167  
FXUS63 KDMX 180026  
AFDDMX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DES MOINES IA  
724 PM CDT SUN JUN 17 2018  
   
..UPDATED FOR 08/00Z AVIATION DISCUSSION
 
 
   
DISCUSSION
 
/TONIGHT THROUGH SUNDAY/  
ISSUED AT 354 PM CDT SUN JUN 17 2018  
 
SPOTTY SHOWERS BENEATH AREAS OF CLOUDS ARE TRAVERSING NORTHWEST AND  
NORTH CENTRAL IOWA AT MID-AFTERNOON. WITH THESE, HAVEN'T SEEN ANY  
LIGHTNING AND GOES-EAST DAY CLOUD PHASE DISTINCTION SHOWS LIMITED IF  
ANY ICE INTRODUCTION UP TO THIS POINT. A FEW THUNDERSTORMS THOUGH  
HAVE RECENTLY FORMED AND MOVING INTO THE OMAHA METRO. ALL OF THIS  
ACTIVITY IS BEING FORCED BY A SUBTLE SHORTWAVE TROUGH MOVING THROUGH  
THE AREA NOW. BETTER CHANCE FOR WIDESPREAD STORMS WILL GENERALLY BE  
NORTH OF THE STATE ALONG THE FRONT THAT WILL EVENTUALLY SLIP INTO  
IOWA, BUT STILL LIKELY TO SEE RAIN AND STORMS OVER OUR FAR NORTHERN  
COUNTIES TONIGHT. PRECIPITABLE WATER VALUES WILL BE OVER 2 INCHES TO  
NEAR 2.5 INCHES WITH WARM CLOUD DEPTHS OF 13000 TO 14500 FEET. MEAN  
FLOW OF 25 TO 30 KNOTS WILL KEEP STORMS MOVING, BUT MAY END UP  
PARALLEL TO THE FRONT YIELDING TRAINING STORMS. RAINFALL AMOUNTS  
WERE INCREASED USING A BLEND OF THE HREF, NBM, AND SUPERBLEND  
GUIDANCE, WHICH PUTS AMOUNTS NEAR 1 INCH TOWARD ESTHERVILLE. LOCALLY  
HIGHER VALUES STILL POSSIBLE. SPC STILL HAS OUR NORTHERN COUNTIES  
WITH A MARGINAL RISK OF HAIL OR DAMAGING WIND GUSTS AND WHILE MLCAPE  
OF 1000 J/KG IS SUFFICIENT FOR STORMS, BETTER ORGANIZATION WILL BE  
LIMITED BY DEEP LAYER SHEAR OF LESS THAN 30 KNOTS.  
 
THE FRONT WILL SLOWLY DROP INTO THE STATE ON MONDAY WITH AN OVERALL  
LULL IN THE CONVECTION. THE HEAT ADVISORY WILL BE ALLOWED TO EXPIRE  
FOR THE NORTHERN PART OF THE STATE THIS EVENING AS CLOUDS OR SHOWERS  
WILL BRING RELATIVELY COOLER WEATHER ON MONDAY. FOR THE I-80  
COUNTIES AND POINTS SOUTH, WILL EXTEND ADVISORY AS WARM AND QUITE  
HUMID AIR WILL CONTINUE. THERE IS STILL POTENTIAL, ESPECIALLY NEAR I-  
80 COUNTIES, THAT SHOWERS AND STORMS WILL REACH THIS AREA BEFORE  
PEAK HEATING AND HIGHEST HEAT INDEX VALUES ARE REALIZED. HOWEVER,  
BOUNDARY WILL BE CLOSE BY SO COULD HAVE ADDITIONAL MOISTURE  
POOLING/HIGHER DEWPOINTS LEADING TO HEAT INDEX VALUES EDGING OVER  
100 DEGREES.  
 
THE NEXT ROUND OF STORMS AS ALLUDED TO ABOVE WILL BEGIN TO DEVELOP  
MONDAY AFTERNOON AS BETTER Q-VECTOR CONVERGENCE MOVES ACROSS THE  
AREA LATER MONDAY AFTERNOON INTO MONDAY NIGHT. THE HIGHEST CHANCES  
WILL BE NORTH OF HIGHWAY 30. PRECIPITABLE WATER VALUES WILL BE  
AROUND OR ABOVE 2 INCHES ONCE AGAIN WITH WARM CLOUDS DEPTHS OF 13000  
TO NEAR 15000 FEET ACROSS CENTRAL IOWA. MEAN LAYER FLOW WON'T BE AS  
STRONG AT 15 TO 20 KNOTS SO BETTER CHANCE FOR SLOWER MOVING,  
EFFICIENT RAIN PRODUCING STORMS THAN TONIGHT. SIMILAR ADJUSTMENTS  
WERE MADE FOR RAIN AMOUNTS MONDAY NIGHT AS TONIGHT, WHICH BRING A  
GENERAL 1 TO 1.5 INCHES ACROSS MANY AREAS SOUTH OF HIGHWAY 3 AND  
NORTH OF I-80 ROUGHLY WITH LOCALLY HIGHER AMOUNTS EXPECTED. RAIN IS  
EXPECTED TO LINGER INTO TUESDAY AS THE FRONT CONTINUES TO SLOWLY  
MOVE/MEANDER SOUTHWARD INTO NORTHERN MISSOURI. WHILE PRECIPITABLE  
WATER VALUES MAY BE SLIGHTLY LOWER, THE REST OF THE HEAVY RAINFALL  
PARAMETERS STAY ON POINT, JUST MORE SO FOCUSED OVER SOUTHERN  
IOWA. ADDITIONAL DISCUSSION ON HYDROLOGY CONCERNS IS BELOW IN THE  
HYDROLOGY DISCUSSION.  
 
