Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 220954 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 554 AM EDT FRI AUG 22 2014 .AVIATION... //DISCUSSION... VARIABLE CONDITIONS ACROSS THE AREA THIS MORNING AS WE TRY TO SCOUR AWAY THE IFR FOG FROM THE OVERNIGHT. THE MOIST AIRMASS WILL REMAIN IN PLACE THROUGH THE TAF CYCLE AS WE STILL RESIDE ON THE NORTH SIDE OF A SLOWLY RETREATING WARM FRONT. THIS WILL RESULT IN A CHANCE OF SHOWERS AND THUNDERSTORMS THROUGH THE DAY AND MORE FOG DURING THE OVERNIGHT. LOW CONFIDENCE IN COVERAGE OF PRECIPITATION AS THERE IS NO REAL FORCING MECHANISM TO KEY IN ON SO WILL LEAVE OUT OF THE TAFS FOR NOW THOUGH BETTER CHANCES WILL BE OVER THE DETROIT TAFS AS OPPOSED TO FNT AND MBS. SKIES WILL ATTEMPT TO CLEAR TONIGHT WHICH WILL AIDE IN IFR/MVFR FOG FORMATION. //DTW THRESHOLD THREATS... * MODERATE CONFIDENCE ON CEILING BELOW 5000 FT THROUGH THIS AFTERNOON. * LOW CONFIDENCE IN COVERAGE AND TIMING OF ANY THUNDERSTORMS TODAY. * LOW CONFIDENCE ON VISIBILITY DROPPING BELOW A 1/2SM TONIGHT. && .PREV DISCUSSION...ISSUED 332 AM EDT FRI AUG 22 2014 SHORT TERM...TODAY AND TONIGHT EASTERLY FLOW WILL PERSIST THROUGH THE FORECAST PERIOD AS WE WILL REMAIN UNDER THE ELEVATED WARM FRONT WHICH IS ROOTED AT THE SFC ALONG MI/OH BORDER. THE SFC WARM FRONT WILL NOT RETURN TO THE AREA BEFORE IT BEGINS TO RETREAT SOUTHWARD LATER TODAY THUS WE WILL BE DEALING WITH ELEVATED CONVECTION PERIODICALLY THROUGH THE DAY. CURRENT RADAR MOSAIC SHOWS THE NEXT CONVECTIVE COMPLEX DEVELOPING OVER THE CHICAGO AREA. IT...AS THE PREVIOUS MCS THURSDAY EVENING DID...WILL TRACK TO THE SOUTH OF THE AREA AS THE SHORTWAVE OVER OHIO CONTINUES TO REORIENTATE THE 850MB JET MORE WEST TO EAST ACROSS THE OHIO VALLEY. EVEN WITHOUT THE FORCING OF THE JET...THE ATMOSPHERE REMAINS VERY RIPE FOR SCATTERED SHOWERS AS RIBBON OF VERY RICH THETA E RESIDES ACROSS SOUTHERN MI. SHOWERS HAVE PERSISTED THROUGH THE NIGHT ON THE NORTHERN EDGE OF THIS RICH AIRMASS...PWATS AROUND 1.75 INCHES. WEAK FLOW INTO THE MID LEVELS...30 KNOTS AT 500 MB PER THE DTX 22.00Z SOUNDING HAS LED TO A SLOW FORWARD SPEED OF THE SHOWERS/STORMS MAKING FLOODING A CONCERN FOR ANY AREA THAT GETS A HEALTHY STORM OR TWO. THE OVERALL PATTERN DOES NOT CHANGE MUCH FROM WHAT WE SEE CURRENTLY INTO THE AFTERNOON TODAY. WITH A LACK OF NOTABLE FORCING MECHANISM OR SHORTWAVE AND MODEL FORECAST CAPE VALUES ONLY AROUND 200 J/KG...FIND IT HARD TO CONTINUE THE LIKELY POPS THUS LOWERED INTO MID/HIGH CHANCE FOR THE SOUTHERN BORDER AND LOWERING AS ONE HEADS NORTH. A GENERAL CHANCE POP WILL HANDLE THE SCENARIO WELL UNTIL A MORE ORGANIZED COMPLEX SHOWS ITSELF. HIRES MODELS ALL AGREE WITH THIS CHANGE BY HAVING MORE ORGANIZED COMPLEXES TRACKING TO THE SOUTH WITH SPORADIC SHOWERS/THUNDERSTORMS OVER THE AREA ON THE ELEVATED FRONTAL SFC. THE TONIGHT PERIOD IS A LITTLE TRICKY. THE STEEPENING OF THE MID LEVEL RIDGE OVER THE UPPER MISSISSIPPI VALLEY WILL PULL THE DEEP MOISTURE AXIS BACK WESTWARD BUT LEAVES SOME RESIDUAL POCKETS OVER THE AREA BEFORE HIGH PRESSURE FROM THE EAST CAN TAKE OVER. OVERALL THE SHOWERS/THUNDERSTORMS LOOK TO SHUT OFF AROUND SUNSET ALTHOUGH WOULD NOT BE SURPRISED TO SEE A LINGER SHOWER BETWEEN 00-03Z. WITH THE RESIDENT BL AIRMASS