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000
FXUS63 KDTX 112337
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
737 PM EDT SAT MAY 11 2013


.AVIATION...

//DISCUSSION...

STRONG COLD FRONT HAS MADE IT THROUGH THE TAF SITES EARLY THIS
EVENING...WITH ONLY A FEW LINGERING SHOWERS OVER THE METRO AIRPORTS
TO START THE TAF PERIOD. MVFR CLOUDS WILL REMAIN SEVERAL HOURS AFTER
FROPA...WITH MOSTLY CLEAR SKIES EXPECTED TO DEVELOP AS COLD DRY AIR
WORKS ITS WAY IN FROM THE WEST. NORTHWEST WINDS TO 30 KNOTS WILL
SLOWLY SUBSIDE WITH NIGHTFALL AS THE ATMOSPHERE DECOUPLES...LEAVING
WINDS AROUND 10 TO 15 KNOTS THROUGH THE OVERNIGHT HOURS. UPSTREAM
OBSERVATIONS SHOW MVFR STRATOCU WILL LIKELY RETURN FROM THE NORTH
AND LAST THROUGH SUNDAY MORNING.

FOR DTW...NORTHWEST WIND GUSTS TO 30 KNOTS WILL CONTINUE FOR ANOTHER
HOUR BEFORE THE SUN SETS AND GUSTS SETTLE AROUND 20 KNOTS BEFORE
DROPPING OFF ENTIRELY SHORTLY AFTER MIDNIGHT. AT THAT POINT
SUSTAINED WINDS ARE EXPECTED IN THE 10 TO 15 KNOT RANGE THROUGH
SUNDAY MORNING.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CIGS BELOW 5000 FEET EARLY THIS EVENING POST
  FROPA.

* HIGH CONFIDENCE OF WIND GUSTS AROUND 30 KNOTS FROM 310 DEGREES
  THROUGH 01Z.

&&

.PREV DISCUSSION...ISSUED 346 PM EDT SAT MAY 11 2013

SHORT TERM... THIS AFTERNOON AND TONIGHT

A STRONG COLD FRONT FOR THIS LATE IN THE SPRING IS ON ITS WAY
THROUGH SE MICHIGAN. CONCERN EARLIER IN THE DAY WAS FOR THUNDERSTORM
POTENTIAL IN THE STRONGLY FORCED SYSTEM; A LITTLE LESS SO AT PRESS
TIME AS SURFACE DEWPOINT HAS SHOWN SOME TENDENCY TO MIX OUT IN THE
SOUTHWEST FLOW AHEAD OF THE FRONT, BUT ALSO SQUIRT UPWARD IN A
NARROW AXIS IMMEDIATELY AHEAD OF THE FRONT. HOURLY MESOANALYSIS
INDICATES EVEN THE NARROW AXIS OF HIGHER SURFACE MOISTURE IS NOT
GENERATING MUCH INSTABILITY WITH MUCAPE LESS THAN 250 J/KG AS OF
3PM. STILL, THE PASSAGE OF THE FRONT DURING THE PEAK OF THE DIURNAL
CYCLE AND LATE ARRIVING SURFACE MOISTURE COULD RESULT IN A 63/50
PARCEL, ESPECIALLY NEAR THE OHIO BORDER, RESULTING IN MUCAPE
REACHING UP TO AROUND 850 J/KG AND WARRANTS MAINTAINING THE OUTSIDE
MENTION OF A THUNDERSTORM UNTIL THE FRONT EXITS SE MICHIGAN BY 8 PM.
THAT BEING THE CASE, SOME VIGILANCE IS REQUIRED OUT OF RESPECT FOR
THE WIND FIELD AND FRONTAL DYNAMICS THAT COULD RESULT IN A 40 TO 50
MPH SURFACE WIND GUST SHOULD AN UPDRAFT BE ABLE TO SUSTAIN WITHIN A
0-6KM SHEAR PROFILE PUSHING 50 KNOTS.

