823
FXUS63 KDTX 200733
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
333 AM EDT SAT MAR 20 2010
SHORT TERM
TODAY
THE WIND SHIFT ASSOCIATED WITH THE COLD FRONT HAS PASSED ALL THE WAY
THROUGH THE CWA EARLY THIS MORNING. HOWEVER THE COLD AIR IS LAGGING
BEHIND AS TEMPERATURES ARE STILL IN THE 40S SOUTH OF INTERSTATE 96.
THE PUSH OF COLD AIR WILL CHANGE OVER THE RAIN AND SNOW MIX OVER TO
ALL SNOW LATER THIS MORNING ALONG AND NORTH OF INTERSTATE 69 AS SNOW
HAS ALREADY MIXED IN ACROSS SOME OF THESE SITES. FURTHER SOUTH THE
BOUNDARY LAYER REMAINS FAIRLY WARM DURING THE DAY AS THE LOWEST 1-2K
FT REMAINS ABOVE FREEZING. THIS SHOULD KEEP PRECIPITATION AS ALL
RAIN ACROSS THE EXTREME SOUTHERN CWA WITH A MIX OF RAIN AND SNOW
BETWEEN THE ALL RAIN AND ALL SNOW AREAS.
WHILE THE QUESTION OF PRECIPITATION ITSELF DOES NOT APPEAR TO BE THE
MAIN ISSUE AS THE AREA OF PRECIPITATION IS SLOWLY MAKING ITS WAY
SOUTH ACROSS THE AREA...THE QUESTION IS WILL IT PRECIPITATE ENOUGH
TO MEASURE ABOVE A TRACE. THE SETUP IS NOT FAVORABLE FOR MUCH QPF AS
THERE IS A NARROW RIBBON OF RH ACROSS THE CWA WITH AREAS OF DRY AIR
SQUEEZING IN FROM THE NORTH AND SOUTH. IN ADDITION THE FORCING DOES
NOT FOLLOW THE PRECIPITATION DURING THE DAY AS THE RIGHT REAR OF THE
JET MAINTAINS ITS POSITION ACROSS THE NORTHERN GREAT LAKES INSTEAD
OF MOVING SOUTH. THE MAIN DRIVING FEATURE APPEARS TO BE MID LEVEL
FRONTOGENESIS BETWEEN 850 AND 700 MB WHICH WEAKENS AS IT HEADS SOUTH
DURING THE DAY. GIVEN THESE FACTORS THIS APPEARS TO BE A HIGH
COVERAGE LOW QPF SCENARIO AND WITH THE STRUGGLE TO MEASURE WITH THE
CURRENT PRECIPITATION HEADING FOR THE AREA WILL MAINTAIN THE 70 POPS
ACROSS THE CWA TODAY WITH THE HIGHEST POPS MIGRATING FROM NORTH TO
SOUTH IN LINE WITH THE MOVEMENT OF THE MID LEVEL FRONTOGENESIS.
WITH THE LOW AMOUNT OF QPF EXPECTED TODAY SNOWFALL
ACCUMULATIONS...IF ANY...WILL BE VERY LIGHT AND LIMITED TO LOCATIONS
ALONG AND NORTH OF INTERSTATE 69.
LONG TERM
SPLIT FLOW PATTERN ANTICIPATED OVER THE NEXT SEVERAL DAYS...WITH
THE SOUTHERN GREAT LAKES ON THE SOUTHERN FRINGE OF THE NORTHERN
BRANCH...WHICH SHOULD TRANSLATE TO TEMPERATURES ABOVE NORMAL FOR
THE FIRST HALF OF THE WEEK. LATEST WATER VAPOR IMAGERY SHOWS THE
UPPER LEVEL TROUGH MOVING INTO THE SOUTHERN PLAINS IN THE PROCESS
OF CUTTING OFF...WITH MODEL CONSENSUS INDICATING THE 500 MB LOW
DOWN TO 540 DAM SUNDAY MORNING OVER THE WESTERN GULF COAST STATES.
THIS CUTOFF SYSTEM WILL HAVE A MINIMAL IMPACT ON OUR WEATHER...BUT
STILL MAY PROVIDE A GLANCING BLOW TO FAR SOUTHEASTERN AREAS...IN
THE FORM OF A LITTLE BIT OF LIGHT RAIN SUNDAY-MONDAY TIME
FRAME...BUT BOTH NAM/GFS KEEP MEASURABLE RAINFALL JUST OUTSIDE OF
THE CWA....AND WILL MAINTAIN JUST LOW CHANCE POPS.
