Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 270405 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 1205 AM EDT WED MAY 27 2015 .AVIATION...
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A STRAY SHOWER WILL BE POSSIBLE DURING THE EARLY MORNING BUT COVERAGE WILL BE TOO SPARSE TO INCLUDE AT ANY ONE TERMINAL LOCATION. INTENSITY WILL ALSO BE CONSIDERABLY LIGHTER COMPARED TO EARLIER IN THE NIGHT. THAT LEAVES A MIX OF MVFR CEILING AND FOG AS THE MAIN AVIATION CONCERN THROUGH THE MORNING. AFTER A BRIEF CLEARING TREND...THE LATEST DATA POINTS TO THE BEST CHANCE FOR CEILING TO OCCUR AT MBS DOWN TO FNT AS SOUTHERLY FLOW OF HUMID AIR PERSISTS DURING THE NIGHT. THERE COULD BE POCKETS OF CLOUDS AT PTK THROUGH DTW AND ANY FOG THAT DEVELOPS WILL BE LIMITED TO MVFR BY WIND STAYING ABOVE 5 KNOTS THROUGH MID MORNING. CONVECTIVE POTENTIAL DURING THE AFTERNOON INTO WEDNESDAY EVENING WILL SUPPORT ENOUGH SHOWER ACTIVITY FOR A PROB GROUP DURING PEAK HEATING BUT WILL HOLD OFF ON THUNDER AT THIS POINT IN THE FORECAST. FOR DTW... OUTSIDE OF A STRAY SHOWER...WEATHER CONCERNS WILL BE LIMITED TO MVFR FOG AND PATCHY MVFR CEILING DURING THE MORNING. CONFIDENCE IS HIGH ENOUGH IN SHOWER COVERAGE FOR A PROB GROUP DURING THE AFTERNOON BUT NOT YET FOR THUNDERSTORMS. //DTW THRESHOLD PROBABILITIES... * MEDIUM PROBABILITY FOR CEILING BELOW 5000 FT AFTERNOON INTO EVENING. * LOW POTENTIAL FOR THUNDERSTORMS AFFECTING THE TERMINAL AFTERNOON INTO EVENING.
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&& .PREV DISCUSSION...
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ISSUED 1037 PM EDT TUE MAY 26 2015 UPDATE... POCKETS OF SHOWERS WILL REMAIN POSSIBLE INTO THE EARLY OVERNIGHT HOURS. THERE COULD ALSO BE A STRAY THUNDERSTORM BUT SUPPORT FOR DEEP CONVECTION HAS WANED CONSIDERABLY SINCE SUNSET. HOURLY MESOANALYSIS DEPICTS LAPSE RATES AT SUB 6 C/KM LEVELS AND MUCAPE SUB 500 J/KG. FORCING FOR SHOWERS IS MAINLY TIED TO THE UPPER LOW BEING ABLE TO WRING OUT THE LAST BIT OF ELEVATED INSTABILITY ALONG THE TRAILING EDGE OF THE LOW LEVEL THETA-E RIDGE. EVENING WATER VAPOR IMAGERY AND MODEL UPPER AIR FIELDS ALSO SHOW A SMALLER SCALE WAVE ABLE TO FOCUS SOME BROKEN LINES OF SHOWERS THAT WILL SLIDE THROUGH AND OUT OF SE MICHIGAN SHORTLY AFTER MIDNIGHT. PREV DISCUSSION...ISSUED 302 PM EDT TUE MAY 26 2015 SHORT TERM...THIS AFTERNOON AND TONIGHT CONFIDENCE IS INCREASED IN SEVERE POTENTIAL 5PM-10PM THIS EVENING, FOR WHICH A SEVERE TSTORM WATCH IS FORTHCOMING FOR ALL OF SE MICHIGAN. POTENT SHORTWAVE IS NOTED ON WV IMAGERY LIFTING TOWARD WESTERN WISCONSIN BY 00Z. INITIAL BAND OF SHOWERS/STORMS ALONG THE BACK EDGE