Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 211106 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 706 AM EDT MON APR 21 2014 .AVIATION...
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//DISCUSSION... VFR CONDITIONS WILL HOLD TODAY WITHIN DEVELOPING SOUTHWEST FLOW IN ADVANCE OF APPROACHING LOW PRESSURE. SCATTERED SHRAS WILL BRUSH MBS DURING THE AFTERNOON...BUT HOLD OFF AT THE OTHER TERMINALS UNTIL EVENING AS AFOREMENTIONED LOW PRESSURE TRACKS BY THE REGION AND THE ATTENDING COLD FRONT SWINGS SOUTHEAST INTO THE AREA. MVFR CONDITIONS CAN BE EXPECTED AT TIMES WITH THIS ACTIVITY. THE PASSAGE OF THE FRONT BETWEEN 07Z-09Z OR SO WILL BRING AN END TO SHOWERS OVERNIGHT. NORTHWEST WINDS BEGIN TO INCREASE IN THE WAKE OF THIS FROPA TOWARDS THE END OF THE FORECAST PERIOD. //DTW THRESHOLD THREATS... * MEDIUM CONFIDENCE IN CEILINGS AOB 5000 FEET AT TIMES 03Z-09Z TONIGHT.
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&& .PREV DISCUSSION...
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ISSUED 344 AM EDT MON APR 21 2014 SHORT TERM...TODAY AND TONIGHT FORECAST REASONING HAS CHANGED LITTLE FOR THIS FORECAST PACKAGE. EXPECT A VERY MILD DAY TODAY AS SOUTHWEST FLOW DEVELOPS IN ADVANCE OF AN APPROACHING LOW PRESSURE SYSTEM AND COLD FRONT. FOR MOST OF THE AREA...WILL MAINTAIN THE CURRENT MAXIMUM TEMPERATURE FORECAST IN THE MIDDLE 70S...BUT WILL LOWER THE FAR NORTHERN SAGINAW VALLEY AND THUMB CLOSER TO 70 AS CLOUD COVER WILL BE MORE PREVALENT AS SHOWER ACTIVITY DEVELOPS EARLIER IN THE DAY IN THESE AREAS. OTHERWISE...RELATIVELY WEAK SOUTHERN STREAM SHORTWAVE IS STILL FORECAST TO BE PULLED NORTHEAST INTO THE AREA THIS AFTERNOON IN ADVANCE OF A MUCH STRONGER POLAR SHORTWAVE DIGGING INTO THE GREAT LAKES LATE TODAY INTO TONIGHT. TIMING OF THESE FEATURES STILL SUGGEST THAT SCATTERED SHOWERS WILL BECOME INCREASINGLY LIKELY THROUGH THE COURSE OF THE AFTERNOON...WITH THE BEST CHANCE OF SHOWERS THEN COMING IN THE 00Z-06Z TIME FRAME AS A LOW PRESSURE SYSTEM PASSES JUST NORTH OF THE CWA AND PULLS A COLD FRONT INTO THE AREA DURING THE EVENING. WILL MAINTAIN A MENTION OF THUNDER AS THE STRONG WARMING TODAY DOES ALLOW FOR SOME MARGINAL INSTABILITY OVER THE AREA...DESPITE A DECIDED LACK OF LOW LEVEL MOISTURE...SURFACE DEWPOINTS 45-50F. ANY RESIDUAL INSTABILITY WILL BE FORCED FAIRLY DECENTLY BY THE COLD FRONTAL BOUNDARY AS POLAR SHORTWAVE AMPLIFIES NOTABLY AS IT MOVES INTO THE REGION LATE. THE PASSAGE OF THE COLD FRONT WILL LEAD TO AN END TO SHOWER/THUNDERSTORM ACTIVITY OVERNIGHT...GENERALLY AFTER 08Z OR SO. TEMPERATURES WILL BEGIN COOLING DOWN...BUT GIVEN THE LATE ARRIVAL OF THE COLD AIR...MINIMUM TEMPERATURES WILL RANGE NEAR 40 OVER THE FAR NORTHWEST CWA TO 50 DETROIT SOUTH. LONG TERM...TUESDAY THROUGH NEXT SUNDAY ENERGETIC LOW AMPLITUDE LONGWAVE PATTERN WILL BECOME MORE AMPLIFIED ON TUESDAY AS A DEEPENING TROUGH OVER THE WEST COAST HAS A RIPPLING EFFECT DOWNSTREAM. THIS WILL DRAW THE JET STREAM AS A WHOLE SOUTHWARD OVER THE GREAT LAKES WHICH WILL RESULT IN THE NEXT FEW MID LATITUDE CYCLONES TARGETING SOUTHERN MI. THIS WILL ALSO BRING COOLER AIR BACK TO THE STATE...ESPECIALLY IN THE WAKE OF THE LOWS...BRINGING SLIGHTLY BELOW NORMAL TEMPERATURES BACK