114  
FXUS63 KDMX 300841  
AFDDMX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DES MOINES IA  
341 AM CDT THU MAR 30 2017  
   
SHORT TERM
 
/TODAY THROUGH TONIGHT/  
ISSUED AT 341 AM CDT THU MAR 30 2017  
 
MESSAGE OF THE DAY: RAIN AND CLOUDS CONTINUE...THOUGH LESS RAIN  
TODAY THAN YESTERDAY.  
HAZARDS: MINIMAL CHANCE OF THUNDER POSSIBLE SOUTH, RIVER RISES  
FORECAST CONFIDENCE: MEDIUM-HIGH  
 
SYNOPTICS... 08Z THU WATER VAPOR IMAGERY EASILY PICKING UP UPPER  
LEVEL LOW SPINNING OVER NORTHEASTERN KANSAS AND SLOWLY PROPAGATING  
TO THE NORTHEAST. ADDITIONALLY, WATER VAPOR IMAGERY PICKING UP ON A  
LONGWAVE TROUGH COMING ONSHORE ALONG THE PACIFIC COAST AND DIGGING  
ITS WAY THROUGH CALIFORNIA. THIS TROUGH IS PROGGED TO STRENGTHEN  
INTO A CLOSED LOW BY THURSDAY NIGHT AND WILL HELP PUSH OUR KANSAS  
UPPER LOW EAST OF THE REGION. MODEL CONSENSUS GENERALLY GOOD TO  
FOLLOW, WITH A LEAN TOWARDS THE ECMWF SOLUTION WHICH HAS BEEN MORE  
CONSISTENT RUN-TO-RUN WITH THE EVOLUTION OF THIS SYSTEM.  
 
MESOSCALE... BEST MOISTURE TRANSPORT ALREADY EAST OF THE DMX CWA AS  
WESTERN EDGE OF THE LLJ OUT OF IOWA BY 15Z THU. SUBSEQUENTLY, BEST  
INSTABILITY AND ISENTROPIC/ADIABATIC LIFT ALSO EAST OF THE CWA. THIS  
WILL LEAD TO MUCH LESS PRECIP TODAY THAN YESTERDAY. BY 12Z-15Z THU,  
MODELS TRYING TO PICK UP A BAND OF VORTICITY/FRONTOGENETICAL FORCING  
ORIENTED SW TO NE MOVING ACROSS THE CWA FROM WEST TO  
EAST...PRIMARILY IMPACTING OUR NORTHERN COUNTIES. FCST SOUNDINGS  
SUPPORT SATURATION, WITH CLOUD DEPTHS UPWARDS OF 7 KFT. THIS  
SUGGESTS LIGHT RAIN AS THIS BAND TRAVERSES EASTWARD. AS THE CORE OF  
THE LOW PROPAGATES ACROSS NORTH-CENTRAL MISSOURI, BEST BAND OF 950-  
800MB FRONTOGENETICAL FORCING AND INSTABILITY AXIS WILL REMAIN IN  
MISSOURI, PERHAPS BARELY CLIPPING OUR FAR SOUTHERN/SE CWA BETWEEN  
15Z AND 18Z TODAY. THUS HAVE ISOLATED THUNDER MENTION, BUT  
CONFIDENCE IS LOW IN THUNDER OCCURRENCE. TEMPERATURES TODAY SHOULD  
BE CLOSE TO WHERE THEY WERE YESTERDAY. NO MAJOR CHANGES IN TERMS OF  
CAA OR WAA. SEE NO REASON TO BREAK UP THE ST DECK, MEANING ANOTHER  
GREY DAY ACROSS IOWA WITH A HEAVY LEAN TO PERSISTENCE.  
   
