549  
FXUS63 KDMX 241743  
AFDDMX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DES MOINES IA  
1143 AM CST TUE JAN 24 2017  
   
..UPDATED AVIATION DISCUSSION
 
 
   
SHORT TERM
 
/TODAY THROUGH WEDNESDAY/  
ISSUED AT 349 AM CST TUE JAN 24 2017  
 
LOTS TO LOOK AT WITH THE IMPENDING STORM SYSTEM WITH OVERALL MODELS  
IN FAIR AGREEMENT ON TRACK, TIMING AND AMOUNTS. BIGGEST ISSUE IS A  
VERY INTENSE BAND OF HIGHER SNOWFALL RATES/SNOWFALL AMOUNTS EXPECTED  
TO SETUP SOMEWHERE IN NRN/NW IOWA, SO HARD TO NAIL THAT DOWN.  
ADDITIONALLY, EXPECT A VERY SHARP GRADIENT ON THE SOUTH/SOUTHEAST  
SIDE OF THE SNOW SETTING UP SOMEWHERE ACROSS CENTRAL IA. THEREFORE  
THERE COULD BE A BIG SPREAD IN AMOUNTS OF SNOWFALL FROM A LOT TO  
VERY LITTLE ACROSS EVENING ONE COUNTY.  
 
CURRENTLY HAVE AN AREA OF HIGH PRESSURE SITUATED ACROSS THE EASTERN  
CWA WITH THIS QUICKLY MOVING EAST AS THE DEVELOPING AREA OF LOW  
PRESSURE SITUATED ACROSS SE CO/SW KS/WRN OK LIFTS ENE TODAY. MODELS  
HAVE ALL INITIALIZED FAIRLY WELL WITH CURRENT PLACEMENT OF THE SFC  
LOW, WITH THE SFC LOW TO LIFT INTO FAR NE KS BY 00Z THIS EVENING AND  
CONTINUE LIFTING INTO IOWA TO BE SITUATED ACROSS EAST CENTRAL IA BY  
12Z WEDNESDAY. MOISTURE TO STREAM NORTHWARD AHEAD OF THE LOW TODAY,  
WITH STRONG WAA AND THETA-E ADVECTION. LIFT TO INCREASE ACROSS THE  
CWA TODAY AND BE STRONGEST ACROSS THE AREA BY LATE AFTERNOON INTO  
TONIGHT. MODEL CROSS-SECTIONS INDICATING LARGE AREA OF INSTABILITY  
ALOFT ESPECIALLY ACROSS THE SOUTHEASTERN 2/3RDS THIS  
AFTERNOON/EVENING, THEREFORE HAVE ADDED IN SOME THUNDER TO MUCH OF  
THE AREA. THIS COINCIDES WITH THE TIMING OF THE SFC LOW TRACKING  
ACROSS THE SOUTHERN PORTION OF THE STATE AND THE SFC WARM FRONT  
LIFTING NORTHWARD INTO THE SOUTHERN CWA. INSTABILITY ALOFT ACROSS  
THE FAR NORTH AS WELL INTO THIS EVENING, WITH -EPV SUGGESTING CHANCE  
FOR THUNDER SNOW AND MESOSCALE BANDING OF SNOW POSSIBLE. VERY STRONG  
LIFT IN THE DENDRITIC ZONE AS WELL SHOW EXPECT ENHANCED SNOW RATES  
THIS EVENING IN THE NORTH. QPF HAS INCREASED GREATLY WITH THIS  
STORM, THUS THE RISING SNOW TOTALS. GREATER MOISTURE AND INSTABILITY  
WILL LEAD TO ANOTHER PUSH OF SNOW AMOUNTS HIGHER ACROSS THE FAR  
NORTH/NORTHWEST WITH TOTALS CLOSE TO 8-12 INCHES IN THE FAR  
NORTH/NORTHWESTERN TIERS. COULD EVEN SEE A VERY NARROW BAND OF  
HIGHER AMOUNTS POSSIBLE IN THE FAR NORTH/NORTHWEST TOWARD PALO  
ALTO/EMMET/KOSSUTH COUNTY REGIONS TOWARD HANCOCK AND WINNEBAGO AS  
WELL.  
 
HWY 20 CORRIDOR TO SEE MODERATE TO HEAVY AMOUNTS OF SNOW AND MAY  
HAVE SOME SHORTER PERIODS OF ENHANCED RATES WITH SOME INSTABILITY,  
AND WITH THE SLIGHTLY FURTHER SOUTH/COLDER TRACK WITH THE LATEST  
SOLUTIONS EXPECT HIGHER SNOWFALL INTO WEST CENTRAL IA/HWY 30  
CORRIDOR. THEREFORE SOME ADDITIONS TO THE WINTER STORM WARNING AND  
ADVISORY HAVE BEEN MADE. OTHERWISE FURTHER SOUTH MAINLY RAIN  
EXPECTED WITH THAT TIGHT GRADIENT BETWEEN MODERATE ACCUMULATIONS OF  
SNOW AND MAINLY RAIN. AS COLDER AIR WRAPS INTO THE SYSTEM AND  
DEFORMATION ZONE MOVES THROUGH THE CWA WEDNESDAY SOME LIGHT SNOW  
ACCUMULATIONS ALSO EXPECTED WHERE THE RAIN IS EXPECTED TODAY. MAINLY  
A TRACE TO POSSIBLE 1-2 INCHES EXPECTED IN THAT AREA. WINDS ALSO  
PICK UP ON THE BACKSIDE OF THE SYSTEM WITH PUSH OF COLDER AIR LATE  
TONIGHT INTO WEDNESDAY. STILL HAVE 25-35 KTS IN THE MIXED LAYER  
ACROSS THE NORTH, SO AREAS OF BLOWING SNOW STILL A CONCERN THROUGH  
THE DAY WEDNESDAY. CONFINED MENTION OF BLOWING SNOW TO AREAS THAT  
ARE EXPECTED TO RECEIVE AT LEAST A FEW INCHES OF SNOW. ALTHOUGH SOME  
VERY MINOR BLOWING OF SNOW POSSIBLE WHILE SNOW IS FALLING IN THE  
OTHER AREAS AS WELL. OVERALL KEPT TIMING OF THE WSW SIMILAR, ONLY  
DELAYING THE START TIME EAST OF I-35 TO 12Z GIVEN SLIGHT DELAY IN  
ONSET OF STEADIER PRECIPITATION. STILL LOOKS LIKE MAJORITY OF THE  
SNOW AND DIMINISHING WINDS EXPECTED BY WEDNESDAY EVENING/00Z  
THURSDAY SO WILL KEEP THE END TIME AS IS.  
   
