Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 261145 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 745 AM EDT TUE MAY 26 2015 .AVIATION... FOG AND LOW STRATUS IS BEGINNING TO LIFT NORTHWARD INTO MI AND SHOULD INFLUENCE THE TERMINALS UNTIL LATE MORNING WHEN MIXING COMMENCES AND SCATTERS SKIES OUT. SURFACE OBS SHOW THIS STRATUS TO BE FAIRLY EXTENSIVE TO OUR SOUTH THOUGH CIRRUS DEBRIS IS HIDING IT IN SATELLITE IMAGERY. VFR CONDITIONS THROUGH THE AFTERNOON UNTIL CONVECTION BEGINS TO DEVELOP AROUND 22Z. COVERAGE WILL PEAK AROUND 00-03Z THIS EVENING SO WILL INCLUDE THIS PERIOD FOR TSRA. SOME LINGERING SHOWERS WILL CONTINUE INTO THE OVERNIGHT BEFORE WE SEE A TRANSITION BACK TO A LOW STRATUS DECK. FOR DTW...MAINLY MVFR STRATUS FIELD LIFTING NORTH TOWARD THE TERMINAL SHOULD AFFECT THE TERMINAL THROUGH ABOUT 15-16Z. CIGS WILL SCATTER OUT THIS AFTERNOON BEFORE SHOWERS AND THUNDERSTORMS DEVELOP LATE THIS AFTERNOON AND EVENING. A STRAY SHOWER/TSTORM CANNOT BE RULED OUT BETWEEN 21-00Z BUT THE BETTER COVERAGE LOOKS TO FALL BETWEEN 00-03Z THIS EVENING. //DTW THRESHOLD PROBABILITIES... * MEDIUM IN CIGS BELOW 5000 FT THIS MORNING...AND AGAIN THIS EVENING THROUGH THE OVERNIGHT. * LOW IN THUNDERSTORMS LATE THIS AFTERNOON...MEDIUM THIS EVENING. && .PREV DISCUSSION...ISSUED 349 AM EDT TUE MAY 26 2015 SHORT TERM...TODAY AND TONIGHT THE OVERALL LONGWAVE SETUP HAS NOT CHANGED OVER THE LAST SEVERAL DAYS WITH THE SLOWLY DRIFTING TROUGH ENGULFING MUCH OF THE WEST/CENTRAL CONUS WHILE RIDGE OVER THE EAST COAST HOLDS STRONG. THIS HAS LEAD TO SE MI BEING LOCATED IN BETWEEN THE TWO DOMINATE FEATURES WITH PERSISTENT SWERLY FLOW KEEPING A WARM AND HUMID AIRMASS IN PLACE. TODAY WILL BE SLIGHTLY DIFFERENT IN THE SENSE THAT THE TROUGH WILL BECOME A LITTLE MORE PROGRESSIVE WITH THE STRONG VORT MAX...NOW AN OPEN WAVE...MOVING FROM NE TO MN/WI. THIS MEAN THE NEXT SHORTWAVE TRACKING UP THROUGH THE TROUGH WILL TRACK THROUGH THE WESTERN GREAT LAKES. THIS WILL HELP PROVIDE A BIT STRONGER FORCING OVER THE AREA THAN WE HAVE SEEN WITH THE SHORTWAVES THE PREVIOUS COUPLE DAYS. ADDITIONALLY...MODELS ARE ADVERTISING THIS WAVE TO BE A BIT STRONGER THAN YESTERDAYS WAVE WHICH RESULTED IN A FEW ISOLATED THUNDERSTORMS AND WINDS GUSTS 50 TO 60 MPH. CURRENT RIDGING ALOFT WILL REMAIN OVERHEAD THROUGH THIS AFTERNOON BEFORE THE MID LEVEL SHORTWAVE BEGINS TO SWING UP INTO SOUTHERN MI. MOST OF THE DAY WILL FEATURE ONLY CIRRUS CLOUDS FILLING THE SKY AS THE MID LEVELS ARE QUITE DRY AND MIXING WILL LIMIT THE CU FIELD TIL THE AFTERNOON. THE WAVE WILL LIFT