Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 150857
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
357 AM EST MON DEC 15 2014

.SHORT TERM... TODAY AND TONIGHT

DENSE FOG HAS BEEN STEADILY LIFTING FROM SOUTH TO NORTH ACROSS THE
ADVISORY AREA DURING THE EARLY MORNING WHICH WILL ALLOW THE ADVISORY
TO BE CANCELLED WITH THE NEW FORECAST PACKAGE. THE FOG WILL GIVE WAY
TO CONTINUED MILD TEMPERATURES THROUGHOUT THE AREA TODAY AS MOST
LOCATIONS WARM INTO THE LOWER 50S. THIS WILL BE FOLLOWED BY RAIN
MOVING INTO THE REGION TONIGHT WITH MILD AIR REINFORCED BY SOUTH
WIND AHEAD OF LOW PRESSURE MOVING TOWARD THE SOUTH END OF LAKE
MICHIGAN BY SUNRISE TUESDAY.

EARLY MORNING OBSERVATIONS INDICATE ALL LOCATIONS REPORTING
VISIBILITY ABOVE 1/4SM AT PRESS TIME...AND JUST A FEW AT 1/2SM TO
3/4SM. THIS IS EVIDENCE OF SLIGHTLY DRIER AIR MAKING NORTHWARD
PROGRESS FROM THE DETROIT METRO AREA AND POINTS SOUTH OF THE OHIO
BORDER WHERE VISIBILITY HAS BEEN GOOD ALL NIGHT. EXPECT CONDITIONS
TO CONTINUE IMPROVING ACROSS THE REST OF THE AREA DURING THE MORNING
AS THE MODEST DRY AIR ADVECTION PROGRESSES AHEAD OF THE CENTRAL
PLAINS LOW PRESSURE SYSTEM. THE 00Z MODELS HAVE A GOOD HANDLE ON THE
LOW LEVEL MOISTURE PROFILE AND EVEN SUGGEST SOME BREAKS IN THE LOW
CLOUDS WILL BE POSSIBLE IN THE DETROIT AREA DURING THE AFTERNOON AS
BACKED LOW LEVEL FLOW SIPHONS EVEN MORE DRY AIR FROM THE SURFACE
HIGH OVER THE MID APPALACHIANS. THIS MAY BE A BIT OPTIMISTIC GIVEN
EARLY MORNING OBSERVATIONS TOWARD THE OHIO VALLEY...AND THAT HIGH
CLOUDS FROM THE LOW WILL MOVE OVERHEAD AT THE SAME TIME...BUT THE
MAX TEMPERATURE FORECAST IS NUDGED A LITTLE MORE INTO THE LOWER 50S
NEAR THE OHIO BORDER TO ACCOUNT FOR THE POTENTIAL OF EXTRA SURFACE
HEATING.

RAIN FROM THE PLAINS LOW PRESSURE SYSTEM WILL HOLD OFF UNTIL EVENING
BUT THEN MAKE STEADY PROGRESS ACROSS SE MICHIGAN AS THE SYSTEM
SLIDES TOWARD LAKE MICHIGAN. EARLY MORNING RADAR COMPOSITE SHOWS A
SOLID BAND OF SHOWERS MOVING INTO THE MID MISSISSIPPI VALLEY
ASSOCIATED WITH A WELL ORGANIZED PLUME OF GULF MOISTURE. MODEL
ANALYSIS FIELDS CAPTURE THIS WELL IN LOW TO MID LEVEL THETA-E FIELDS
AND UPPER AIR ANALYSIS INDICATES A 40-50 KNOT LOW LEVEL JET FEEDING
UP TO 10C DEWPOINT INTO THE MOISTURE AXIS AT 850 MB. THE LOW WILL
OCCLUDE BEFORE THIS MUCH MOISTURE CAN REACH LOWER MICHIGAN...BUT
WHAT DOES MAKE IT THIS FAR NORTH WILL BE PLENTY FOR CATEGORICAL POPS
BY MIDNIGHT. THE DESTABILIZING NATURE OF LOW LEVEL THETA-E ADVECTION
WILL GIVE WAY TO A SHORT BREAK IN THE ACTION AS THE DRY SLOT MOVES
OVERHEAD...BUT THAT WILL JUST HELP WITH MORE DRIZZLE AND FOG BEFORE
SHOWERS PICK UP AGAIN ASSOCIATED WITH THE UPPER LOW. EXPECT COLDER
AIR ALOFT...STRONG DCVA...AND DEFORMATION WILL WRING OUT MOISTURE
FROM A BROAD MID LEVEL TROWAL OVERHEAD TO KEEP SHOWERS GOING THROUGH
SUNRISE TUESDAY.

&&

.LONG TERM...

THE MIDWEEK PORTION OF THE FORECAST WILL BE DOMINATED BY THE PHASING
OF TWO SIZABLE UPPER LEVEL TROUGHS OVER THE UPPER MIDWEST AND THE
RESULTANT SURFACE LOW PRESSURE SYSTEM THAT WILL LIFT THROUGH THE
CENTRAL GREAT LAKES ON TUESDAY AND TUESDAY NIGHT. BOTH OF THE TROUGH
STRUCTURES APPEAR TO BE OF EQUAL WAVELENGTH AND INTENSITY...SUCH THE
INTERACTION OF THE TWO WAVES WILL BE A DIFFICULT ONE. MODEL
SOLUTIONS SUPPORT A RATHER DIFFUSE AND EXPANSIVE CENTER OF LOW
PRESSURE LOCALLY...BEFORE RENEWED CYCLOGENESIS TAKES OVER ALONG
THE ATLANTIC COAST BY WEDNESDAY NIGHT. WILL LIST SOME FORECAST
HIGHLIGHTS BELOW IN CHRONOLOGICAL ORDER.

