Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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554
FXUS63 KDTX 032009
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
309 PM EST WED FEB 3 2016

.DISCUSSION...

WEAK DEEP COLUMN COOLING UNDERWAY LOCALLY...SE MICHIGAN STILL
HOLDING WITHIN A WELL MIXED SOUTHWESTERLY GRADIENT JUST DOWNSTREAM
OF THE MAIN HEIGHT FALL GRADIENT NOW LIFTING OUT OF LAKE MICHIGAN.
SOLID GUST COMPONENT PEAKING MID AFTERNOON ALONG THE LEAD
EDGE OF THE INBOUND DEEPER MOISTURE PLUME...WINDOW FOR GUST
POTENTIAL WITHIN THE 40 TO 45 MPH RANGE ALONG FAR EASTERN SECTIONS
/PORT HURON TO MONROE/ CLOSING QUICKLY OVER THE NEXT 1-2 HOURS AS A
THICKENING STRATUS DECK CUTS INTO THE MIXING QUALITY.  OTHERWISE...
STRONG CVA TIED TO THIS MID LEVEL FEATURE WILL TEND TO SHEAR
NORTHEAST OF THE AREA...BUT WILL PROVIDE A MORE CONSOLIDATED BUT
BRIEF PERIOD OF COLD AIR ADVECTION WITH THE PASSAGE OF AN ATTENDANT
LOW LEVEL FRONT BY THIS EVENING.  OVERLAKE THERMODYNAMIC PROFILE
WILL REMAIN MODEST /CONVECTIVE DEPTH HOLDING BELOW 7K FT/...
SUGGESTING THE OVERALL DOWNSTREAM RESPONSE WILL REMAIN SOMEWHAT
MUTED.  WITH THAT SAID...IMPROVING SYNOPTIC MOISTURE DEPTH
CORRELATING WITH RENEWED/STRENGTHENING COLD AIR ADVECTION WITHIN THE
ENCROACHING MEAN TROUGH AND FRONTAL PASSAGE EARLY TONIGHT MAY SUPPORT
A PERIOD OF LIGHT SNOW SHOWER ACTIVITY.  A LOWER END PRECIPITATION
MENTION WITH LITTLE TO NO ACCUMULATION REMAINS APPROPRIATE FOR
TONIGHT.

EXTENSIVE LOW CLOUD IN PLACE THROUGH THURSDAY WITH LOW LEVEL THERMAL
TROUGHING FIRMLY ENTRENCHED.  THE COOLER RESIDENT AIR MASS STILL
ARRIVES IN THE VICINITY OF EARLY FEBRUARY NORMS...READINGS WITHIN
THE LOWER AND MIDDLE 30S RANGE.  THE COMBINATION OF A STEEPENING
LAPSE RATE ENVIRONMENT AND A PORTION OF THE LINGERING SUFFICIENTLY
DEEP MOIST LAYER AT/BELOW THE -12C ISOTHERM WILL ALLOW FOR SOME
FLURRIES.  RAPID REDUCTION IN INVERSION HEIGHTS AND CORRESPONDING
MOISTURE DEPTH TOWARD EVENING AS WEAK WARM AIR ADVECTION ENSUES
UNDER BACKING LOW LEVEL FLOW.  THIS PROCESS WILL WORK TOWARD
REDUCING THE COVERAGE OF STRATUS INTO THE OVERNIGHT PERIOD.  THIS
WILL LEAD IN A RELATIVELY BENIGN PERIOD ON FRIDAY...MARKED BY WEAK
LOW-MID LEVEL RIDGING WITHIN THE EXISTING WEST-SOUTHWEST FLOW.
GRADUAL/MODEST WARMING THROUGH THE LOWEST 5 KFT UNDER A GENERAL
INCREASE IN UPPER HEIGHTS WILL NUDGE DAYTIME TEMPERATURES UP SEVERAL
DEGREES FROM READINGS NOTED THURSDAY...HIGHS MID-UPPER 30S.

