Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 041002 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 602 AM EDT FRI SEP 4 2015 .AVIATION...
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CLOUDS HAVE HELD FIRM OVER MUCH OF THE AREA OVERNIGHT REDUCING THE COVERAGE/INTENSITY OF FOG ACROSS THE TAF SITE. WINDS AROUND 5-7 KNOTS HAVE ALSO PROVEN ENOUGH TO KEEP MORE OF A LOW STRATUS THREAT THUS FAR. WILL BE A BIT OPTIMISTIC AND FAVOR PREVAILING VFR/MVFR WITH SOME IFR NOT OUT OF THE QUESTION. THE LOW STRATUS AND FOG WILL LIFT THIS MORNING AND ATTENTION THEN TURNS TO PRECIPITATION CHANCES ONCE AGAIN. CHANCES ARE LOWER TODAY AS THE MAIN FORCING HAS PUSHED EAST BUT THERE REMAINS A CHANCE OF SHOWERS AND THUNDERSTORMS THROUGH TONIGHT. AT THIS POINT WITH NO CLEAR FORCING TO KEY OFF...COVERAGE MAY BE TOO SCATTERED TO INCLUDE PRECIP IN THE TAF. BEST CHANCE WILL COME THIS AFTERNOON WITH A DIURNAL BOOST. FOG MAY AGAIN BECOME AN ISSUE LATE TONIGHT AND SATURDAY MORNING. FOR DTW...LOW CONFIDENCE FORECAST THIS MORNING AS OBSERVATIONS HAVE BEEN EITHER VFR OR IFR. CONDITIONS WILL IMPROVE THROUGH THE MORNING AS MIXING INCREASES. SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE TODAY WITH BEST COVERAGE TO THE NORTH OF THE TERMINAL. LOW CONFIDENCE ON TIMING WHEN PRECIPITATION WOULD ACTUALLY HIT THE SITE SO WILL HOLD OFF ON INCLUDING AT THE MOMENT. LOOK FOR FOG TO DEVELOP ONCE AGAIN TONIGHT. //DTW THRESHOLD PROBABILITIES... * MEDIUM FOR CIG AT OR BELOW 5000 FEET THROUGH THE TAF PERIOD. * LOW FOR THUNDERSTORMS THROUGH THE TAF PERIOD.
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&& .PREV DISCUSSION...
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ISSUED 330 AM EDT FRI SEP 4 2015 SHORT TERM...TODAY AND TONIGHT ANOTHER DAY WITH THE STACKED LOW PRESSURE SYSTEM WOBBLING ABOUT LOWER MI. THE MAIN LOBE OF VORTICITY STRUNG OUT N TO S GOT A NOCTURNAL BOOST FROM THE 850MB JET EARLY IN THE OVERNIGHT ENHANCING THE THUNDERSTORM ACTIVITY ACROSS THE SOUTHERN CWA. THE VORT MAX HAS SINCE PUSHED EAST ALIGNING ALONG THE DETROIT AND ST CLAIR RIVERS. THIS FEATURE ALONG WITH THE REGION OF DEFORMATION WRAPPING AROUND THE LOW APPEAR TO BE THE MAIN FORCING MECHANISMS FOR PRECIP CHANCES THROUGH TONIGHT WITH THE LACK OF ANY REAL FLOW AND BULK OF THE INSTABILITY FALLING SOUTH OF THE AREA. THE CYCLONIC FLOW WILL TRY TO PULL SOME INSTABILITY BACK NORTHWARD ALONG THE LOBE OF VORTICITY THIS AFTERNOON ADDING TO COVERAGE. PWATS ARE PROGGED TO BE SLIGHTLY LESS TODAY THAN YESTERDAY BUT STILL VERY HEALTHY ABOVE 1.5 INCHES. MAIN UPDATE FOR TODAY IS TO REALIGN THE POPS TO THE FORCING...KEEPING LIKELY POPS EAST BY THE FORCING AND NORTH CLOSER TO THE CENTER OF THE LOW AND CHANCE ELSEWHERE FOR BROAD LIFT. SEVERE WEATHER IS NOT