Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 181703
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
103 PM EDT SAT OCT 18 2014

.AVIATION...

//DISCUSSION...

NORTHWEST FLOW CARRYING IN COLDER AIR WILL CONTINUE TO SUPPLY CLOUD
COVER OVER SE MICHIGAN DURING THE AFTERNOON INTO THE EVENING.
STUBBORN MVFR CEILING REMAINS EXPECTED TO MIX INTO THE LOWER END OF
VFR BELOW 5000 FT AND THEN LINGER A LITTLE LONGER INTO THE
EVENING...ESPECIALLY THROUGH THE DTW TERMINAL CORRIDOR. UPSTREAM
OBSERVATIONS INDICATE SOME DRYING AND MIXING OCCURRING OVER THE
NORTHERN GREAT LAKES WHICH STILL SUPPORTS A CLEARING TREND OVER SE
MICHIGAN FROM LATE EVENING THROUGH THE OVERNIGHT. ONE THING TO
MONITOR WILL BE COVERAGE OF LAKE INDUCED STRATOCU AND/OR TRAPPING OF
STRATOCU BUT LOW LEVEL WIND FROM ABOUT 320 IS TYPICALLY A DRY
TRAJECTORY INTO OUR AREA FROM NORTHERN LOWER. CLOUDS INDUCED BY LAKE
MICHIGAN MAY BECOME MORE RELEVANT DURING SUNDAY MORNING AS THE LOW
LEVEL WIND BACKS TOWARD THE WEST.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILINGS BELOW 5000 FEET THROUGH EVENING.

&&

.PREV DISCUSSION...ISSUED 1023 AM EDT SAT OCT 18 2014

UPDATE...

THE GOING FORECAST IS ON TARGET CALLING FOR DECREASING CHANCES OF
RAIN THROUGH THE AFTERNOON ALONG WITH A LATE DECREASING CLOUD
TREND. THIS MAY ALLOW MAX TEMPS TO TOUCH 50 BUT NORTHWEST WIND
GUSTING NEAR 20 MPH WILL HOLD APPARENT TEMPERATURE CLOSER TO 40.
THE POTENTIAL FOR LIGHT SHOWERS IS BEING DRIVEN BY STEEP LOW LEVEL
LAPSE RATES DEPICTED IN THE 12Z DTX SOUNDING WHICH WILL BECOME
PROHIBITIVELY SHALLOW BY EARLY AFTERNOON AS SHOWN IN THE APX
SOUNDING. OTHERWISE...PLAN TO MONITOR THE PROGRESS OF THE UPPER
WAVE BRUSHING SW LOWER WITH A PATTERN OF RAIN. THIS IS EXPECTED TO
MAINTAIN A TRACK TO OUR WEST AND SOUTH WHILE PERHAPS BRUSHING THE
SOUTHERN U.S. 23 CORRIDOR.

PREV DISCUSSION...ISSUED 351 AM EDT SAT OCT 18 2014

SHORT TERM...TODAY AND TONIGHT

A POWERFUL COLD FRONT IS MAKING ITS WAY THROUGH SOUTHEAST MICHIGAN
EARLY THIS MORNING. THE MID LEVEL SHORTWAVE ASSOCIATED WITH THE
ATTENDANT LOW IS VERY OBVIOUS ON WATER VAPOR IMAGERY AS IT SURGES
SOUTHEAST THROUGH THE CENTRAL GREAT LAKES REGION. SOME EARLY MORNING
SHOWER ACTIVITY WILL WANE THROUGHOUT THE AFTERNOON AS DRIER AIR AND
RIDGING WORK THEIR WAY IN FROM THE WEST. ALTHOUGH THE COLD FRONT
WILL MOVE THROUGH THIS MORNING...COLD AIR ADVECTION WILL CONTINUE
THROUGHOUT THE DAYTIME HOURS...SEVERAL HOURS BEHIND THE ACTUAL
SURFACE FROPA. DESPITE THE LOWER RAIN CHANCES...COLD AIR ALOFT WILL
MAINTAIN CLOUDY SKIES FOR THE BALANCE OF THE DAY GIVEN THE STEEP LOW
LEVEL LAPSE RATES IN PLACE. GUSTY NORTHWEST WINDS...COLD AIR
ADVECTION...AND ABUNDANT CLOUD COVER BEHIND THE FRONT WILL SEVERELY
LIMIT HIGH TEMPERATURES TODAY TO THE MIDDLE TO UPPER 40S.

THE AFOREMENTIONED RIDGING WILL WORK ITS WAY INTO THE WESTERN GREAT
LAKES TONIGHT...BRINGING CLEARING SKIES AND LIGHTER WINDS DURING THE
OVERNIGHT HOURS. THIS WILL ALLOW FOR RADIATIONAL COOLING WHICH
SHOULD ALLOW TEMPERATURES TO TUMBLE INTO THE LOW TO MID 30S...WITH
TEMPERATURES AROUND 30 POSSIBLE ACROSS THE WEST WHERE MORE CLEARING
IS EXPECTED. THIS SHOULD BRING PATCHY TO WIDESPREAD FROST ACROSS THE
AREA WITH THE WARMEST TEMPERATURES OUT OVER THE EAST WHERE THE
PROXIMITY TO THE LAKES AND LATER CLEARING OUT OF THE CLOUDS IS
EXPECTED.

LONG TERM...