A RIDGE OF HIGH PRESSURE WILL DOMINATE THE SOUTHERN GREAT LAKES
WHILE A WEAK LOW PRESSURE TRACKS ACROSS THE NORTHERN GREAT LAKES ON
SATURDAY...BRINGING SOME SNOW SHOWERS TO THE NORTHERN THUMB AND
SAGINAW VALLEY REGIONS. LITTLE TO NO ACCUMULATION IS EXPECTED AT
THIS TIME. HIGH PRESSURE BUILDS BACK INTO THE REGION FOR SUNDAY
BEFORE THE NEXT LOW PRESSURE SYSTEM MOVES IN ON SUNDAY NIGHT.
THIS SYSTEM WILL TRACK SOUTHEASTWARD OUT OF THE NORTHERN PLAINS AND
SETTLE OVER THE GREAT LAKES BY MONDAY. CURRENT MODEL RUNS ARE
INDICATING THIS SYSTEM REMAINING FAIRLY STATIONARY OVER THE GREAT
LAKES RESULTING IN A ROUND OF SNOW SHOWERS ACROSS SOUTHEAST MICHIGAN
FROM MONDAY THROUGH TUESDAY. ACCUMULATIONS ARE HINTING AT ONLY A FEW
TENTHS...BUT IT IS TOO EARLY TO DETERMINE EXACT AMOUNTS AT THIS
TIME.

&&

.MARINE...

STRONG WINDS WILL CONTINUE TO SPREAD ACROSS THE CENTRAL GREAT LAKES
LATE THIS AFTERNOON AND EVENING AS COLDER AIR SPILLS INTO THE AREA
BEHIND A COLD FRONT. GALE FORCE WIND GUSTS DEVELOPED OVER WESTERN
LAKE ERIE AND LAKE ST CLAIR THIS AFTERNOON...PROMPTING THE ISSUANCE
OF A GALE WARNING FOR THOSE AREAS. STRONG SOUTWEST WINDS WILL
CONTINUE TO GUST TO 35 TO 40 KNOTS THROUGH THE LATE AFTERNOON AND
EARLY EVENING BEFORE SUBSIDING.

THE STRONG WINDS WILL SPREAD NORTHWARD OVER THE NEXT SEVERAL HOURS
AS LOW PRESSURE NORTH OF GEORGIAN BAY TRACKS INTO QUEBEC. THE BEST
POTENTIAL FOR LONG-DURATION GALES STILL REMAINS OVER THE CENTRAL
PORTION OF LAKE HURON...INCLUDING OUTER SAGINAW BAY...WHERE A SHORT
PERIOD OF GALE FORCE WIND GUSTS ARE EXPECTED FROM THE SOUTHWEST AND
THEN WEST LATE THIS AFTERNOON THROUGH THIS EVENING. THE SOUTHERN
PORTION OF THE LAKE AND INNER SAGINAW BAY MAY SEE A FEW GUSTS NEAR
35 KNOTS...HOWEVER GIVEN THAT THE DURATION IS ONLY EXPECTED TO LAST
A FEW HOURS AND SINCE MOST OF SAGINAW BAY IS ICE COVERED...THE GALE
WARNING WILL NOT BE EXPANDED. SURFACE LOW PRESSURE NORTH OF GEORGIAN
BAY WILL LIFT NORTHEAST INTO EASTERN QUEBEC OVERNIGHT. THIS WILL
ALLOW THE SURFACE PRESSURE GRADIENT TO WEAKEN AND END THE THREAT FOR
GALE FORCE WINDS.

ALTHROUGH A FEW SMALL RIPPLES OF LOW PRESSURE WILL WORK ACROSS THE
REGION OVER THE NEXT FEW DAYS...HIGH PRESSURE WILL REMAIN THE
DOMINANT INFLUENCE OVER THE GREAT LAKES THURSDAY AND FRIDAY.

