591  
FXUS63 KMPX 191118  
AFDMPX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN  
618 AM CDT THU APR 19 2018  
   
UPDATE
 
 
ISSUED AT 618 AM CDT THU APR 19 2018  
 
UPDATED TO INCLUDE 12Z AVIATION DISCUSSION BELOW.  
 

 
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 242 AM CDT THU APR 19 2018  
 
EARLY MORNING WATER VAPOR IMAGERY TOGETHER WITH 500MB HEIGHTS AND  
SURFACE OBS SHOWED THE COMPACT UPPER LEVEL VORTICITY MAXIMA OVER  
INDIANA. SURFACE HIGH PRESSURE WAS BUILDING IN THE WAKE OF THIS  
SYSTEM ACROSS THE DAKOTAS, AND THIS WILL MOVE OVER MINNESOTA AND  
WISCONSIN OVER THE NEXT 24 HOURS.  
 
THIS WILL SET THE STAGE FOR CLEAR SKIES AND LIGHT WINDS AND KEEP THE  
REGION DRY. THE ONE AREA OF CONCERN, IF YOU WANT TO CALL IT THAT, IS  
THE POTENTIAL FOR FOG OVERNIGHT. BOUNDARY LAYER MOISTURE WILL  
INCREASE AS SNOW MELTS, AND THE LACK OF MECHANICAL MIXING SHOULD  
KEEP THIS LAYER FAIRLY SHALLOW AND YIELD FAVORABLE CONDITIONS FOR  
RADIATION FOG. DID ADD PATCHY FOG INTO THE FORECAST FOR TONIGHT, AND  
INCREASED TODAY'S HIGHS A BIT ABOVE GUIDANCE GIVEN THE FULL SUN  
EXPECTED THROUGHOUT THE DAY.  
   
LONG TERM
 
(FRIDAY THROUGH WEDNESDAY)  
ISSUED AT 242 AM CDT THU APR 19 2018  
 
THE EXTENDED FORECAST LOOKS WARM AND FAIRLY DRY. THE LONE EXCEPTION  
IS MONDAY NIGHT INTO TUESDAY. THERE IS INCREASING MODEL AGREEMENT  
THAT AN UPPER LEVEL WAVE WILL DRIVE A COLD FRONT ACROSS THE REGION  
WITH RAIN SHOWERS DEVELOPING ALONG IT. AS OF NOW THERMAL PROFILES  
LOOK TOO WARM FOR SNOW EXCEPT PERHAPS NORTH OF I-94, BUT AT MOST  
EXPECTING A RAIN/SNOW MIX WITH NO ACCUMULATION.  
 
THE MAIN AREA OF INTEREST IS A DEEP WESTERN TROUGH THAT BECOME CUT  
OFF ACROSS THE 4-CORNERS REGION FRIDAY AND SATURDAY. THIS UPPER  
LEVEL VORTICITY SLOWLY SLIDES TO THE SOUTHEAST, AND THIS SEEMS  
REASONABLE SINCE IT DOES APPEAR TO BE CAUGHT UP IN THE SUBTROPICAL  
JET. COULD SEE SOME LIGHT RAIN SHOWERS ACROSS SOUTHERN MINNESOTA  
WITH THIS WAVE, BUT THE MORE LIKELY SOLUTION IS JUST MID/HIGH CLOUDS  
OVERSPREADING THE REGION FOR THE WEEKEND. THESE CLOUDS COULD HOLD  
BACK TEMPERATURES ON SATURDAY, SO KEPT HIGHS RIGHT AT THE BLENDED  
GUIDANCE.  
 
NEXT WEEK LOOKS WARM. MOST OF THE SNOW SHOULD BE GONE, AND WARM AIR  
ADVECTION BECOMES MORE COMMON PLACE ACROSS THE UPPER MIDWEST FOR  
SUNDAY AND MONDAY. ASIDE FROM THE WARMER TEMPERATURES, THIS WILL  
ALSO BRING IN STRONGER WINDS TO AID IN MIXING AND HEATING. CONTINUED  
THE TREND OF THE PREVIOUS FORECAST TO RAISE HIGH TEMPERATURES ABOVE  
GUIDANCE FOR SUNDAY AND MONDAY. TUESDAY IS TRICKY WITH THE FRONTAL  
BOUNDARY APPROACHING WITH CLOUDS AND PRECIP, SO CONTINUED WITH THE  
BLEND THE REST OF THE FORECAST.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)  
ISSUED AT 618 AM CDT THU APR 19 2018  
 
A QUIET PERIOD IS EXPECTED AS HIGH PRESSURE CURRENTLY CENTERED  
JUST WEST OF THE AREA DRIFTS EASTWARD. LIGHT AND GENERALLY  
NORTHWESTERLY WINDS TODAY WILL BECOME CALM TONIGHT WITH THE  
SURFACE HIGH OVERHEAD BEFORE BECOMING MORE SOUTHERLY ON FRIDAY.  
GIVEN THE EXPECTED SNOWMELT TODAY, WHICH WILL BOOST BOUNDARY LAYER  
MOISTURE, SOME FOG AND POSSIBLY A BIT OF STRATUS COULD OCCUR  
TONIGHT (ESPECIALLY ACROSS THE EASTERN HALF OF THE AREA). HIT  
THINGS HARDEST AT KRNH AND KEAU, BUT HINTED AT SOME BR AND LOW  
CLOUDINESS AT KMSP AS WELL. SUBSEQUENT FORECASTS MAY NEED TO BE  
MORE AGGRESSIVE IF CONDITIONS AND GUIDANCE CONTINUE TO HINT AT  
THINGS.  
 
KMSP...MAIN ITEM OF UNCERTAINTY IS THE DEGREE OF FOG AND POSSIBLE  
STRATUS OVERNIGHT TONIGHT INTO EARLY FRIDAY. WAS OPTIMISTIC FOR  
NOW, BUT IT'S POSSIBLE CONDITIONS COULD BE WORSE WITH SOME OF THE  
GUIDANCE HINTING AT A BRIEF PERIOD OF IFR VISIBILITIES.  
 
/OUTLOOK FOR KMSP/  
FRIDAY AFTERNOON...VFR. SOUTH WIND LESS THAN 5 KT.  
FRIDAY NIGHT...VFR. VARIABLE WIND LESS THAN 5 KT.  
SATURDAY...VFR. VARIABLE WIND 5 KT OR LESS.  
SATURDAY NIGHT...VFR. SOUTH WIND 5 KT OR LESS.  
SUNDAY...VFR. SOUTHWEST WIND 5 TO 10 KT.  
SUNDAY NIGHT...VFR. SOUTHWEST WIND AROUND 10 KT.  
MONDAY...VFR. SOUTHWEST WIND AROUND 10 KT.  
 

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

 
 

 
 
UPDATE...  
SHORT TERM...JRB  
LONG TERM...JRB  
AVIATION...  
 
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