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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KDTX 240346
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1146 PM EDT THU MAY 23 2013


.AVIATION...

-- Changed Discussion --
//DISCUSSION...

WHAT REMAINS OF LOW VFR TO HIGH MVFR BOUNDARY LAYER CLOUDS WILL WORK
THEIR WAY THROUGH THE AREA WITHIN THE NEXT COUPLE OF HOURS. ONCE
THAT OCCURS, CLEAR SKIES BELOW 10KFT WILL PREVAIL FOR THE BALANCE
OF THE FORECAST PERIOD AS HIGH PRESSURE DOMINATES. DIURNAL HEATING
WILL ALLOW NORTHERLY WINDS TO GUST TO AROUND 20 KTS DURING PEAK
HEATING ON FRIDAY.


//DTW THRESHOLD THREATS...

* NONE
-- End Changed Discussion --

&&

.PREV DISCUSSION...ISSUED 351 PM EDT THU MAY 23 2013

SHORT TERM...THROUGH TONIGHT

UPPER TROUGH CONTINUES TO DIVE THROUGH THE GREAT LAKES THIS
AFTERNOON. WATER VAPOR IMAGERY SHOWS A SMALL SHORTWAVE EMBEDDED IN
SOUTHWEST FLOW AHEAD OF THE TROUGH...NOW PUSHING INTO LAKE ERIE.
THIS FEATURE KICKED OFF A FEW STRONGER RAIN SHOWERS EARLIER THIS
AFTERNOON...AND SLOWED THE SOUTHWARD PROGRESS OF THE FRONTAL
BOUNDARY THROUGH FAR SOUTHEAST MICHIGAN...ONLY BY A FEW HOURS
HOWEVER. MAIN AREA OF ENERGY EMBEDDED WITHIN THE MID-LEVEL TROUGH
WILL PUSH ACROSS THE AREA THIS EVENING. SUBSIDENCE...AND DRY AIR
ADVECTION...BEHIND THIS FEATURE LOOK STRONG AND SHOULD END LIGHT
RAIN THROUGH THE EVENING (FROM NORTH TO SOUTH).

SKIES WILL CLEAR OVERNIGHT UNDER SUBSIDENCE AND DRY AIR. STRONG COLD
AIR ADVECTION DURING THE PRECEDING 18 HOURS SHOULD DROP OVERNIGHT
TEMPERATURES INTO THE MID 30S TO NEAR 40 OVERNIGHT. HIGH PRESSURE
BUILDING INTO THE GREAT LAKES SHOULD REMAIN JUST TO OUR WEST...WHILE
THE AREA OF SURFACE LOW PRESSURE REACHES THE EAST COAST BY DAYBREAK.
THE GRADIENT BETWEEN THESE TWO FEATURES SHOULD KEEP SOME NORTH WIND
AROUND OVERNIGHT...HELPING KEEP THE ATMOSPHERE MIXED AND BRINGING IN
SOME SLIGHTLY WARMER AIR OFF THE GREAT LAKES. SECONDARY PUSH OF COLD
AIR (CROSSING LAKE HURON) WILL ALSO OCCUR LATE...AND POTENTIALLY
EVEN BOOST WIND SPEEDS A FEW KNOTS TOWARDS MORNING WHEN PEAK FROST
FORMATION WOULD OCCUR. HAVE THEREFORE ONLY KEPT A PATCHY MENTION
FROST IN THE FORECAST...AGAIN WITH THE THOUGHT THAT THERE WILL BE
ENOUGH WIND AND ONLY MARGINAL TEMPERATURES FOR FORMATION.

