738
FXUS63 KDTX 161727
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
127 PM EDT WED OCT 16 2013
.AVIATION...
//DISCUSSION...
EXTENSIVE AREA OF MVFR STRATUS NOW FIRMLY PREVALENT ACROSS THE
NORTHERN TAF SITES. HOWEVER DAYTIME HEATING IN A WELL MIXED
SOUTHWEST WIND EFFECTIVELY SLOWING FURTHER EASTWARD PROGRESS.
RECENT OBSERVATIONAL AND SATELLITE TRENDS INDICATE PTK AND THE
DETROIT AREA WILL LIKELY RESIDE ON THE FRINGE PRIOR TO SUNSET.
HIGHER LOW LEVEL MOISTURE WILL BEGIN TO WORK INTO THE CORRIDOR WITH
THE LOSS OF HEATING...REINFORCED BY A SECONDARY PERIOD OF COLD AIR
ADVECTION OVERNIGHT. THIS CONTINUES TO SUPPORT PREDOMINANT MVFR
CEILINGS AT ALL TERMINALS THROUGH THE NIGHTTIME HOURS.
FOR DTW...RECENT SATELLITE DATA NOW INDICATING LOW STRATUS WILL
ARRIVE AFTER 21Z. THE DEGREE OF MIXING WILL LIKELY INTRODUCE THIS
STRATUS IN LOW VFR...THEN LOWERING GRADUALLY WITH TIME WITH THE
LOSS OF HEATING.
//DTW THRESHOLD THREATS...
* HIGH CONFIDENCE CEILINGS WILL BE BELOW 5000 FT LATE AFTERNOON
THROUGH TONIGHT.
&&
.PREV DISCUSSION...ISSUED 354 AM EDT WED OCT 16 2013
SHORT TERM...TODAY AND TONIGHT
THE MID LEVEL WAVE OVER WISCONSIN HAS BEEN WEAKENING OVER THE LAST
SEVERAL HOURS. ALTHOUGH SOME PHASING WITH THE NORTHERN STREAM WAVE
NOW DROPPING ACROSS NRN ONTARIO WILL OCCUR THIS MORNING...CONSENSUS
AMONG THE 00Z MODEL SUITE IS FOR THE MID LEVEL CIRCULATION TO SLIDE
NORTH OF LAKE HURON THIS AFTERNOON...LEAVING JUST A SHEARED MID
LEVEL TROUGH AXIS TO MOVE ACROSS NRN AND CNTL LOWER MI THIS
EVENING. THIS WILL SUSTAIN DEEP LAYER SOUTHWESTERLY FLOW ACROSS SE
MI WELL INTO THE AFTERNOON AND WILL LEAD TO A RATHER SLOW
PROGRESSION OF THE UPSTREAM COLD AIRMASS ACROSS SRN MI TODAY.
THE SFC LOW /LOCATED OVER ERN UPPER MI AS OF 07Z/ WILL LIFT INTO
ONTARIO THIS MORNING...WHILE THE ASSOCIATED COLD FRONT ADVANCES
ACROSS SE MI OVER THE NEXT FEW HOURS. THE FINE LINE OF RETURNS WHICH
HAS BEEN SHOWING UP ON RADAR NOW CROSSING THE SAGINAW VALLEY MARKS
THE SFC COLD FRONT...WHICH WILL CROSS METRO DETROIT AROUND 09Z.
CLOUDS HAVE BEEN CLEARING IN THE WAKE OF THIS FRONT AS A REGION OF
LOW TO MID LEVEL DRY AIR IS ADVANCING INTO SE MI. OUTSIDE OF SOME
LINGERING HIGH CLOUDS SOUTH OF METRO DETROIT...THIS DRY AIR WILL
LEAD TO A PERIOD OF CLEAR SKIES TODAY. THIS WILL OFFSET THE COLD AIR
ADVECTION TO SOME DEGREE AND ALLOW HIGHS TO REBOUND INTO THE MID
50S NORTH TO LOW 60S NEAR DETROIT AND MONROE. THE EXTENSIVE LOW
CLOUDS NOW BLANKETING WISCONSIN WILL ADVANCE INTO SE MI TODAY. MODEL
SOLUTIONS SUGGEST THIS MOISTURE WILL NOT MOVE INTO THE TRI CITIES
UNTIL LATE MORNING AND METRO DETROIT UNTIL THIS EVENING. UPSTREAM
OBSERVATIONS HOWEVER SUGGEST THE LOW CLOUDS ARRIVING MUCH
SOONER...WHICH WILL SUPPORT A LITTLE MORE PESSIMISTIC AFTERNOON
CLOUD FORECAST. CONTINUED COLD AIR ADVECTION DURING THE AFTERNOON
AND EVENING WILL DEEPEN THE CONVECTIVE CLOUD DEPTHS AND LEAD TO
INCREASED INSTABILITY OVER LAKE MICHIGAN. THE BEST CHANCES OF SOME
LIGHT SHOWERS OR SPRINKLES WILL OCCUR ACROSS THE SAGINAW
VALLEY/THUMB THIS AFTERNOON...THEN TRANSITION DOWN TO METRO
DETROIT THIS EVENING AS THE LOW LEVEL FLOW OVER LAKE MI VEERS FROM
W-SW TO W-NW. CONVECTIVE CLOUD DEPTHS WILL LOWER OVERNIGHT AS SHORT
WAVE RIDGING ADVANCES INTO LOWER MI...SUPPORTING A REDUCTION IN POPS
AFTER MIDNIGHT.