CHANGING LITTLE OVER THE NEXT DAY...ELEVATED DEWPOINTS IN THE MID 60S WILL KEEP MIN TEMPS UP BUT ALSO PRODUCE AREAS OF FOG ONCE AGAIN AS SKIES TRY TO CLEAR TOWARD MORNING. LONG TERM... SATURDAY THROUGH THURSDAY ONGOING DEEPENING OF THE LONG WAVE TROUGH OVER THE PACIFIC NORTHWEST WILL LEAD TO DOWNSTREAM AMPLIFICATION OF THE SUBTROPICAL RIDGE OVER THE ERN US THIS WEEKEND. THE LATEST MODEL SUITE CONTINUE TO SUPPORT FAIRLY GOOD MID LEVEL HEIGHT RISES ACROSS SE MI THIS WEEKEND AS THE RIDGE AXIS EXTENDS ACROSS LOWER MI. THE UPPER LEVEL ANTICYCLONE NOW PARKED OVER NRN QUEBEC WILL BUILD SOUTH BEFORE BEING ABSORBED INTO THE EXPANDING SUBTROPICAL RIDGE. THIS WILL FORCE THE LARGE SURFACE HIGH OVER ERN CANADA TO EXPAND INTO THE EASTERN GREAT LAKES THIS WEEKEND...LEADING TO SLIGHTLY STRONGER E-SE FLOW ACROSS THE FORECAST AREA. ADVECTION OF SLIGHTLY COOLER AND LESS HUMID AIR WILL RESULT. MODEL SOUNDINGS SUGGEST DAYTIME INSOLATION WILL STILL BOOST SAT AND SUN HIGHS INTO THE LOW 80S AND DEWPOINTS SHOULD STILL REMAIN IN THE 60S. THE MORE STABLE AIRMASS BUILDING IN FROM THE EAST AND WARMING TEMPS IN THE MID LEVELS WILL SUPPORT A DRY FORECAST FOR THE ENTIRE WEEKEND. ALL OF THE 00Z MODEL SOLUTIONS DO HOWEVER SUGGEST SOME HIGHER LOW LEVEL MOISTURE ADVANCING FROM THE MID ATLANTIC INTO THE ERN GREAT LAKES SAT NIGHT WITHIN SLIGHTLY ENHANCED SE FLOW. THIS COMBINED WITH THE WARM LAKE ERIE WATERS MAY LEAD TO CONSIDERABLE LOW CLOUDS AND/OR FOG SAT NIGHT INTO SUN MORNING. ENERGY EJECTING OUT OF THE WRN US LONG WAVE TROUGH WILL TRACK INTO CNTL AND ERN CANADA EARLY NEXT WEEK. THIS WILL DAMPEN THE MID LEVEL RIDGE AXIS OVER THE GREAT LAKES REGION. THE LOW LEVEL FLOW WILL HOWEVER TURN TOWARD THE S-SW AND WILL OPEN THE DOOR FOR HEAT AND HUMIDITY TO FILTER INTO SE MI. HIGH TEMPS MON AND POSSIBLY INTO TUES MAY TOP 90 DEGREES. MODEL SOUNDINGS ARE SUGGESTING THE ATMOSPHERE WILL BE CAPPED ON MONDAY. THE MOST RECENT ECMWF IS ACTUALLY SUGGESTING A STRONG CAP PERSISTING INTO TUESDAY...SO CONVECTIVE CHANCES MAY ACTUALLY BE QUITE LOW. A TREND TOWARD A MORE PROGRESSIVE FLOW NEXT WEEK HAS BEEN SHOWN BY THE MEDIUM RANGE MODEL SUITE... FEATURING MID LEVEL TROUGHING ADVANCING INTO THE GREAT LAKES BY THE MIDDLE OF NEXT WEEK /TUES NIGHT - WED NIGHT/. DESPITE POOR RUN TO RUN CONTINUITY WITH RESPECT TO TIMING AND AMPLITUDE OF THIS ENERGY...THE MID LEVEL HEIGHT FALLS ACROSS THE MODERATE INSTABILITY OVER SE MI WILL SUPPORT A GOOD CHANCE OF CONVECTION DURING THIS TIME PERIOD. COOLER AND DRIER AIR THEN LOOKS TO FUNNEL IN BY THE END OF THE FORECAST PERIOD. MARINE... A FAIRLY LARGE REGION OF HIGH PRESSURE WILL EXPAND ACROSS THE EASTERN GREAT LAKES OVER THE NEXT COUPLE OF DAYS. THIS WILL LEAD TO LIGHT EAST-SOUTHEAST WINDS ACROSS THE LAKES. SOME SLIGHTLY GUSTIER NE WINDS MAY OCCUR WITHIN THE WARMER WATERS OF SAGINAW BAY FROM TIME TO TIME AS THE WIND GETS FUNNELED INTO THE BAY. OTHERWISE...WINDS AND WAVES WILL PROVIDE FAVORABLE BOATING CONDITIONS. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...NONE. LAKE ST CLAIR...NONE. MI WATERS OF LAKE ERIE...NONE. && $$ AVIATION.....DRK SHORT TERM...DRK LONG TERM....SC MARINE.......SC YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

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