OF THE MID-LEVEL MOISTURE GRADIENT MAY IN THE PROCESS OF BECOMING SECONDARY TO AN ADDITIONAL CONVECTIVE BAND THAT HAS DEVELOPED WITHIN THE PLUME OF GREATEST MOISTURE CONTENT. AN ADDITIONAL FEW UPDRAFTS ARE POPPING UP NEAR THE SOUTHERN MI BORDER ALONG THE LEAD EDGE OF THE H7 GRADIENT. AS NOTED IN THE MIDDAY UPDATE, PWATS WILL JUMP TO 1.6 INCHES WITHIN THE APPROACHING MOISTURE PLUME AROUND 20-21Z. MEAN BOUNDARY LAYER PARCELS STILL HAVE POTENTIAL TO ACHIEVE 1,000 J/KG MLCAPE WITH POCKETS OF 1500 NOT OUT OF THE QUESTION. AMBIENT WIND FIELD IS NOT PARTICULARLY STRONG, WITH WINDS PEAKING AT 35 TO 40 KTS INT HE COLUMN, BUT SHEAR WILL BE SUFFICIENT TO MAINTAIN A SWLY 0-6KM BULK SHEAR VECTOR OF 35 KNOTS IN THE SOUTHEAST TO 45 KTS IN THE SAGINAW VALLEY CLOSER TO THE MID-LEVEL CIRCULATION AND STRONGEST DYNAMIC FORCING, WHICH MAY COMPENSATE FOR POTENTIAL LACKING INSTABILITY FURTHER NORTH. WELL-MIXED BOUNDARY LAYER NOTED ON 18Z DTX SOUNDING WILL MAINLY SUPPORT A WIND THREAT WITH SOME ORGANIZATION INTO DYNAMIC BOWS A POSSIBILITY, ESPECIALLY EARLIER IN THE EPISODE CLOSER TO PEAK HEATING. GIVEN HIGH MOISTURE CONTENT, STORMS WILL ALSO CARRY POTENTIAL FOR TORRENTIAL DOWNPOURS. WEAK COLD FRONT WILL USHER IN ANOTHER ROUND OF LOW CLOUDS AND A LOW COVERAGE OF SHOWERS LATE. CONTINUED FLOW OUT OF SLY QUADRANT WILL SUPPORT ANOTHER NIGHT OF WARMER OVERNIGHT LOWS IN THE MID 60S. LONG TERM... LARGE SCALE UPPER LEVEL SHORTWAVE AND ASSOCIATED LOW PRESSURE WILL LIFT FROM THE NORTHERN GREAT LAKES INTO ONTARIO AND QUEBEC WEDNESDAY INTO WEDNESDAY NIGHT...DRAGGING A COLD FRONT INTO THE AREA FROM LATE AFTERNOON INTO THE EVENING. WHILE THIS FRONTAL BOUNDARY WILL BE THE FOCUS OF SCATTERED TO ISOLATED CONVECTION...MAINLY FROM AFTERNOON INTO THE EARLY EVENING...A PRE-FRONTAL TROUGH IS EXPECTED TO SHIFT THROUGH THE AREA EARLIER IN THE DAY AND FORCE DEEPER MOISTURE AND INSTABILITY EAST AND SOUTHEAST OUT OF THE AREA. THIS WILL LIMIT THE OVERALL COVERAGE AND INTENSITY OF SHOWERS AND STORMS DURING COLD FROPA. AS THE AFOREMENTIONED LOW PASSES NORTH OF THE REGION...THE PRESSURE GRADIENT WILL TIGHTEN NOTABLY OVER LOWER MICHIGAN AND ONCE THE LOW LEVEL FLOW VEERS MORE SOUTHWEST IN THE WAKE OF THE TROUGH...EXPECT GUSTY WINDS TO AFFECT THE AREA MUCH OF THE DAY. WOULD NOT BE TOO SURPRISED TO SEE WIND GUSTS OF 30 TO 35 MPH WITH SUSTAINED WINDS AOA 20 MPH. THE WEATHER QUIETS SUBSTANTIALLY FROM LATE WEDNESDAY EVENING AND OVERNIGHT ON INTO THURSDAY AS THE COLD FRONT EASES SOUTHEAST OF THE AREA AND A RIDGE OF SURFACE HIGH PRESSURE BUILDS INTO AND THROUGH THE AREA DURING THE MIDDLE OF THE WEEK AS THE CENTER OF HIGH PRESSURE BUILDS ACROSS