ANTICIPATED DUE TO LACK OF FLOW AND FORCING BUT ABUNDANT MOISTURE WILL RESULT IN LOCALLY HEAVY RAINFALL IN ANY THUNDERSTORM THAT DEVELOPS. THE STRONGEST STORMS WILL BE CAPABLE OF WIND GUSTS TO 45 MPH PRIMARILY DUE TO PRECIP LOADING. AS THE UPPER LOW LIFTS NORTHEASTWARD AWAY FROM LOWER MI TONIGHT...THE DEFORMATION BAND ON THE BACKSIDE WILL SLIDE THROUGH THE AREA. WILL CONTINUE A CHANCE POP TIL THE EXTENT OF THE PRECIP CAN BE BETTER DEFINED BUT MAY BE ABLE TO TRIM OUT SOME OF THE SOUTHERN COUNTIES. LONG TERM... SOUTHEAST MICHIGAN WILL REMAIN ENGULFED IN THE AMPLIFIED SUBTROPICAL RIDGE THROUGH EARLY NEXT WEEK. 850MB TEMPERATURES WILL HOVER BETWEEN 17-19C THROUGH THIS TIME INDICATING HIGH TEMPERATURES LIKELY CONFINED TO THE MID 80S TO LOW 90S LARGELY CONTINGENT ON CLOUD COVER AND PRECIP TRENDS EACH DAY. LIKEWISE, DEWPOINTS WILL REMAIN ELEVATED NEAR 70 DEGREES WHICH WILL EFFECTIVELY PUT A FLOOR ON OVERNIGHT LOWS AND ENSURE MUGGY CONDITIONS UNTIL AT LEAST THE MIDDLE OF NEXT WEEK. MODERATE DESTABILIZATION OF 1500-200 J/KG MLCAPE IS STILL ON THE TABLE FOR SATURDAY WITH THERMODYNAMIC PROGS INDICATING UNIMPRESSIVE CAPPING. MID-LEVELS WILL REMAIN COOLER WITH THE DAMPENING CLOSED CIRCULATION STILL PRESENT IN SOME RESPECT OVER THE CENTRAL GREAT LAKES, AND THIS WILL BE SUFFICIENT TO MOVE FORWARD WITH THE INHERITED CHC POPS - LACK OF STRONGER FORCING PRECLUDING A MORE AGGRESSIVE POP. AMBIENT WINDS WILL BE WEAK AND POORLY SHEARED. ANY CONVECTION WILL BE ORDINARY AND THE PRIMARY THREAT WILL ONCE AGAIN BE HEAVY RAIN DUE TO SLUGGISH STORM MOTION. ESSENTIALLY A MODIFIED PERSISTENCE FORECAST THEN FOR SUNDAY TO ACCOUNT FOR CONTINUED DECLINE OF RESIDENT FORCING IN ADDITION TO WARMING MID-LEVELS, PARTICULARLY ABOVE 700MB. CONVECTIVELY ENHANCED SHORTWAVE LIFTING ACROSS THE FRONT RANGE DURING THE PREDAWN HOURS THIS MORNING WILL BE STEERED AROUND THE PERIPHERY OF THE RIDGE AND MAY BE SUFFICIENT TO TRIGGER SCATTERED CONVECTION AROUND THE EDGE OF THE CAP, WHICH WOULD FAVOR NORTHERN AREAS ON SUNDAY AFTERNOON. FOR NOW, WILL INTRODUCE A CHC POP BUT WILL CONFINE IT TO THE WATERS OF LAKE HURON FOR NOW. MARINE... THUNDERSTORMS WILL ESSENTIALLY REMAIN A DAILY THREAT ACROSS THE WATERS THROUGH AT LEAST THE MIDDLE OF NEXT WEEK. OTHERWISE, LIGHT TO MODERATE WINDS PREDOMINANTLY OUT OF THE SOUTH WILL BE COMMON INTO NEXT WEEK. A MORE CONCERTED MODERATE SOUTHWEST WIND WILL DEVELOP IN ADVANCE OF AN APPROACHING LOW LATE SUNDAY INTO MONDAY BUT WIND GUSTS ARE EXPECTED TO BE NO MORE THAN 20 KNOTS AT THIS TIME.
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&& .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....JVC MARINE.......JVC YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

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