Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 240459
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1159 PM CDT SAT AUG 23 2014

...UPDATED AVIATION DISCUSSION...

.SHORT TERM /TONIGHT/...
ISSUED AT 235 PM CDT SAT AUG 23 2014

VERY HUMID AND UNSTABLE AIRMASS OVER THE CWA. THOUGH PLENTY OF
CAPE AVAILABLE...IT IS LESS LIKELY FIRE OFF CONVECTION TONIGHT
WITH SOMEWHAT DRIER AIR MOVING INTO THE AREA IN THE MID LEVELS.
WOULD NEED SOME SATURATION TO REALIZE THE ELEVATED POTENTIAL THERE
FRONTAL BOUNDARY REMAINS ACROSS THE CWA WITH FRONT FROM SOUTHWEST
IA INTO SRN IL. EXPECT TO SEE SOME CLEARING TONIGHT LOOKING AT
SATELLITE PICTURES AND WILL ALLOW TEMPS TO FALL OFF LOWER THAN
CURRENT DEW POINTS THAT IS OF CONCERN CONSIDERING THE UPS FOG
FORECASTING RULE. LOCAL STUDIES SUGGEST FOG IS NOT ALL THAT LIKELY
WITH THE BL WINDS UP AROUND 20 KTS...SO DIDN`T PLAY THE FOG CARD
TONIGHT.

.LONG TERM /SUNDAY THROUGH SATURDAY/...
ISSUED AT 235 PM CDT SAT AUG 23 2014

EARLY SUNDAY A LARGE UPPER LOW OVER THE NORTHERN ROCKIES WILL
BEGIN TO SHIFT INTO THE NORTHERN PLAINS. THIS WILL AMPLIFY THE
UPPER RIDGE TO OUR EAST WHILE PUSHING THE RIDGE AXIS INTO IL AND
LEAVING IOWA IN BROAD SOUTH TO SOUTHWEST FLOW. I AM NOT EXPECTING
THE CLOUD COVER THAT WE HAVE HAD THE PAST SEVERAL DAYS SO TEMPS
SHOULD REALLY WARM UP TOMORROW. IN ADDITION...MOISTURE IN GENERAL
BUT ESPECIALLY LOWER LEVEL MOISTURE WILL NOT BE AS BAD AS WE HAVE
SEEN THE LAST FEW DAYS. HEAT INDICES ARE FORECAST TO CLIMB ONCE
AGAIN TO AROUND 100 OR THE LOW 100S BUT FALL SHY OF HEAT ADVISORY
CRITERIA. THE HEAT HOWEVER WILL BE FELT FOR MORE OF THE DAY SINCE
WE WILL SEE THE SUN MUCH OF THE DAY.

LATE IN THE DAY SUNDAY AND SUNDAY NIGHT A SURFACE LOW OVER THE
NORTHERN PLAINS WILL SHIFT NORTHEAST AND DRIVE A FRONTAL BOUNDARY
EASTWARD. THERE IS SOME MODEL DISAGREEMENT TO THE EASTWARD EXTENT
OF THE BOUNDARY BY 00Z BUT THERE IS REASONABLE CERTAINTY THAT THE
FAR WESTERN PART OF THE FORECAST AREA MAY SEE ISOLATED STORMS
BEGINNING TO DEVELOP. THE FRONT THEN DOES PUSH THROUGH AT LEAST
THE NW HALF OF IOWA BEFORE STALLING OR DRIFTING SLOWLY TO THE
SOUTHEAST DURING THE DAY MONDAY. THIS WILL KEEP THUNDERSTORM
CHANCES GOING ACROSS THE AREA.

TUESDAY INTO LATE WEDNESDAY A SECONDARY COLD FRONT PUSHES INTO
IOWA AND SLOWS OR STALLS ONCE AGAIN AS ANOTHER DEEP TROUGH
DEVELOPS OVER THE ROCKIES AND WORKS ITS WAY EAST THROUGH THURSDAY.
ONCE AGAIN THERE WILL BE A FAIRLY PROLONGED PERIOD FOR SCATTERED
STORMS. WHILE THERE MIGHT BE SOME POTENTIAL FOR LARGE HAIL OR
DAMAGING WIND THE OVERALL SEVERE THREAT IS FAIRLY LOW BUT THESE
STORMS WILL ONCE AGAIN BE HEAVY RAINFALL PRODUCERS AND WITH THE
RAIN WE`VE RECEIVED THUS FAR...WE WILL NEED TO KEEP THE
POSSIBILITY OF FLOODING IN THE FORECAST...ESPECIALLY IF STORMS
MOVE ACROSS RECENTLY FLOODED AREAS. BASED ON RECENT RAINFALL AND
THE LENGTH OF TIME IT IS TAKING FOR WATER TO RECEDE...SOILS ARE
PRETTY MOIST AND MANY CREEKS AND RIVERS ARE REPORTED AT OR NEAR
BANKFULL. HEAVY RAINFALL IN THESE SAME AREAS ACROSS THE FAR SOUTH
COULD BE PROBLEMATIC.

BY LATE IN THE WEEK AND NEXT WEEKEND WE WILL BE IN COOLER AND LESS
HUMID AIR WITH LITTLE CHANCE OF RAINFALL.

&&

.AVIATION...24/06Z
ISSUED AT 1146 PM CDT SAT AUG 23 2014

IFR STRATUS WILL CONTINUE OVERNIGHT ACROSS MCW/FOD AND EXPECTING
IFR CIGS TO AFFECT DSM/OTM/ALO BY 08Z AND POSSIBLY SOONER. LOWER
CONFIDENCE WITH DSM SEEING PREVAILING IFR CIGS OVERNIGHT AS ON THE
SOUTHWEST FRIDGE OF THE STATUS DECK. OTHERWISE...MIXING INCREASES
LATE SUNDAY MORNING INTO THE AFTERNOON.

&&

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

&&

$$

SHORT TERM...MS
LONG TERM...FAB
AVIATION...PODRAZIK



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