Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
000
FXUS63 KDTX 310405
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1205 AM EDT FRI OCT 31 2014

.AVIATION...

//DISCUSSION...

AN ACTIVE PERIOD OF AVIATION WEATHER IS IN STORE TODAY THROUGH
FRIDAY NIGHT AS A STRONG LOW PRESSURE SYSTEM AND COLD FRONT MOVE
THROUGH THE GREAT LAKES. THE GREATEST IMPACT WILL BE IFR AND 30+
KNOT NORTH WIND ALONG AND BEHIND THE FRONT ACCOMPANIED BY RAIN AND
POSSIBLY A MIX OF RAIN AND SNOW TOWARD SUNSET. THE FIRST CHANCE OF
RAIN WILL ARRIVE WITH THE LEADING SURFACE TROUGH/FRONT AROUND
SUNRISE. THIS WILL BE FOLLOWED BY A DRY SLOT THAT WILL LEAD TO
BREAKS IN THE RAIN PATTERN FROM MID MORNING THROUGH EARLY AFTERNOON
BUT MVFR CEILING AND PERHAPS SOME FOG RESTRICTION WILL PERSIST
BETWEEN THE SURFACE TROUGH AND PRIMARY COLD FRONT. THE PASSAGE OF
THE FRONT WILL BRING IFR IN THE FORM OF LOW CEILING AND HEAVIER RAIN
THAT WILL PERSIST INTO FRIDAY EVENING POSSIBLY MIXING WITH SNOW LATE
IN THE DAY.

FOR DTW... TURNING POINTS IN THE FORECAST WILL BE WITH THE
PREFRONTAL TROUGH/FRONT SHORTLY AFTER SUNRISE WHICH WILL BRING MVFR
CEILING...SOME LIGHT RAIN SHOWERS...AND PERHAPS SOME FOG. THIS WILL
BE FOLLOWED BY THE COLD FRONT BY MID AFTERNOON WHICH WILL BRING A
SHARP TURN IN THE WINDS FROM THE NORTH LIKELY GUSTING TO 30 KNOTS OR
GREATER...IFR CEILING...AND HEAVIER RAIN. A MIX OF RAIN AND SNOW IS
POSSIBLE LATE IN THE DAY BUT THE MIX WILL LIKELY PREVENT
ACCUMULATION ON THE RELATIVELY WARM GROUND SURFACES.

//DTW THRESHOLD THREATS...

* MEDIUM CONFIDENCE IN CEILING BELOW 5000 FEET DURING THE NIGHT...
  HIGH CONFIDENCE DURING THE DAY AND FRIDAY NIGHT.

* MEDIUM CONFIDENCE IN SNOW MIXING WITH RAIN LATE TOWARD EVENING AND
  FRIDAY NIGHT.

&&

.PREV DISCUSSION...ISSUED 920 PM EDT THU OCT 30 2014

UPDATE...

LOW PRESSURE IS DEVELOPING ON SCHEDULE OVER THE NORTHERN GREAT
LAKES TONIGHT WHICH WILL BRING AN ACTIVE PERIOD OF WEATHER TO SE
MICHIGAN IN THE FORM OF INCREASING SHOWER COVERAGE LATER TONIGHT
AND THEN WIDESPREAD SHOWERS AND STRONG WIND FRIDAY. NORTH WIND IS
EXPECTED TO DEVELOP DURING FRIDAY AFTERNOON WITH GUSTS OF 30 TO 40
MPH LIKELY TO COMBINE WITH RAIN SHOWERS AND POSSIBLY A MIX OF SNOW
FOR HARSH WEATHER TOWARD SUNSET. GUSTS NEAR 45 MPH WIND ADVISORY
LEVELS HAVE GREATER POTENTIAL TOWARD FRIDAY EVENING WHEN THE BEST
ISENTROPIC DESCENT AND MID LEVEL SUBSIDENCE IS INDICATED IN MODEL
DATA AS THE LOW EXITS THE REGION. TIMING ON ANY ISSUANCE OF
HEADLINES REMAINS BEST SUITED FOR THE OVERNIGHT FORECAST PACKAGE.

