Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 311742
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1242 PM CDT SUN AUG 31 2014

.SYNOPSIS...
ISSUED AT 315 AM CDT SUN AUG 31 2014

A COLD FRONT FROM ND INTO THE TX PANHANDLE WILL MOVE THROUGH IA
TONIGHT AND MONDAY. HIGH PRESSURE WILL FOLLOW TUE. AN ACTIVE
PATTERN WILL CONTINUE WITH THE NEXT SYSTEM TO PASS THROUGH ABOUT
FRIDAY.

&&

.SHORT TERM /TODAY/...
ISSUED AT 315 AM CDT SUN AUG 31 2014

GIVEN AMPLE LOW LEVEL MOISTURE AND LIGHT WINDS...SOME AREAS OF FOG
HAVE DEVELOPED ACROSS THE CWA...ESPECIALLY IN THE EAST AND MAY
BECOME MORE WIDESPREAD THROUGHOUT THE EARLY MORNING HOURS.
HOWEVER...GIVEN INCREASING WINDS...DO NOT ANTICIPATE FOG TO BECOME
DENSE...THOUGH WILL LINGER A BIT LONGER ACROSS THE EAST.

MAIN CONCERN FOR TODAY WILL BE WITH PRECIPITATION TRENDS...AND
CHANCES FOR SEVERE THUNDERSTORMS. FRONTAL BOUNDARY CURRENTLY LOCATED
IN CENTRAL NE WILL PUSH EASTWARD THROUGHOUT THE DAY...THIS WILL BE
THE MAIN FOCUS FOR CHANCES FOR THUNDERSTORMS AND SEVERE WEATHER.
HOWEVER...HIGH RES MODELS ARE INDICATING A CHANCE FOR DEVELOPMENT IN
THE WEST AND SOUTHWEST LATE IN THE MORNING/EARLY IN THE AFTERNOON
ALONG A BAND OF THETA-E ADVECTION LIFTING NORTHEAST ACROSS THE STATE
AHEAD OF BOUNDARY. THIS SEEMS REASONABLE GIVEN CURRENT PRECIPITATION
TRENDS IN NORTHERN KS/SOUTHERN NE. BETTER THREAT WILL COME AS
BOUNDARY NEARS...WITH MODELS INDICATING ARRIVAL NEAR MO RIVER VALLEY
NEAR 00Z. THUNDERSTORMS ARE EXPECTED TO DEVELOP AHEAD OF THE
BOUNDARY BEGINNING IN THE LATE AFTERNOON...INCREASING AND SPREADING
EASTWARD THROUGH THE END OF THE PERIOD.

GOOD SOUTHERLY FLOW WILL ALLOW FOR TEMPERATURES TO WARM THROUGHOUT
THE DAY...AND ALSO WILL ALLOW FOR INSTABILITY WILL CONTINUE TO
INCREASE THROUGHOUT THE DAY. CAPE VALUES WILL BE NEAR 2000 J/KG IN
THE EARLY AFTERNOON THROUGH EVENING HOURS. SHEAR WILL NOT BE
OPTIMIZED...BUT WILL BE SUFFICIENT TO ALLOW FOR STORMS WHICH DEVELOP
TO MAINTAIN...THEREFORE ANY STORMS WHICH DEVELOP THROUGHOUT THE DAY
HAVE A THREAT TO BECOME SEVERE WITH LARGE HAIL AND DAMAGING WINDS
THE MAIN THREATS. SOME MODELS INDICATING GOOD LOW LEVEL SHEAR WHICH
MAY ALLOW FOR AN ISOLATED TORNADO THREAT AS WELL. HEAVY RAINFALL
WILL REMAIN POSSIBLE WITH STORMS AS WELL WITH PWAT VALUES REMAINING
NEAR 1.5 INCHES OR HIGHER.