THROUGH THE AREA LATE THIS AFTERNOON THROUGH THE EVENING HOURS...BETWEEN ABOUT 22-04Z. AN ENHANCED BAND OF THETA E WITH DECENT ISENTROPIC ASCENT BETWEEN 305- 310K WILL LIFT NORTHWARD PROVIDING THE FOCUS FOR THE STORMS. SLIGHTLY BETTER CONDITIONS SHOULD EXIST TODAY FOR STORM DEVELOPMENT WITH THE CLOSER PROXIMITY TO THE WAVE AND FAVORABLE TIMING OF CONVECTIVE INITIATION OCCURRING DURING PEAK HEATING. MODELS ARE ALL IN THE BALLPARK OF AROUND 500 J/KG WITH THE NAM COMING IN A FEW HUNDRED HIGHER WHICH IS TYPICAL. LAPSE RATES HAVE STRUGGLED THE LAST FEW DAYS BUT APPEAR TO BE FAVORABLE UP TO AROUND 750MB TODAY WHICH SHOULD HELP STORMS GET GOING. A LL JET WILL NOSE UP INTO THE AREA IN THE EVENING RESULTING IN DEEP LAYER WIND SPEEDS AROUND 40 KNOTS. BR SHEAR VALUES WILL INCREASE TO AROUND 30 KNOTS. ALL IN ALL IT LOOKS LIKE WE WILL SEE A LINE/BAND OF SHOWERS AND THUNDERSTORMS LIFT NORTH THIS EVENING WITH THE POSSIBILITY OF SOME STORMS REACHING SEVERE LIMITS WHILE TRAVELING NE AT 35 MPH. PRIMARY THREAT APPEARS TO BE DAMAGING WIND WITH LESSER THREATS BEING HAIL AND TORNADOS. BRIEF HEAVY DOWNPOURS AND LOCALIZED FLOODING WILL ALSO BE POSSIBLE AS PWATS RISE TO NEAR 1.75 INCHES. SPC HAS UPGRADED ALL OF LOWER MI FROM MARGINAL TO SLIGHT RISK. SOME SHOWERS AND THUNDERSTORMS MAY LINGER THROUGH THE OVERNIGHT AS IT APPEARS THE UPPER LOW WILL TRY TO PULL ANOTHER WEAKER LOBE OF VORTICITY THROUGH THE REGION WHILE THE MID LEVEL COOL POOL SLIDES THROUGH NORTHERN LOWER. TEMPERATURES WILL STAY MILD IN THE MID 60S AS SW FLOW CONTINUES AHEAD OF THE COLD FRONT LOCATED UP THROUGH THE MIDWEST. LONG TERM... ABOVE NORMAL TEMPERATURES AND A COUPLE MORE ROUNDS OF ORGANIZED ACTIVITY THROUGH THE END OF THE WEEK AS SOUTHEASTERN MICHIGAN REMAINS UNDER ELEVATED HEIGHTS/UPPER LEVEL RIDGE. PATTERN BREAKING COLD FRONT TO PUSH THROUGH NEXT WEEKEND. WEDNESDAY...NUMERICAL OUTPUT HAS CONVERGED OVER THE PAST 24 HOURS IN ADVERTISING A SOLUTION FOR A STRONGER SURFACE LOW CENTER TRACKING THROUGH THE NORTHERN GREAT LAKES ON WEDNESDAY. THE DIFFERENCE STEMS FROM MORE EFFICIENT PHASING OF SOUTHERN PLAINS AND CENTRAL PLAINS VORTICITY ANOMALIES...AND ASSOCIATED JET ENTRANCE REGION. THIS JET ENTRANCE REGION AND SOUTHERN TAIL OF VORTICITY ANOMALY WILL DRAG THROUGH SOUTHEASTERN MICHIGAN ON WEDNESDAY PROVIDING SYNOPTIC SCALE SUPPORT TO THE CWA. PERSISTENCE IN THERMODYNAMIC PROFILE SUGGESTS SIMILAR CAPE VALUES WED WITH AS MUCH AS 1000-1200 J/KG OF SBCAPE/MLCAPE POSSIBLE. SURFACE TROUGH/THETA E GRADIENT/WEAK COLD FRONT IS EXPECTED TO PUSH INTO SOUTHEASTERN MICHIGAN DURING