INTO THE FORECAST. THE FIRST LOW WILL BE EXITING THE AREA BY TUESDAY MORNING WITH THE COLD FRONT WELL THROUGH THE AREA BY THEN. A TRAILING TROUGH WILL BE DROPPING DOWN THROUGH THE EASTERN GREAT LAKES THOUGH AS COOLING HIGH PRESSURE SYSTEM BEGINS TO BUILD INTO THE AREA. THIS WILL BRING A SLIGHT CHANCE OF SOME RAIN SHOWERS TO OUR EASTERN COUNTIES AS NORTHERLY FLOW INCREASES CAA WHICH STEEPENS LL LAPSE RATES WITH UPPER LEVEL LIFT COINCIDENT TO IT. MODELS ALSO CONTINUE TO ADVERTISE ELEVATED WIND SPEEDS/GUSTS IN THE AFTERNOON. DEPTH OF MIXING WILL REACH AROUND 850-900 MB DURING PEAK HEATING WHICH WILL TRY TO BRING SOME HIGHER GUSTS TO THE SFC. WINDS UP TO 850MB ARE FORECAST TO PEAK AT AROUND 30 KNOTS WHICH WILL PUT A CAP ON WIND POTENTIAL. MODEL SOUNDINGS SUGGEST IT WILL TAKE TIL CLOSE TO 18Z BEFORE WE MIX OUT SO MAY SEE WINDS PICK UP AFTER 16Z FOR A FEW HOURS BEFORE DIURNAL PROCESSES CEASE. LOOK FOR GUSTS TO REACH 25 TO 30 MPH. WITH COOL HIGH PRESSURE SETTLING IN OVERNIGHT...TEMPS WILL DROP ONCE AGAIN TO NEAR THE FREEZING MARK. WE WILL SEE THE NEXT CHANCE OF PRECIP TOWARD THE END OF THE WORK WEEK AS AN OCCLUDED SFC LOW TIED TO A MID LEVEL LOW OVER THE NORTHERN PLAINS HAS NEW DEVELOPMENT ALONG THE SOUTHEASTWARD EXTENDING COLD FRONT WHICH IS SURGING OUT WELL OUT AHEAD OF IT. THE NEW SFC LOW IS UNDER A SHORTWAVE DROPPING THROUGH THE TROUGH WHICH IS WORKING THROUGH THE PLAINS AT THAT TIME. THE PAIR OF SURFACE FEATURES LOOK TO PHASE TOGETHER AS THE MID LEVEL TROUGH STALLS OVER THE GREAT LAKES. WE WILL SEE SOME SHOWERS LATE THURSDAY INTO FRIDAY AS THE NEW LOW LIFTS THROUGH SOUTHERN MI AND A SECOND BATCH OF SHOWERS AS THE PRIMARY LOW DROPS INTO THE AREA FRIDAY NIGHT. THE BAROCLINIC ZONE LOOKS TO RESIDE SOUTH OF THE AREA WITH NORTHEASTERLY FLOW OVER THE REGION THROUGH THE END OF THE WEEKEND KEEPING THE AREA SLIGHTLY BELOW NORMAL. MARINE... CONDITIONS WILL START OFF FAIRLY QUIET AS A FRONTAL BOUNDARY REMAINS DRAPED ACROSS NORTHERN LAKE HURON. IN ADDITION THE WESTERN EXTENT OF A HIGH PRESSURE SYSTEM WILL KEEP SOME INFLUENCE OVER THE EASTERN LAKES AS WELL. THIS WILL KEEP A VERY STABLE AIRMASS IN PLACE THROUGH THE DAY TODAY BEFORE A DEVELOPING LOW PRESSURE SYSTEM PASSES THROUGH LAKE HURON LATE MONDAY EVENING PULLING A COLD FRONT THROUGH THE REGION. WINDS WILL SWITCH TO NORTHWESTERLY BEHIND THE FRONT WHICH WILL BRING COLDER AND MORE UNSTABLE AIR OVER THE LAKES BY TUESDAY MORNING. WINDS WILL BECOME GUSTY BUT SHOULD BE LIMITED TO AROUND 25 KNOTS DUE TO REDUCED FLOW ALOFT. THIS SHOULD KEEP ANY GALES FROM FORMING BUT MAY BE SUFFICIENT FOR SMALL CRAFTS...ESPECIALLY ALONG THE LAKE HURON SHORELINE WHERE WAVES HEIGHTS WILL BE PILING UP. HIGH PRESSURE WILL THEN BRING CALMING CONDITIONS THROUGH THE MIDDLE OF THE WEEK BEFORE SOUTHWEST TO WEST WINDS INCREASE LATE IN THE WEEK WITH THE APPROACH OF THE NEXT LOW PRESSURE SYSTEM.
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&& .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...NONE. LAKE ST CLAIR...NONE. MI WATERS OF LAKE ERIE...NONE. && $$ AVIATION.....99 SHORT TERM...DG LONG TERM....DRK MARINE.......DRK YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

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