UNTIL THEN...EVENING SURFACE ANALYSIS INDICATES LOW PRESSURE
ORGANIZING OVER THE STRAITS REGION WITH THE FIRST COLD FRONT OR
PREFRONTAL TROUGH EXTENDING THROUGH SOUTHERN WISCONSIN. THIS
PLACES WEAK SOUTHWEST FLOW AHEAD OF THESE FEATURES OVER LOWER
MICHIGAN THAT WILL BRING IN MILD AIR FOR THE BULK OF THE NIGHT AND
MAINTAIN TEMPS MOSTLY IN THE LOWER 40S. PLENTIFUL CLOUD COVER AND
POCKETS OF LIGHT RAIN ARE BEING FORCED BY GENTLE ISENTROPIC LIFT
AS THE LOW AND MID LEVEL THETA-E RIDGE FORMS AHEAD OF THE FRONT.
THE LATEST MODEL OUTPUT SHOWS THE THETA-E RIDGE BECOMING WELL
DEFINED DURING THE NIGHT REPRESENTING A SURGE OF LOW LEVEL
MOISTURE THAT WILL INTERACT WITH THE FIRST FRONTAL PASSAGE AND
DYNAMIC SUPPORT FROM THE UPPER LEVEL CIRCULATION. AN UPTICK IN
BOTH COVERAGE AND INTENSITY OF RAIN IS THEN EXPECTED ALONG THE
FRONT AS IT PASSES THROUGH SE MICHIGAN...FIRST IN THE TRI CITIES
AFTER MIDNIGHT AND THROUGH THE DETROIT AREA TOWARD SUNRISE
LASTING THROUGH ABOUT MID FRIDAY MORNING. THE GOING FORECAST LOOKS
SOLID RAMPING UP TO CATEGORICAL POPS DURING THIS TIME.

PREV DISCUSSION...ISSUED 422 PM EDT THU OCT 30 2014

SHORT TERM...THROUGH TONIGHT

UPPER LEVEL FEATURE OF NOTE IS A VIGOROUS...TIGHT PV ANOMALY
DROPPING SOUTHWARD INTO FAR NORTHERN MN AT 17Z. 12Z SUITE IN GOOD
AGREEMENT WITH THE PROGRESSION OF THIS FEATURE IN THE SHORT
TERM...PLACING IT NEAR THE WI/IL BORDER BY 12Z FRIDAY. CURRENTLY
OVER THE LOCAL AREA...SHORTWAVE RIDGING HAS PUSHED EAST OF THE
REGION...AND THE PATTERN WILL BE CHARACTERIZED BY GRADUAL HEIGHT
FALLS/WEAK WAA AS THE UPPER FEATURE NEARS. THIS WILL SUSTAIN THE
MIDLEVEL CLOUD DECK AND MAY ALLOW FOR SOME SPRINKLES/LIGHT SHOWERS
TO EXPAND SOUTHWARD WITH TIME INTO OUR REGION THROUGH THE EARLY PART
OF THE OVERNIGHT HOURS. ASCENT INCREASES FURTHER TOWARD THE END OF
THE PERIOD AS THE UPPER LEVEL FEATURE NEARS. SURFACE LOW WILL BE
ROUGHLY OVER SAGINAW BAY BY 12Z FRIDAY WITH A COLD FRONT EXTENDING
SWWD. THE HEAVIER BANDED PRECIP ASSOCIATED WITH FGEN CIRCULATION
SHOULD STILL MOSTLY BE TO OUR NORTHWEST IN THE COLDER POST-FRONTAL
AIR AT THAT POINT...BUT ASCENT SHOULD BE ENOUGH TO WARRANT
CATEGORICAL/LIKELY POPS AFTER 09Z OVER THE SAGINAW VALLEY/FLINT
REGIONS...RESPECTIVELY. LOWS WILL NOT DROP TOO MUCH TONIGHT WITH THE
INSULATING CLOUD DECK...EXPECTING MAINLY LOW 40S.

