Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 292035
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
335 PM CDT MON SEP 29 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 335 PM CDT MON SEP 29 2014

FRONTAL BOUNDARY WILL CONTINUE TO SLIDE SOUTH ACROSS THE REMAINDER
OF THE STATE THIS EVENING WITH DECENT PUSH FROM HIGH PRESSURE MOVING
INTO THE NORTHERN GREAT LAKES. HOWEVER...THIS BOUNDARY WILL LOSE
MOMENTUM IN NORTHERN MISSOURI AS STRONG UPPER SYSTEM LIFTS INTO
THE NEBRASKA PANHANDLE. WARM ADVECTION WILL BE ON THE INCREASE
TOWARD DAYBREAK IN RESPONSE TO THE APPROACHING UPPER SYSTEM WITH
SOUTHWEST 850MB FLOW STRENGTHENING. LOW LEVELS WILL MOISTEN
QUICKLY WITH LOW CLOUDINESS LIKELY DEVELOPING ACROSS MUCH OF THE
FORECAST AREA OVERNIGHT. AT THIS POINT...HAVE LEFT OUT THE THREAT
OF PRECIPITATION AS MID AND HIGH LEVELS REMAIN RELATIVELY DRY AND
LIFT REALLY DOESNT GET GOING UNTIL TUESDAY.

.LONG TERM /TUESDAY THROUGH MONDAY/...
ISSUED AT 335 PM CDT MON SEP 29 2014

THE LONG TERM FORECAST REMAINS ON TRACK WITH OUR MILD AND DRY
WEATHER TRYING TO HANG ON THROUGH TUESDAY MORNING...THEN BEING
REPLACED BY A VERY WET AND INCREASINGLY COOL WEATHER PATTERN FOR
THE REST OF THE WEEK. SHOWERS AND STORMS LOOK TO ENTER OUR WESTERN
COUNTIES SHORTLY AFTER NOON ON TUESDAY AND FADE OUT AS THEY
PROGRESS EASTWARD THROUGH TUESDAY EVENING...THEN ADDITIONAL ROUNDS
OF STORMS WILL DEVELOP FROM LATE TUESDAY NIGHT INTO
WEDNESDAY...AND AGAIN ON WEDNESDAY NIGHT. LOW LEVEL FLOW WILL BE
FROM THE SOUTHEAST DURING THIS TIME FRAME...WITH THE SYNOPTIC
COLD FRONT REMAINING TO OUR NORTHWEST AND THE PRECIPITATION BEING
GENERATED BY A SERIES OF SHORTWAVE TROUGHS MOVING THROUGH THE
CYCLONIC FLOW ALOFT. ANY SEVERE WEATHER THREAT WILL BE LIMITED DUE
TO A RELATIVE LACK OF INSTABILITY AND WEAK LOW LEVEL FLOW...BUT
THERE IS SOME MARGINAL THREAT MAINLY IN OUR WESTERN COUNTIES
CLOSER TO THE STRONG VERTICAL FORCING ASSOCIATED WITH THE PATH OF
THE VARIOUS VORTICITY MAXIMA MOVING OVERHEAD. OF GREATER
CONSEQUENCE WILL BE THE POTENTIAL FOR HEAVY RAIN...WHICH DOES NOT
APPEAR PARTICULARLY IMPRESSIVE AT ANY GIVEN TIME BUT WITH SEVERAL
ROUNDS OF RAINFALL FORECAST COULD RESULT IN SOME HIGHER TOTAL
ACCUMULATIONS OVER THE TWO DAYS OR SO OF THIS PATTERN.

ON THURSDAY THE SYNOPTIC FRONT WILL FINALLY BLOW THROUGH...LIKELY
CLEARING OUT THE RAIN FOR A TIME DURING THE DAY...HOWEVER THERE IS
AN INCREASING SIGNAL THAT ANOTHER SHARP 500 MB WAVE MOVING THROUGH
ON THURSDAY AFTERNOON AND EVENING COULD TRIGGER ONE MORE ROUND OF
SHOWERS DURING THAT PERIOD. THIS WILL BE DEPENDENT ON HOW MUCH
ATMOSPHERIC MOISTURE REMAINS IN THE COLUMN AS WELL AS THE TIMING
AND ORIENTATION OF SAID SHORTWAVE...BUT FEEL IT IS WORTH INCLUDING
CHANCE POPS UNTIL THESE DETAILS BECOME CLEARER. AT ANY RATE THE
LATE THURSDAY WAVE AND ANOTHER CLOSE ON ITS HEELS THURSDAY NIGHT
WILL REALLY SCOUR THINGS OUT FOR THE WEEKEND. FROM FRIDAY ONWARD
TEMPERATURES WILL BE SHARPLY COOLER...ALTHOUGH NO FREEZE IS
ANTICIPATED...AND IT WILL FEEL POSITIVELY FALL LIKE WITH STRONG
BREEZES...PARTICULARLY ON FRIDAY...AND A CRISP FEEL TO THE AIR AS
DEWPOINTS FALL INTO THE 30S AND 40S.

&&

.AVIATION...29/18Z
ISSUED AT 1231 PM CDT MON SEP 29 2014

BOUNDARY DRAPED ACROSS THE STATE WILL CONTINUE TO SETTLE TO THE
SOUTH THROUGH THIS EVENING AS HIGH PRESSURE MOVES ACROSS THE GREAT
LAKES. LOW STRATUS ON THE BACKSIDE OF THE BOUNDARY HAS GENERALLY
HALTED ITS ADVANCE ACROSS THE FAR NORTH WITH MVFR TO IFR CONFINED
THERE. ELSEWHERE...WIDESPREAD VFR CONDITIONS WILL CONTINUE THIS
AFTERNOON INTO THE EVENING HOURS WITH LIGHT SURFACE WINDS. LIKELY
TO SEE SOME LOWER CEILINGS DEVELOP ON THE BACKSIDE OF THE FRONT
LATE TONIGHT AS WARM ADVECTION AND LIFT INCREASE OVER THE FRONT
OVERNIGHT. HAVE GONE WITH MVFR TO IFR CEILINGS AND VSBYS OVERNIGHT
WITH SOME IMPROVEMENT ON TUESDAY MORNING ALTHOUGH THIS MAY BE A
BIT ROBUST GIVEN THE TIME OF YEAR AND LATER SHIFTS MAY HAVE TO
ADJUST TIMING BACK EVEN MORE.

&&

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

&&

$$

SHORT TERM...COGIL
LONG TERM...LEE
AVIATION...COGIL



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