Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 280727
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
327 AM EDT TUE APR 28 2015

.SHORT TERM...TODAY AND TONIGHT

THE DEEP CYCLONIC FLOW WHICH HAS BEEN IN PLACE ACROSS LOWER MI THE
LAST SEVERAL DAYS WILL FINALLY LOOSEN ITS GRIP ON THE AREA TODAY AS
THE ELONGATED MID LEVEL TROUGH AXIS PUSHES OFF THE EAST COAST. MID
LEVEL RIDGING WILL IN TURN BUILD INTO LOWER MI FROM THE WEST. THE
REGIONAL WATER VAPOR LOOP IS IN SUPPORT OF MODEL SOLUTIONS DEPICTION
OF A WEAK MID LEVEL IMPULSE OVER NRN LOWER MI. THIS FEATURE WILL
SLOW CONSIDERABLY AS IS ADVANCES INTO SRN LOWER MI THIS AFTERNOON
DUE TO THE WEAKENING IN THE MID LEVEL FLOW. HI RES SOLUTIONS SUGGEST
THIS FEATURE WILL SUSTAIN A WEAKNESS IN THE MID LEVEL HEIGHT FIELD
OVER LOWER MI TODAY...WHICH WILL AID IN THE DEVELOPMENT OF A
THERMALLY INDUCED SFC TROUGH OVER LOWER MI.

REGIONAL SATELLITE DATA OVERNIGHT HAS SHOWN A CONSIDERABLE AMOUNT OF
CLOUD COVER ACROSS LAKE HURON. ONGOING N-NE LOW LEVEL FLOW HAS
BROUGHT SOME INCREASE IN LOW LEVEL MOISTURE INTO SE MI...ALTHOUGH THE
CLOUDS HAVE THUS FAR HAD A DIFFICULT TIME SUSTAINING THEMSELVES. BOTH
00Z DTX AND APX SOUNDINGS SHOWED A DEEP LOW LEVEL INVERSION. SLIGHT
WARMING ABOVE THE INVERSION BASE TODAY SHOULD SUSTAIN THIS INVERSION
DESPITE DAYTIME HEATING. THE LOW LEVEL FLOW WILL BACK TOWARD THE
NORTHWEST THIS MORNING...THUS DECREASING THE FEED OF LOW LEVEL
MOISTURE INTO SE MI. ENOUGH MOISTURE SHOULD STILL BE IN PLACE UNDER
THE INVERSION TO ALLOW THE ONSET OF DAYTIME HEATING TO CAUSE THE
RAPID DEVELOPMENT OF A BROKEN TO OVERCAST STRATO CU FIELD. THESE
CLOUDS SHOULD HAVE DIFFICULTY DECREASING DURING THE LATTER HALF OF
THE DAY CONSIDERING THE DEPTH OF THE INVERSION AND NO REAL PUSH OF
DRIER AIR. YESTERDAYS TEMPS CERTAINLY STRUGGLED WITH THE CLOUD
COVER. MODEL SOUNDINGS SUGGEST THE MOISTURE DEPTH WILL NOT BE AS
HIGH AS YESTERDAY AND THERE APPEARS TO BE A BETTER POTENTIAL FOR
SOME INTERVALS OF SUN TODAY...ESPECIALLY THIS MORNING. SO OPTIMISTIC
AFTERNOON HIGHS AROUND 60 WILL BE MAINTAINED. THE LOSS OF DAYTIME
HEATING WILL LEAD TO SOME EROSION OF THE CLOUDS THIS EVENING. THE
BOUNDARY LAYER WILL RAPIDLY DECOUPLE UNDER ANY PERIOD OF CLEAR SKIES
TONIGHT GIVEN THE WEAK GRADIENT FLOW. THIS WILL SUPPORT FCST MIN
TEMPS DOWN INTO THE 30S TONIGHT /40S IN URBAN DETROIT/.

&&

.LONG TERM...WEDNESDAY THROUGH MONDAY

MID TO UPPER LEVEL RIDGING IN PLACE AT 12Z WEDNESDAY WILL BREAK DOWN
RAPIDLY AS A ROBUST SHORTWAVE WILL DIVE SOUTHWARD THROUGH THE
WESTERN GREAT LAKES DURING THE DAY. AN ATYPICAL SYSTEM TO DEAL WITH
GIVEN THE LARGER WAVLENGTH OF THE SHORTWAVE ALONG WITH THE NEAR
STRAIGHT SOUTHWARD TRAJECTORY OF THE CIRCULATION. NORTHERLY SYSTEMS
TEND TO BE DRY ONES FOR THE AREA. MODELS PROG DRY AIR TO BEGIN THE
DAY...WITH DEEPER SYSTEM MOISTURE NOT PIVOTING INTO THE WESTERN AND
CENTRAL SECTIONS OF THE LOWER PENINSULA UNTIL AFTER 20Z. FORECASTED
THERMODYNAMIC PROFILES SUGGEST DIURNAL HEATING WILL BE NEEDED TO
GENERATE A CONVECTIVELY UNSTABLE (<100 J/KG MUCAPE) LAYER BETWEEN
SHOWERS 5-12 KFT AGL LAYER. A GOOD CONSENSUS EXISTS THE BEST
POTENTIAL WILL RESIDE ACROSS THE WESTERN PART OF THE STATE. DRIER
AIR IN THE LOWER TROPOSPHERE STILL SUPPORTS TEMPERATURES REACHING
THE LOW TO MID 60S.

