938
FXUS63 KDTX 032331
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
731 PM EDT FRI JUL 3 2009
AVIATION
CLEARING TREND WILL CONTINUE OVER THE NEXT COUPLE HOURS WITH THE
LOSS OF DIURNAL HEATING. WIND FIELD WILL WEAKEN AS WELL WITH WEAK
HIGH PRESSURE BUILDING IN OVERNIGHT. VFR CONDITIONS WILL HOLD
THROUGH THE REMAINDER OF THE NIGHT WITH HIGHER CLOUDS BEGINNING TO
FILTER IN. CLOUDS WILL THICKEN AND LOWER INTO SATURDAY AS A LOW
PRESSURE SYSTEM TRACKS THROUGH THE OHIO VALLEY AND DIURNAL HEATING
ONCE AGAIN ENHANCES THE STRATO-CU DEVELOPMENT. CEILINGS WILL REMAIN
AOA 5K FT DURING THIS TIME. LGT/VARIABLE WINDS EARLY WILL SHIFT
TOWARD THE SOUTHWEST LATE IN THE DAY AS THE SURFACE RIDGE SLIDES
EAST.
PREV DISCUSSION
ISSUED 326 PM EDT FRI JUL 3 2009
SHORT TERM...TONIGHT
LAST GASP FROM THE PERSISTENT UPPER LOW COMPLEX IS UNDERWAY WITH YET
ANOTHER CLOUD FILLED AFTERNOON. SIGNS OF THE END OF THIS EPISODE
ARE ON THE DISTANT WESTERN HORIZON WHERE CLOUDS ARE BECOMING MORE
SCATTERED. TODAY/S CLOUD COVER HAS BEEN AIDED BY THE BRIEF INFLUX
OF SUN THIS MORNING IN COMBINATION WITH THERMAL TROUGHING IN THE
925-850MB LAYER. AS THIS FEATURE EXITS STAGE RIGHT...EXPECT THE
CLOUD FIELD TO THIN AND THEN NEARLY DISSIPATE POST-DUSK. HIGH
CLOUDS POISED OVER THE MID/UPPER MISSISSIPPI VALLEY WILL ADVANCE
EAST OVER THE AREA OVERNIGHT. OTHERWISE...TEMPERATURES WILL SLIP
BACK INTO THE LOWER-MID 50S TONIGHT AS WINDS SUBSIDE IN RESPONSE TO
BUILDING HIGH PRESSURE AT THE SURFACE.
LONG TERM...
115+ KNOT UPPER LEVEL JET DIVING SOUTH THROUGH THE WESTERN GREAT
LAKES...WITH THE UPPER LEVEL RIDGE AXIS JUST TO THE WEST QUICKLY
FLATTENING...AS SHORTWAVES RIDING ALONG THE SOUTHERN CANADIAN BORDER
TRACK SOUTHEAST THROUGH THE NORTHERN GREAT LAKES REGION TOMORROW
AND SUNDAY.
WITH THE UPPER LEVEL RIDGE FLATTENING/FOLDING OVER AND LOW LEVEL JET
VEERING OVER MISSOURI TONIGHT...LOOKING AT THE WARM
FRONTAL/CONVECTIVE ACTIVITY DEVELOPING OVER THE MIDWEST TONIGHT TO
TRACK SOUTH OF THE CWA DURING SATURDAY...BUT WILL MAINTAIN THE LOW
CHANCE POPS TOWARD THE OHIO BORDER JUST IN CASE THE SUBTLE
SHORTWAVE/JET STREAK MOVING THROUGH THE CENTRAL PLAINS IS A BIT
STRONGER AND 700 MB FGEN ZONE SHIFTS SLIGHTLY NORTH. WITH AT LEAST
SOME MID/HIGH CLOUDS AROUND (ESPECIALLY SOUTH)...TEMPERATURES WILL
PROBABLY HOLD IN THE MID 70S...AND JUST USED THE MAV GUIDANCE...AS
CU RULES ALSO SUGGEST SOME LOW CLOUDS AS WELL.
THE TREND FOR THE SECOND HALF OF THE WEEKEND IS FOR A BIT STRONGER
UPPER WAVE/FARTHER WEST WITH THE 500 MB LOW...WHICH INCREASES THE
CHANCE FOR SOME INSTABILITY SHOWERS BY SUNDAY EVENING ASSOCIATED
WITH THE MID TROPOSPHERIC COLD POOL (-20 C AT 500 MB SWINGING
THROUGH LAKE HURON). DO FAVOR THE SLOWER NAM/CANADIAN TIMING OVER
THE GFS...AND WILL CARRY ISOLATED SHOWERS DURING THE SUNDAY
EVENING/NIGHT PERIOD...AS SHOWALTER INDEX DOES DROP DOWN TO AROUND
ZERO. BANKING ON THE SKINNY CAPE/SUB -20 C EQL TO KEEP THUNDERSTORM
MENTION OUT. BASED ON THE EVEN SLOWER/MORE AMPLIFIED SOLUTION
OF THE 12Z EUROPEAN...INCLUDED AN ISOLATED SHOWER MENTION ACROSS THE
NORTH HALF OF CWA INTO MONDAY AS WELL.
LOOKING AT A CONTINUED RELATIVELY COOL (70S) START TO THE WORK WEEK
WITHIN THE NORTHWEST CONFLUENT FLOW OF DEPARTING UPPER LEVEL
LOW/TROUGH...BUT A WARMING TREND IS THEN EXPECTED AS HEIGHTS BEGIN
TO BUILD IN RESPONSE TO THE UPPER LEVEL RIDGE ANCHORED OVER THE
SOUTHWEST CONUS EXTENDING NORTHEAST INTO THE SOUTHERN GREAT LAKES BY
WEEKS END...PUSHING TEMPERATURES WELL INTO THE 80S. WILL LEAVE A
SLIGHT CHANCE/LOW CHANCE OF SHOWERS/THUNDERSTORMS DURING THE MIDWEEK
PERIOD AS THE WARM FRONT LIFTS NORTH...BUT BEST FORCING LOOKS TO BE
NORTH AND WEST OF THE CWA.
MARINE...
NORTHWEST WINDS WILL SUBSIDE THROUGH THE EVENING AS PERSISTENT LOW
PRESSURE EXITS TO THE EAST OF THE REGION. WINDS WILL BRIEFLY SWING
TO SOUTHWEST ON SATURDAY IN ADVANCE OF A WEAK FRONTAL BOUNDARY ONLY
TO RETURN TO NORTHWESTERLY IN IT/S WAKE. WINDS AND WAVES ARE
EXPECTED TO REMAIN BELOW ADVISORY CRITERIA.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
AVIATION.....MR
SHORT TERM...MANN
LONG TERM....SF
MARINE.......MANN
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