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000
FXUS63 KDTX 101124
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
624 AM EST WED FEB 10 2010

.AVIATION...

CONDITIONS GRADUALLY IMPROVING THIS MORNING AS SNOW CONTINUES TO
DIMINISH IN COVERAGE AND INTENSITY.  LINGERING IFR/MVFR VISIBILITY
IN LIGHT SNOW WILL CONTINUE FOR ANOTHER 2-3 HOURS BEFORE THE SNOW
TAPERS OFF.  WINDS WILL STRENGTHEN TODAY OUT OF THE NORTH IN THE
WAKE OF THE DEPARTING WINTER STORM WITH GUSTS OF 20-25 KNOTS
COMMON.  THIS WILL LEAD TO A PROLONGED PERIOD OF BLOWING AND
DRIFTING SNOW TODAY.  WINDS WILL DIMINISH WHILE VEERING TO THE
NORTHWEST OVERNIGHT AS THE PRESSURE GRADIENT RELAXES.  VFR/HIGH
MVFR STRATUS WILL PERSIST FOR THE REMAINDER OF THE TAF PERIOD.

&&

.PREV DISCUSSION...ISSUED 430 AM EST WED FEB 10 2010

SHORT TERM...TODAY

EXPANSIVE AREA OF LIGHT TO MODERATE SNOW DRIVEN BY PERSISTENT
ISENTROPIC ASCENT AND MID LEVEL DEFORMATION FORCING ENCOMPASSING THE
ENTIRE FORECAST AREA.  THE HEAVIEST SNOWFALL NOW WORKING ACROSS THE
NORTHWEST PORTIONS OF THE WARNING AREA AS THE DEFORMATION STARTS TO
PIVOT ON THE NORTHWEST FLANK OF THE MID LEVEL PV ANOMALY SHIFTING
ACROSS SOUTHERN OHIO.  IN ADDITION...RADAR CONTINUES TO DEPICT A
PERSISTENT AREA OF MODERATE SNOW EXTENDING FROM THE SAGINAW BAY
SOUTHWEST THROUGH SOUTHERN BAY/SAGINAW AND NORTHERN SHIAWASSEE
COUNTIES.  THIS WOULD SUGGEST SOME ADDITIONAL ENHANCED LOW LEVEL
CONVERGENCE WITH A POSSIBLE LAKE COMPONENT AS THE FLOW RUNS PARALLEL
TO THE BAY.  RADAR ESTIMATES AND RECENT SPOTTER REPORTS INDICATE
SNOWFALL RATES OF UP TO AN INCH PER HOUR AT TIMES.  SNOW RATIOS
THUS FAR THROUGH THE EVENT HOLDING IN THE 15:1 RANGE.

LATEST HIRES WRF SEEMS TO CAPTURE ONGOING TRENDS THE BEST AND
DEPICTS A MATURE/WEAKENING DEFORMATION ZONE ROTATING EAST-SOUTHEAST
ACROSS THE AREA THROUGH THE MID-LATE MORNING HOURS.  IT ALSO
CAPTURES THE ONGOING LOCALIZED BAND WORKING OFF THE BAY AND SUSTAINS
THIS ACTIVITY FOR SEVERAL MORE HOURS.  IN LIGHT OF THIS AND GIVEN
CURRENT RADAR TRENDS...RECENT REPORTS AND LATEST OBSERVATIONS
WILL GO AHEAD AND UPGRADE BAY COUNTY FOR A SHORT DURATION WARNING
THROUGH THE MID MORNING HOURS. CALLS AROUND THIS AREA INDICATE AT
LEAST 5-7 INCHES OVER THE SOUTHERN PART OF THE COUNTY WITH
SUBSTANTIAL BLOWING AND DRIFTING...WITH THE POTENTIAL FOR AN
ADDITIONAL 2-3 INCHES ACROSS THE SOUTHEASTERN CORRIDOR OF THE
COUNTY /INCLUDING BAY CITY/.

ELSEWHERE...SNOWFALL INTENSITY/COVERAGE WILL CONTINUE TO DIMINISH
WITH TIME AS THE FORCING WEAKENS.  AN ADDITIONAL 1-2 INCHES STILL
LOOKS ATTAINABLE AS THIS PROCESS UNFOLDS...ESPECIALLY ALONG THE
I-75 CORRIDOR.  A BACKING FLOW TOWARD THE NORTH-NORTHEAST WILL ALSO
INTRODUCE A SLIGHT LAKE COMPONENT FOR THE EASTERN THUMB TODAY...
ALTHOUGH THE THERMODYNAMIC SETUP REMAINS UNIMPRESSIVE /SUB 4K FT
INVERSION HEIGHTS AND 850 MB TEMPS WARMER THAN -10C/ SO THE
CONTRIBUTION APPEARS TO BE LIMITED.