LONG TERM...FRIDAY THROUGH THURSDAY

THE ADVERTISED DRY...COOL AND QUIET WEATHER PATTERN WILL BE WELL
ESTABLISHED ON FRIDAY AND CONTINUE THROUGH THE MEMORIAL DAY WEEKEND.
MODELS ARE IN DECENT AGREEMENT...ESPECIALLY FOR SE LOWER MI. THE
ONLY DIFFERENCE IS THE GFS STRONGER AND CONVECTIVELY ACTIVE
SHORTWAVE OVER THE UPPER MS RIVER VALLEY ON SATURDAY VS. THE OTHER
MODELS WHICH HAVE MUCH MORE CONVECTION WITH THE SOUTHERN WAVE
THROUGH IA/MO AND THE MID MS RIVER VALLEY. THE END RESULT OF GOING
WITH EVERY OTHER MODEL FOR THE WEEKEND IS LESS MID AND HIGH CLOUD
THAN THE GFS IS DEPICTING.  WITH THAT SAID...THERE WILL BE PERIOD OF
DECENT MOISTURE ABOVE 700 MBS LATE FRIDAY NIGHT AND SATURDAY MORNING
FROM THAT NORTHERN SHORTWAVE AS IT SPILLS OVER THE CENTRAL U.S.
RIDGE AND INTO THE CONFLUENT FLOW OVER THE GREAT LAKES. THIS WILL BE
ENOUGH FOR MOSTLY CLOUDY SKIES FOR A KEY WINDOW WHEN A FROST
ADVISORY WOULD HAVE BEEN OTHERWISE NEEDED. EXPECT THOSE CLOUDS TO
KEEP TEMPS ON FRIDAY NIGHT/SATURDAY MORNING CLOSER TO 40.

OTHERWISE...JUST FEW TO SCT CU EXPECTED DURING THE DIURNAL CYCLE AND
SCT/THIN CI FOR THE REST OF THE EXTENDED WEEKEND. DEW POINTS SHOULD
BE IN THE 20S ON FRIDAY AND THEN MAINLY THE 30S FOR THE REST OF THE
WEEKEND. THIS DRY AIR SHOULD LEAD TO 20-30 DEGREE DIURNAL SPREADS
EACH DAY.  THEREFORE WILL LEAN TOWARD WIDENING THE GUIDANCE TEMPS BY
LOWER THE MIN TEMPS A DEGREE OR TWO AND RAISING MAX TEMPS A DEGREE
OR TWO TOO.

IN THE EXTENDED...RIDGE BUILDS EASTWARD ALLOWING A WARM UP TO ABOVE
NORMAL TEMPS. MODELS HAVE SOME DIFFERENCES WHEN THE WARM FRONT
PUSHES INTO LOWER MICHIGAN AND HOW FAR NORTH IT GOES. WILL GO WITH
ECMWF WHICH IS CONSISTENT WITH THE PREVIOUS FORECAST AND TO SOME
EXTENT THE UK. NOT TOO SURPRISING THAT THE GFS IS THE FASTEST WITH
SOME ISSUES THAT LOOK TO BE CONVECTIVE FEEDBACK. WILL HAVE THE
CHANCES OF THUNDERSTORMS FROM TUESDAY NIGHT THROUGH WEDNESDAY NIGHT
WITH THE WARM FRONTAL PASSAGE.

MARINE...

GUSTY NORTH WINDS WILL CONTINUE INTO TONIGHT AS COLD AIR POURS INTO
THE REGION BEHIND A STRONG COLD FRONT. WINDS WILL CONTINUE TO GUST
BETWEEN 25 AND 30 KNOTS THROUGH THIS EVENING...WITH GUSTS
OCCASIONALLY TOPPING 30 KNOTS OVER THE FAR SOUTHERN PORTION OF LAKE
HURON. WINDS OVER THE WATERS WILL THEN DECREASE IN SPEED ACROSS THE
CENTRAL GREAT LAKES BY LATE EVENING...BEFORE ANOTHER PUSH OF COLD
AIR COMING DOWN FROM CANADA BRINGS ANOTHER SURGE OF NORTH WINDS DOWN
ACROSS LAKE HURON OVERNIGHT. THIS WILL KEEP WAVE HEIGHTS
ELEVATED...IN ADDITION TO INCREASING WIND SPEEDS AGAIN OVERNIGHT
THROUGH FRIDAY AFTERNOON. HIGH PRESSURE BUILDING INTO THE AREA WILL
THEN BRING LIGHT WINDS THROUGH THE HOLIDAY WEEKEND.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
MI...NONE.

LAKE HURON...
     SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
     HURON INCLUDING OUTER SAGINAW BAY...UNTIL 6 PM FRIDAY.

LAKE ST CLAIR...
     SMALL CRAFT ADVISORY...UNTIL MIDNIGHT FRIDAY.

MI WATERS OF LAKE ERIE...
     SMALL CRAFT ADVISORY...UNTIL MIDNIGHT FRIDAY.
-- End Changed Discussion --

&&

$$

AVIATION.....JVC
SHORT TERM...HLO
LONG TERM....RBP
MARINE.......HLO


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