393  
FXUS63 KMPX 142222  
AFDMPX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN  
522 PM CDT TUE AUG 14 2018  
   
UPDATE
 
FOR 00Z AVIATION DISCUSSION BELOW  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH WEDNESDAY)  
ISSUED AT 218 PM CDT TUE AUG 14 2018  
 
THE MAIN FORECAST CONCERN IS INITIATION OF THUNDERSTORMS ALONG TWO  
BOUNDARIES DEPICTED ON REGIONAL RADAR AND SATELLITE IMAGERY THIS  
AFTERNOON. THE FIRST WAS LOCATED JUST SOUTH OF THE TWIN CITIES,  
WITH A DIFFUSE AREA IN SOUTH CENTRAL MINNESOTA WHERE EARLIER  
CONVECTION HAD DISSIPATED PRIOR TO 2 PM. THE SECOND AREA WAS NEAR  
WILLMAR, EAST-NORTHEAST TO ELK RIVER AND NORTHEAST INTO NORTHWEST  
WISCONSIN. BETWEEN THESE TWO AREAS, A DENSE CIRRUS SHIELD HAD LED  
TO LOWER TEMPERATURES AND LIMITING THE POTENTIAL OF CONVECTIVE  
INITIATION. HOWEVER, WITH THE MID-LEVEL SHORT WAVE STILL WEST OF  
WEST CENTRAL/CENTRAL MINNESOTA AND AMPLE MID-LEVEL MOISTURE  
REMAINING ACROSS SOUTHERN MINNESOTA INTO WEST CENTRAL WISCONSIN,  
THE POTENTIAL IS HIGH THAT THUNDERSTORMS WILL CONTINUE TO INCREASE  
IN AREAL COVERAGE BETWEEN THESE TWO BOUNDARIES THIS AFTERNOON.  
 
ONCE THE SUN SETS, COVERAGE WILL DECREASE ALONG WITH THE ACTIVITY  
SLOWLY PROPAGATING TO THE SOUTHEAST ACROSS SOUTHERN MINNESOTA. I  
WOULDN'T BE SURPRISED TO SEE ADDITIONAL ACTIVITY DEVELOP TOWARD  
SUNRISE IF A WEAK LOW LEVEL JET DEVELOPS ALONG THE WEAK FRONT  
SAGGING INTO FAR SOUTHERN MINNESOTA. MOST OF THE THUNDERSTORMS  
SHOULD BE ACROSS IOWA AND INTO SOUTHERN WISCONSIN BY WEDNESDAY  
AFTERNOON AS THE MAIN SHORT WAVE HOLDS SOUTH OF THE AREA. ONLY FAR  
SOUTHWEST/SOUTH CENTRAL MINNESOTA MAY SEE A FEW SHOWERS OR STORMS  
WEDNESDAY AFTERNOON IF THE CURRENT UPPER LEVEL LOW IN MONTANA  
MEANDERS FURTHER TO THE NORTH ACROSS SOUTH DAKOTA, AND NORTHWEST  
IOWA WEDNESDAY AFTERNOON.  
   
LONG TERM
 
(WEDNESDAY NIGHT THROUGH TUESDAY)  
ISSUED AT 218 PM CDT TUE AUG 14 2018  
 
OVERALL, THERE IS VERY LITTLE CHANGE FROM THE PREVIOUS FORECAST  
INTO THIS ONE AS THE MODELS HAVE REMAINED FAIRLY CONSISTENT IN THE  
IDEA OF A SPLIT FLOW PATTERN KEEPING THE AREA MOSTLY DRY THROUGH  
THE REST OF THIS WEEK WITH A LITTLE MORE ACTIVE PATTERN FOR NEXT  
WEEK.  
 
WEDNESDAY NIGHT THROUGH SATURDAY...A UPPER LEVEL RIDGE OVER THE  
WESTERN CONUS MIDWEEK WILL EVER-SO-SLOWLY NUDGE ITSELF EAST OVER  
THE ROCKIES AND EXTEND INTO THE NORTHERN PLAINS DURING THE LATTER  
PORTION OF THE WEEK. THE INCOMING RIDGE WILL HELP SUPPRESS TO THE  
SOUTH A WEAK MID-TO-UPPER LEVEL SHORTWAVE WHICH MAY PRODUCE A FEW  
ISOLATED SHOWERS OVER FAR SOUTHERN PORTIONS OF THE WFO MPX  
COVERAGE AREA WEDNESDAY NIGHT INTO THURSDAY. OTHERWISE, THE AREA  
WILL REMAIN DRY WITH BUILDING HEIGHTS ALOFT AND GENERAL SURFACE  
HIGH PRESSURE PREVAILING OVER THE AREA. THE MAIN RESULT WILL BE A  
SLIGHT UPTICK IN TEMPERATURES FROM THE MIDWEEK PERIOD INTO THE  
WEEKEND. HIGHS WILL CLIMB FROM AROUND 80 DEGREES ON THURSDAY TO  
THE MID-80S ON FRIDAY AND SATURDAY.  
 
