESENT. DECENT INSTABILITY...THOUGH ELEVATED
IS NOT LOOKING LIKE IT IS IN THE CARDS. ECMWF DOES NOT CARRY THIS
FEATURE AND FEEL IT IS THE WAY TO GO. EXPECT MAX TEMPS TODAY WILL
WARM 3 TO 5 DEGREES ABOVE SUNDAYS HIGH WITH THE BIGGEST ISSUE
BEING THE RISE IN DEW POINTS. CORN CROP AT IT MAXIMUM
EVAPOTRANSPIRATION RATE AROUND NOW AND WILL CONTRIBUTE MOISTURE TO
THE BROAD RIBBON OF MOISTURE THAT HAS BEEN DRAWN NORTH ACROSS THE
PLAINS. DEW POINT VALUES LIKELY TO REACH THE MID 70S ACROSS THE
CWA BY AFTERNOON.

.LONG TERM /TONIGHT THROUGH SUNDAY/...
ISSUED AT 345 AM CDT MON JUL 21 2014

HOT AND HUMID CONDITIONS ON TUESDAY BEFORE A GENERALLY DRY COLD
FRONT MOVES THROUGH LATE TUESDAY AFTERNOON AND EVENING. LEANED
TOWARD THE DRIER ECMWF/GFS FOR TUESDAY INTO WEDNESDAY...THEN MORE
TOWARDS THE GFS LATE IN THE WEEK AS THE 00Z ECMWF WAS COMPLETELY
DIFFERENT FROM PREVIOUS RUN AND LOW CONFIDENCE IN USING THE NEW
SOLUTION ATTM WITH THE INCONSISTENCY.

TONIGHT INTO WEDNESDAY...WAA TONIGHT WILL KEEP LOW TEMPERATURES UP
WELL INTO THE 70S AND TWEAKED LOWS UP SLIGHTLY. NORTHERN IOWA MAY
GET CLIPPED WITH MCS THAT IS EXPECTED TO DEVELOP OVER MINNESOTA
AND HEAD SOUTHEAST THROUGH WISCONSIN OVERNIGHT. HAVE SLIGHT TO LOW
CHANCE POPS GOING FOR A SHORT TIME FRAME B/T 06-12Z TUESDAY...BUT
CUT BACK CONSIDERABLY ON POPS OVERNIGHT.

WITH THE WARM START TUESDAY MORNING AND DECENT MIXING STILL
PROGGED TO AROUND 900MB...ONGOING TEMPERATURE FORECAST SEEMED
REASONABLE. ONLY TWEAK WAS TO MAX TEMPS ACROSS THE NORTH WHERE THE
MCS OVERNIGHT LOOKS TO STAY FURTHER NORTH AND SHOULD NOT BE AS
AFFECTED BY CLOUD COVER.

VERY HIGH CAPE VALUES ON TUESDAY BUT BELIEVE THE FROPA WILL
REMAIN DRY AS THE 700MB TEMPS AT +16C TO +17C. HENCE...CONFIDENT
THE CAP SHOULD HOLD ANY THUNDERSTORM DEVELOPMENT UNTIL PAST 00Z
WEDNESDAY WHEN CAP WEAKENS SOMEWHAT WITH SUNSET. STORMS LOOK TO BE
MAINLY CONFINED TO THE SOUTHEAST ATTM. LOWERED POPS AND COVERAGE
ON TUESDAY.

MUCH COOLER TEMPERATURES FORECAST ON WEDNESDAY WITH CAA THROUGHOUT
THE DAY. GUIDANCE CONTINUES TO TREND COLDER AND LOWERED MAX TEMPS
A DEGREE OR TWO ON WEDNESDAY TO REFLECT THE COLDER TREND.

THURSDAY AND FRIDAY...LARGE UPPER LEVEL RIDGE BEGINS TO FLATTEN
OUT LATER IN THE WEEK AND ALLOWS FOR MORE ZONAL TO NORTHWEST FLOW
BY FRIDAY. GFS/ECMWF IN DECENT AGREEMENT WITH SURFACE LOW
DEVELOPING OVER THE CENTRAL PLAINS AND AN UPPER LEVEL SHORTWAVE TO
MOVE THROUGH THE REGION ON FRIDAY. A GOOD AMOUNT OF THETA-E
ADVECTION AND A FAIR AMOUNT OF FORCING WITH THIS SYSTEM FRIDAY
NIGHT...SO BEST POTENTIAL FOR RAIN IN THE EXTENDED IS DURING THIS
TIME FRAME.

SATURDAY THROUGH SUNDAY...ANOTHER SHORTWAVE LOOKS TO CLIP NORTHEAST
IOWA SUNDAY BUT LOW CONFIDENCE WITH TIMING AND KEPT LOW CHANCE POPS
GOING ACROSS THE NORTH.

&&

.AVIATION...21/18Z
ISSUED AT 1222 PM CDT MON JUL 21 2014

AREA OF STRATUS HAS EXPANDED IN NORTHWEST IOWA THIS MORNING AND
WILL CONTINUE FOR A FEW HOURS INTO THE AFTERNOON BUT SHOULD BEGIN
TO MIX OUT LATER. THIS WILL IMPACT KFOD...KMCW AND POSSIBLY KALO
WITH MVFR CEILINGS FOR A SHORT WHILE THIS AFTERNOON. GENERALLY VFR
CONDITIONS ARE EXPECTED OVERNIGHT ALTHOUGH SOME PATCHY AREAS OF
HAZE/LGT FOG WILL BE POSSIBLE. WINDS WILL BE FROM THE SOUTH TO
SOUTHEAST THROUGH TONIGHT BUT WILL BECOME NORTHWEST BEHIND A FRONT
DROPPING SOUTH THROUGH THE STATE ON TUESDAY.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
HEAT ADVISORY UNTIL 7 PM CDT TUESDAY FOR ADAIR-ADAMS-APPANOOSE-
AUDUBON-BLACK HAWK-BOONE-BREMER-BUTLER-CALHOUN-CARROLL-CASS-
CERRO GORDO-CLARKE-CRAWFORD-DALLAS-DAVIS-DECATUR-EMMET-FRANKLIN-
GREENE-GRUNDY-GUTHRIE-HAMILTON-HANCOCK-HARDIN-HUMBOLDT-JASPER-
KOSSUTH-LUCAS-MADISON-MAHASKA-MARION-MARSHALL-MONROE-PALO ALTO-
POCAHONTAS-POLK-POWESHIEK-RINGGOLD-SAC-STORY-TAMA-TAYLOR-UNION-
WAPELLO-WARREN-WAYNE-WEBSTER-WINNEBAGO-WORTH-WRIGHT.

&&

$$

SYNOPSIS...MS JUL 14
SHORT TERM...MS JUL 14
LONG TERM...PODRAZIK
AVIATION...COGIL



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