LONG TERM
 
/FRIDAY THROUGH WEDNESDAY/  
ISSUED AT 341 AM CDT THU MAR 30 2017  
 
IOWA WILL BE IN-BETWEEN SYSTEMS ON FRIDAY WITH SUBSIDENCE AS  
BRIEF UPPER RIDGING SLIDES THROUGH THE MIDWEST. THIS WILL LIKELY  
BE THE BEST DAY TO SEE A LITTLE SUNSHINE IN SOME LOCATIONS ACROSS  
THE STATE, MOST LIKELY THE NORTH WHERE DRIER AIR WILL BE DEEPER.  
HOWEVER, WARM ADVECTION BEGINS TO INTENSIFY ON FRIDAY NIGHT INTO  
SATURDAY AHEAD OF NEXT SYSTEM DROPPING INTO THE CENTRAL PLAINS.  
ISENTROPIC LIFT STRENGTHENS INTO SATURDAY WITH CLOUDS THICKENING  
AND SOME LIGHT RAIN POSSIBLE BY AFTERNOON, ESPECIALLY IN WESTERN  
IOWA WHERE DEEPER SATURATION WILL OCCUR AFTER MIDDAY. THE BETTER  
SURGE OF MOISTURE ARRIVES SATURDAY NIGHT WITH LIGHT RAIN BECOMING  
WIDESPREAD ACROSS MUCH OF CENTRAL IOWA. SOUTHERN IOWA WILL SEE THE  
BEST SHOT OF PRECIPITATION AND QPF AMOUNTS WHERE FORCING WILL BE  
MAXIMIZED NORTH OF THE SURFACE LOW TRACK. THE SYSTEM IS EXPECTED  
TO DEPART ON SUNDAY AFTERNOON WITH STRONG SUBSIDENCE SPREADING  
ACROSS THE STATE BY SUNDAY NIGHT.  
 
QUIET WEATHER IS EXPECTED ON MONDAY WITH SUBSIDENCE AND DRIER AIR  
OVERSPREADING THE STATE. SURFACE RIDGE AXIS WILL SLIDE OVERHEAD ON  
MONDAY NIGHT, HOWEVER CLOUDS ARE EXPECTED TO INCREASE QUICKLY ON  
THE BACKSIDE OF THE RIDGE WITH WARM ADVECTION TAKING OFF EARLY  
TUESDAY. WHILE A FEW SHOWERS WILL BE POSSIBLE INTO TUESDAY, DRY  
LOW LEVEL AIR WILL TEND TO LIMIT THE OVERALL THREAT. DEEPER AND  
STRONGER FORCING ARRIVES WITH UPPER SYSTEM ON TUESDAY NIGHT INTO  
WEDNESDAY AND THIS WILL BE THE BEST CHANCE OF PRECIPITATION INTO  
THE MIDDLE OF NEXT WEEK. WITH SURFACE LOW TRACKING CLOSE TO THE  
IOWA/MISSOURI BORDER, MUCH OF THE FORECAST AREA WILL BE IN THE  
'COOL' SECTOR WITH STEADIER RAINFALL, HOWEVER CONVECTIVE  
INSTABILITY WILL BE CLOSE TO SOUTHERN IOWA AND A FEW THUNDERSTORMS  
CANNOT BE RULED OUT AT THIS POINT.  
 

 
   
AVIATION
 
/FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING/  
ISSUED AT 614 PM CDT WED MAR 29 2017  
 
IFR CONDITIONS WILL PREVAIL THROUGH MUCH OF THE FORECAST PERIOD  
WITH SOME IMPROVEMENT EXPECTED AFTER 20Z. AN EASTERLY WIND AT  
20G30KTS THIS EVENING WILL GRADUALLY DIMINISH OVERNIGHT THEN  
BECOME NORTHEAST AT 10-20KTS AFT 15Z. SOME CONCERN FOR CONVECTION  
MOVING INTO SOUTHERN TAF LOCATIONS. I DID INCLUDE A TEMPO GROUP  
FOR A FEW HOURS MID TO LATE EVENING IN DSM AND OTM TAF'S.  
 

 
   
DMX WATCHES/WARNINGS/ADVISORIES
 
NONE.  
 

 
 

 
 
SHORT TERM...KOTENBERG  
LONG TERM...COGIL  
AVIATION...FAB  
 
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