Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 230852
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
352 AM CDT TUE SEP 23 2014

.SHORT TERM /TODAY/...
ISSUED AT 325 AM CDT TUE SEP 23 2014

WELL DEFINED UPPER SYSTEM IN WATER VAPOR IMAGERY NEAR THE BLACK
HILLS OF SOUTH DAKOTA WILL CONTINUE TO DRIFT NORTHEAST TODAY WITH QG
FORCING SPREADING INTO IOWA.  MEANWHILE...WEAK MOISTURE TRANSPORT
AND THETA-E ADVECTION WILL INCREASE INTO WESTERN IOWA DURING THE
DAY.  THESE FACTORS ARE EXPECTED TO MAINTAIN THE ONGOING SHOWER
ACTIVITY IN NEBRASKA WITH THE PRECIPITATION SPREADING INTO WESTERN
IOWA DURING THE MORNING AND EVENTUALLY TO THE INTERSTATE 35 CORRIDOR
BY THE END OF THE PERIOD IF NOT SLIGHTLY EAST.  INSTABILITY WILL
CONTINUE TO BE WEAK AND HAVE MENTIONED THUNDER ONLY DURING THE
AFTERNOON WITH PEAK HEATING AND STRONGEST LIFT PASSING ACROSS THE
STATE.  OTHERWISE...CLOUDS WILL INCREASE FROM WEST TO EAST DURING
THE MORNING HOURS WITH THE FAR EAST SEEING SOME DECENT SUN THIS
MORNING BEFORE CLOUDS OVERSPREAD THE AREA.  FARTHER WEST...CLOUDS
WILL BE RATHER THICK FROM THE GET-GO AND THIS WILL INHIBIT HIGHS
WITH READINGS HELD BELOW 70.

.LONG TERM /TONIGHT THROUGH MONDAY/...
ISSUED AT 325 AM CDT TUE SEP 23 2014

PAINFULLY SLOW MOVING UPPER TROUGH WILL CONTINUE TO INCH TO THE
EAST AS IT LIFTS ACROSS THE NORTHERN/CENTRAL PLAINS.
AFOREMENTIONED THETA-E ADVECTION WILL LINGER THIS EVENING AS IT
CONTINUES LIFT OFF TO THE NORTHEAST. THERE IS ALSO SOME WEAK QC
FORCING THAT WILL PUSH ACROSS IOWA TONIGHT INTO WEDNESDAY WHILE
THE FORCING AND THETA-E ADVECTION WILL REMAIN NOT PHASED...THEY
WILL BOTH PLAY A PART IN CONTINUING CHANCES FOR LIGHT SHOWERS OR
AN ISOLATED THUNDERSTORM.

BY WEDNESDAY NIGHT AN UPPER RIDGE REALLY AMPLIFIES OVER THE
ROCKIES AND PUSHES THE TROUGH TOWARDS THE UPPER GREAT LAKES.
THERE SHOULD STILL BE A TROUGH OVER THE EASTERN THIRD OR SO OF
IOWA WEDNESDAY INTO WEDNESDAY NIGHT WITH BROAD AND WEAK THETA-E
ADVECTION AND SOME FORCING ACROSS NORTHEAST IOWA FOR CONTINUED
SLIGHT CHANCE POPS DURING THIS PERIOD. WE MAY CONTINUE TO SEE A
STRAY SHOWER OR ISOLATED STORM INTO WEDNESDAY EVENING BUT PRECIP
SHOULD BE LARGELY DONE BY THAT TIME.

THE VERY LARGE UPPER LEVEL RIDGE PUSHES INTO THE UPPER MIDWEST FOR
LATE WEEK KEEPING THINGS DRY WITH A GRADUAL WARMING TREND.A LOW
OVER THE SOUTHERN PLAINS IS PROGGED TO GET CAUGHT UP IN THE WEAK
FLOW UNDER THE HIGH AND MEANDER AROUND A BIT UNDER THE HIGH BUT
WITH NOTHING TO FOCUS ON I THINK IT WILL REMAIN DRY THROUGH THE
WEEKEND. BY EARLY NEXT WEEK MODELS DIFFER A BIT BUT THE EURO HAS A
TROUGH UNDERCUTTING THE RIDGE FROM THE NORTHWEST AND PUSHING IT
TO THE EAST. THE GFS HAS MORE OF A LOW CLOSING OFF OVER THE
NORTHWEST BUT BOTH MODELS SPREAD PRECIP INTO THE AREA LATE MONDAY
THROUGH TUESDAY OF NEXT WEEK. POPS HAVE BEEN INTRODUCED IN THE
FORECAST AREA BEGINNING MONDAY NIGHT. THE DAY SHIFT CAN EVALUATE
TUESDAY IN THE NEXT FORECAST CYCLE.

&&

.AVIATION...23/06Z
ISSUED AT 1153 PM CDT MON SEP 22 2014

HIGH PRESSURE TO EAST OF IA WILL CONTINUE TO MOVE AWAY AS UPPER
LOW OVER THE NRN ROCKIES AND NORTHERN HIGH PLAINS MOVES EAST
TOWARD IA. AREA OF SHOWERS AND LOWER CLOUDS TO THE WEST WILL
ADVANCE INTO THE WESTERN TAF SITES BY 06Z/24...BUT THE EAST WILL
REMAIN DRY. VFR CONDITIONS THROUGHOUT THE TAF PERIOD OTHER THAN
SOME PATCHY FOG IN THE KOTM AREA AROUND SUNRISE.

OUTLOOK...UPPER LOW WILL CONTINUE EAST WITH UNSETTLED WEATHER AND
AREAS OF MVFR CONDITIONS WED AND WED NIGHT. IMPROVEMENT IS
EXPECTED THURSDAY AND  FRIDAY WITH HIGH PRESSURE BUILDING INTO
THE AREA.

&&

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

$$

SHORT TERM...COGIL
LONG TERM...FAB
AVIATION...MS SEP 14



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