TWEAKED MAXES UP ON MONDAY WITH SOME SUNSHINE EXPECTED ACROSS THE
NORTH HALF OF THE CWA...WITH SURFACE RIDGING BUILDING IN FOR MONDAY
NIGHT...PROVIDING FAVORABLE RADIATING CONDITIONS...WITH MINS
DROPPING INTO THE MID 20S TO AROUND 30. GOOD INSOLATION ON TUESDAY
SHOULD TRANSLATE TO A SOLID REBOUND...AND WILL CALL FOR HIGHS IN THE
LOW/MID 50S BASED ON 925 MB TEMPS SEEN WARMING TO AT LEAST 5 C. 850
MB TEMPS OF 3 C SUPPORT HIGHS AROUND 60...BUT NOT ANTICIPATING
MIXING THAT HIGH WITH THE SURFACE RIDGE AXIS IN PLACE. EXACT
STRENGTH OF THE SHORTWAVE TROUGH AND TIMING OF THE WEAK COLD FRONT
ON WEDNESDAY WILL DICTATE THE TEMPERATURES. THE 12Z GFS/EUROPEAN ARE
BOTH FASTER...COMING THROUGH IN THE MORNING HOURS...BUT THE EUROPEAN
IS LESS AMPLIFIED AND SUBSEQUENTLY INDICATES 850 MB TEMPS FALLING TO
AROUND ZERO...WHICH CAN STILL SUPPORT MAXES IN THE MID 50S.
MARINE
A COLD FRONT HAS MADE ITS WAY THROUGH THE CENTRAL GREAT LAKES EARLY
THIS MORNING...BRINGING GUSTY NORTHERLY WINDS TO THE WATERS.
ALTHOUGH WIND GUSTS ARE NOT EXPECTED TO EXCEED 20 KNOTS...THE LONG
FETCH ACROSS LAKE HURON WILL BRING WAVES IN EXCESS OF 4 FEET FROM
PORT AUSTIN TO PORT SANILAC THROUGH THE AFTERNOON HOURS. A SMALL
CRAFT ADVISORY IS THEREFORE IN EFFECT.
A RIDGE OF HIGH PRESSURE WILL BRIEFLY EXTEND INTO THE NORTHERN GREAT
LAKES LATER TODAY BEHIND THE FRONT...BEFORE TWO LOW PRESSURE SYSTEM
MOVE INTO THE REGION ON SUNDAY. THE FIRST WILL TRACK THROUGH
SOUTHERN CANADA ON SUNDAY...WHILE THE OTHER LIFTS ACROSS THE
SOUTHERN OHIO VALLEY SUNDAY NIGHT. THIS WILL BRING UNSETTLED WEATHER
TO THE SOUTHERN GREAT LAKES INTO THE BEGINNING OF NEXT WEEK. THIS
WILL ALSO ALLOW NORTHEAST WINDS TO INCREASE ACROSS ALL MARINE AREAS
ON MONDAY.
PREV DISCUSSION
ISSUED 1255 AM EDT SAT MAR 20 2010
AVIATION...
THE COLD FRONT WILL BE ADVANCING SOUTH OF THE DETROIT TERMINALS NEAR
THE START OF THE 06Z TAF ISSUANCE. POST FRONTAL MOISTURE WILL
STEADILY INCREASE DURING THE MORNING...LEADING TO WIDESPREAD MVFR
CEILINGS. A MIX OF LIGHT RAIN AND SNOW IS EXPECTED DEVELOP AND
CHANGE OVER TO ALL SNOW DURING THE COURSE OF THE MORNING AT
PTK...FNT AND MBS. CONDITIONS WILL IMPROVE FROM NORTH TO SOUTH
DURING THE AFTERNOON AND EVENING AS DRIER AIR ADVECTS IN UNDER THE
PERSISTENT NORTHERLY FLOW.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...
SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
SANILAC...UNTIL 4 PM SATURDAY.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
SHORT TERM...KURIMSKI
LONG TERM....SF
MARINE.......KURIMSKI
AVIATION.....KURIMSKI
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