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000
FXUS63 KDTX 041740
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1240 PM EST WED DEC 4 2013


.AVIATION...

//DISCUSSION...

CEILINGS AND VISIBILITIES WILL CONTINUE TO LIFT TO MVFR AND VFR THIS
AFTERNOON. ADDITIONAL MOISTURE IS EXPECTED TO SURGE INTO THE AREA
EARLY THIS EVENING AHEAD OF AN APPROACHING LOW PRESSURE SYSTEM. THIS
SHOULD BRING ADDITIONAL RAIN SHOWERS...DRIZZLE...AND FOG BACK INTO
THE AREA TONIGHT. THERE IS HIGH CONFIDENCE WITH IFR CONDITIONS FOR A
PERIOD AT ALL SOUTHEAST MICHIGAN TERMINALS TONIGHT...ALTHOUGH TIMING
OF OCCURRENCE IS STILL A LITTLE UNCERTAIN. THE BEST POTENTIAL WILL
BE AFTER 01Z AND BEFORE A COLD FRONT WORKS WEST TO EAST ACROSS THE
AREA BETWEEN 07Z AND 13Z. CONDITIONS WILL IMPROVE BEHIND THE FRONT
ALTHOUGH MUCH COLDER AIR WILL WORK INTO THE REGION AND WEST WINDS
WILL GUST TO 25 KNOTS THURSDAY FROM LATE MORNING THROUGH EARLY
EVENING.

FOR DTW...CONDITIONS WILL DETERIORATE AGAIN DURING THE VERY LATE
AFTERNOON AND EVENING AS ADDITIONAL MOISTURE SURGES UP INTO SOUTHERN
LOWER MICHIGAN. THE BEST TIMING FOR IFR CONDITIONS TO DEVELOP LOOKS
TO BE JUST AHEAD OF THE FRONTAL PASSAGE...STARTING AT AROUND 07Z.
WILL HAVE TO MONITOR POTENTIAL FOR IFR CONDITIONS TO DEVELOP AS
EARLY AS 01Z HOWEVER.


//DTW THRESHOLD THREATS...

* LOW CONFIDENCE WITH CEILINGS AT OR BELOW 5000 FEET THROUGH
23Z...THEN HIGH CONFIDENCE WITH CEILINGS BELOW 5000 FEET THROUGH
THURSDAY MORNING.

* LOW CONFIDENCE WITH CEILINGS BELOW 200 FEET OR VISIBILITY BELOW
1/2 MILE TONIGHT.

&&

.PREV DISCUSSION...ISSUED 255 AM EST WED DEC 4 2013

SHORT TERM...TODAY AND TONIGHT

NOW THAT ISENTROPIC LIFT ALONG LEAD EDGE OF WARM FRONT HAS SHIFTED
NORTHEAST OF THE AREA AND TAKEN LAST BATCH OF SIGNIFICANT RAIN/SNOW
WITH IT...EXPECT LITTLE TO NO PRECIPITATION FOR THE REMAINDER OF THE
MORNING. HOWEVER...FOG WILL BE PREVALENT AS THE SURFACE WARM FRONT
WILL BE SLOW TO CLEAR THE AREA TODAY...WAITING UNTIL DEEPENING LOW
PRESSURE LIFTS QUICKLY NORTH THROUGH THE UPPER MIDWEST/WESTERN LAKES
THIS AFTERNOON/EVENING. TEMPERATURES WILL MODERATE CONSIDERABLY AS
WINDS VEER FROM EAST/SOUTHEAST TO SOUTH OVER THE NEXT 18 HOURS...SO
ANTICIPATE HIGH TEMPERATURES TO CLIMB INTO THE 50S FOR MOST OF THE
AREA...PERHAPS HOLDING JUST SHORT OF THAT FROM THE SAGINAW VALLEY TO
THUMB.

AS LOW PRESSURE LIFTS ACROSS WISCONSIN THIS AFTERNOON...THETA-E
RIDGE WILL SPREAD NORTHEAST INTO THE AREA AND BRING A RETURN OF
DEEPER MOISTURE. THIS WILL LEAD TO AN INCREASE IN SHOWER CHANCES
FROM MID AFTERNOON INTO THE EVENING...WITH SHOWERS PERSISTING OFF
AND ON INTO MUCH OF THE NIGHT AS TROUGH AXIS/COLD FRONT APPROACH
FROM THE WEST. THE TIMING OF THIS FRONT STILL APPEARS TO BE PRETTY
CLOSE TO 12Z THURSDAY MORNING...SO WILL NOT ADJUST POP/TEMPERATURE
FORECAST MUCH AS THE AREA TRANSITIONS TO A COLDER/DRIER PERIOD.
SO...WILL LOWS TONIGHT WILL ULTIMATELY END UP IN THE UPPER 30S TO
MIDDLE 40S...50+ READINGS WILL BE PREVALENT WELL AFTER MIDNIGHT AS
MILD SOUTH/SOUTHWEST FLOW PREVAILS UNTIL DAYBREAK.