1024MB SURFACE HIGH PROPAGATING ACROSS THE LOWER OHIO VALLEY WILL
SUSTAIN A STABLE LOW LEVEL ANTICYCLONIC FLOW LOCALLY ON SUNDAY.  A
HIGHER DEGREE OF INSOLATION WILL WORK TOWARD MODERATING A COOLER
RESIDENT AIRMASS...ALTHOUGH THE OVERALL THERMAL RESPONSE WILL BE
HELD IN CHECK WITH THE EMERGING WARM AIR ADVECTION UPSTREAM LARGELY
HOLDING OFF UNTIL SUNDAY NIGHT.  850 MB TEMPERATURES SETTLE INTO THE
2 TO 4 C RANGE BY LATE AFTERNOON...GOOD FOR A HIGH TEMPERATURE
DISTRIBUTION AGAIN WITHIN THE UPPER 40S AND LOWER 50S RANGE.

SHORTWAVE ENERGY CURRENT RESIDING OVER CENTRAL MANITOBA WILL EJECT
SOUTHEAST OVER THE WEEKEND...UNDERGOING STEADY AMPLIFICATION AS IT
ENTERS THE NORTHERN GREAT LAKES BY SUNDAY NIGHT.  LOW LEVEL
SOUTHWEST FLOW WILL INCREASE BRIEFLY IN RESPONSE IMMEDIATELY
DOWNSTREAM OF THE INBOUND HEIGHT FALLS.  THIS WILL RESULT IN A
MODEST PERIOD OF MID LEVEL WARM AIR ADVECTION SUNDAY NIGHT AND EARLY
MONDAY.  THIS WILL QUICKLY BLANKET THE LOWER PENINSULA UNDER AN MORE
EXTENSIVE HIGHER LEVEL CLOUD DECK OVERNIGHT...LIKELY CAPPING LOWS
IN THE 40S MOST LOCALES.  THE BETTER ISENTROPIC ASCENT WILL EXIST
ACROSS NORTHERN AND CENTRAL LOWER MICHIGAN...WITH BOTH THE
MOISTURE QUALITY AND OVERALL FORCING DIMINISHING WITH SOUTHWARD
EXTENT.  THIS CONTINUES TO FAVOR A MORE DEFINED POP GRADIENT FROM
NORTH TO SOUTH...HIGHEST POPS STRIPED ACROSS THE TRI-CITIES AND
THUMB.

THE COMPACT MID LEVEL VORTICITY CENTER AND ASSOCIATED SURFACE LOW
WILL TRANSLATE ACROSS SOUTHEAST MICHIGAN DURING THE MONDAY PERIOD.
MODEL CONSENSUS FOCUSES THE GREATEST ATTENDANT MID LEVEL ASCENT
DURING THE LATTER HALF OF THE DAY...WITH SOME AUGMENTATION LIKELY
FROM DIURNAL PROCESSES.  THIS POINTS TO SEEING A PERIOD OF
INCREASING SHOWER COVERAGE MONDAY AFTERNOON AND EARLY EVENING.
TRAILING CYCLONIC FLOW TUCKED WITHIN THE BROADER MID LEVEL TROUGHING
WILL BE SLOW TO RELEASE EASTWARD.  THIS COMBINED WITH SOME RENEWED
MOISTURE FLUX OFF LAKE HURON UNDER A DEVELOPING NORTHEAST FLOW/WEAK
INVERTED SURFACE TROUGHING WILL SUSTAIN A COOL AND UNSETTLED PATTERN
THROUGH TUESDAY.

MID LEVEL SUBSIDENCE WILL TAKE PROGRESSIVE HOLD BY MID WEEK AS THE
REGION SETTLES BETWEEN A DEEP CLOSED LOW OVER THE EAST COAST AND MID
LEVEL RIDGING OVER THE MISSISSIPPI VALLEY.  THIS HIGH AMPLITUDE WILL
RESULT A STRETCH OF DRY CONDITIONS...WITH TEMPERATURES SLOWLY
MODERATING BACK TO AROUND NORMAL.

MARINE...

STRONG NORTHWEST WINDS WILL EXIST ACROSS LAKE HURON THROUGH TODAY.
GALE FORCE GUSTS WILL BE COMMON ACROSS MUCH OF CENTRAL AND SOUTHERN
PORTIONS OF LAKE...INCLUDING EXPOSED NEARSHORE ZONES FROM PORT
AUSTIN TO PORT SANILAC.  GUSTS AS HIGH AS 40 KNOTS WILL BE POSSIBLE
THROUGH THIS TIME.   SIGNIFICANT WAVE HEIGHTS OVER THE SOUTHERN LAKE
HURON WILL BUILD TO AROUND 10 FEET THIS MORNING. WINDS IN THE
PARTIALLY SHELTERED ZONES OF SAGINAW BAY AND THE NEARSHORE ZONES
FROM PORT SANILAC TO PORT HURON MAY APPROACH MARGINAL GALES AT
TIMES...BUT WILL STRUGGLE TO SUSTAIN TRUE GALE CONDITIONS. SMALL
CRAFT ADVISORIES REMAIN IN EFFECT FOR THESE LOCATIONS.  WINDS WILL
DECREASE TONIGHT INTO SUNDAY AS A RIDGE OF HIGH PRESSURE BUILDS INTO
THE REGION.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...NONE.

LAKE HURON...
     GALE WARNING...LHZ362-LHZ363-LHZ441-LHZ442-LHZ462-LHZ463-
     LHZ464...UNTIL 4 PM SATURDAY.

     SMALL CRAFT ADVISORY...LHZ421-LHZ422-LHZ443...UNTIL 2 AM SUNDAY.

LAKE ST CLAIR...
     SMALL CRAFT ADVISORY...UNTIL 4 PM SATURDAY.

MI WATERS OF LAKE ERIE...
     SMALL CRAFT ADVISORY...UNTIL 4 PM SATURDAY.

&&

$$

AVIATION.....BT
UPDATE.......BT
SHORT TERM...KURIMSKI
LONG TERM....MR
MARINE.......MR


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