&&

.AVIATION...ISSUED 102 PM EST WED FEB 3 2016

STRONG SOUTHWEST WIND GUSTS WILL CONTINUE TO SPREAD INTO SOUTHEAST
MICHIGAN THIS AFTERNOON BEHIND A FRONT AS COLDER AIR DEEPENS THE
BOUNDARY LAYER. GUSTS LOOK TO REACH UP TO AROUND 30 KNOTS INTO EARLY
EVENING BEFORE LOW PRESSURE LIFTING AWAY FROM THE AREA DECREASES THE
SURFACE PRESSURE GRADIENT AND WINDS. MEANWHILE...MOISTURE WRAPPING
INTO THE BACKSIDE OF LOW PRESSURE NORTH OF LAKE HURON WILL STREAM
ACROSS MICHIGAN TODAY. DRIER AIR MIXING INTO THE LOWER LEVELS SHOULD
KEEP CEILINGS LOW-END VFR THIS AFTERNOON. SECONDARY FRONTAL PASSAGE
THIS EVENING LOOKS TO BRING IN ADDITIONAL MOISTURE AND COOLER
AIR...ESPECIALLY FROM PTK SOUTH. EXPECT CEILINGS AT ALL SOUTHEAST
MICHIGAN TERMINALS TO FALL BETWEEN 1000 AND 2000 FEET BY LATE
EVENING (AROUND 01Z). THIS IS ALREADY SUPPORTED IN UPSTREAM
OBSERVATIONS OVER SOUTHERN WISCONSIN AND ILLINOIS. ADDITIONAL SHOT
OF COOL AIR WILL BOOST LAKE EFFECT RESPONSE...WITH ADDITIONAL
MOISTURE PICKED UP FROM THE LAKE GENERATING A FEW LIGHT SNOW SHOWERS
THIS EVENING ALONG THE SECONDARY FRONT BETWEEN 00-06Z. COVERAGE AND
PLACEMENT OF ANY LAKE EFFECT SHOWERS AFTER 06Z WILL BE SPOTTY...AND
TOO UNCERTAIN FOR MENTION IN 18Z TAFS.

FOR DTW...STRONG WINDS FROM 230-250 DEGREES WILL CONTINUE THIS
AFTERNOON AND EARLY THIS EVENING...WITH GUSTS EXPECTED TO REACH
ABOUT 30 KNOTS. DRIER AIR AND GOOD MIXING IN THE LOWER LEVELS SHOULD
HOLD CEILINGS AT LOW-END MVFR THIS AFTERNOON AND EVENING. ADDITIONAL
SHOT OF COLD AIR AND MOISTURE ON THE BACKSIDE OF LOW PRESSURE THIS
EVENING IS EXPECTED TO BRING MVFR CEILINGS AND A FEW SNOW SHOWERS TO
THE AREA. STILL SOME UNCERTAINTY WITH TIMING...BUT BEST WINDOW FOR
SHSN LOOKS BETWEEN 01-04Z THIS EVENING. ADDITIONAL SNOW SHOWERS ARE
POSSIBLE OVERNIGHT AS LAKE EFFECT KICKS IN A LITTLE. LITTLE TO NO
ACCUMULATION IS EXPECTED.

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CEILINGS BELOW 5000 FT THROUGH THE TAF PERIOD. MEDIUM
  AFTER 09Z TONIGHT.

* LOW IN REACHING CROSSWIND THRESHOLDS FROM 250 DEGREES THIS
  AFTERNOON.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WARNING UNTIL 10 PM EST THIS EVENING FOR LHZ362-363-421-462.

LAKE ST CLAIR...GALE WARNING UNTIL 7 PM EST THIS EVENING FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...GALE WARNING UNTIL 7 PM EST THIS EVENING FOR LEZ444.

&&

$$

DISCUSSION...MR/RK
MARINE.......HLO
AVIATION.....HLO


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