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000
FXUS63 KDTX 040506
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1206 AM EST WED DEC 4 2013


.AVIATION...

//DISCUSSION...

MESSY CIG/VSBY FORECAST UPCOMING AS WARM FRONT GRADUALLY LIFTS
THROUGH THE AREA AND LOW LEVEL MOISTURE CONTINUES TO INCREASE OVER
THE AREA. INITIALLY...AREA OF RAIN (SOME SNOW/SLEET MIXED NEAR MBS)
WILL LIFT TO THE EAST/NORTHEAST WITH SHORTWAVE EARLY IN THE FORECAST
AND LEAVE AREA WITH LINGERING SCT -SHRAS OVERNIGHT IN WEDNESDAY WITH
CIGS BOUNCING BETWEEN UPPER MVFR TO VFR. WITH BREAKS IN THE LOWEST
STRATUS...VSBYS WILL MOST LIKELY DROP WITH BR INTO DAYBREAK. THE
NEXT SURGE OF MOISTURE HOLDS OFF UNTIL 18Z-21Z WEDNESDAY AS WINDS
GRADUALLY VEER TO THE SOUTH INTO WEDNESDAY NIGHT IN ADVANCE OF COLD
FRONT APPROACHING FROM THE WEST. EXPECT PERIODS OF -SHRAS/-DZ WITH
BR AS CIGS LOWER BACK TO MVFR (IFR AT TIMES) AS THETA-E RIDGE SHIFTS
OVER AREA LATE WEDNESDAY.

FOR DTW...BREAKS IN STRATUS WILL BRING PERIODS OF VFR CIGS OVERNIGHT
BUT THIS SHOULD ASSIST IN BRINGING VSBYS DOWN SOMEWHAT AS BOUNDARY
LAYER COOLING WILL BE A BIT MORE PRONOUNCED. THESE CONDITIONS WILL
PERSIST INTO WEDNESDAY WITH CIGS/VSBYS DROPPING LATE IN THE DAY INTO
WEDNESDAY NIGHT AS SOUTHERLY FLOW BRINGS ABUNDANT MOISTURE TO THE
AREA WITH PERIODS OF -SHRAS/-DZ ALSO EXPECTED.


//DTW THRESHOLD THREATS...

* MEDIUM CONFIDENCE IN CEILINGS BELOW 5000 FT THROUGH 12Z WITH HIGH
CONFIDENCE AFTER 12Z.

&&

.PREV DISCUSSION...ISSUED 818 PM EST TUE DEC 3 2013

UPDATE...

ONE QUICK UPDATE TO THE PREVIOUS HEADLINE WAS TO CHANGE THE
FREEZING RAIN ADVISORY TO A WINTER WEATHER ADVISORY. THE BAND OF
PRECIPITATION THAT MOVES THROUGH THE SAGINAW VALLEY HAD QUITE A
BIT OF SNOW WITH IT DUE TO THE CONVECTIVE NATURE OF THE BAND
GETTING DEEP ENOUGH INTO THE COLD LAYER TO TAP INTO THE DENDRITIC
GROWTH ZONE. SOME REPORTS IN THE BAND WERE SNOWFALL ESTIMATES OF
AROUND 2 INCHES. GIVEN THE MULTIPLE PRECIPITATION TYPES AND
FREEZING RAIN NO LONGER BEING THE DOMINANT TYPE HAVE CHANGED THE
HEADLINE WITH THIS ISSUANCE.

PREV DISCUSSION...ISSUED 649 PM EST TUE DEC 3 2013

UPDATE...