WEDNESDAY INTO SATURDAY, CHANCES FOR SHOWERS AND STORMS WILL  
CONTINUE ACROSS THE STATE WITH THE BEST CHANCES OVER CENTRAL TO  
SOUTHERN IOWA. HIGH TEMPERATURES WILL BE MORE SEASONAL WITH HIGHS IN  
THE UPPER 70S TO LOW 80S. A MORE SUBSTANTIAL TROUGH MOVES TOWARD  
THE AREA ON THURSDAY WITH THE GFS AND NOW THE ECMWF SHOWING IT  
PROPAGATING THROUGH ON FRIDAY INTO SATURDAY WITH DRIER AIR PERHAPS  
BY LATER SATURDAY.  
 

 
   
AVIATION
 
/FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING/  
ISSUED AT 724 PM CDT SUN JUN 17 2018  
 
OFFICIAL TAFS HAVE VFR CONDITIONS THROUGHOUT THIS PERIOD. HOWEVER,  
CHALLENGES REMAIN ON IMPACTS OF STORMS LATER TONIGHT OVER NORTHERN  
IOWA. BETTER CHANCE FOR SHOWERS AND STORMS WITH MVFR OR PERHAPS IFR  
CONDITIONS WILL BE TONIGHT AS A COLD FRONT SINKS INTO THE STATE WITH  
FOCUS ON FOD AND MCW. THEY MAY ALSO IMPACT ALO, BUT THIS IS A LOWER  
CHANCE. LASTLY, A PERIOD OF LOW LEVEL WIND SHEAR IS POSSIBLE TONIGHT  
ACROSS NORTHERN AND CENTRAL IOWA.  
 

 
   
HYDROLOGY
 
 
ISSUED AT 354 PM CDT SUN JUN 17 2018  
 
OVER THE LAST 7 DAYS, THERE HAVE BEEN SEVERAL ROUNDS OF HEAVY  
RAINFALL ACROSS PARTS OF CENTRAL IOWA. DOPPLER RADAR ESTIMATES  
SHOW A GENERAL 2 TO 4 INCHES HAS FALLEN IN AN AREA ROUGHLY BOUNDED  
BY A POLYGON FROM EMMETSBURG TO GRINNELL TO OSKALOOSA TO OSCEOLA  
TO ATLANTIC TO CARROLL AND BACK TO EMMETSBURG. ESTIMATES WITHIN  
THIS POLYGON HAVE LOCAL MAXIMA OF 5 TO 6 INCHES. AMES COOP  
OBSERVER 5 MILES SOUTHEAST OF THE CITY RECORDED 7.56 INCHES FOR  
THIS SAME TIME PERIOD. THIS DOESN'T INCLUDE THE RAIN THAT FELL THE  
FIRST FULL WEEK OF JUNE OVER NORTH CENTRAL IOWA WITH FLOODING IN  
MASON CITY ALONG WILLOW CREEK AND THE WINNEBAGO RIVER AS WELL AS  
ALONG THE SHELL ROCK RIVER IN CLARKSVILLE AND GREENE, WHICH  
LINGERED INTO LAST WEEKEND AND EARLY THIS WEEK.  
 
CURRENT FORECAST RAINFALL THROUGH TUESDAY NIGHT HAS 1.5 TO 2  
INCHES AVERAGE NORTH OF I-80. STILL EXPECTING SOME HIGHER END  
TOTALS CLOSER TO 4 OR 5 INCHES FROM VARIOUS DETERMINISTIC MODELS.  
WITH ANTECEDENT CONDITIONS SETTING THE STAGE AND EXPECTED  
RAINFALL, ISOLATED FLASH FLOODING WILL BE POSSIBLE WITH WPC  
EXCESSIVE RAINFALL OUTLOOK OVER PARTS OF OUR AREA THE NEXT THREE  
DAYS. WHILE RIVER FORECAST CENTER ENSEMBLE HYDROGRAPHS USING BEST  
ESTIMATE 72 HOUR RAINFALL WOULD KEEP MOST RIVERS BELOW FLOOD  
STAGE, THE HIGHER END RAIN TOTALS COULD LEAD TO MINOR OR PERHAPS  
MODERATE FLOODING AS SOME GAUGES. WILL CONTINUE TO MONITOR IN  
FUTURE FORECAST CYCLES IF CONDITIONS WARRANT ISSUANCE OF ANY  
WATCHES.  
 

 
   
DMX WATCHES/WARNINGS/ADVISORIES
 
 
HEAT ADVISORY UNTIL 7 PM CDT MONDAY FOR IAZ057>062-070>075-  
081>086-092>097.  
 
HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR IAZ004>007-015>017-  
023>028-033>039-044>050.  
 

 
 

 
 
DISCUSSION...ANSORGE  
AVIATION...ANSORGE  
HYDROLOGY...ANSORGE  
 
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