382  
FXUS63 KMPX 231203  
AFDMPX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN  
703 AM CDT SAT JUN 23 2018  
   
UPDATED FOR 12Z AVIATION DISCUSSION
 
 
ISSUED AT 700 AM CDT SAT JUN 23 2018  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 315 AM CDT SAT JUN 23 2018  
 
TODAY SHOULD BE MOSTLY DRY, BUT COULD SEE SOME SHOWERS AND  
THUNDERSTORMS MOVE IN FROM THE DAKOTAS ACROSS WESTERN MINNESOTA.  
OVERNIGHT THIS PRECIPITATION IS EXPECTED TO SLOWLY SHIFT EASTWARD  
AND EVENTUALLY REACH WESTERN WISCONSIN BY SUNDAY MORNING. STORM  
MOTION WILL BE SLOW, SO LOCALIZED AREAS OF HEAVY RAIN ARE POSSIBLE,  
BUT IT SHOULD NOT BE WIDESPREAD. THE THREAT FOR SEVERE WEATHER IS  
VERY LOW. AFTERNOON HIGHS WILL BE NEAR 80 WITH LIGHT WINDS AND  
INCREASING CLOUDS.  
 
EARLY MORNING SATELLITE IMAGERY SHOWED CYCLONIC CIRCULATION ACROSS  
THE DAKOTAS WITH A FEW COLD CLOUD TOPS INDICATING AREAS OF  
CONVECTION. RAP13 H500 VORTICITY IDENTIFIED THESE AREAS OF POSITIVE  
VORTICITY, BUT WHAT STOOD OUT WHAT THE LACK OF WIND SPEED ASSOCIATED  
WITH THESE PV ANOMALIES. THIS LACK OF WIND MEANS 2 THINGS. FIRST  
OFF, THE FORCING ASSOCIATED WITH THESE WAVES IS WEAK, SO THE  
PRECIPITATION IS SMALL IN COVERAGE. SECONDLY, THE STORMS WILL BE  
MOVING SLOWLY, SO ISOLATED HEAVY RAINFALL IS POSSIBLE OVER SMALL  
AREAS.  
 
THE WPC MARGINAL RISK OF EXCESSIVE RAIN IS SOUTHWEST OF THE FORECAST  
AREA, BUT THERE IS STILL A NON-ZERO THREAT ACROSS MINNESOTA, AND  
WISCONSIN. FORECAST SOUNDINGS SHOW VERY WEAK WINDS OF GENERALLY LESS  
THAN 20KTS THROUGHOUT THE TROPOPAUSE, AND THE MBE VELOCITIES ARE IN  
THE SINGLE DIGITS. PWAT VALUES OF AROUND 1.5 INCHES ARE HIGH, BUT  
NOT OFF THE CHARTS.  
 
IN THE END, THE LACK OF PREDICTABILITY OF WHERE THE THE RAIN WILL  
FALL IS THE MAIN REASON WHY THE EXCESSIVE RISK OF RAINFALL DOES NOT  
EXTEND INTO THE NWS CHANHASSEN FORECAST AREA. WILL PROBABLY SEE  
SCATTERED SHOWERS AND THUNDERSTORMS LATER TODAY AND OVERNIGHT, WITH  
A FEW SLOW MOVING STORMS PUTTING DOWN A QUICK COUPLE INCHES OF RAIN  
OVER ISOLATED AREAS.  
   
LONG TERM
 
(SUNDAY THROUGH FRIDAY)  
ISSUED AT 325 AM CDT SAT JUN 23 2018  
 
NO MAJOR CHANGES IN THE EXTENDED PERIOD AS THE BEST CHANCE OF  
WIDESPREAD RAINFALL WILL OCCUR MONDAY AND TUESDAY. PAST TUESDAY, A  
STRONG WEST TO EAST FLOW ALOFT WILL DEVELOP, WITH AN INCREASING  
UPPER RIDGE BUILDING ACROSS THE CENTER OF THE NATION. THIS UPPER  
RIDGE IS FORECAST TO EXPAND NORTHEAST AND STRENGTHEN ACROSS THE  
GREAT LAKES, AND NORTHEAST U.S BY NEXT WEEKEND.  
 