SOUTHERN CANADA. WHILE A COLD FRONT DOES BRING A SLIGHTLY COOLER AND DRIER AIRMASS INTO THE AREA...MAXIMUM TEMPERATURES WILL STILL CLIMB TO AROUND 80F ON THURSDAY. IT WILL JUST BE LESS HUMID THAN THE EARLY PART OF THE WEEK. THIS DRIER AIRMASS WILL...HOWEVER...LEAD TO COOLER MINIMUM TEMPERATURES AS RADIATIONAL COOLING WILL BE STRONG. SO...EXPECT LOW TEMPERATURES RANGING IN THE 50S TO AROUND 60 BOTH WEDNESDAY AND THURSDAY NIGHT. ONCE THIS HIGH PRESSURE RIDGE SHIFTS EAST...SOUTHWESTERLY FLOW WILL INCREASE AGAIN FRIDAY INTO FRIDAY NIGHT AS THE NEXT LOW PRESSURE SYSTEM LIFTS FROM THE NORTHERN PLAINS TOWARDS JAMES BAY AS A RATHER VIGOROUS SHORTWAVE PIVOTS INTO SOUTHERN CANADA AROUND MEAN UPPER LEVEL LOW POSITIONED AROUND HUDSON BAY. THIS WILL BRING ANOTHER WARM DAY INTO FRIDAY WITH 80S PREVALENT. A SIGNIFICANT COOLING WILL THEN ENSUE NEXT WEEKEND AS THE ATTENDANT COLD FRONT MOVES THROUGH THE AREA ON SATURDAY. HIGHS BY SUNDAY WILL BE LIMITED AROUND 60 DEGREES WITH LOWS IN THE 40S IN MANY LOCATIONS BY EARLY SUNDAY AND MONDAY MORNINGS. THE APPROACH AND PASSAGE OF THIS SYSTEM WILL ALSO BRING THE NEXT SUBSTANTIAL CHANCE OF SHOWERS AND THUNDERSTORMS FROM LATE FRIDAY INTO EARLY SATURDAY. THE LARGE HIGH PRESSURE SYSTEM BRINGING THE COOLER WEATHER WILL ALSO QUASH PRECIPITATION CHANCES BY THE END OF THE FORECAST PERIOD AND THE WARM/HUMID AIR OF LATE IS FORCED WELL SOUTH OF THE FORECAST AREA. MARINE... SOUTH TO SOUTHWEST FLOW WILL CONTINUE OVER THE GREAT LAKES REGION LATE TODAY INTO WEDNESDAY...RANGING FROM 10 TO 15 KNOTS WITH GUSTS TO 20 KNOTS INTO TONIGHT...BUT INCREASING SLIGHTLY INTO WEDNESDAY AS A WEAK COLD FRONT APPROACHES AND THE PRESSURE GRADIENT TIGHTENS. AT THIS TIME...IT APPEARS CONDITIONS WILL NOT WARRANT SMALL CRAFT ADVISORIES ANYWHERE...ALTHOUGH FUNNELING OF SOUTHWEST FLOW UP SAGINAW BAY MAY ALLOW GUSTS TO APPROACH 25 KNOTS LATE TONIGHT INTO THE FIRST HALF OF WEDNESDAY. THE WARM...MOIST FLOW OVER THE COLD WATERS WILL ALSO PRODUCE SOME FOG AND STRATUS OVER LAKE HURON INTO TONIGHT. THERE WILL BE A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS LATE THIS AFTERNOON INTO THIS EVENING...WITH ANOTHER CHANCE WEDNESDAY AS THE COLD FRONT MOVES THROUGH THE AREA. DRY CONDITIONS ARE THE EXPECTED THURSDAY AND MUCH OF FRIDAY.
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&& .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...NONE. LAKE ST CLAIR...NONE. MICHIGAN WATERS OF LAKE ERIE...NONE. && $$ AVIATION.....BT UPDATE.......BT SHORT TERM...JVC LONG TERM....DG MARINE.......DG YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

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