513  
FXUS63 KMPX 191145  
AFDMPX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN  
645 AM CDT SUN AUG 19 2018  
   
UPDATED FOR 12Z AVIATION DISCUSSION
 
 
ISSUED AT 639 AM CDT SUN AUG 19 2018  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 357 AM CDT SUN AUG 19 2018  
 
MAIN CONCERN IN THE SHORT TERM IS THE POTENTIAL FOR HEAVY RAIN  
ACROSS WESTERN MINNESOTA LATER TODAY AND TONIGHT. THE AREA HAS BEEN  
FAIRLY DRY, SO THIS SHOULD MITIGATE THE FLOODING THREAT. HOWEVER,  
STORM MOTION WILL BE NEARLY STATIONARY SO COULD SEE ISOLATED AMOUNTS  
OF 3 TO 5 INCHES OVER VERY LOCALIZED AREAS. DID INCREASE RAIN  
CHANCES ACROSS THE WESTERN MN, WHILE AT THE SAME TIME LOWERING AND  
DELAYING THEM ACROSS EASTERN MN AND WESTERN WI. THE SEVERE WEATHER  
THREAT IS LOW. THE CAPE PROFILE IS SKINNY, AND THERE IS VERY WEAK  
DEEP LAYER SHEAR. THE PRIMARY STORM MODE SHOULD BE MULTICELLULAR.  
 
EARLY MORNING SATELLITE IMAGERY WITH RAP13 H500 WINDS AND HEIGHTS  
SHOWED A SLOW-MOVING UPPER LEVEL SHORTWAVE ACROSS WESTERN SD, WITH  
CONVECTION DEVELOPING AHEAD OF IT. OVER THE NEXT 36 HOURS, THIS  
SHORTWAVE WILL DEVELOP A SURFACE LOW ALONG THE MISSOURI RIVER VALLEY  
AND TAKES IT EASTWARD ACROSS SOUTHERN IOWA BY MONDAY MORNING. A  
MOISTURE-RICH AIRMASS WILL WRAP AROUND THIS LOW AND BRING HEAVY RAIN  
NORTHEAST OF ITS TRACK. MOST OF THIS RAIN SHOULD STAY SOUTH OF I-90.  
 
MEANWHILE, ANOTHER AREA OF PRECIP WILL DEVELOP ALONG A WEAK FRONTAL  
BOUNDARY FROM WEST CENTRAL MINNESOTA THROUGH NORTHERN LAKE SUPERIOR  
TODAY AND TONIGHT. FORECAST SOUNDINGS SHOW A TROPICAL TROPOPAUSE  
WITH WINDS LESS THAN 20KTS BELOW 500MB, AND THE STRONGEST WINDS  
ABOVE 200MB. THIS SHOULD PROMOTE THUNDERSTORMS WITH SLOW STORM  
MOTION, WHILE AT THE SAME TIME ALLOWING THE OUTFLOW TO EXPEL  
NORTHEAST OF THE CONVECTION. THIS TOO IS FAVORABLE SETUP FOR HEAVY  
RAIN. HIRES MODELS ARE IN GOOD AGREEMENT WITH 5+ INCHES SOMEWHERE  
NEAR THE MN/SD/ND BORDER. THERE IS STILL UNCERTAINTY WHERE EXACTLY  
THIS WILL OCCUR, BUT DID ADD HEAVY RAIN WORDING TO THE FORECAST TO  
CONVEY THIS POTENTIAL. THIS NORTHERN AREA OF CONVECTION WILL WEAKEN  
OVERNIGHT AS THE FORCING BECOMES MORE FOCUSED WITH THE DEVELOPING  
SURFACE LOW TO THE SOUTH.  
   
