Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 170455
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1155 PM CDT THU APR 16 2015

...UPDATED FOR AVIATION DISCUSSION...

.SHORT TERM /TONIGHT/...
ISSUED AT 334 PM CDT THU APR 16 2015

MAIN FORECAST CONCERN DEALT WITH LOW TEMPERATURES
OVERNIGHT AND LIGHT SHOWER POTENTIAL ACROSS SOUTHWEST IOWA THIS
EVENING. LARGE SURFACE HIGH LOCATED OVER THE GREAT LAKES REGIONS
CONTINUES TO HELP FEED DRY AIR INTO THE STATE AND VOID ANY AREA OF
SHOWER POTENTIAL ACROSS THE FORECAST AREA. A WEAK RIPPLE OF
VORTICITY AND QG FORCING LOOKS TO MOVE NORTHWARD INTO EASTERN
NEBRASKA AND SNEAKS INTO WESTERN IOWA TONIGHT AHEAD OF THE VERY SLOW
MOVING CUTOFF LOW OVER THE DESERT SOUTHWEST. HOWEVER...LOW
CONFIDENCE WITH ANY MEASURABLE PRECIPITATION WITH THE LIMITED
MOISTURE AVAILABLE AND THIS ENERGY SHOULD STAY IN FAR WESTERN IOWA.
WENT COMPLETELY DRY FOR THE FORECAST AREA TONIGHT INTO FRIDAY
MORNING. THE HIRES MODELS KEEP CONDITIONS DRY THIS EVENING. FOR
TEMPERATURES...WENT SLIGHTLY WARMER WRT TO LOWS TONIGHT FROM
PREVIOUS FORECAST...MAINLY BASED ON A LITTLE MORE CLOUD COVER AND
MUCH OF CENTRAL IOWA GETTING WARMER THIS AFTERNOON. STILL WENT
SLIGHTLY BELOW GUIDANCE OVERALL.

.LONG TERM /FRIDAY THROUGH THURSDAY/...
ISSUED AT 334 PM CDT THU APR 16 2015

PATTERN WILL BE SLOW TO EVOLVE THROUGH THE PERIOD WITH MUCH OF THE
SENSIBLE WEATHER ON THE COOL SIDE OF SPRING...ESPECIALLY BY NEXT
WEEK.  INITIAL CONCERN WILL BE THE EVOLUTION OF LARGE MEANDERING
CLOSED UPPER LOW...CURRENTLY NEAR THE FOUR CORNERS REGION...WHICH
SHOULD OPEN AS IT APPROACHES THE MO VALLEY SUN. FORCING ASSOCIATED
WITH THIS FEATURE WILL GRADUALLY MATURE WITH A SLOW WEST TO EAST
INCREASE IN PRECIP CHANCES FRI INTO SAT. LITTLE IS ANTICIPATED FRI
DURING THE DAY OUTSIDE OF POSSIBLY WEST...LIKELY SOMETHING SIMILAR
TO WHAT IS CURRENTLY OVER ERN NE. THIS WILL ALLOW LOW LEVEL TEMPS
TO CONTINUE SLOWLY WARMING WITH A CATEGORY OR TWO INCREASE IN
HIGHS FROM TODAY.

BY SATURDAY KINEMATIC AND THERMODYNAMIC FORCING WILL BE ON THE MOVE
AND MATURE SOMEWHAT PRODUCING MORE WIDESPREAD PRECIP AND BETTER
SATURATION. HAVE CATEGORICAL AND LIKELY POPS BY LATE IN THE DAY
TO REFLECT THIS THINKING. SOME SHALLOW MIXING WILL ALLOW FOR SOME
SURFACE BASED POTENTIAL...BUT GENERALLY MOIST ADIABATIC LAPSE
RATES WILL KEEP INSTABILITY ON THE LOW SIDE. SOUNDINGS SHOW WINDS
FAIRLY UNIDIRECTIONAL AS WELL SO LITTLE EFFECTIVE SHEAR OR SEVERE
THREAT. LAST ROUND OF FORCING WITH IMMEDIATE SHORT WAVE PASSAGE
WILL REACH IA SUN WITH ANOTHER ROUND OF LIKELY POPS.

SHORT WAVE CURRENTLY OFF THE BC COAST WILL THEN MATURE AS IT CROSSES
THE SRN CANADIAN PROVINCES AND NRN U.S. PLAINS EVENTUALLY PHASING
WITH MO VALLEY REMNANTS TO FORM WRN GREAT LAKES MEAN TROUGH. THIS
WILL MOVE LITTLE IN THE EXTENDED...ONLY REACHING THE ERN GREAT
LAKES BY THU KEEPING KEEP TEMPS AT OR BELOW NORMAL INTO NEXT WEEK
AND PRECIP PATTERN FAIRLY INACTIVE. NW FLOW WAVES MAY BRING LIGHT
PRECIP NORTH AND EAST AROUND WED AND POSSIBLY ALONG MO VALLEY
BAROCLINIC ZONE THU...BUT ANY PRECIP WOULD APPEAR TO BE TRANSIENT
AND ON THE WEAK SIDE WITH LITTLE FORCING.

&&

.AVIATION...17/06Z
ISSUED AT 1153 PM CDT THU APR 16 2015

KEPT VFR CONDITIONS THROUGHOUT THE FCST PERIOD...REMOVING MENTION
OF BR FROM PVS TAF PACKAGE. THERE MAY BE EVENING SHOWERS IN WEST
CENTRAL IA...IMPACTING KFOD AND POSSIBLY KDSM. CONFIDENCE IN
TIMING TOO LOW AND PRECIP MAY NOT ARRIVE UNTIL 12Z SAT. WILL
MONITOR IN FUTURE UPDATES.

&&

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

$$

SHORT TERM...PODRAZIK
LONG TERM...SMALL
AVIATION...KOTENBERG



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