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000
FXUS63 KDTX 081654
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1154 AM EST SAT MAR 8 2014

.AVIATION...

//DISCUSSION...

DRIER AIR IS SLOWLY WORKING INTO SOUTHEAST MICHIGAN THIS
AFTERNOON...BUT NORTHEAST LOW LEVEL FLOW OFF LAKE HURON...COUPLED
WITH LINGERING LOW LEVEL LOW MOISTURE WILL LIKELY ALLOW AREAS OF
MVFR CEILINGS TO PERSIST INTO THE EVENING HOURS. PRONOUNCED
SUBSIDENCE AND SURFACE HIGH BUILDING IN TOWARD SUNRISE SHOULD ALLOW
FOR COMPLETE CLEARING AFTER MIDNIGHT. CLEAR SKIES ARE THEN EXPECTED
TO START SUNDAY...BUT DIURNAL COMPONENT SHOULD THEN LEAD TO AT LEAST
SCT DEVELOPMENT...IF NOT BKN AT MBS/FNT WITH INCREASING SOUTHWEST
PUSH OF LAKE MICHIGAN.

FOR DTW...AREA OF LIGHT SNOW NEAR THE OHIO BORDER SHOULD CONTINUE TO
WORK SOUTH AND EAST OF THE AIRPORT...AND NO ACCUMULATING SNOW IS
EXPECTED.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILINGS AOB 5000 FEET THROUGH THIS EVENING.

&&

.PREV DISCUSSION...ISSUED 350 AM EST SAT MAR 8 2014

SHORT TERM...TODAY AND TONIGHT

WELL THE DEEP LAYER OF WARM AIR...WITH TEMPS IN THE UPPER 30S AT THE
SFC...PROVED TOO MUCH FOR COOLING PROCESSES TO OVERCOME LEADING TO A
PURE RAIN EVENT TO KICK OFF THE FRONTAL PASSAGE ACROSS SOUTHERN MI.
WE WILL CONTINUE TO HAVE PTYPE ISSUES INTO THE MORNING HOURS AS THE
COLD FRONT CONTINUES TO WORK THROUGH THE AREA. AS OF 08Z THE FRONT
IS JUST THROUGH MBS AND SHOULD PASS SOUTH OF DTW SHORTLY AFTER 12Z.
THE FRONT IS ALIGNING WITH THE MEAN FLOW WHICH WILL LEAD TO A SLOW
EXIT OUT OF THE STATE INTO THE OHIO VALLEY. THE FRONT ITSELF IS VERY
WEAK WITH MINIMAL FORCING FOUND ANYWHERE ALONG IT ALTHOUGH AN
APPROACHING SHORTWAVE AND JET MAX DEVELOPING OVERHEAD WILL INITIATE
A BAND OF WEAK FGEN AROUND 850MB. THIS FGEN BECOMES CO-LOCATED WITH
AN AREA OF FAVORABLE OMEGA IN A MOISTURE RICH AIRMASS JUST ALONG THE
FRONT WITH SPECIFIC HUMIDITY VALUES OF 3G/KG FROM THE SFC TO 700MB.
IN ADDITION...MODELS SHOW THE SHORTWAVE CAUSING A FLARE UP IN THE
ISENTROPIC ASCENT OVER THE FRONT. THAT SAID...THE FRONT SHOULD
CONTINUE PRODUCING PRECIP INTO THE EARLY AFTERNOON HOURS BEFORE IT
FINALLY DROPS FAR ENOUGH SOUTH TO ALLOW THE DRY AIR BEHIND IT TO PUT
AN END TO IT. AS NOTED ABOVE...PTYPE MAY BE AN ISSUE IN THE EARLY
PART OF THE DAY AS WE ONCE AGAIN UNDERGO AIRMASS REPLACEMENT WITH
COLDER/DRIER AIR FILLING INTO THE AREA. MODEL SOUNDINGS SHOW THIS
WELL WITH THE LOWEST 50-100MB COOLING RAPIDLY POST FRONTAL WITH A
SLOWER RESPONSE ALOFT. THIS SHOULD LEAD TO THE CURRENT RAIN TURNING
INTO SNOW FOR A PERIOD. HIGH PRESSURE TO OUR WEST WILL SLIDE IN
BEHIND THE FRONT WHICH WILL DRY THE MID LEVELS OUT THIS AFTERNOON
BUT WE MAY HOLD ON TO LOW LEVEL MOISTURE/SATURATION LONG ENOUGH TO
GET A SHORT PERIOD OF FREEZING RAIN AS NOTED BY THE PREVIOUS
FORECASTER. WITH THE THERMAL/MOISTURE PROFILE WALKING SUCH A THIN
LINE...DO NOT SEE A REASON TO CHANGE THE TYPES AT THE MOMENT FOR THE
MORNING/AFTERNOON. THE 12Z SOUNDING WILL PROVIDE MORE INFORMATION IN
THAT REGARD FOR FINE TUNING. CONTINUED WITH THE AGGRESSIVE LOW TEMPS
FOR TONIGHT...UPPER SINGLE DIGITS ACROSS THE NORTH AND LOW TO MID
TEENS ACROSS THE SOUTH. EVEN WITH THE EXTENSIVE STRATUS LASTING INTO
THE EVENING...UPSTREAM OBS ARE SHOWING QUICK DROP OFFS UNDER THE SFC
RIDGE AS SOON AS THEY CLEAR OUT. TIMING THE CLEARING WILL BE KEY.

LONG TERM...

