Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 071644
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1244 PM EDT MON JUL 7 2014


.AVIATION...

//DISCUSSION...

LOW VFR CLOUDS WITHIN THE LOW-LEVEL MOISTURE PLUME WILL SCATTER OUT
FROM NORTHWEST TO SOUTHEAST LATE THIS AFTERNOON INTO THIS EVENING AS
A WEAK COLD FRONT MOVES THROUGH THE AREA. IN THE MEANTIME...
LINGERING MVFR PORTION OF THE CLOUD DECK IS EXPECTED TO EITHER MIX
OUT COMPLETELY OR AT LEAST LIFT OUT OF THE MVFR CATEGORY WITHIN THE
NEXT COUPLE OF HOURS. WESTERLY WINDS WILL GUST TO 20-25KTS UNTIL THE
ONSET OF NOCTURNAL STABILIZATION THIS EVENING. MOSTLY CLEAR SKIES
THROUGH THE FIRST HALF OF THE NIGHT WILL ONCE AGAIN GIVE WAY TO
LOWERING CEILINGS AND A SHOWER/TSTORM THREAT IN ADVANCE OF ANOTHER
COLD FRONT 12-18Z TUESDAY.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILINGS BELOW 5KFT

* LOW CONFIDENCE THAT A THUNDERSTORM WILL IMPACT KDTW

&&

.PREV DISCUSSION...ISSUED 347 AM EDT MON JUL 7 2014

SHORT TERM... TODAY AND TONIGHT

ANY EXISTING CONVECTIVE ACTIVITY STILL ANCHORED ON THE EXITING
DEEPER THETA-E PLUME AND LOW LEVEL JET SUPPORT WILL STEADILY TAPER
OFF WHILE SHIFTING SOUTHEAST THIS MORNING AS THE PRIMARY BACKGROUND
FORCING PULLS OUT.  TRAILING COLD FRONT REMAINS FORECAST TO SHIFT
ACROSS SOUTHEAST MICHIGAN EARLY THIS AFTERNOON.  GOOD PRE-FRONTAL
THERMAL RESPONSE IS ANTICIPATED UNDER SOLID MIXING POTENTIAL AND AT
LEAST PARTIAL INSOLATION.  THIS WILL BRING HIGHS INTO THE LOWER AND
MIDDLE 80S.  THIS WILL LEAVE A STEEPENING LAPSE RATE ENVIRONMENT
WITH MODEST INSTABILITY FOR THE FRONTAL PASSAGE.  THE OVERALL LOSS
OF GREATER MOISTURE QUALITY WILL BE A LARGE LIMITING FACTOR IN ANY
RENEWED DEVELOPMENT...BUT THERE REMAINS AT LEAST A LOW PROBABILITY
FOR A FEW SHOWERS/THUNDERSTORMS TO EMERGE ALONG FAR SOUTHEAST
SECTIONS BEFORE THE FRONT EXITS TO THE EAST.

TRANQUIL CONDITIONS THROUGH THE FIRST HALF OF TONIGHT AS SLIGHTLY
DRIER POST-FRONTAL WESTERLY FLOW HOLDS WITHIN WEAK MID LEVEL
TROUGHING.  LEAD EDGE OF THE MAIN HEIGHTS ASSOCIATED WITH A STRONG
MID LEVEL WAVE DIGGING ACROSS THE UPPER MS VALLEY WILL ARRIVE LATE
TONIGHT.  STRENGTHENING LOW LEVEL FLOW IMMEDIATELY DOWNSTREAM WILL
INITIATE A QUICK INCREASE IN NORTHEASTWARD MOISTURE TRANSPORT.  THIS
WILL LIKELY ESTABLISH AN INCREASING COVERAGE OF CONVECTION
UPSTREAM...THIS ACTIVITY EVENTUALLY SPILLING EASTWARD BACKED BY
INCREASING MID LEVEL ASCENT AND LOW LEVEL JET SUPPORT.  THIS WILL
CONTINUE TO SUPPORT A CHANCE FOR SHOWERS AND THUNDERSTORMS AFTER 08Z
TONIGHT.

LONG TERM...

