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000
FXUS63 KDTX 132338
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
738 PM EDT THU JUN 13 2013


.AVIATION...

//DISCUSSION...

SURFACE HEATING IS RAPIDLY WANING...RESULTING IN A MARKED REDUCTION
IN THE CU FIELS ACROSS SOUTHEAST MICHIGAN EARLY THIS EVENING.
NORTHERLY WINDS ARE EXPECTED TO DIMINISH DURING THE EVENING ALONG
WITH A GRADUAL DECREASE IN HIGH BASED CU/LOWER AC. THE MORE
CHALLENGING ASPECT OF THE FORECAST IS FOR THE POTENTIAL FOR STRATOCU
COVERAGE FROM JUST BEFORE SUNRISE THROUGH FRIDAY MORNING. VEERING
FLOW ABOVE THE SURFACE BASED INVERSION TO ABOUT 850 MB IS EXPECTED
TO KEEP LOW LEVEL MOISTURE OBSERVED OVER THE NORTHERN LAKES TODAY IN
PLAY OVER THE SOUTHERN LAKES LATER TONIGHT. THE POTENTIAL FOR MVFR
CEILING LOOK GREATER FROM PTK INTO THE DTW AREA AT THIS EARLY STAGE.

//DTW THRESHOLD THREATS...

* MEDIUM CONFIDENCE IN CEILINGS BELOW 5000 FEET AFTER 10Z WITH STRATUS.

&&

.PREV DISCUSSION...ISSUED 354 PM EDT THU JUN 13 2013

SHORT TERM... AFTERNOON THROUGH TONIGHT

COOLER BUT JUST SLIGHTLY LESS HUMID AIR WILL CONTINUE TO SPREAD OVER
SE MICHIGAN THROUGH THE REST OF THE DAY AND TONIGHT. EVIDENCE OF THE
CHARACTER OF THIS AIR MASS IS APPARENT IN THE AFTERNOON PATTERN OF
CLOUDS AND SHOWERS SETTING UP OVER CENTRAL LOWER MICHIGAN AT PRESS
TIME. STRONG SURFACE HEATING, COMBINED WITH SURFACE DEWPOINT IN THE
MID TO UPPER 50S, IS EXPLOITING STEEP LOW LEVEL LAPSE RATES FOR THE
SHALLOW BUT VIGOROUS CONVECTIVE RESPONSE. MODEL SOUNDINGS ILLUSTRATE
LAPSE RATES AVERAGING 7.5-8.5 C/KM IN THE CLOUD LAYER ROUGHLY
BETWEEN 875 MB AND 650 MB AND SUGGEST SHOWER POTENTIAL WILL EASILY
LAST INTO THE EVENING PAST PEAK HEATING. IT WILL TAKE A LITTLE
LONGER FOR THE CLOUDS TO DISSIPATE AS THEY SETTLE UNDER THE MID
LEVEL SUBSIDENCE INVERSION THAT WILL BE INCREASING WITH CONFLUENT
FLOW ALOFT AS THE UPPER WAVE PULLS AWAY.

EXPECT AT LEAST PARTLY CLOUDY AND DRY CONDITIONS BY MIDNIGHT AROUND
SE MICHIGAN WITH ATTENTION TURNING TO THE POTENTIAL FOR STRATOCU TO
DEVELOP TOWARD SUNRISE. OBSERVATIONAL EVIDENCE OF THIS WAS
CONVINCING OVER THE NORTHERN LAKES DURING THE MORNING AND WILL
LIKELY REMAIN A FACTOR IN OUR AREA AS SURFACE DEWPOINT REMAINS IN
THE MID 50S EVEN IN ONTARIO NORTH OF GEORGIAN BAY. VEERING FLOW
ABOVE THE SURFACE BASED INVERSION TO ABOUT 850 MB IS THEN EXPECTED
TO KEEP THE LOW LEVEL MOISTURE THAT IS OBSERVED OVER THE NORTHERN
LAKES IN PLAY OVER THE SOUTHERN LAKES FOR AT LEAST 50-50 COVERAGE IN
SE MICHIGAN BY SUNRISE FRIDAY.

LONG TERM...FRIDAY THROUGH NEXT THURSDAY

UPPER RIDGE AXIS SHIFTING INTO THE MIDWEST WILL ALLOW SURFACE
HIGH PRESSURE TO BECOME CENTERED OVERHEAD FRIDAY INTO FRIDAY NIGHT.
THIS WILL ALLOW FOR QUIET WEATHER CONDITIONS. NORTHERLY FLOW OFF
LAKE HURON WILL HELP HOLD AFTERNOON TEMPERATURES BELOW
NORMAL...ESPECIALLY ACROSS THE THUMB WHERE MAXES SHOULD ONLY REACH
INTO THE 60S.