TUESDAY...MAIN FOCUS HERE IS PRECIPITATION POTENTIAL AND TO
LESSER EXTENT HIGH TEMPERATURES. SOUTHERN STREAM PV
ANOMALY/SHORTWAVE WILL LIFT THROUGH SOUTHERN LOWER MICHIGAN DURING
THE DAY...WITH SOUTHERLY WARM SECTOR FLOW IN PLACE AT LEAST
THROUGH APPROXIMATELY 20Z. THE PRIOR DISCUSSION SET UP THE
SCENARIO WELL WITH REGARDS TO MOISTURE...PWATS OF UP TO 3/4 INCH.
285-290K SYSTEM RELATIVE ISENTROPIC ASCENT AND 925-650MB LOW
STABILITY IS GOOD FOR LIKELY TO LOW CATEGORICAL POPS THIS CYCLE.
FORECAST ANALYSIS OF ISENTROPIC SURFACES SUGGESTS A PSEUDO TROWAL
STRUCTURE DEVELOPING OVER THE NORTHERN HALF OF THE CWA BETWEEN
15-21Z. TEMPERATURES MIDDAY TUESDAY SHOULD REACH THE UPPER 40S TO
LOWER 50S.

TUESDAY EVENING...FORECAST ITEM OF INTEREST HERE IS THE OVERALL WIND
POTENTIAL ASSOCIATED WITH A PREFRONTAL TROUGH SET TO PASS THROUGH
AT/AROUND 00Z WED. MODEL PROGS ARE NOT SUPPORTIVE OF A GOOD ONE...OR
AT LEAST ONE OUTSIDE OF DECEMBER CLIMATOLOGY. GOOD COLD AIR
ADVECTION WILL LAG THE PREFRONTAL TROUGH BY 6 HOURS OR SO.

WEDNESDAY...TWO THINGS FOR WEDNESDAY. THE FIRST IS THE RETURN TO
WINTER LIKE CONDITIONS WITH WIND CHILLS STUCK IN THE LOWER 20S.
CONDITIONS OUTSIDE WILL BE VERY DIFFERENT THAN WHAT WAS SEEN THIS
WEEKEND/MONDAY/TUESDAY. THE SECOND IS AGAIN WIND POTENTIAL AS
DIURNAL MIXED LAYER GROWS AND MATURES. THERE IS A LACK WIND IN THE
COLUMN...BUT SUSPECT THAT BEST GRADIENT FLOW WILL BE CONCENTRATED
NEAR THE SURFACE AND IS SLIGHTLY UNDERDONE. PRECIPITATION POTENTIAL
IS LOW...PREFER TO INCLUDE A CHANCE OF FLURRIES FOR ANYTHING ABLE
TO SHAKE OUT OF STRATOCUMULUS.

&&

.MARINE...

MILD AND MOIST AIR WILL CONTINUE TO STREAM INTO THE CENTRAL GREAT
LAKES THROUGH TUESDAY. THE LIGHT WIND AND INCREASED STABILITY OVER
THE WATER WILL RESULT IN FAVORABLE WAVE CONDITIONS UNTIL THE NEXT
LOW PRESSURE SYSTEM SLIDES THROUGH THE SOUTHERN GREAT LAKES TUESDAY.
THIS SYSTEM WILL BRING RAIN TO THE AREA FOLLOWED BY COLDER AIR AND
STRONGER NORTHWEST WINDS GUSTING NEAR 30 KNOTS OVER THE OPEN WATERS
OF NORTHERN LAKE HURON TUESDAY NIGHT INTO WEDNESDAY.

&&

.AVIATION...ISSUED 1159 PM EST SUN DEC 14 2014

//DISCUSSION...

VLIFR/LIFR CIGS/VSBYS REMAIN LOCKED IN AT PTK/FNT/MBS AND WILL MOST
LIKELY REMAIN THAT WAY MUCH OF THE NEXT 8-10 HOURS BEFORE SOMEWHAT
RAPID IMPROVEMENT ENSUES WITH INCREASED SOUTH/SOUTHEAST WINDS WITH
APPROACHING LOW PRESSURE MIDDAY MONDAY. MVFR CIGS WILL MOST LIKELY
LOWER TO IFR YIP/DTW OVERNIGHT INTO EARLY MONDAY AS LOWER CIGS OUT
TO THE WEST SHOULD SHIFT BACK INTO AREA...EVEN IF SOUTHERN EDGE OF
STRATUS CURRENTLY OVER THE AREA DOES NOT SINK ANY FURTHER SOUTH.
CIGS/VSBYS WILL THEN FALL AGAIN LATE IN THE FORECAST AS -RA AND BR
SPREAD THROUGH THE AREA WITH THE AFOREMENTIONED LOW PRESSURE BY 00Z-
02Z OR SO.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILINGS BELOW 5000 FEET THROUGH THE TAF PERIOD.

* LOW CONFIDENCE IN CIGS AT 200 FEET AND/OR VSBYS AOB 1/2SM BY
  10Z-14Z MONDAY AM.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.

&&

$$

SHORT TERM...BT
LONG TERM....CB
MARINE.......CB
AVIATION.....DG


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



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