LONG TERM...THURSDAY THROUGH TUESDAY
AN INTERESTING MIX OF ORGANIZED DYNAMICS ARE SET TO SLIDE THROUGH
SOUTHEASTERN MICHIGAN BETWEEN 12-00Z THURSDAY. MODELS ADVERTISE THE
TRAILING PV ANOMALY NOW OVER THE FOUR CORNERS WILL REMAIN
PROGRESSIVE ON THE BACK OF A CONSOLIDATED UPPER LEVEL JET CORE.
OVERALL UPPER LEVEL DYNAMICS ARE WELL PUT TOGETHER...CENTER OF PV
ADVECTION WILL SET ITS SIGHTS ON THE AREA ALONG WITH A GOOD AMOUNT
OF LEFT EXIT REGION DYNAMICS. A DEPRESSION IN THE UPPER LEVEL JET
STREAK AND D/DT IN CURVATURE SUGGESTS A RAMP UP IN DEFORMATION
FORCING. DETERMINISTIC SOLUTIONS DO SUPPORT GOOD 700-500MB
DEFORMATION WITH VERY LITTLE DOWN NEAR THE SURFACE. GENERALLY...THE
QUALITY OF THERMODYNAMICS WILL BE THE LIMITING FACTOR. FAVORABLE
WEAK STABILITY AND FRONTAL FORCING IS FORECASTED...BUT REALLY HIGH
UP AT 10 KFT AGL AND ABOVE. IN ADDITION...MODEL SOUNDINGS DO SHOW
STEEP LAPSE RATES IN A MINOR LAYER OF INSTABILITY BETWEEN
900-800MB...BUT THE ISSUE IS THERE IS VERY LITTLE GOING ON IN THAT
LAYER FROM A FORCING MECHANISM STANDPOINT. WITH ALL OF THESE FACTORS
WORKING IN THE BACKGROUND OF ISENTROPIC DOWNGLIDE...EXPECTATIONS ARE
FOR YET ANOTHER EVENT WITH LESS THAN AWE INSPIRING QPF AMOUNTS.
GENERALLY LOOKING AT A TENTH POSSIBLE WITH PERHAPS A HIGH END TWO
TENTHS OF AN INCH.
SHORTWAVE RIDGING AND LITTLE TO NO CHANGE IN THE UPPER LEVEL JET
CONFIGURATION LOCALLY SUGGESTS NO WIDESPREAD FORCING FOR PRECIPITATION
ON FRIDAY. ONLY THING TO WATCH WILL BE TROUGH AND COOLER MIDLEVEL
AIR SETTLING INTO THE NORTHERN GREAT LAKES THROUGHOUT THE DAY. THE
INHERITED FORECAST CARRIED A CHANCE ACROSS THE NORTH FOR THE
AFTERNOON HOURS. THIS IS CERTAINLY REASONABLE AND WILL LEAVE ALONE.
THE TROUGH AXIS IN THE VERY LARGE WAVELENGTH CANADIAN LOWER HEIGHT
ANOMALY/ROSSBY WAVE WILL PIVOT THROUGH THE GREAT LAKES ON SATURDAY.
THE OVERALL MASS ADJUSTMENT OF THIS PROCESS IS EXPECTED TO INDUCE
HEIGHT FALLS AGAIN OVER LOWER MICHIGAN. THERE ARE MID TO HIGH CHANCE
POPS GOING AND THIS IS GOOD. ONLY QUESTION MARK IS ON TIMING AND
RIGHT NOW DO NOT HAVE MUCH OF A GUT FEELING THERE. WITH THE LOWERED
HEIGHT ANOMALY...COOLER TEMPERATURES ARE EXPECTED SAT. FORECASTED
HIGHS ARE ACROSS THE BOARD...8 DEGREES BELOW NORMAL.
VIRTUALLY IMPOSSIBLE TO ANTICIPATE WHAT SHORTWAVE ENERGY TO TARGET
FOR SUNDAY. CYCLONIC FLOW SUPPORTS A CHANCE POP...TEMPERATURES ARE
NOT EXPECTED TO MODERATE MUCH OFF OF THE SATURDAY HIGHS.
MARINE...
THE PASSAGE OF A COLD FRONT EARLY THIS MORNING WILL LEAD TO
INCREASING UNSTABLE CONDITIONS ACROSS THE LAKES AS COLD AIR ADVANCES
INTO THE REGION. POST FRONTAL WINDS WILL BE SOUTHWESTERLY. UPSTREAM
OBSERVATIONS SUGGEST FREQUENT GUSTS AT OR ABOVE 20 KNOTS. THE
STRONGEST WINDS WILL OCCUR FROM SAGINAW BAY INTO CENTRAL LAKE HURON
AS THE WINDS ARE FUNNELED ACROSS THE BAY. THE LOW LEVEL WINDS WILL
VEER TO WEST TONIGHT AND WILL WEAKEN AS THE LOW PRESSURE SYSTEM NOW
OVER ERN UPPER MI EXITS THE REGION TO THE NORTHEAST. AN EXTENDED
PERIOD OF WEST-SOUTHWEST WINDS WILL THEN PREVAIL THROUGH THE END OF
THE WEEK AND INTO NEXT WEEKEND. WINDS AND WAVES WILL GRADUALLY BUILD
DURING THE WEEKEND AS MUCH COLDER AIR ADVANCES INTO THE GREAT LAKES
REGION.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...
SMALL CRAFT ADVISORY...SAGINAW BAY...UNTIL 10 PM WEDNESDAY.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....MR
SHORT TERM...SC
LONG TERM....CB
MARINE.......SC
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