Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 131737
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1237 PM CDT SAT SEP 13 2014

.SHORT TERM /TODAY/...
ISSUED AT 323 AM CDT SAT SEP 13 2014

FROST HEADLINE IS SOMEWHAT MARGINAL AT THIS POINT WITH DEWPOINTS
STILL 33-39F IN THE ADVISORY AREA BUT WILL RIDE IT OUT UNTIL 12Z
EXPIRATION AS TEMPS AND DEWPOINTS WILL STILL FALL A FEW DEGREES
INCREASING THE LIKELIHOOD. OTHER THAN THAT THERE IS LITTLE SENSIBLE
WEATHER THIS PERIOD. EFFECTS OF EXITING LONG WAVE TROUGH ARE WELL TO
THE EAST WITH LITTLE FORCING OR MOISTURE UPSTREAM RESULTING IN
PLENTY OF SUNSHINE. AIRMASS HAS CERTAINLY MODERATED SOMEWHAT FROM
FRI BUT IS STILL ANOMALOUSLY COOL. MIXING SUGGESTS HIGHS IN THE
UPPER 50S PUSHING 60F IN SPOTS.

.LONG TERM /TONIGHT THROUGH FRIDAY/...
ISSUED AT 323 AM CDT SAT SEP 13 2014

THE LONG TERM FORECAST IS CHARACTERIZED BY CONTINUED COOL AND
GENERALLY DRY WEATHER FOR MOST OF THE NEXT WEEK. TWO 500 MB
NORTHERN STREAM TROUGHS WILL MOVE OVER THE UPPER MIDWEST IN THE
NEXT FEW DAYS...THE FIRST ON SATURDAY NIGHT AND THE SECOND FROM
SUNDAY NIGHT INTO MONDAY. THE FIRST WILL PUSH A WEAK SURFACE COOL
FRONT ACROSS MINNESOTA INTO FAR NORTHERN IOWA BY MIDDAY
SUNDAY...PROVIDING A FOCUS MECHANISM THAT WILL COMBINE WITH
SLOWLY INCREASING ATMOSPHERIC MOISTURE TO SUPPORT RAIN DEVELOPING
WITH THE SECOND 500 MB TROUGH ON SUNDAY NIGHT/MONDAY MORNING. IT
APPEARS THE MOST LIKELY TIME FOR PRECIPITATION WILL BE LATE SUNDAY
NIGHT AND HAVE INCREASED POPS TO 50 TO 70 ACROSS MUCH OF THE AREA
DURING THIS TIME FRAME...HOWEVER WITH MOISTURE AND INSTABILITY
LIMITED THE RAIN SHOULD BE RELATIVELY LIGHT WITH THUNDER CHANCES
LIMITED TO THE SOUTH AND NO REAL IMPACTS ANTICIPATED.

BEHIND THE SUNDAY NIGHT/MONDAY MORNING SYSTEM A COOL SURFACE HIGH
PRESSURE CENTER WILL MOVE INTO THE REGION...BRINGING RAPID
CLEARING AND COOLER TEMPERATURES MONDAY NIGHT IN A SIMILAR
SITUATION TO WHAT WE ARE EXPERIENCING AT THE CURRENT TIME.
HOWEVER...TEMPERATURES ALOFT WILL BE WARMER WITH THE MONDAY NIGHT
SYSTEM AND FROST/FREEZE THRESHOLDS ARE NOT EXPECTED TO BE MET AT
THIS TIME. DID LOWER MIN TEMPS FOR MONDAY NIGHT APPROPRIATE FOR
THE SET UP. FROM MONDAY THROUGH ABOUT THURSDAY MODEST
NORTHWESTERLY 500 MB FLOW WILL DOMINATE OUR WEATHER RESULTING IN
MOSTLY CLEAR SKIES...LIGHT WINDS AND ONLY A SLOW WARMING TREND. BY
THURSDAY A SUBSTANTIAL 500 MB RIDGE WILL HAVE BUILT DOWN THE
ROCKIES AND HIGH PLAINS OF THE CENTRAL U.S. WITH A LONGWAVE TROUGH
EXTENDING DOWN THE WEST COAST. TOWARD THE END OF NEXT WEEK LONG
RANGE MODEL SOLUTIONS ARE QUITE DIVERGENT AND INCONSISTENT IN
THEIR EVOLUTION OF THIS PATTERN...BUT IN ANY EVENT THE TROUGH WILL
EVENTUALLY MAKE ITS WAY EASTWARD IN SOME FORM BRINGING A RETURN OF
RAIN CHANCES AROUND FRIDAY OR NEXT WEEKEND.

&&

.AVIATION...13/18Z
ISSUED AT 1234 PM CDT SAT SEP 13 2014

GENERALLY QUIET CONDITIONS EXPECTED THROUGH THE PERIOD. VFR BKN
BEGINNING TO FILL IN ON BACK EDGE OF RIDGE AS IT EXITS THE AREA
THIS AFTERNOON. SW WINDS ARE RETURNING AS WELL. WILL SEE CLOUDS
THIN TOWARD 00Z AND WINDS LESSEN AFT 00Z AS MIXING ENDS. OVERNIGHT
WEAK TROUGH APPROACHES WITH MID TO HIGH LEVEL CLOUDS AND SLIGHT
INCREASE IN WINDS AFT 14Z ACROSS THE AREA. OTHERWISE...LITTLE
CONCERN THROUGH THE PERIOD. /REV

&&

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

$$

SHORT TERM...SMALL
LONG TERM...LEE
AVIATION...REV



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