SUNDAY THROUGH TUESDAY...SEVERAL FACTORS WILL COME INTO PLAY  
DURING THE START OF NEXT WEEK WHICH WILL FORCE THE INCLUSION OF  
CHANCE-RANGE POPS FOR EARLY NEXT WEEK. A POTENT UPPER LEVEL  
SHORTWAVE WILL DRIVE SOUTHEAST FROM WESTERN CANADA, EVOLVING INTO  
A DEEP UPPER LEVEL LOW OVER THE HUDSON BAY AREA WITH WEAKER  
SHORTWAVES RIDING AROUND THE PERIPHERY OF THE UPPER LOW. AT THE  
SURFACE, A COLD FRONT WILL DROP INTO THE REGION FROM SOUTH-CENTRAL  
CANADA THEN STALL OUT OVER MN/WI SUNDAY-TUESDAY. IN ADDITION, A  
PLUME OF WESTERN GOMEX MOISTURE WILL BE SHUNTED WELL NORTH INTO  
THE MID-AND-UPPER MISSISSIPPI RIVER VALLEY REGIONS AROUND THE  
BERMUDA HIGH, GIVING THE FEATURES AT THE SURFACE AND ALOFT  
MOISTURE TO WORK WITH TO PRODUCE AT LEAST SCATTERED SHOWERS AND  
STORMS EARLY NEXT WEEK. THESE FEATURES WILL ALSO ACT TO BUMP DOWN  
TEMPERATURES ONCE AGAIN FOR THE EARLY PORTION OF NEXT WEEK. HIGHS  
WILL DROP INTO THE MID-TO-UPPER 70S WITH LOWS BACK INTO THE 50S.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)  
ISSUED AT 523 PM CDT TUE AUG 14 2018  
 
SCATTERED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE AT  
CENTRAL/SOUTHERN SITES THROUGH SUNSET (KRWF/KMKT/KMSP/KRNH/KEAU).  
ATTENDANT MVFR CEILINGS AND MVFR/IFR VISIBILITIES ARE POSSIBLE  
WITH ANY SHOWERS/STORMS. MVFR CEILINGS ARE ALSO DEVELOPING BEHIND  
THE FRONT, AND SHOULD BECOME MORE WIDESPREAD FROM SOUTH/EAST  
CENTRAL MN ACROSS WEST CENTRAL WI OVERNIGHT THROUGH A GOOD PORTION  
OF WEDNESDAY. KMSP/KRWS/KRNH WILL BE ON THE NORTHERN FRINGES,  
WHILE KMKT/KEAU HAVE THE HIGHEST CHANCE TO SEE A PROLONGED MVFR  
DECK. VARIABLE WINDS WILL BE PRIMARILY NORTH/NORTHEAST FOR  
WEDNESDAY AT 5-8 KNOTS. ANOTHER ROUND OF SHOWERS/STORMS IS  
POSSIBLE ON WEDNESDAY AFTERNOON, BUT CURRENTLY ANTICIPATE THE  
AREA TO BE SOUTH/EAST OF THE SITES, WITH POSSIBLY THE EXCEPTION OF  
KEAU.  
 
KMSP...  
THERE WILL BE A THREAT FOR THUNDER AT THE SITE TO START THE TAF  
PERIOD AS A BOUNDARY PASSES, BUT THAT WILL DIMINISH WITH SUNSET.  
THE NEXT CONCERN IS THE POTENTIAL FOR MVFR CEILINGS (ABOVE 1800  
FEET) OVERNIGHT. HAVE INCLUDED A SCATTERED MENTION FOR NOW AND  
WILL MONITOR TRENDS.  
 
/OUTLOOK FOR KMSP/  
THU...VFR. WIND NNE 5 KTS.  
FRI...VFR. WIND NE 5 KTS.  
SAT...VFR. WIND LIGHT/VARIABLE BCMG SE 5 KTS.  
 

 
   
MPX WATCHES/WARNINGS/ADVISORIES
 
 
WI...NONE.  
MN...NONE.  

 
 

 
 
SHORT TERM...JLT  
LONG TERM...JPC  
AVIATION...LS  
 
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