THE AFTERNOON PROVIDING A FOCUSING MECHANISM. TIMING OF THIS FEATURE IS IMPORTANT FOR THE FORECAST...WITH QUICKER TIMING NEGATING ANY POTENTIAL FOR INSTABILITY DURING THE AFTERNOON. EVEN IN SLOWER SOLUTION...RICHEST EQUIVALENT POTENTIAL TEMPERATURE IS FORECASTED TO RESIDE IMMEDIATELY SOUTH AND EAST OF LOWER MICHIGAN. EXPECTATIONS ARE FOR SHOWERS AND THUNDERSTORMS TO BECOME SCATTERED COVERAGE POST 18Z...WITH AN ISOLATED SHOWER SCENARIO PRIOR TO 18Z. THE DEEPER WIND FIELD WILL HAVE STRIPPED OUT BY WEDNESDAY...WITH 0-6 KM BULK SHEAR RANGING 15-25 KNOTS. THE CONDITIONAL UNCERTAINTY OF INSTABILITY COMBINED WITH MARGINAL DEEP LAYER SHEAR SUPPORTS MESSAGING OF JUST A STANDARD THUNDERSTORM RISK FOR WEDNESDAY. LATEST SWODY2 KEEPS MARGINAL DESIGNATION TO THE SOUTH AND EAST OF MICHIGAN...TIED TO RICHER THETA E CONTENT. THURSDAY...DOWNSTREAM RIDGING WILL EXPAND EASTWARD ACROSS THE CENTRAL GREAT LAKES ON THURSDAY. VERY WEAK SURFACE RIDING IS EXPECTED TO BUILD INTO THE STATE...WITH MODELS INDICATING THE LOW LEVEL ANTICYCLONIC CIRCULATION TRACKING LOCALLY...SEEKING OUT THE LAKE HURON/ERIE AGGREGATE. GONE DRY THURSDAY...WITH WARM AIR ADVECTION AND LOW SKY FRACTION ALLOWING TEMPERATURES TO PUSH INTO THE LOWER 80S. FRIDAY...WILL BE WATCHING THE NEXT DAY OR SO HOW THE MODELS HANDLE THE AMPLIFICATION OF THE RIDGE OVER SECTIONS OF NORTHERN CANADA. IT REMAINS POSSIBLE QUICKER STRENGTHENING OF THE RIDGE COULD OCCUR AND SERVE AS BLOCKING FOR THE DEVELOPING COLD FRONT AND FORCING. FOR NOW...PRECIPITATION CHANCES START EARLY ON FRIDAY...BUT THIS VERY WELL COULD BE PUSHED BACK WITH TIME. ADDITIONALLY...A SLOWER SOLUTION WOULD SUPPORT HIGHER TEMPS THAN WHAT IS ALREADY IN THE GRIDS. MIDDLE TO POSSIBLY UPPER 80S COULD BE IN PLAY. MARINE... SOUTHWESTERLY FLOW WILL REMAIN IN PLACE OVER THE GREAT LAKES REGION THROUGH MIDWEEK. WINDS TODAY ARE EXPECTED TO RANGE 10 TO 15 KNOTS WITH GUSTS TO 20 KNOTS THIS AFTERNOON. WINDS ARE FORECASTED TO INCREASE ON WEDNESDAY...WITH FREQUENT GUSTS RANGING 20 TO 25 KNOTS. THE CHANCE OF SHOWERS AND THUNDERSTORMS WILL INCREASE LATE THIS AFTERNOON AND EVENING...LINGERING INTO WEDNESDAY. A WEAK SURFACE TROUGH WILL PASS THROUGH THE STATE LATE WEDNESDAY. DRY CONDITIONS ARE THE EXPECTED THURSDAY AND MUCH OF FRIDAY. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...NONE. LAKE ST CLAIR...NONE. MICHIGAN WATERS OF LAKE ERIE...NONE. && $$ AVIATION.....DRK SHORT TERM...DRK LONG TERM....CB MARINE.......CB YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

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