LONG TERM
 
(MONDAY THROUGH SATURDAY)  
ISSUED AT 357 AM CDT SUN AUG 19 2018  
 
DURING THE DAY ON MONDAY, THE MAIN AREA OF PRECIP SHIFTS SOUTH TO  
THE WIDESPREAD BAND OF PRECIPITATION ASSOCIATED WITH THE SURFACE  
LOW OVER NORTHERN MISSOURI. THIS TRACK WOULD PLACE THE HEAVIEST  
RAIN ACROSS IOWA INTO SOUTHWESTERN WISCONSIN AS THE MAIN RAIN BAND  
DEVELOPS TO THE NORTH OF THE SURFACE LOW, BUT WE COULD STILL SEE  
SOME HEAVIER RAIN ACROSS THE I-90 CORRIDOR IN MINNESOTA UP THROUGH  
SOUTHEAST MINNESOTA INTO THE EAU CLAIRE AREA. THE NAM/EURO ALONG  
WITH LONGER-RANGE CAMS ALL DIMINISH PRECIP ALONG THE INVERTED  
TROUGH/COLD FRONT ACROSS WESTERN MINNESOTA MONDAY AFTERNOON, WITH  
THE GFS REMAINING THE BULLISH SOLUTION ON BRINGING A BAND OF  
SHOWERS/THUNDERSTORMS EAST INTO MONDAY EVENING. THIS WILL LIKELY  
RESULT IN A RELATIVE MINIMA IN RAINFALL AMOUNTS ACROSS EASTERN  
MINNESOTA INTO NORTHWEST WISCONSIN. CURRENTLY EXPECTING STORM-  
TOTAL AMOUNTS OF 1-2" IN TWO SEPARATE BANDS, ONE FROM WESTERN  
MINNESOTA UP INTO THE MINNESOTA ARROWHEAD AND THE OTHER GENERALLY  
SOUTH AND EAST OF I-90. BETWEEN THESE TWO BANDS LESSER AMOUNTS OF  
0.25-0.5 INCHES ARE EXPECTED ACROSS CENTRAL MINNESOTA INTO  
NORTHWESTERN WISCONSIN.  
 
SHOWERS SHOULD WRAP UP QUICKLY AFTER MIDNIGHT ACROSS WESTERN  
WISCONSIN AS THE SURFACE LOW HEADS EAST INTO THE GREAT LAKES.  
TUESDAY COULD BE A BIT BREEZY WITH GUSTY NORTHERLY WINDS DEVELOPING  
WITH THE TIGHT PRESSURE GRADIENT BETWEEN THE LOW OVER THE GREAT  
LAKES AND AN APPROACHING AREA OF HIGH PRESSURE OVER THE NORTHERN  
PLAINS. HIGH PRESSURE DOMINATES TUESDAY INTO THURSDAY WITH FAIR  
SKIES AND TEMPERATURES RIGHT AROUND NORMAL IF NOT A FEW DEGREES  
BELOW. WITH NORTHWEST FLOW ALOFT WILL HAVE TO WATCH FOR THE RETURN  
OF SMOKE FROM CANADIAN WILDFIRES AND WEATHER IT HAS ANY IMPACTS ON  
AIR QUALITY.  
 
THE NEXT SYSTEM COMES OUR WAY THURSDAY NIGHT INTO FRIDAY AS A  
SHORTWAVE APPROACHES ALONG THE US/CANADIAN BORDER. EURO/GFS BOTH  
HAVE GENERATE WIDESPREAD HEAVY PRECIP WITH THIS SYSTEM OVERNIGHT  
THURSDAY INTO FRIDAY WITH PW VALUES INCREASING OVER 1.5". HEAT AND  
HUMIDITY LOOKS TO RETURN INTO THE WEEKEND AND BEYOND AS RIDGING  
BUILDS OVER THE MID-MISSISSIPPI VALLEY.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)  
ISSUED AT 639 AM CDT SUN AUG 19 2018  
 
PATCHY FOG AGAIN THIS MORNING WILL QUICKLY GIVE WAY TO VFR  
CONDITIONS TODAY BUT SHOWERS AND THUNDERSTORMS WILL MOVE IN FROM  
THE WEST AND COULD BRING MFVR CONDITIONS. WINDS WILL BE LIGHT AND  
VARIABLE, BUT SHOULD TAKE ON A SOUTHEAST DIRECTION TODAY, WITH A  
NORTHEAST DIRECTION TONIGHT.  
 
KMSP...  
VFR CONDITIONS THROUGHOUT, BUT COULD SEE SOME MVFR/-SHRA LATE  
TONIGHT AND EARLY MONDAY MORNING AS PRECIPITATION MOVES ACROSS THE  
REGION. THE PRECIPITATION WILL BE WEAKENING, SO CONTINUED WITH THE  
PROB30 FOR THIS TAF ISSUANCE. LIGHT SOUTHEAST WINDS TODAY WILL  
EVENTUALLY BECOME NORTHEAST LATER TONIGHT.  
 
/OUTLOOK FOR KMSP/  
 
MON...MVFR POSSIBLE WITH -SHRA/TSRA, IFR POSSIBLE. WIND N 5-10  
KTS.  
TUE...MVFR POSSIBLE EARLY, THEN VFR. WIND NNW AT 10G15 KTS.  
WED...VFR. WIND NW AT 5 KTS.  
 

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

 
 

 
 
SHORT TERM...JRB  
LONG TERM...ETA  
AVIATION...JRB  
 
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