LIGHT SNOW WILL TRANSITION TO SCATTERED SNOW SHOWERS INTO THE
AFTERNOON AS THE MID LEVEL CIRCULATION HEADS TOWARD THE EAST COAST.
CONSIDERABLE BLOWING AND DRIFTING OF SNOW WILL CONTINUE THROUGH THE
DAY WITH A TIGHT PRESSURE GRADIENT ENSURING NORTHERLY GUSTS REACH
30 MPH AT TIMES.  THIS WILL ALSO CONTRIBUTE TO SINGLE DIGIT WIND
CHILL READINGS INTO THE AFTERNOON AS TEMPERATURES HOVER IN THE 20S.

LONG TERM...TONIGHT THROUGH NEXT TUESDAY

THE LONG TERM FORECAST WILL FEATURE A COOL AND DRY NORTHWESTERLY
FLOW AS THE NEXT LONGWAVE TROUGH SETS UP ACROSS THE EASTERN UNITED
STATES. INITIALLY...SURFACE HIGH PRESSURE WILL TRY TO BUILD INTO THE
WESTERN GREAT LAKES ON THURSDAY BUT BROAD CYCLONIC FLOW ASSOCIATED
WITH THE DEPARTING LOW PRESSURE SYSTEM WILL CONTINUE TO HAVE AN
INFLUENCE OVER THE REGION INTO FRIDAY. CLOUDS MAY BRIEFLY SCATTER
OUT ON THURSDAY MORNING BUT SKY CONDITIONS WILL CONTINUE TO
FLUCTUATE BETWEEN PARTLY TO MOSTLY CLOUDY SKIES THROUGH THE
REMAINDER OF THE WEEK.

THE TWO FEATURES TO WATCH FOR THE WEEKEND INCLUDE A WEAK CLIPPER
APPROACHING FROM WESTERN CANADA AND THE NEXT UPPER LOW DROPPING
SOUTH ACROSS CANADA FROM THE ARCTIC. SOME DIFFERENCES DO EXIST
BETWEEN THE LONG RANGE MODELS BUT GENERALLY PREFER THE ECMWF/UKMET
WHICH EVENTUALLY CARVE OUT A DEEPER TROUGH AND PUSH THE PREVAILING
STORM TRACK SOUTH OF THE OHIO VALLEY. ANY SNOW ASSOCIATED WITH THE
CLIPPER IS EXPECTED TO BE BOTH LIGHT AND LARGELY REMAIN SOUTH OF
THE STATE LINE SO THE GOING FORECAST WITH JUST A CHANCE OF SNOW
STILL LOOKS GOOD.

MARINE...

GALE FORCE WINDS WILL CONTINUE TODAY AS THE LOW PRESSURE SYSTEM
OVER EASTERN LAKE ERIE PULLS AWAY TO THE EAST COAST. FREQUENT
GUSTS TO 35 KNOTS CAN BE EXPECTED BEFORE WIND GRADUALLY DECREASE
LATE THIS AFTERNOON INTO TONIGHT. THE STRONG WINDS AND BUILDING
WAVES WILL CONTRIBUTE TO FREEZING SPRAY.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER STORM WARNING...MIZ055-MIZ062-MIZ063...UNTIL 1 PM WEDNESDAY.

     WINTER STORM WARNING...MIZ048-MIZ053-MIZ054-MIZ060-MIZ061-MIZ068-
     MIZ069-MIZ070-MIZ075-MIZ076-MIZ082-MIZ083...UNTIL 10 AM
     WEDNESDAY.

     WINTER WEATHER ADVISORY...MIZ047...UNTIL 10 AM WEDNESDAY.

     WINTER WEATHER ADVISORY...MIZ049...UNTIL 1 PM WEDNESDAY.

LAKE HURON...
     GALE WARNING...LHZ362-LHZ363-LHZ421-LHZ422-LHZ441-LHZ442-LHZ443-
     LHZ462-LHZ463-LHZ464...UNTIL 7 PM WEDNESDAY.

LAKE ST CLAIR...
     BRISK WIND ADVISORY...UNTIL 4 PM WEDNESDAY.

MI WATERS OF LAKE ERIE...
     BRISK WIND ADVISORY...UNTIL 4 PM WEDNESDAY.

&&

$$

AVIATION.....MR
SHORT TERM...MR
LONG TERM....KEC
MARINE.......KEC


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