Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 282339
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
539 PM CST SUN DEC 28 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 331 PM CST SUN DEC 28 2014

MAIN CONCERN WILL BE PRECIP TRENDS THROUGH THE PERIOD. LONG WAVE
TROUGH CONTINUES TO MATURE OVER THE WRN CONUS WITH ONLY MINOR SHORT
WAVES DRIFTING THROUGH THE CENTRAL PLAINS BETWEEN STRONGER SRN AND
NRN STREAMS. THESE FEATURES HAVE INDUCED SOMEWHAT WEAK KINEMATIC
FORCING WHICH IS EXPECTED TO SPREAD INTO IA OVERNIGHT. MID LEVEL
FORCING AND MAINLY VIRGA SHOULD REACH WELL ACROSS NRN IA BY 06Z.
HOWEVER DRIER AIR BELOW 3KM WILL LIMIT WHAT REACHES THE
GROUND...MAINLY TO W CENTRAL SECTIONS. OMEGA AND QG FORCING MAX WILL
ATTEMPT TO PRODUCE HIGHER RATES ALONG THE MO RIVER NEAR OMAHA...BUT
MOISTURE WILL BE A LIMITING FACTOR. LIFT IS FAIRLY WEAK...BUT WITH
MAX UPWARD VERTICAL MOTION NEAR THE DENDRITIC GROWTH ZONE THIS HAS
ENHANCED SNOW RATIOS SOMEWHAT INTO THE UPPER TEENS. WEAK LIFT AND
RESULTANT LOW QPF AMOUNTS WILL NOT MAKE THIS TOO SIGNIFICANT
HOWEVER. TEMPS WILL BE RELATIVELY FLAT TONIGHT WITH INCREASING
CLOUDINESS. INITIAL SURFACE PRESSURE TROUGH/WIND SHIFT WILL SAG
SOUTHWARD THROUGH IA...BUT ACTUAL ARCTIC BOUNDARY WILL REMAIN
JUST NORTH OF IA THROUGH 12Z.

.LONG TERM /MONDAY THROUGH SUNDAY/...
ISSUED AT 331 PM CST SUN DEC 28 2014

EXPECT PRECIPITATION TO BE ONGOING FOR BEGINNING OF PERIOD IN THE
WEST. BEST FORCING WILL BE BETWEEN 12-18Z...AND HAVE KEPT HIGHEST
POPS WITHIN THIS TIME. FORCING WILL REMAIN RELATIVELY WEAK
HOWEVER...AND HAVE KEPT TOTALS AROUND AN INCH. BEST FORCING WILL
BE ACROSS THE SOUTHWEST CORNER OF IOWA...AND HAVE KEPT POPS
CONFINED TO THIS AREA...THOUGH MODELS CONTINUE TO ATTEMPT TO
PRODUCE PRECIPITATION FURTHER NORTH. HAVE CONCERNS WITH EXTENT OF
MOISTURE ACROSS THE NORTH AS VERY LARGE AREA OF HIGH PRESSURE
PUSHES INTO AREA. THIS WILL ALSO HELP TO LIMIT DURATION OF
SNOWFALL...AND MAY HAVE HELD ONTO POPS TOO LONG MONDAY.

AREA OF HIGH PRESSURE WILL THEN PUSH SOUTH THROUGH
NE/KS...DOMINATING WEATHER THROUGH MID WEEK. CONDITIONS WILL BE
DRY...HOWEVER VERY COLD AIR WILL SPILL OVER THE AREA. WITH HIGH
PUSHING IN MONDAY...WILL SEE GENERALLY STEADY TEMPERATURES IN THE
NORTH AND TEMPERATURES DROPPING QUICKLY THROUGH THE LATE
AFTERNOON. COLD TEMPERATURES WILL REMAIN THROUGH TUESDAY NIGHT
BEFORE HIGH PULLS EAST AND SURFACE WINDS RETURN TO
SOUTHERLY...HELPING TO BRING A SLIGHT WARM UP.
OVERALL...TEMPERATURES WILL BE 10 DEGREE OR MORE BELOW NORMAL
THROUGH WEDNESDAY. MAIN CONCERN WILL BE WITH OVERNIGHT LOWS AND
WIND CHILL VALUES. WINDS WILL REMAIN STRONGER WITH CENTER OF HIGH
WELL TO THE WEST. WINDS MAY HELP TO KEEP TEMPERATURES FROM
DROPPING TO COLD OVERNIGHT...THOUGH HAVE KEPT TEMPERATURES BELOW
ZERO MONDAY NIGHT AND TUESDAY NIGHT ACROSS AREAS WITH SNOW IN THE
NORTH. WITH COLD TEMPERATURES AND WINDS NEAR 10KTS...WILL SEE
BITTERLY COLD WINDCHILL VALUES...ESPECIALLY IN THE NORTH. WILL
LIKELY NEED A WIND CHILL ADVISORY ACROSS THE NORTH MONDAY NIGHT
AND POSSIBLY TUESDAY NIGHT. HOWEVER...WILL LEAVE FOR FUTURE SHIFTS
TO FINE TUNE LOW TEMPERATURES AND WINDS AS A SHIFT IN THE TRACK
OF THE HIGH WOULD IMPACT CURRENT FORECAST.