SNOW CONTINUES TO CHANGEOVER TO RAIN ACROSS THE SAGINAW VALLEY AND
NORTHERN THUMB THIS EVENING. HOWEVER A LOW LEVEL LAYER OF COLD AIR
CONTINUES TO CAUSE ISSUES AS THE RAIN FALLS INTO A SUB FREEZING
SURFACE COLD LAYER. DESPITE EARLIER SNOWFALL AND TREATED
ROADWAYS...SEVERAL REPORTS FROM COUNTY DISPATCH AND SPOTTERS
INDICATE THAT MANY ROADWAYS HAVE BECOME ICE COVERED...MAINLY ON
UNTREATED ROADWAYS AND OVERPASSES. A MIXED BAG OF
SNOW...SLEET...RAIN AND FREEZING RAIN ARE EXPECTED THIS EVENING
ACROSS THE NORTHERN THUMB AND SAGINAW VALLEY THIS EVENING AHEAD OF
THE WARM FRONT AS UPSTREAM RADAR OBSERVATIONS SHOW PLENTY OF
UPSTREAM PRECIPITATION. DESPITE THE MIXED BAG...FREEZING RAIN IS
EXPECTED TO BE THE MAIN CULPRIT IN SLICK ROADWAYS...THEREFORE WILL
ISSUE A FREEZING RAIN ADVISORY THROUGH THE EVENING HOURS FOR THE
AFOREMENTIONED TROUBLE SPOTS. TEMPERATURES ARE EXPECTED TO SLOWLY
RISE THROUGH THE OVERNIGHT HOURS INTO THE MID 30S AROUND MIDNIGHT.
WITH THIS TIME WINDOW IN MIND WILL ISSUE THE ADVISORY THROUGH
MIDNIGHT.

PREV DISCUSSION...ISSUED 333 PM EST TUE DEC 3 2013

SHORT TERM...TONIGHT

A WARM FRONT WILL CONTINUE TO PUSH NORTHWARD ALLOWING RAIN SHOWERS
TO CONTINUE THROUGH THIS EVENING.  WITH TEMPERATURES STAYING WELL
ABOVE FREEZING...ALL PRECIPITATION WILL BE IN THE FORM OF RAIN. HAVE
KEPT A CHANCE OF RAIN THROUGH THE FIRST HALF OF THE OVERNIGHT HOURS
ESPECIALLY FOR THE NORTHERN WHERE IT WILL TAKE LONGER FOR THE FRONT
TO MAKE IT THROUGH THE AREA. WHILE SOUTH OF I-69 SHOULD BE MOSTLY
CLEAR OF RAIN AFTER MIDNIGHT...THE MAIN CONCERN FOR THIS REGION WILL
BE CHANCE OF FOG DEVELOPMENT AS SIGNIFICANT LOW LEVEL MOISTURE
FILTERS IN BEHIND THE FRONT AND THE GROUND REMAINS MOIST FROM
AFTERNOON RAIN SHOWERS. CONFIDENCE IS STILL A LITTLE UNCERTAIN
REGARDING HOW MUCH FOG WILL DEVELOP AND LOCATION OF GREATEST IMPACT.
THEREFORE...HAVE ONLY INCLUDED PATCHY FOG FOR THE CWA AT THIS TIME.
THIS WILL PROBABLY HAVE TO BE FINE TUNED AS THE EVENING PROGRESSES.
MINIMUM TEMPERATURES WILL BE WELL ABOVE NORMAL FOR THIS TIME OF YEAR
ACROSS THE CWA. EXPECT LOW TEMPS IN THE UPPER 30S ON TOWARDS THE
OHIO BORDER AND LOWS IN THE MID 30S IN THE NORTHERN CWA.

LONG TERM...

UPPER LEVEL TROUGH/ENERGY OVER THE PACIFIC NORTHWEST DROPPING SOUTH
THIS AFTERNOON...WITH ADDITIONAL ENERGY EXTENDING NORTHWEST INTO THE
GULF OF ALASKA. LONGWAVE TROUGH WILL ENCOMPASS THE WESTERN THIRD OF
THE CONUS TOMORROW MORNING...WITH RAPID CYCLOGENESIS TAKING PLACE
OVER THE MIDWEST. THE STRENGTHENING LOW IS THEN EXPECTED TO TRACK
NORTHEAST THROUGH LAKE SUPERIOR WEDNESDAY NIGHT. GOOD SURGE OF
MOISTURE WITH ANOTHER WARM FRONT TOMORROW AFTERNOON/EVENING...AS PW
VALUES SHOWN TO INCREASE AND EXCEED SLIGHTLY EXCEED 1 INCH WITH GOOD
SURGE OF ISENTROPIC ASCENT. THE QUESTION IS AFTER 00Z THURSDAY...AS
AGGRESSIVE DRY SLOT (700 MB RH OF 30 PERCENT) MOVES INTO SOUTHEAST
MICHIGAN (PER GFS/NAM). THERE STILL WILL BE SOME LINGERING LOW LEVEL
MOISTURE/CONVERGENCE ALONG/AHEAD OF THE COLD FRONT WHICH TAKES
MOST/ALL OF THE NIGHT TO WORK THROUGH...ALONG WITH HIGHER DEW PTS
(50+ DEGREES). THE 12Z EURO IS SLOWER WITH MOISTURE AXIS/WARM
FRONT...AND FORECAST WILL BE WEIGHTED HEAVILY IN THIS
DIRECTION...FOCUSING THE RAIN SHOWERS AROUND 00Z MARKER. TEMPS WERE
BUMPED UP WEDNESDAY NIGHT INTO THURSDAY WITH THE SLOWER TIMING.