.LONG TERM /TONIGHT THROUGH SATURDAY/...
ISSUED AT 315 AM CDT SUN AUG 31 2014

A LINE OF STRONG TO SEVERE THUNDERSTORMS WILL MOVE ACROSS THE
STATE TONIGHT IN A FAVORABLE ENVIRONMENT. STRONG THETA-E ADVECTION
WITH DIVERGENCE ALOFT WILL BE IN PLACE. PWAT VALUES IN THE 1.5 TO
2 INCH RANGE AND DECENT CAPE WILL MAKE THE STORMS EFFICIENT RAIN
PRODUCERS. SEVERE WEATHER CHANCES WILL BE BEST ACROSS THE WEST
HALF OF THE STATE LATE TODAY INTO TONIGHT...WITH LOWER
PROBABILITIES OVER NIGHT OVER THE EAST.

EXPECT PRECIPITATION TO EXIT THE CWA FAIRLY EARLY ON MONDAY WITH
COOLER AND DRIER AIR MOVING WITH HIGH PRESSURE. TEMPERATURES WILL
REMAIN AT OR A LITTLE ABOVE NORMAL THROUGH MUCH OF THE WEEK.

THE NEXT FRONTAL SYSTEM LATER THIS WEEK WILL ALSO BE PRETTY
POTENT WITH INSTABILITY AT LEAST AS HIGH AS THE CURRENT SYSTEM.
THIS SYSTEM WILL NEED TO BE MONITORED FOR THE POTENTIAL OF SEVERE
WEATHER ONCE AGAIN. TEMPERATURES WILL WARM WELL ABOVE NORMAL
AHEAD OF THIS SYSTEM WITH WED AND THU WELL ABOVE NORMAL.

A STRONGER PUSH OF COOLER AIR WILL FOLLOW THIS COLD FRONT WITH
BELOW NORMAL TEMPERATURES EXPECTED BY NEXT WEEKEND.

&&

.AVIATION...31/18Z
ISSUED AT 1240 PM CDT SUN AUG 31 2014

BREEZY SOUTHERLY WINDS WILL PREVAIL IN ADVANCE OF A COLD FRONT
WHICH WILL PASS ACROSS THE AREA LATE TONIGHT INTO MONDAY MORNING.
THE PRIMARY AVIATION CONCERN WILL BE WIDESPREAD THUNDERSTORMS
MOVING ACROSS THE STATE OVERNIGHT. STORMS WILL LIKELY HAVE STRONG
WINDS ALONG THE LEADING EDGE AND SIGNIFICANTLY REDUCED
VISIBILITIES IN HEAVY RAIN. A PERIOD OF MVFR STRATUS IS POSSIBLE
BEHIND THE STORMS. THE STRATUS SHOULD BEGINS TO SCATTER AS DRIER
AIR ARRIVES BEHIND THE BOUNDARY.

&&

.HYDROLOGY...
ISSUED AT 1241 PM CDT SUN AUG 31 2014

CONCERNS FOR FLOODING CONTINUE VERY LATE THIS AFTERNOON AND
TONIGHT. CURRENT PROFILES REMAIN QUITE DRY BELOW 700 MB HOWEVER
MOISTURE ADVECTION LATE AFTERNOON AND INTO TONIGHT SHOULD HELP
PUSH PWAT VALUES TO NEAR 1.6 INCHES OVER A NARROW CORRIDOR BY THIS
EVENING. RECENT RAINFALL...ESPECIALLY SOUTHWEST INTO THE CENTRAL
COUNTIES...HAVE PRODUCED NEAR SATURATED GROUND ENOUGH TO LOWER
THE THREE HOUR FFG VALUES TO NEAR 1.5 TO 2.5 INCH RANGE AS A
RESULT OF HIGH RUNOFF RATES. A WIDESPREAD ONE TO TWO INCH
RAINFALL WITH SPOTTY THREE INCH AMOUNTS IS LIKELY OVERNIGHT.
GIVEN THE LOW FFG VALUES...LOCAL FLASH FLOODING IS A POSSIBILITY.
CONTINUE TO MONITOR THE NEED FOR HEADLINES OVERNIGHT.

&&

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

$$

SYNOPSIS...MS AUG 14
SHORT TERM...AWB
LONG TERM...MS AUG 14
AVIATION...DONAVON
HYDROLOGY...MS AUG 14/DONAVON


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