COLD WILL BE RELATIVELY SHORT LIVED AS LOW LIFTS OUT FOR END OF
THE PERIOD...TEMPERATURES WILL WARM...RETURNING TO NEAR NORMAL
FOR END OF WEEK AND BEGINNING OF THE NEW YEAR.
HOWEVER...TEMPERATURES WILL REMAIN GENERALLY NEAR OR BELOW
FREEZING. MODELS CONTINUE TO BE IN POOR AGREEMENT WITH NEXT LOW
PRESSURE SYSTEM FOR END OF PERIOD. MODELS HAVE COME INTO BETTER
AGREEMENT WITH EVOLUTION OF SYSTEM...THOUGH TIMING REMAINS
INCONSISTENT. LOW PRESSURE SYSTEM IS EXPECTED TO LIFT NORTHEAST
FROM FOUR CORNERS REGION. GFS IS MUCH FASTER WITH SYSTEM...LIFTING
LOW THROUGH MISSOURI BY SATURDAY. ECMWF IS SLOWER AND FURTHER
SOUTH...BRINGING SYSTEM INTO SOUTHERN MISSOURI AND NORTHERN
ARKANSAS BY SUNDAY. HAVE TRENDED FORECAST TOWARDS GFS WITH
PRECIPITATION CHANCES BEGINNING FRIDAY...AS THIS HAS BEEN A
SLIGHTLY MORE CONSISTENT WITH HANDLING OF SYSTEM. HOWEVER...MAIN
CONCERN WILL BE WITH HOW QUICKLY HIGH DEPARTS...AS THIS MAY SLOW
PROGRESSION OF LOW OR PUSH IT FURTHER SOUTH...CLOSER TO ECMWF
SOLUTION. THIS SYSTEM WILL NEED TO BE MONITORED...ESPECIALLY GIVEN
MODEL INCONSISTENCIES AND POSSIBILITY FOR ACCUMULATING SNOWFALL.
BEYOND PERIOD...MODELS BRING IN ANOTHER SHOT OF COLD AIR FOR
REGION EARLY NEXT WEEK.

&&

.AVIATION...29/00Z
ISSUED AT 539 PM CST SUN DEC 28 2014

MAINLY VFR CONDITIONS ARE EXPECTED TONIGHT...WITH LOWER CIGS
LIKELY BY MONDAY MORNING. CURRENTLY A NARROW BAND OF MVFR AND
LOWER CIGS IS APPROACHING FROM SOUTHERN MN...BUT THE CIGS BLO
FL010 ARE CONFINED TO SW MN AND SHOULD NOT IMPACT THE TERMINALS.
HOWEVER...FORECAST SOUNDINGS AND HI RES MODELS INDICATE
INCREASING LOW LEVEL MOISTURE WITH STRATUS DEVELOPING IN SITU
ACROSS PARTS OF CENTRAL IA OVERNIGHT DESPITE THE RELATIVELY DRY
AIR COMING IN FROM HIGH PRESSURE TO THE NORTH. FOR NOW HAVE
ADVERTISED FEW-SCT ANYWHERE FROM FL020 DOWN LATER TONIGHT BUT WILL
NEED TO WATCH THIS CLOSELY. BY MONDAY MORNING MVFR CIGS AND -SN
SHOULD BE COMMONPLACE...THEN END/IMPROVE LATER MONDAY AS THE HIGH
PRESSURE AREA REALLY BEGINS TO ASSERT ITSELF.

&&

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

&&

$$

SHORT TERM...SMALL
LONG TERM...AWB
AVIATION...LEE



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