LONG TERM...FRIDAY THROUGH NEXT THURSDAY

UPPER WAVE OVER WESTERN ONTARIO WILL DIVE THROUGH THE WESTERN GREAT
LAKES AND THEN TOWARDS THE TENNESSEE VALLEY BY FRIDAY EVENING IN
RESPONSE TO AN AMPLIFICATION OF THE UPPER PATTERN OVER NORTH
AMERICA...WHICH WILL RESULT IN STRONG RIDGING EXTENDING UP THROUGH
CENTRAL CANADA. AS THE WAVE DROPS SOUTH...LOW PRESSURE NOW NORTH OF
LAKE SUPERIOR WILL DEEPEN AS IT TRACKS THROUGH LAKE HURON FRIDAY
MORNING AND INTO LAKE ERIE FRIDAY EVENING. THE PASSAGE OF THIS
SYSTEM THROUGH THE AREA WILL PULL AN ARCTIC COLD FRONT DOWN THROUGH
THE AREA. THE FRONT IS CURRENTLY DROPPING THROUGH NORTHERN
MINNESOTA...WHERE SURFACE OBSERVATIONS HAVE BEEN SHOWING GUSTY
WINDS...FALLING TEMPERATURES AND A CHANGE OVER IN PRECIPITATION TYPE
FROM RAIN TO SNOW.

PRECIPITATION SHOULD BE WORKING DOWN INTO THE AREA AT THE START OF
THE DAY TOMORROW AS THE FRONT APPROACHES. EXPECTING BEST COVERAGE
AND PRECIP RATES AS DEFORMATION AXIS AND EVEN A WEAK TROWAL ON THE
NORTH SIDE OF THE SYSTEM DROPS ACROSS SOUTHEAST MICHIGAN FROM EARLY
AFTERNOON THROUGH EVENING. DEFORMATION AXIS IS EXPECTED TO LINGER A
BIT LONGER OVER THE FAR EASTERN PORTION OF MICHIGAN FRIDAY NIGHT AS
THE LOW TAKES ON MORE OF A SOUTHERLY TRAJECTORY ACROSS LAKE ERIE.
ARCTIC FRONTAL BOUNDARY WILL ALSO DROP ACROSS THE AREA...WITH TIMING
CURRENTLY EXPECTED FROM VERY LATE MORNING THROUGH EARLY EVENING.
MODEL FORECAST SOUNDINGS CONTINUE TO SUPPORT A CHANGEOVER IN
PRECIPITATION TYPE FROM RAIN TO SNOW AS COLDER AIR WORKS IN BEHIND
THE FRONT. ACCUMULATIONS IF ANY LOOK LIGHT AT THIS TIME...AND
CONFINED MAINLY TO GRASSY AND ELEVATED SURFACES. WILL HAVE TO WATCH
LAKE EFFECT POTENTIAL FROM OFF LAKE HURON BEHIND THE FRONT WITH
STEEP LAPSE RATES DEVELOPING OVER THE WARMER LAKE WATERS AND STRONG
NORTHERLY FLOW. LAKE-MODIFIED AIRMASS ALSO MAKES PRECIP TYPE A
LITTLE MORE CHALLENGING...AS IT COULD KEEP PRECIP RAIN OR A MIX OF
RAIN/SNOW OVER THE EASTERN HALF OF THE AREA.

OTHER CONCERN TOMORROW WILL BE THE STRONG CORE OF 50 KT WINDS AT 925-
850MB WORKING DOWN ON THE BACKSIDE OF THE SYSTEM FROM LATE AFTERNOON
INTO THE OVERNIGHT. FORECAST SOUNDINGS FROM BOTH THE NAM AND GFS
SHOW THE BOUNDARY LAYER SHOULD BE SUFFICIENTLY DEEP ENOUGH BEHIND
THE FRONT FOR GUSTS TO 45 OR PERHAPS EVEN 50 MPH TO WORK DOWN TO THE
SURFACE AS LAPSE RATES ALSO STEEPEN. MODELS HAVE WAVERED A BIT ON
THIS OVER THE PAST FEW RUNS...AND DO NOT SHOW STRONG DESCENT LIKE WE
HAVE HAD WITH WIND EVENTS IN THE PAST. WILL WATCH FOR ANOTHER ROUND
OF MODEL RUNS...BUT A WIND ADVISORY MAY BE REQUIRED.