SE MICHIGAN WILL BE ON THE SOUTH FLANK OF THE UPPER JET SUNDAY
THROUGH TUESDAY WHICH WILL KEEP THE TRACK OF FAST MOVING BUT SMALLER
SCALE PRESSURE FEATURES TO OUR NORTH. THE RESULT FOR US WILL BE
MOSTLY DRY CONDITIONS AND A TEMPERATURE REBOUND BY MONDAY. MODEL
AGREEMENT IS REASONABLE ON THE ARRIVAL OF THE NEXT WAVE INTO
NORTHWEST ONTARIO SUNDAY AFTERNOON. THIS WILL DRIVE SURFACE HIGH
PRESSURE QUICKLY INTO THE OHIO VALLEY AND BRING UP SOUTHWEST
SURFACE WIND DURING THE DAY OVER OUR AREA. IT WILL TAKE A DAY FOR
THE RENEWED SOUTHWEST FLOW TO SCOUR OUT THE COLDER AIR LEFT BEHIND
BY TODAY`S COLD FRONT BUT STEADY WARM ADVECTION WILL HELP BOOST
READINGS INTO THE MID 30S MOST LOCATIONS. PERSISTENT GRADIENT WIND
SUNDAY NIGHT WILL THEN ONLY ALLOW A MODEST DROP INTO THE UPPER 20S
FOR MIN TEMPS SUNDAY EVENING BEFORE READINGS RESUME RISING
OVERNIGHT. ALL THE WHILE, WARM ADVECTION FORCED PRECIPITATION
WILL BE DIRECTED WELL TO OUR NORTH AND EAST WITH THE POSSIBLE
EXCEPTION OF A PASSING SNOW SHOWER THROUGH THE THUMB SUNDAY NIGHT.

MONDAY WILL EASILY BE THE WARMEST DAY OF THE EARLY WEEK AS SOUTHWEST
LOW LEVEL FLOW CONTINUES AHEAD OF THE ONTARIO LOW PRESSURE SYSTEM.
PARTIALLY BASED ON THE TEMPERATURE PERFORMANCE YESTERDAY,
EXPECTATIONS FOR MONDAY ARE RAISED INTO THE MID AND UPPER 40S GIVEN
EVEN GREATER LOW LEVEL THICKNESS WARMING BUT ALSO CONSIDERING
GREATER CLOUD COVER THAT WILL LIMIT STRENGTHENING MARCH SUNSHINE TO
A LATE DAY APPEARANCE. THE TUESDAY TEMPERATURE TREND WILL BE
COMPLICATED BY THE TIMING AND CHARACTER OF THE POLAR FRONT PASSAGE.
THE GFS SUGGESTS A WEAK PREFRONTAL TROUGH WHILE THE ECMWF INDICATES
A STEADY SOUTHWARD LEAK OF POLAR AIR ON A NORTHEAST WIND SHIFT BY
EVENING. THIS UNCERTAINTY DOES NOT SUPPORT AN AGGRESSIVE TEMP
FORECAST TUESDAY INTO TUESDAY NIGHT, BUT THE POTENTIAL IS THERE FOR
ANOTHER 40 DEGREE DAY.

MODEL TIMING ON THE PASSAGE OF THE POLAR FRONT IS CENTERED ON
TUESDAY NIGHT, TIED TO THE PACE OF LONG WAVE AMPLIFICATION AND UPPER
LEVEL HEIGHT FALLS OVER THE GREAT LAKES. THE FRONT IS SHOWN TO
INTERACT WITH SOUTHERN STREAM SURFACE CYCLOGENESIS OVER THE
TENNESSEE VALLEY BY WEDNESDAY MORNING ACTIVATING A CHANCE OF RAIN
AND SNOW THROUGH THE MID LEVELS OF THE FRONTAL ZONE OVER OUR AREA.
OTHERWISE, THE SOUTHWARD TREND ON THE TRACK OF THE PRIMARY LOW IS
PRESERVED IN THE 00Z MODEL PACKAGE. THERE IS GOOD AGREEMENT ON
THIS ROUND OF POLAR AIR ONLY AMOUNTING TO A ONE DAY EVENT FOR
WEDNESDAY. GLOBAL MODEL SOLUTIONS INDICATE QUICK DEVELOPMENT OF
ANOTHER SIZABLE LOW PRESSURE SYSTEM OVER CENTRAL CANADA THURSDAY
WHICH APPEARS ABLE TO SCOUR OUT THE POLAR AIR BY FRIDAY AND A
RETURN OF 40 DEGREE TEMPERATURE.

MARINE...

NORTHERLY WIND BEHIND THE MORNING COLD FRONT WILL HAVE GUSTS AT 25
KNOTS OR LESS BEFORE DIMINISHING AND THEN TURNING QUICKLY BACK TO
THE SOUTHWEST BY SUNDAY. SPEED WILL INCREASE MODERATELY AGAIN BY
SUNDAY NIGHT THROUGH MONDAY BUT THE ICE COVERED LAKES AND MILDER AIR
STREAMING INTO THE AREA WILL LEAD TO STABLE NEAR SURFACE PROFILES
AND LIMITED GUST POTENTIAL. A STRONG COLD FRONT REMAINS ON TRACK TO
MOVE THROUGH LAKE HURON AND LOWER MICHIGAN TUESDAY AND TUESDAY
NIGHT. THIS FRONT WILL BRING IN A RENEWED SURGE OF ARCTIC AIR THAT
WILL LAST THROUGH WEDNESDAY.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

AVIATION.....SF
SHORT TERM...DRK
LONG TERM....BT
MARINE.......BT


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