OTHER THAN THE CONVECTIVE POTENTIAL, THERE HAS BEEN SOME CONCERN FOR
SURFACE WIND GUSTS ASSOCIATED WITH THE FRONT ITSELF. UPSTREAM
OBSERVATIONS OF GUSTS IN THE 30 TO 40 MPH RANGE CONTINUE TO REFLECT
THE MODERATE DYNAMIC POTENTIAL ILLUSTRATED IN THE 12Z MODEL DATA.
THERE IS ABOUT A 20 KNOT ISALLOBARIC COMPONENT TO THE SURGE RIGHT AT
WIND SHIFT ASSOCIATED WITH A 3-4 MB/3HR PRESSURE RISE THAT WILL
SLIDE OVER SE MICHIGAN WITH THE SYSTEM. THERE IS ALSO SOME
SUBSIDENCE INDICATED TRAILING FARTHER BEHIND THE WIND SHIFT BUT IT
IS SHALLOW/UP TO 850 MB JUDGING FROM THETA/THETA-E CROSS SECTIONS.
MODEL SOUNDINGS THEN INDICATE STRONG BOUNDARY LAYER DECOUPLING BY
LATE EVENING WHICH WILL CAUSE THE GUST POTENTIAL TO CEASE BY
MIDNIGHT. AFTER THAT, IT WILL JUST BE WEAK BUT STEADY COLD ADVECTION
THROUGH THE OVERNIGHT. STRATOCU WILL BE ON THE INCREASE LATE,
ESPECIALLY INTO THE TRI CITIES AND NORTHERN THUMB AS MIN TEMPS DROP
INTO THE MID AND UPPER 30S BY SUNRISE SUNDAY, 5-10 DEGREES BELOW
NORMAL.

LONG TERM...SUNDAY THROUGH FRIDAY

THE LONGWAVE PATTERN ONCE AGAIN LOOKS TO TRANSITION FROM HIGHLY
AMPLIFIED TO A ZONAL SPLIT FLOW REGIME BY THE WEEKEND. CURRENT BROAD
TROUGH OVER THE NORTHEAST CONUS AND GREAT LAKES WILL DEEPEN
SIGNIFICANTLY SUNDAY INTO MONDAY AS A POTENT SHORTWAVE DIVES INTO
THE MIDWEST BRINGING UNSEASONABLY COOL AIR TO THE GREAT LAKES. THIS
AMPLIFIED WESTERN CONUS RIDGE AND EASTERN CONUS TROUGH WILL HOLD
UNTIL AROUND TUESDAY WHEN ANOTHER STRONG SHORTWAVE LOOKS TO BARREL
THROUGH THE RIDGE FLATTENING IT AND PRODUCING A PROGRESSIVE JET
STREAM ACROSS SOUTHERN CANADA. THE CENTRAL PORTIONS OF THE CONUS
WILL ONCE AGAIN FALL IN A REGION OF WEAK UPPER LEVEL FLOW AS THE
NORTHERN AND SOUTHERN STREAMS OF THE JET SPLIT. THOUGH THE MODELS
ARE FAIRLY IN LINE WITH THIS GENERAL PATTERN...WHERE THE NORTHERN
STREAM SETS UP WHICH IN TURN DECIDES WHERE THE STALLING COLD FRONT
AND STORM TRACK SETS UP IS STILL A BIT UP IN THE AIR. A FEW CONCERNS
FOR THE EXTENDED ARE FREEZING TEMPERATURES SUNDAY NIGHT...A WARM
FRONT LIFTING THROUGH THE REGION ON WEDNESDAY...AND CHANCES OF
THUNDERSTORMS THROUGH MUCH OF THE LATTER HALF OF THE WORK WEEK.

FIRST OFF...THE STRONG SHORTWAVE DIVING INTO THE TROUGH ON SUNDAY
WILL BRING IN A COLD AIRMASS WITH 850MB TEMPS AROUND -5 TO -10C. IN
ADDITION HIGH PRESSURE WILL BE BUILDING INTO STATE FROM THE SW IN
THE WAKE OF A DEPARTING COLD FRONT. THE INCREASING SUBSIDENCE SHOULD
HELP CLEAR OUT THE CLOUDS LEADING TO CLEARING SKIES WITH
NORTHWESTERLY CAA WHICH WILL ALLOW TEMPS TO DROP TO AROUND 30
DEGREES FOR MOST LOCATIONS AND UPPER 20S FOR TYPICALLY COOLER
LOCATIONS AWAY FROM THE LAKES. A FREEZE WATCH HAS BEEN ISSUED FOR
SUNDAY NIGHT INTO MONDAY MORNING TO ACCOUNT FOR THIS. THERE IS A
CHANCE FOR SOME FROST FORMATION BUT WINDS MAY STAY ELEVATED JUST
ENOUGH TO KEEP FROST AT A MINIMUM.