DRIER AIR LOOKS TO ARRIVE SATURDAY AFTERNOON AS RIDGING BUILDS INTO
THE GREAT LAKES AHEAD OF THE AMPLIFIED RIDGE AXIS OVER THE PLAINS.
THE DRIER AIR AND LOWERING INVERSION HEIGHTS SHOULD PUT AN END TO
LAKE EFFECT FROM OFF LAKE HURON BY AFTERNOON. POST-FRONTAL
TEMPERATURES WILL BE QUITE COLD...WITH HIGHS ONLY IN THE UPPER 30S
AND LOW 40S. CLEAR SKIES AND LIGHT WINDS SATURDAY NIGHT WILL SET US
UP FOR THE COLDEST NIGHT OF THE SEASON SO FAR...WITH LOWS SOLIDLY IN
THE 20S.

AS SURFACE HIGH PRESSURE SHIFTS TOWARDS THE EAST ON SUNDAY...FLOW
TURNS SOUTHERLY AND SOUTHEAST MICHIGAN RECOVERS FROM THE FRIGID
CONDITIONS FROM THE PREVIOUS TWO DAYS. HIGHS WILL REACH THE MID 50S
BY TUESDAY. A SOUTHWEST JET WILL THEN USHER IN PACIFIC MOISTURE TO
COMBINE WITH A FRONTAL SYSTEM TUESDAY INTO EARLY WEDNESDAY. LOCATION
AND FORWARD SPEED OF THE FRONT IS UP FOR DEBATE...SO THERE COULD A
LARGE TEMP SWING/ERROR ON DAYS 6-7.

MARINE...LOW PRESSURE WILL DEEPEN AS IT TRACKS FROM LAKE SUPERIOR
TO SOUTH OF LAKE ERIE BY FRIDAY EVENING. AS THE SYSTEM DROPS THROUGH
THE CENTRAL GREAT LAKES...IT WILL PULL AN ARCTIC COLD FRONT DOWN
ACROSS THE REGION. THE COLD AIR WILL FILL IN OVER THE WARMER LAKE
WATERS...ALLOWING A STRONG CORE OF WINDS ALOFT TO MIX DOWN TO THE
LAKE SURFACE. GALE FORCE WIND GUSTS ARE EXPECTED TO DEVELOP OVER
LAKE HURON ON FRIDAY...AND SPREAD TO LAKE ST CLAIR AND WESTERN LAKE
ERIE BY FRIDAY NIGHT. THE STRONG AND PERSISTENT NORTHERLY WINDS WILL
ALLOW WAVE HEIGHTS TO BUILD AS HIGH AS 15 FEET OVER THE SOUTHERN
PORTION OF LAKE HURON BY FRIDAY EVENING. WINDS WILL GRADUALLY
DIMINISH ON SATURDAY AS A RIDGE OF HIGH PRESSURE SLIDES INTO THE
AREA. LARGE WAVES OVER SOUTHERN LAKE HURON WILL BE SLOW TO SUBSIDE
HOWEVER...NOT DROPPING BELOW 4 FEET UNTIL SATURDAY EVENING.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...NONE.

LAKE HURON...GALE WARNING FROM 11 AM THIS MORNING TO 8 AM EDT SATURDAY FOR
     LHZ363-421-422-441-462.

     GALE WARNING FROM 2 PM THIS AFTERNOON TO 10 AM EDT SATURDAY FOR
     LHZ442-443-463-464.

     GALE WARNING FROM 8 AM THIS MORNING TO 8 PM EDT THIS EVENING FOR
     LHZ361.

     GALE WARNING FROM 8 AM THIS MORNING TO 2 AM EDT SATURDAY FOR LHZ362.

LAKE ST CLAIR...GALE WARNING FROM 8 PM THIS EVENING TO 10 AM EDT SATURDAY FOR
     LCZ460.

MICHIGAN WATERS OF LAKE ERIE...GALE WARNING FROM 8 PM THIS EVENING TO 10 AM EDT SATURDAY FOR
     LEZ444.

&&

$$

AVIATION.....BT
UPDATE.......BT
SHORT TERM...DT
LONG TERM....HLO/MM
MARINE.......HLO


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



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.