LONG TERM
 
/WEDNESDAY NIGHT THROUGH MONDAY/  
ISSUED AT 349 AM CST TUE JAN 24 2017  
 
BY WEDNESDAY NIGHT THE EARLY WEEK STORM SYSTEM DISCUSSED IN THE  
SHORT TERM SECTION ABOVE WILL BE PULLING OFF TO THE EAST, WITH  
JUST SOME LINGERING LIGHT SNOW AND GRADUALLY DIMINISHING WINDS  
OVERNIGHT. THE REMAINDER OF THE LONG TERM FORECAST IS GENERALLY  
QUIET, WITH PERIODIC LIGHT SNOW CHANCES AND OVERALL MODERATE  
TEMPERATURES.  
 
BETWEEN THURSDAY NIGHT AND SUNDAY THREE MORE SHORTWAVE TROUGHS  
WILL MOVE OVER IOWA THROUGH A LARGE CYCLONIC FLOW REGIME ALOFT.  
THIS WILL KEEP TEMPERATURES A BIT COOLER, THOUGH STILL NEAR OR  
JUST ABOVE NORMAL FOR THE SEASON, AND PROVIDE ADDITIONAL  
OPPORTUNITIES FOR FLURRIES OR LIGHT SNOW AT TIMES BUT WITH LITTLE  
ACCUMULATION. THE BEST SNOW CHANCES WILL LIKELY COME AROUND  
SATURDAY NIGHT AND SUNDAY WITH THE PASSAGE OF THE THIRD AND  
STRONGEST TROUGH, BUT MOISTURE WILL BE LIMITED AND AT THIS TIME IT  
APPEARS THAT ONLY A LIGHT SNOW EVENT WOULD BE IN STORE.  
 
FROM SUNDAY NIGHT INTO MONDAY A DEEP LAYER RIDGE WILL MOVE QUICKLY  
THROUGH THE REGION, ALLOWING TEMPERATURES TO MODERATE A BIT. JUST  
BEYOND THE END OF THE SEVEN-DAY FORECAST PERIOD, AROUND NEXT  
MONDAY NIGHT AND TUESDAY, THERE MAY BE ANOTHER PRECIPITATION  
EVENT. LONG RANGE MODELS DIVERGE RATHER SIGNIFICANTLY IN THEIR  
SOLUTIONS DURING THIS PERIOD, BUT AT THIS TIME IT APPEARS THAT  
IOWA WOULD BE ON THE SOUTHERN FRINGE OF ANY APPRECIABLE  
PRECIPITATION FROM THIS SYSTEM.  
 

 
   
AVIATION
 
/FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON/  
ISSUED AT 1138 AM CST TUE JAN 24 2017  
 
BAND OF HEAVY SNOW WILL IMPACT FOD TO MCW THIS AFTERNOON AND  
CONTINUE THROUGHOUT THE EVENING TONIGHT. LIFR VISIBILITY AND  
CEILINGS ARE LIKELY WITH THIS BAND TONIGHT AND THEN WINDS  
INCREASE PAST 06Z AND LOOK TO CAUSE IFR AND POSSIBLY LIFR  
VISIBILITY DUE TO BLSN. ALO IS ON THE SOUTHERN FRINGE OF THE HEAVY  
BAND BUT WILL SEE EXPERIENCE IFR/LIFR CEILINGS BUT LOWER  
CONFIDENCE IN THE VISIBILITY RESTRICTIONS AS THE PRECIP MAYBE A  
RAIN/SNOW MIX AT TIMES. THUNDER IS POSSIBLE AT DSM AND OTM AND  
HAVE MENTIONED THIS EVENING. STILL ANTICIPATING LIFR/IFR CEILINGS  
AT OTM/DSM FOR MUCH OF THE TAF PERIOD WITH LIFR TO MVFR VISIBILITY  
RESTRICTIONS.  
 

 
   
DMX WATCHES/WARNINGS/ADVISORIES
 
 
WINTER WEATHER ADVISORY UNTIL 6 PM CST WEDNESDAY FOR IAZ047-048-  
057-058.  
 
WINTER STORM WARNING UNTIL 6 PM CST WEDNESDAY FOR IAZ004>006-015-  
016-023>025-033>036-044>046.  
 
WINTER STORM WARNING FROM 3 PM THIS AFTERNOON TO 6 PM CST  
WEDNESDAY FOR IAZ007-017-026>028-037.  
 
WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 6 PM CST  
WEDNESDAY FOR IAZ038-039.  
 

 
 

 
 
SHORT TERM...BEERENDS  
LONG TERM...LEE  
AVIATION...PODRAZIK  
 
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