LONG TERM...

SHEARED STRUCTURE OF THE NOAM LONGWAVE ALONG THE NORTHERN PERIPHERY
OF A DEVELOPING 170KT JET STREAK WILL LIMIT EASTWARD PROGRESS OF THE
COLD FRONT ONCE IT CLEARS THE AREA LATE TONIGHT. COLDER TEMPERATURES
WILL THEREFORE ONLY SLOWLY BUILD BACK INTO THE AREA THURS THROUGH
SATURDAY. DURING THIS TIME, H85 TEMPS WILL FALL FROM AROUND 4C THURS
MORNING TO -12C BY SATURDAY MORNING. THE INITIAL WAVE OF COLD
ADVECTION WILL, HOWEVER, STILL BE STRONG ENOUGH TO SUPPORT FALLING
TEMPERATURES THROUGH THE DAY THURSDAY FOLLOWED BY MINIMAL REBOUNDING
TO AROUND 30 ON FRI AFTN AND AROUND 25 BY SAT AFTN. WHILE A
SUBSTANTIAL LAKE RESPONSE IS NOT EXPECTED, THE COMBINATION OF COLD
ADVECTION AND A MODEST LAKE RESPONSE LOOKS TO BE JUST ENOUGH TO
SUSTAIN A PARTIAL COVERAGE OF BOUNDARY LAYER STRATOCU THROUGH THE
DAY ON THURSDAY.

ATTENTION THEN TURNS TO THE STALLED BAROCLINIC ZONE WHICH WILL SERVE
AS A FOCUS FOR A COUPLE ROUNDS OF LIGHT SNOWFALL THAT WILL LARGELY
BE FOCUSED SOUTH OF THE AREA THURSDAY NIGHT AND FRIDAY. THE MAIN
FORCING MECHANISM FOR THIS SNOW WILL BE A PLUME OF MID-LEVEL THETA-E
ADVECTION/ISENTROPIC ASCENT ASSOCIATED WITH VERY LOW AMPLITUDE
ENERGY OFF THE BAJA PENINSULA BEING ENTRAINED INTO THE PREVAILING
SOUTHWEST FLOW ALOFT. CONSENSUS REMAINS SOLID AMONG THE
ECMWF/GFS/NAM, WITH THE ECMWF EXHIBITING THE BEST CONTINUITY OF THE
THREE, THAT ACCUMULATIONS ON THE ORDER OF A FEW TENTHS OF AN INCH
WILL BE POSSIBLE ACROSS THE SOUTHERN TIER OR TWO OF COUNTIES
THURSDAY EVENING INTO FRIDAY. THE BEST OUTSIDE SHOT FOR UP TO AN
INCH OF SNOW WILL BE MONROE COUNTY. THE GEM REMAINS CONSIDERABLY
MORE AGGRESSIVE IN ITS DEPICTIONS OF THIS ENERGY AND THUS SUGGESTS A
MORE WIDESPREAD SNOW, BUT WITH NO EVIDENCE TO CONTRADICT THE
EXISTING CONSENSUS, WILL CONTINUE LEANING AWAY FROM GEM SOLUTIONS.

MARINE...

A STRONG SOUTHERLY BREEZE WILL PRECEDE THE ARRIVAL OF A DEEPENING
LOW PRESSURE THAT WILL LIFT ACROSS LAKE SUPERIOR TONIGHT. AS IT
LIFTS TOWARD JAMES BAY DURING THE DAY ON THURSDAY...COLDER AIR WILL
WRAP IN BEHIND THE LOW AND FRESH TO STRONG WESTERLY WINDS WILL GUST
TO AROUND GALE FORCE ACROSS NORTHERN LAKE HURON ON THURSDAY
AFTERNOON. THE GALE WATCH REMAINS IN TACT AND WILL NOT BE UPGRADED
TO A WARNING DUE TO UNCERTAINTY OWING TO THE MARGINAL NATURE OF THE
POTENTIAL GALE EVENT

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.

LAKE HURON...
     SMALL CRAFT ADVISORY...OUTER SAGINAW BAY AND THE NEARSHORE WATERS
     FROM PORT AUSTIN TO HARBOR BEACH...UNTIL 5 AM FRIDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM HARBOR BEACH TO PORT
     HURON...UNTIL 7 PM THURSDAY.

     SMALL CRAFT ADVISORY...INNER SAGINAW BAY...FROM 4 AM THURSDAY TO 10
     PM THURSDAY.

     GALE WATCH...LHZ361-LHZ362...FROM 5 AM THURSDAY TO MIDNIGHT FRIDAY.

LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

AVIATION.....HLO
SHORT TERM...DG
LONG TERM....JVC
MARINE.......JVC


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