THE COOL START TO JULY LOOKS TO BE PERSISTING...AS DEEP UPPER LEVEL
TROUGH (500 MB HEIGHT STANDARDIZED ANOMALIES OF -1.5 TO -2.0)
WILL ENCOMPASS THE GREAT LAKES REGION TUESDAY/WEDNESDAY...AS A
SERIES OF STRONG UPPER WAVES OVER WESTERN CANADA DIVE SOUTHEAST.
THERE ARE SOME TIMING UNCERTAINTIES...COUPLED WITH MAIN MOISTURE
AXIS/850-700 MB THETA-E DISPLACED TO OUR SOUTH ON TUESDAY.
HOWEVER...THE MORNING HOURS CERTAINLY LOOK GOOD FOR SHOWERS AND
THUNDERSTORMS WITH A COUPLED JET STRUCTURE WORKING THROUGH THE
CENTRAL GREAT LAKES. THERE IS GOOD WIND SHEAR...AS 0-6 KM BULK SHEAR
CHECKS IN BETWEEN 40 TO 45 KNOTS...SO ANY SIGNIFICANT UPTICK IN
INSTABILITY WILL BE A CONCERN. SOME DRYING LOOKS TO BE OCCURRING
DURING THE LATE AFTERNOON...BUT STILL HAVE COLD FRONT/SURFACE TROUGH
IN PLACE WHICH COULD STILL SERVE AS A FOCUS...AND NOT READY TO SLICE
THE END OF THE DAY OUT OF THE LIKELY POPS JUST YET. THE NUMEROUS
ACTIVITY EXPECTED TO HOLD MAXES PREDOMINATELY BELOW 80 DEGREES.

ANOTHER VIGOROUS UPPER LEVEL WAVE/JET STREAK WILL BE TRACKING
THROUGH LOWER MICHIGAN ON WEDNESDAY...BUT WILL BE FIGHTING
RELATIVELY DRY AIR. STILL...SFC-850 MB LI`S DO REACH AND FALL
SLIGHTLY BELOW ZERO FOR A PERIOD...AS 500 MB TEMPS FALL TO -19 C.
CAPE DENSITY IN THE MID LEVELS LOOKS PRETTY GOOD (PER NAM
SOUNDINGS)...AND CERTAINLY THINK LOW CHANCE POPS ARE VALID. LOW
FREEZING LEVELS WILL BE CONDUCIVE FOR SMALL HAIL IF ANY
THUNDERSTORMS MATERIALIZE.

UPPER LEVEL TROUGH/COLD POOL WILL SLOWLY WORK EAST ON THURSDAY...BUT
WITH THE COOL START AND 850 MB TEMPS HOLDING IN THE MID TO UPPER
SINGLE NUMBERS...MAXES ARE EXPECTED TO REMAIN IN THE MID 70S.

TEMPERATURES WILL WARM UP FRIDAY/SATURDAY...POTENTIALLY WARMER THAN
THE CURRENT FORECAST AS SOME OF THE HOT AIR OVER THE EASTERN ROCKIES
ATTEMPTS TO SLIP NORTHEAST. HOWEVER...ANOTHER DEEP UPPER LEVEL LOW
IS PROGGED TO MOVE INTO ONTARIO FOR THE LATTER HALF OF THE WEEKEND.

MARINE...
COLD FRONT SLOWLY SINKING SOUTH THROUGH LOWER MICHIGAN THIS
MORNING...AND WINDS HAVE WEAKENED ENOUGH OVER SAGINAW BAY TO DROP
SMALL CRAFT ADVISORIES. GUSTS OVER LAKE ERIE WILL APPROACH SMALL
CRAFT CRITERIA JUST AHEAD OF THE FRONT BUT LOOK TO STAY JUST BELOW
THUS FAR. ADDITIONAL THUNDERSTORMS WILL BE POSSIBLE ON TUESDAY AS
ANOTHER COLD FRONT SWEEPS THROUGH...AND WINDS OVER SAGINAW BAY MAY
AGAIN EXCEED 20 KNOTS FOR A PERIOD. LIGHT WINDS WILL THEN PREVAIL
WEDNESDAY AND THURSDAY AS HIGH PRESSURE DOMINATES.

&&

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

&&

$$

AVIATION.....JVC
SHORT TERM...MR
LONG TERM....SF
MARINE.......SF


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).





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