HIGH PRESSURE WILL SLIDE THROUGH MONDAY AND TUESDAY LEADING TO A
SLOW WARMING TREND BEFORE THE NEXT SHORTWAVE TRACKS THROUGH SOUTHERN
CANADA LIFTING A WARM FRONT NE THROUGH SOUTHERN MI. THE WARM SECTOR
WILL LIFT INTO THE AREA WITH PEAK HEATING ON WEDNESDAY PRODUCING A
VERY WARM DAY WITH TEMPS BACK UP AROUND 80. WESTERLY IN THE WAKE OF
THIS SHORTWAVE WILL KEEP MILD AIR STREAMING INTO THE REGION ALLOWING
MAX TEMPS TO LINGER IN THE 70S THROUGH THE END OF THE WEEK. THIS
WILL OF COURSE BE DEPENDENT ON CONVECTIVE ACTIVITY. BOTH THE GFS AND
EURO ARE TRENDING A BIT SOUTH WITH THE COLD FRONT THAT WEDNESDAY
SYSTEM WILL DROP THROUGH THE AREA. THIS WOULD KEEP THE BULK OF
CONVECTIVE ACTIVITY TO OUR SOUTH THROUGH THE END OF THE WEEK WITH
CHANCE POPS OVER SE MI AND MORE SO FOR LOCATIONS CLOSER TO THE OHIO
BORDER. SOMETHING TO KEEP AN EYE OUT FOR WILL BE A SECONDARY COLD
FRONT DROPPING INTO THE GREAT LAKES AS ADDITIONAL VORTICITY LOBES
PINWHEEL AROUND THE POLAR VORTEX OVER NORTHERN ONTARIO. THIS WOULD
LIKELY HOLD OF TIL LATE IN THE WEEK THOUGH.

MARINE...

THE STRONG COLD FRONT PASSING THROUGH LAKE HURON AND LOWER MICHIGAN
DURING THE LATE AFTERNOON AND EVENING WILL LEAVE COLD NORTHWEST FLOW
IN ITS WAKE. THE WIND PATTERN ASSOCIATED WITH THIS SYSTEM WILL
INCREASE EVEN MORE DURING SUNDAY, ESPECIALLY OVER THE OPEN WATERS OF
LAKE HURON WHERE GALE WARNINGS HAVE BEEN EXTENDED SOUTHWARD TO
HARBOR BEACH, INCLUDING SAGINAW BAY. SMALL CRAFT ADVISORIES REMAIN
IN EFFECT FOR ALL OTHER MARINE AREAS.

LOW PRESSURE DEEPENING NEAR THE NORTH SHORE OF GEORGIAN BAY TONIGHT
WILL HELP INCREASE THE WIND OVER THE REGION AND RESULT IN GALES OVER
THE NORTH AND CENTRAL PORTIONS OF LAKE HURON DURING SUNDAY AS
UNSEASONABLY COLD AIR MOVES OVER THE MILDER WATERS OF LAKE HURON.
THIS WILL PRODUCE UNSTABLE CONDITIONS CONDUCIVE TO HIGHER WIND GUSTS
AND LARGER WAVES. FARTHER SOUTH, WESTERLY WINDS WILL EASILY GUST TO
30 KNOTS THROUGH THE WEST END OF LAKE ERIE DURING SUNDAY AFTERNOON.
HIGH PRESSURE WILL THEN BUILD INTO THE AREA MONDAY BRINGING
IMPROVEMENT TO MARINE CONDITIONS INTO TUESDAY.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...FREEZE WATCH...MIZ047-MIZ048-MIZ049-MIZ053-MIZ054-MIZ055-MIZ060-
     MIZ061-MIZ062-MIZ063-MIZ068-MIZ069-MIZ070-MIZ075-MIZ076-MIZ082-
     MIZ083...FROM MIDNIGHT MONDAY TO 8 AM MONDAY.

LAKE HURON...
     GALE WARNING...LHZ361-LHZ362-LHZ363-LHZ421-LHZ422-LHZ441-
     LHZ462...FROM 8 AM SUNDAY TO 8 PM SUNDAY.

     SMALL CRAFT ADVISORY...SAGINAW BAY AND THE NEARSHORE WATERS FROM
     PORT AUSTIN TO HARBOR BEACH...UNTIL 8 AM SUNDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM HARBOR BEACH TO PORT
     HURON...UNTIL 8 PM SUNDAY.

LAKE ST CLAIR...
     SMALL CRAFT ADVISORY...UNTIL 8 PM SUNDAY.

MI WATERS OF LAKE ERIE...
     SMALL CRAFT ADVISORY...UNTIL 8 PM SUNDAY.

&&

$$

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


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