THE EASTWARD PUSH OF THE BAROCLINIC ZONE/COLD FRONT AND
CORRESPONDING SURFACE RIDGING/DRYING FOR THURSDAY WILL BE
IMPORTANT...AS ONE IF NOT TWO UPPER LEVEL WAVES/JET STREAKS EJECT
FROM TEXAS AND TRACK NORTHEAST THURSDAY NIGHT/FRIDAY TIME FRAME. THE
MAIN UPPER LEVEL PV SOURCE APPEARS TO BE THE SOUTHERN UPPER LEVEL
LOW LOCATED AT 25N 131W IN PACIFIC. THERE IS NO QUESTION IT LOOKS TO
BE A CLOSE CALL FOR ACCUMULATING SNOW TOWARD THE OHIO BORDER...AS
12Z EURO SHOWS 850-700 MB SPECIFIC HUMIDITY JUMPING TO 3 C THURSDAY
NIGHT...WHILE THE 12Z NAM IS LIKING THE FRIDAY UPPER WAVE EVEN
BETTER. UPPER LEVEL FLOW IF HIGHLY CONFLUENT...AND CONFIDENCE IS NOT
HIGH WITH SUCH SHARP LOW LEVEL GRADIENT/BAROCLINIC ZONE.

ARCTIC AIR WILL CONTINUE TO FILTER INTO THE AREA OVER THE
WEEKEND...WITH HIGHS BOTH SATURDAY AND SUNDAY IN THE LOW TO MIDDLE
20S AND LOWS IN THE TEENS...A GOOD 10 TO 15 DEGREES BELOW NORMAL.

MARINE...

DEEPENING LOW PRESSURE WILL LIFT OUT OF THE MIDWEST TOMORROW AND
THROUGH THE WESTERN GREAT LAKES TOMORROW NIGHT. EASTERLY WINDS OUT
AHEAD OF THIS LOW TONIGHT AND WEDNESDAY...WITH GUSTS TO 25 KNOTS
EXPECTED OVER THE NORTH THIRD OF LAKE HURON...AS WARM FRONT LIFTS
NORTH AND FUNNELING OF WINDS OCCURS. A GOOD DEAL OF WARM AIR
SPREADING OVER THE CENTRAL GREAT LAKES WEDNESDAY NIGHT WILL LEAD
TO MORE STABLE LOW LEVEL PROFILES AHEAD OF THE COLD FRONT.
HOWEVER...EXCELLENT LOW LEVEL COLD ADVECTION BEHIND THE FRONT
WILL PROMOTE MUCH BETTER MIXING...AND IT APPEARS AS THE STRONG LOW
MOVES OVER JAMES BAY...THE GRADIENT SHOULD BE SUFFICIENT TO
PRODUCE WESTERLY GALES OVER THE NORTH THIRD/HALF OF LAKE
HURON...AND HAVE GONE AHEAD AND ISSUED A GALE WATCH. COLDER AIR
WILL CONTINUE TO FILTER INTO THE GREAT LAKES REGION ON
FRIDAY...BUT WINDS WILL DECREASE AS GRADIENT LOOSENS.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY...MIZ047-MIZ048-MIZ049-MIZ053-MIZ054-
     MIZ055...UNTIL 4 AM WEDNESDAY.

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

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

&&

$$

AVIATION.....DG
UPDATE.......KURIMSKI
SHORT TERM...RK
LONG TERM....SF/DE
MARINE.......SF


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