THE QUESTION THEN BECOMES WHAT SORT OF POTENTIAL WILL EXIST FOR
CONTINUED SHOWERS WEDNESDAY NIGHT WITH THE LACK OF DIURNAL HEATING.
MODELS SEEM TO BE CONVERGING ON A SIGNAL THAT HEART OF THE CYCLONIC
CIRCULATION AND DEEPER MOISTURE WILL TUMBLE OR WOBBLE RAPIDLY DOWN
INTO SECTIONS OF IL/IN FOR WEDNESDAY NIGHT. MODELS ARE NOW
STRUGGLING TO KEEP SHOWERS GOING...LIKELY DUE TO THE LACK OF A
FORCING MECHANISM. WILL KEEP A LOW CHANCE MENTION GOING OUT OF
RESPECT FOR THE CYCLONIC FLOW. OVERALL A LOW CHANCE/LOW QPF TYPE
FORECAST.

FORECAST DETAILS AND REASONING HAS CHANGED SINCE 24 HOURS AGO
CONCERNING THE THURSDAY FORECAST. A CONSENUS IS EMERGING THAT
COLDEST OF MIDLEVEL AIR WILL REMAIN WEST OF MICHIGAN. IN
FACT...MODEL DATA IS NOW SUGGESTING THAT WARMER 850MB TEMPERATURES
WILL ADVECT FROM THE NORTHEASTERN UNITED STATES WESTWARD INTO THE
CENTRAL GREAT LAKES. THE INBOUND AIRMASS WILL CONTAIN HIGHER THETA E
CONTENT AS WELL. NWP SUGGESTS A POTENTIAL FOR DECENT CONVECTIVE
DEPTHS DEVELOPING DIURNALLY AND WILL CONTINUE THE LOW CHANCE POPS
FOR THURSDAY. THE MESSAGE IS AGAIN A LACK OF A FORCING
MECHANISM/TRIGGER. TEMPEATURES ON THURSDAY ARE NOW EXPECTED TO REACH
THE 60 DEGREE MARK.

&&

.MARINE...

FAVORABLE MARINE CONDITIONS TODAY AS SURFACE HIGH PRESSURE WILL
RESIDE ACROSS THE CENTRAL GREAT LAKES...PROVIDING LIGHT WINDS AND
LOW WAVES. WEAKENING HIGH PRESSURE WILL BE REPLACED BY WEAK SURFACE
TROUGHING TONIGHT...BUT WINDS ARE STILL EXPECTED TO REMAIN BELOW 20
KNOTS. HOWEVER...WINDS WILL BE NORTHERLY...AND THERE COULD BE
ONSHORE COMPONENT TO SUPPORT SLIGHTLY HIGHER WAVES ALONG THE
NEARSHORE WATERS.

&&

.AVIATION...ISSUED 1223 AM EDT TUE APR 28 2015

ANOTHER FEED OF MOISTURE ADVECTION FROM THE NORTHEAST IS LEADING TO
SOME EXPANDING CLOUD COVER ACROSS PORTIONS OF SE MI. THE 00Z DTX
SOUNDING SHOWS A VERY DEEP INVERSION BASED NEAR 5500 FT...WHICH IS
CAUSING THIS MOISTURE ADVECTION TO SPREAD OUT INTO A SCT-BKN CLOUD
DECK BASED BETWEEN 5K AND 6K FT. THE INVERSION IS EXPECTED TO LOWER
A LITTLE DURING THE COURSE OF THE MORNING UNDER SLIGHT WARMING ABOVE
THE INVERSION BASE. THIS WILL CAUSE THE CLOUD BASES TO SETTLE INTO
THE 4K TO 5K FT RANGE BY DAYBREAK. INDICATIONS IN THE AVAILABLE 00Z
MODEL DATA IS FOR THESE CLOUDS TO SUSTAIN THEMSELVES UNDER THE
DIURNAL HEATING CYCLE AND THUS PERSIST WELL INTO THE AFTERNOON.

FOR DTW...RECENT SATELLITE DATA IS SHOWING THE BETTER FEED OF
MOISTURE OCCURRING NORTHWEST OF METRO. IT IS BECOMING INCREASINGLY
UNCERTAIN WHETHER OR NOT A CLOUD DECK BASED BELOW 5000 FT WILL
EXPAND INTO METRO PRIOR TO DAYBREAK. IN LIGHT OF RECENT OBSERVATIONS
AND AVAILABLE 00Z MODEL DATA...A 4-5K FT CEILING WILL BECOME MORE
LIKELY AT METRO ONCE THE DIURNAL HEATING CYCLE KICKS IN LATE THIS
MORNING.

//DTW THRESHOLD PROBABILITIES...

* LOW IN CEILINGS AT OR BELOW 5000 FT THIS MORNING. MEDIUM THIS
  AFTERNOON.

&&

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

$$

SHORT TERM...SC
LONG TERM....CB
MARINE.......CB
AVIATION.....SC


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



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