Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 212347
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
647 PM CDT THU APR 21 2016

.SHORT TERM.../TONIGHT/
ISSUED AT 409 PM CDT THU APR 21 2016

H300 CUTOFF LOW THAT HAS AFFECTED IOWA SINCE MONDAY WILL FINALLY
BEGIN TO PROGRESS EASTWARD AS IT PHASES WITH A BROAD NORTHERN STREAM
TROUGH AND RIDGING BUILDS OVER THE HIGH PLAINS. SCATTERED CONVECTION
THAT DEVELOPED THIS AFTERNOON WILL WANE THIS EVENING WITH THE LOSS
OF SOLAR INSOLATION. DECAYING DEF ZONE ON THE BACKSIDE OF THE LOW
WILL KEEP A BAND OF CLOUDS PRESENT ACROSS IOWA FOR MUCH OF THE
NIGHT. HAVE NUDGED UP LOWS SLIGHTLY GIVEN THE INCREASE IN FORECAST
CLOUD COVER FROM THE PREVIOUS PACKAGE. LOW LEVEL MOISTURE IN THE
FORM OF A STRATUS DECK ACROSS WEST CENTRAL MINNESOTA PUSHES
SOUTHEASTWARD ACROSS IOWA TOMORROW WHILE WEAK CAA CONTINUES AHEAD OF
THE SURFACE RIDGE AXIS THAT WILL REACH CENTRAL IOWA BY 00Z SATURDAY.
THESE TWO FACTORS WILL KEEP HIGHS ON FRIDAY IN THE LOW TO MID 60S
ACROSS THE CWA WITH H850 TEMPS OF +4 TO +7C.

.LONG TERM.../FRIDAY THROUGH THURSDAY/
ISSUED AT 409 PM CDT THU APR 21 2016

UPPER LEVEL RIDGING WILL MOVE OVER IOWA FRIDAY NIGHT AND WILL
ALLOW WARM ADVECTION TO SPREAD ACROSS THE STATE. AS A RESULT...SATURDAY
WILL BE WARMER WITH HIGH TEMPERATURES RISING INTO THE 70S. ANOTHER
ROUND OF THETA-E ADVECTION WILL ARRIVE OVER WESTERN AND CENTRAL
IOWA BY SATURDAY AFTERNOON. CURRENTLY HAVE NO POPS IN THE FORECAST
FOR SATURDAY AFTERNOON AS THE THETA-E ADVECTION ARRIVES. CERTAINLY
WILL BE ACCOMPANIED BY SOME CLOUDS AND WILL NEED TO MONITOR
POTENTIAL FOR SHOWER CHANCES IF ENOUGH INSTABILITY CAN DEVELOP.
AMOUNT OF DRY AIR THROUGH THE MID LEVELS WILL BE THE LIMITING
FACTOR. THE THERMAL RIDGE WILL MOVE THROUGH SUNDAY AND SUNDAY
NIGHT AS AN UPPER LEVEL LOW APPROACHES FROM THE WEST. THIS SYSTEM
WILL BE OPENING UP AS IT ARRIVES IN A WEAKENING STATE. AN ISOLATED
SEVERE STORM COULD OCCUR.

THE NEXT SYSTEM ON THE HORIZON WILL ARRIVE LATE TUESDAY INTO
TUESDAY NIGHT. THIS WILL FEATURE A CLOSED LOW POTENTIALLY BECOMING
NEGATIVELY TILTED AS IT ARRIVES INTO THE MIDWEST. THIS SYSTEM
LOOKS TO BE MUCH MORE DYNAMIC THAT THIS WEEKENDS SYSTEM. THE
POTENTIAL FOR SURFACE BASED CONVECTIVE DEVELOPMENT WILL DEPEND ON
TIMING. AT THIS TIME...THE PRIMARY DYNAMICS ARRIVE TUESDAY
NIGHT...WHICH WOULD LESSEN THE SURFACE BASED THREAT.

&&

.AVIATION.../FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING/
ISSUED AT 647 PM CDT THU APR 21 2016

ISOLATED SHOWERS AND THUNDERSTORMS SHOULD WANE DURING THE EARLY
EVENING HOURS WITH ATTENTION TURNING TO MN MVFR STRATUS. DETAILS
ARE NOT CLEAR CUT IN TIMING AND COVERAGE OF ITS PROGRESSION...BUT
HAVE ADDED SUB 2KFT MVFR CIGS FOR A PERIOD OVERNIGHT INTO THE
EARLY MORNING HOURS. CONFIDENCE IS NOT THERE FOR IFR AT THIS
POINT...BUT IS A POSSIBILITY AND WILL MONITOR TRENDS. THIS SHOULD
BE FOLLOWED BY VFR AS THE CLOUDS LIFT FROM MIDDAY THROUGH THE END
OF THE PERIOD.

&&

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

&&

$$

SHORT TERM...SKOW
LONG TERM...DONAVON
AVIATION...SMALL



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