390 FXUS63 KMPX 072008 AFDMPX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 308 PM CDT TUE SEP 7 2010 .DISCUSSION... THINGS QUIETING DOWN THIS AFTERNOON AS POWERFUL SYSTEM THAT CAME ACROSS THE AREA OVERNIGHT SPINS EAST ACROSS THE GREAT LAKES. IN ITS WAKE...LARGE H5 HEIGHT RISES /OVER 150 M 12 HOUR RISES/ ARE WORKING ACROSS THE NRN PLAINS IN ITS WAKE...WHICH WILL LEAD TO AT LEAST ONE QUIET NIGHT TONIGHT AND DAY TOMORROW. NEXT CHANCES FOR RAIN STILL LOOK TO COME INTO WRN MN WEDNESDAY NIGHT...WITH A BREAK IN THE ACTION THURSDAY AND MOST OF FRIDAY BEFORE ANOTHER COLD BRINGS SHOWERS AND THUNDERSTORMS TO THE ENTIRE AREA FRIDAY AFTERNOON THROUGH FRIDAY NIGHT. AT THIS POINT...THE WEEKEND IS LOOK PLEASANT...BEFORE ANOTHER COLD FRONT BRINGS ABOUT ANOTHER CHANCE FOR RAIN THE BEGINNING OF NEXT WEEK. FOR TONIGHT...ONLY POTENTIAL ISSUE WILL BE WITH FOG IN WESTERN AND CENTRAL MN. SFC RIDGE CURRENTLY OVER THE DAKOTAS WILL BE CENTERED OVER MN BY TOMORROW MORNING...WITH THE SKIES CLEARING OUT AND WINDS CALMING DOWN IN RESPONSE. THOUGH HAVE SEEN A GOOD BOUT OF CAA DURING THE DAY ON THE BACKSIDE OF THE GREAT LAKES LOW...DRY AIR ADVECTION HAS ONLY BEEN MODEST...WITH MOST OF THE AREA STILL SEEING DEWPS IN THE MID 40S. WITH A CROSS OVER TEMPERATURE IN THE MID 40S...HIGHEST PROBABILITY FOR FOG WILL BE IN WESTERN AND CENTRAL MN...WHERE COMBINATION OF HEAVY RAINS LAST NIGHT AND LOWS IN THE UPPER 30S AND LOWER 40S WILL SET UP THE POTENTIAL FOR SOME FOG THERE...SO HAVE A MENTION OF IT IN GRIDS. THOUGH WITH MOS GUIDANCE AND SREF PROBS NOT REALLY PLAYING UP FOG POTENTIAL...NOT ENOUGH SUPPORT FOR A FOG ADVISORY AT THIS TIME. FOR WEDNESDAY...UPPER RIDGE WILL BE MOVING OVERHEAD...BUT A SHORTWAVE CURRENTLY NEAR LAS VEGAS WILL BE HEADING NORTHEAST ACROSS THE PLAINS. MODELS STARTING TO COME INTO BETTER AGREEMENT ON THIS SYSTEM...WHICH LOOKS TO BRING A RETURN TO WET CONDITIONS FOR W/SW MN WEDNESDAY NIGHT. THIS WAVE WILL BE ASSOCIATED WITH STRONG AREAS OF MID LEVEL WAA AND FGEN...WHICH SHOULD HELP PRODUCE A SHIELD OF MAINLY RAIN WITH EMBEDDED THUNDERSTORMS. THIS AREA COMES INTO WRN AND SW PORTIONS OF CWA AFTER MIDNIGHT WEDNESDAY NIGHT...SO HAVE FAVORED POPS/QPF THERE. DURING THE DAY ON THURSDAY HOWEVER...MODELS CONSISTENT WITH DISSOLVING THIS AREA OF FORCING...AS FGEN AND WAA BECOME CONCENTRATED TO THE NW OVER NODAK/SRN CANADA AS A STRONG SFC LOW SPINS UP IN THE NRN HIGH PLAINS IN RESPONSE TO ANOTHER STRONG SHORTWAVE EMANATING FROM THE PAC NW AND MOISTURE GETS ABSORBED BY THE REMNANTS OF TS HERMINE MOVING INTO THE MID MS VALLEY. THIS SPLIT NATURE OF MOISTURE AND FORCING LOOKS TO KEEP THE AREA PRIMARILY DRY FROM THURSDAY AFTERNOON THROUGH FRIDAY MORNING...SO HAVE FURTHER CUT BACK ON POPS IN THIS TIME PERIOD. BY LATE FRIDAY AFTERNOON...COLD FRONT ASSOCIATED WITH HIGH PLAINS LOW WILL BE MOVING INTO THE ERN DAKOTAS. SIGNAL FROM MODELS AGAIN FAIRLY STRONG FOR PRECIP ALONG THE FRONT FROM LATE FRIDAY AFTERNOON THROUGH FRIDAY NIGHT...SO HAVE INCREASED POPS TO LIKELY DURING THIS PERIOD...AS THE REST OF THE CWA LOOKS TO GET INTO SOME PRECIP. AS FOR SEVERE POTENTIAL...IT LOOKS RATHER MINIMAL...AS DEWPS LOOKS TO ONLY CREEP UP INTO THE MID 50S TO NEAR 60 AHEAD OF THE FRONT. THIS LEADS TO RATHER MARGINAL INSTABILITY...THOUGH ENOUGH WILL BE PRESENT TO AT LEAST GENERATE A FEW RUMBLES OF THUNDER WITH THE PASSING SHOWERS. FOR THE WEEKEND...CAA BEHIND THIS FRONT LOOKS TO KEEP HIGHS SATURDAY ABOUT 5 TO 10 DEGREES BELOW NORMAL WITH WAA AHEAD OF NEXT WEEKS SYSTEM RETURNING TEMPERATURES TO NEAR NORMAL FOR SUNDAY. AS FOR NEXT WEEK...THE ECMWF HAS BEEN CONSISTENT THE LAST COUPLE OF RUNS WITH TAKING ANOTHER SHORTWAVE ACROSS NRN MN MONDAY...WITH A COLD FRONT COMING THROUGH THE MPX CWA...WARRANTING THE INTRODUCTION OF POPS FOR THEN. && .AVIATION.../18Z TAF ISSUANCE/ CYCLONIC CURVATURE AROUND STRONG LOW PRESSURE OVER THE GREAT LAKES WILL GRADUALLY WEAKEN THIS AFTERNOON FOLLOWED BY BUILDING HIGH PRESSURE OVERNIGHT. MVFR CIGS LIFTING TO LOW VFR FROM WEST TO EAST DURING THE AFTERNOON AND THEN CLEARING AS HIGH PRESSURE MOVES IN TONIGHT. THERE IS A RISK OF PATCHY FOG LOWERING VSBYS TO LIFR AT THE FAVORED TAF SITES...INCLUDING KSTC...KAXN...AND KEAU. KMSP..LOW VFR CIGS BECOMING SCT LATE AFTERNOON AND THEN CLEAR OVERNIGHT. STILL GUSTY NW WINDS UP TO 28 KNOTS. WIND DECREASING TO LESS THAN 10 KNOTS AFTER 02Z. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ MPG/JPR