WEEKEND FORECAST...ESPECIALLY THE CONVECTIVE ELEMENT...REMAINS A
LITTLE CHALLENGING AS IT LOOKS LARGELY DEPENDENT ON MESOSCALE
FEATURES SUCH AS CONVECTIVELY INDUCED WAVES THAT HAVE NOT DEVELOPED
YET AND ACTIVITY COULD BE LIMITED BY WHAT INSTABILITY CAN BUILD
DURING THE DAY. UPPER LOW OVER THE PACIFIC NORTHWEST WILL LIFT INTO
CENTRAL CANADA...EFFECTIVELY BREAKING DOWN THE UPPER RIDGE BEFORE IT
CAN MOVE INTO THE GREAT LAKES. LOW WILL BEGIN TO SHEAR APART OVER
THE WEEKEND..WITH THE MAIN CHUNK OF ENERGY NOW EXPECTED TO MOVE
ACROSS THE AREA DURING THE MONDAY/TUESDAY TIMEFRAME. FOR THE
WEEKEND...THIS SHOULD KEEP LOWER MICHIGAN WITHIN PROGRESSIVE
WESTERLY FLOW. A FRONTAL BOUNDARY NOW DRAPED OVER THE CENTRAL PLAINS
IS FORECAST TO LIFT INTO THE OHIO VALLEY AS LOW-MID LEVEL FLOW TURNS
SOUTHERLY IN RESPONSE TO THE LOW OVER THE U.S. AND CANADIAN BORDER.
THIS FRONT SHOULD REMAIN QUASI-STATIONARY THROUGH THE WEEKEND...WITH
THE ELEVATED PORTION OF THE FRONT POTENTIALLY POISED OVER SOUTHERN
LOWER MICHIGAN. SMALL WAVES ARE EXPECTED TO RIDE OVER THE FRONT
GENERATING ROUNDS OF PRECIPITATION...BUT NONE OF THESE WAVES ARE
CURRENTLY TRACEABLE ON WATER VAPOR AND LOOK TO BE INDUCED BY
CONVECTION WITHIN THE MODELS. DO THINK THESE FEATURES WILL DEVELOP
HOWEVER...BUT TIMING/PLACEMENT IS UNCERTAIN. HAVE KEPT HIGHEST
CHANCES FOR RAIN/TSTORMS SOUTH OF THE M-59 CORRIDOR THROUGH THE
WEEKEND. EXPECTATION IS THAT BEST COVERAGE AND INTENSITY OF STORMS
WILL REMAIN SOUTH OF THE I-94 CORRIDOR...AND ESPECIALLY OVER INDIANA
AND OHIO. GFS/NAM DO MANAGE TO BUILD 1000-2000 J/KG OF SB CAPE OVER
SOUTHEAST MICHIGAN ON SUNDAY (MODEL SURFACE TEMPS IN LOW
80S)...WHICH IS ASSUMING WE CAN MAXIMIZE HEATING AND REMAIN FREE OF
UPSTREAM CONVECTIVE DEBRIS...AND THAT ANY CONVECTION THAT IS
GENERATED SATURDAY NIGHT CLEARS OUT EARLY. SHOULD NOTE...LOW-END
THUNDERSTORM CHANCES ON SATURDAY ARE ACTUALLY TIED TO A SURGE OF
THETA-E BETWEEN 700-850MB.

UPPER SHORTWAVE SHOULD MOVE ACROSS THE AREA MONDAY OR TUESDAY.
MODELS HAVE BEEN VARYING WITH THE TIMING OVER THE PAST FEW
DAYS...WITH THE NEW 13.12Z EURO COMING IN AT THE FASTER EDGE OF THE
GUIDANCE ENVELOPE (MONDAY). SEVERE CHANCES WILL DEPEND GREATLY ON
TIMING...BUT DO HAVE CONCERN CONSIDERING THE STRONG COLD FRONT THE
12Z EURO IS DROPPING THROUGH THE AREA MONDAY AFTERNOON AND EVENING.
GFS LAGS BY ALMOST 24 HOURS...WITH A WEAKER FRONT DROPPING DOWN ON
TUESDAY.

DOWNSTREAM RIDGE AMPLIFICATION WILL ALLOW AN EXPANSIVE AREA OF HIGH
PRESSURE TO SETTLE IN OVER MICHIGAN WEDNESDAY AND THURSDAY. THIS
WILL BRING A RETURN TO QUIET CONDITIONS.

MARINE...

COOLER AND SLIGHTLY LESS HUMID AIR WILL CONTINUE TO SPREAD OVER LAKE
HURON AND LOWER MICHIGAN TONIGHT. LINGERING NORTHERLY WIND WITH 20
KNOT GUSTS WILL MAINTAIN ELEVATED WAVES OVER SOUTHERN LAKE HURON
TONIGHT BUT THE SMALL CRAFT ADVISORY WILL BE ALLOWED TO EXPIRE WITH
THE WAVE RESPONSE PAST ITS PEAK. CONDITIONS WILL THEN CALM CONSIDERABLY
HEADING INTO THE WEEKEND AS A LARGE HIGH PRESSURE SYSTEM BUILDS OVER
THE GREAT LAKES.

&&

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

&&

$$

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


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