A DEEPENING TROUGH IS EXPECTED ACROSS THE PACIFIC NORTHWEST LATE  
NEXT WEEK. AS THE TROUGH CONTINUES TO DEEPEN, AND THE UPPER RIDGE  
HOLD IN THE GREAT LAKES, AND NORTHEAST, THE NORTHERN PLAINS, AND  
UPPER MIDWEST WILL LIKELY EVOLVE INTO A QUASI-WEST-SOUTHWEST FLOW  
ALOFT. TYPICALLY, THIS TYPE OF FLOW, AND A FRONTAL BOUNDARY  
EXPECTED NEAR THE AREA, THUNDERSTORM POTENTIAL INCREASES. AS WIND  
SHEAR INCREASING FROM THE OVERHEAD JET STREAM, SEVERE WEATHER  
POTENTIAL WILL ALSO INCREASE.  
 
FOR MONDAY AND TUESDAY... MODELS HAVE BEEN FAIRLY CONSISTENT IN  
THE EVOLUTION OF AN UPPER SHORT WAVE THAT MOVES ACROSS THE UPPER  
MIDWEST EARLY NEXT WEEK. DUE TO A STRONGER UPPER RIDGE EXPECTED  
TO BUILD ACROSS THE GREAT LAKES, THE UPPER SHORT WAVE WILL LIKELY  
WEAKEN AS IT MOVES INTO A MORE CONFLUENT FLOW ALOFT. HOWEVER, IT  
IS STILL POTENT ENOUGH TO GENERATE A WIDE AREA OF SHOWERS AND  
THUNDERSTORMS STARTING MONDAY, AND CONTINUING THROUGH TUESDAY  
MORNING. INSTABILITY WILL BE LIMITED AS ABUNDANT CLOUD COVER AND  
PRECIPITATION WILL HOLD ACROSS THE AREA. THEREFORE, SEVERE WEATHER  
POTENTIAL IS LOW.  
 
THERE IS ANOTHER ASPECT TO THIS SYSTEM AS IT MOVES SLOWLY ACROSS  
THE UPPER MIDWEST. AS PRECIPITABLE WATER VALUES REMAIN ABNORMALLY  
HIGH, AND ROUNDS OF SHOWERS AND THUNDERSTORMS DEVELOP, HEAVY  
RAINFALL AND FLOODING INCREASES. IN ADDITION, AREA RIVERS ARE  
ALREADY NEAR OR ABOVE FLOOD STAGE IN MANY AREAS OF SOUTHERN  
MINNESOTA. THEREFORE, I WOULDN'T BE SURPRISED TO SEE ADDITIONAL  
RISES OR ANOTHER CREST IF CONDITIONS WARRANT.  
 
THE POTENTIAL OF HEAT AND HUMIDITY REMAINS ON TRACK FOR THE  
FOLLOWING WEEKEND, AND INTO THE FIRST WEEK OF JULY. 90S AND HIGHER  
HUMIDITY VALUES WILL LEAD TO HEAT INDICES APPROACHING 100-105  
DEGREES.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)  
ISSUED AT 700 AM CDT SAT JUN 23 2018  
 
THE MORNING FOG WILL QUICKLY BURN OFF THIS MORNING. THEN EXPECT  
VFR CONDITIONS THROUGHOUT WITH LIGHT SOUTHEAST WINDS TODAY AND  
INCREASING CLOUDS THROUGH TONIGHT, ALONG WITH A CHANCE OF SHOWERS  
OR THUNDERSTORMS SLOWLY MOVING FROM WEST TO EAST. AT THIS TIME  
ONLY INCLUDED VCSH IN THE TAF.  
 
KMSP...  
VFR CONDITIONS THROUGHOUT WITH LIGHT SOUTHEAST WINDS TODAY,  
INCREASING CLOUDS TONIGHT, AND A CHANCE OF SHOWERS OR  
THUNDERSTORMS LATE TONIGHT INTO SUNDAY. AT THIS TIME ONLY  
INCLUDED VCSH IN THE TAF.  
 
/OUTLOOK FOR KMSP/  
SUN...VFR. CHANCE -TSRA. WIND SE 5-10 KTS.  
MON...MVFR POSSIBLE. -SHRA/-TSRA LIKELY. WIND SE 15G25 KTS.  
TUE...MVFR POSSIBLE. -SHRA/-TSRA LIKELY. WIND SW 5-10 KTS.  
 

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

 
 

 
 
SHORT TERM...JRB  
LONG TERM...JLT  
AVIATION...JRB  
 
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