Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 300405
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1205 AM EDT SAT APR 30 2016


.AVIATION...

THE STALLED OUT DEFORMATION AXIS WILL BRING A SLOW CLEAR TREND OVER
THE SOUTHERN HALF OF THE CWA TONIGHT. LATEST PROGS SUPPORT TRAPPED
MOISTURE/STRATUS BELOW 5000 FT AGL...THROUGH ABOUT 09Z WITH RAPID
DISSIPATION THEREAFTER. KEPT WITH THE PESSIMISTIC THEME PROVIDED IN
THE EARLIER TAF FORECASTS. THE QUIET AVIATION WEATHER WILL PERSIST
THROUGHOUT MUCH OF THE DAY DUE TO A STABLE EAST WIND. CONDITIONS
WILL THEN DEGRADE DURIGN THE LATE AFTERNOON AND EARLY EVENING AS AN
ACTIVE AND MOISTURE LADEN WARM FRONT WILL LIFT INTO SOUTHEASTERN
MICHIGAN. SYNOPTIC SCALE FORCING FOR ASCENT WILL BE VERY FAVORABLE
AND EXPECTING A PERIOD OF MODERATE WITH LOCALLY HEAVY RAINFALL
SOMETIME BETWEEN 00-06Z.

FOR DTW...A LIGHT AND VARIABLE EASTERLY WIND IS EXPECTED TRHOUGH
TONIGHT. RELATIVELY QUIET AVIATION WEATHER IS EXPECTED THROUGH THE
LATE AFTERNOON...BEFORE CIGS AND VSBYS LOWER SUBSTANTIALLY DUE TO
INCREASING RAIN ACTIVITY AND AN ACTIVE FRONTAL BOUNDARY.

//DTW THRESHOLD PROBABILITIES...

* HIGH FOR CEILINGS AT OR BELOW 5000 FEET THROUGHOUT MUCH OF THE
  NIGHT. LOW SATURDAY...HIGH AGAIN BY THE BEGINNING OF SATURDAY
  EVENING.

&&

.PREV DISCUSSION...ISSUED 306 PM EDT FRI APR 29 2016

DISCUSSION...

UPPER WAVE/COLD POOL (-22 C AT 500 MB) NOW ENTERING THE EASTERN
GREAT LAKES...WHICH SHOULD ALLOW SKIES TO CLEAR OUT IN THE POST WAVE
SUBSIDENCE/NORTHWEST CONFLUENT FLOW OVER THE CENTRAL GREAT LAKES
(CLOUDS ARE ALREADY TRENDING/BREAKING UP THIS AFTERNOON).
THIS WILL ALLOW FOR A COLD NIGHT TONIGHT...WITH MINS FALLING INTO
THE 30 TO 40 DEGREE RANGE. SOME HIGH CLOUDS SLIPPING UP FROM THE
SOUTHWEST TOWARD SUNRISE AND LIGHT NORTHEAST FLOW COULD BE JUST
ENOUGH TO MITIGATE FROST POTENTIAL...BUT NOT REAL COMFORTABLE WITH
THIS SCENARIO. OTHERWISE...NORTHERN THUMB REGION STANDS GOOD CHANCE
FOR TEMPS AT OR BELOW FREEZING...BUT GROWING SEASON HAS NOT STARTED
THAT FAR NORTH...AND THUS FROST HEADLINES WILL BE ISSUED JUST FOR M-
59/I-69 CORRIDORS...FOR MINS PREDOMINATELY IN 32-36 DEGREE
RANGE...AROUND 30 DEGREES SOUTHERN THUMB REGION.

EVEN WITH INCREASING CLOUDS TOMORROW...LATEST GUIDANCE SUGGESTS
TEMPERATURES TOPPING OUT AROUND 60 DEGREES. GOOD SURGE OF MOISTURE
AND UPPER LEVEL SUPPORT FROM EJECTING UPPER LEVEL PV OVER THE
CENTRAL CONUS EXPECTED TO ARRIVE AROUND AND AFTER 00Z...AS POSITIVELY
TILTED NORTHERN STREAM TROUGH AXIS ROTATES THROUGH THE NORTHERN GREAT
LAKES SATURDAY EVENING...AND ENOUGH MOISTURE TRANSPORT/FORCING IS
EXPECTED TO PRODUCE RAINFALL FOR MAJORITY/ALL OF SOUTHEAST MICHIGAN
SATURDAY NIGHT...AS 850-700 MB THETA-E RIDGE AXIS MAKES IT TO THE
SOUTHERN MICHIGAN BORDER...WITH SHOWALTER INDEX ALSO TRENDING TOWARD
ZERO RIGHT NEAR THE SOUTHERN MICHIGAN BORDER...YIELDING SLIGHT
CHANCE OF THUNDERSTORMS...AS 850 MB SHEAR/CONVERGENCE AXIS SLIPS
NORTH JUST PAST THE BORDER ON SUNDAY. TEMPS EXPECTED TO HOLD IN THE
50S DURING THE DAY WITH NORTHEAST FLOW LOCKED IN AS SURFACE LOW(S)
TRACK THROUGH NORTHERN OHIO VALLEY...PER 12Z EURO.

DRYING/CLEARING TREND EXPECTED SUNDAY NIGHT AS PREVIOUSLY MENTIONED
NORTHERN STREAM TROUGH AXIS SLIPS EAST OF THE CENTRAL GREAT LAKES
AROUND 12Z MONDAY...DELIVERING ANOTHER SOLID SHOT OF COLD AIR (850
MB TEMPS FALLING TO AROUND ZERO). AT THIS POINT...ENOUGH
CLOUDS/NORTHEAST GRADIENT TO PREVENT FROST EVEN WITH EXPECTED
MINS IN THE MID 30S TO LOWER 40S.

WEAK HIGH PRESSURE WILL SETTLE INTO THE GREAT LAKES BEHIND THE
WEEKEND SYSTEM. THIS WILL START MONDAY OFF WITH DRY CONDITIONS AND
TEMPERATURES SLIGHTLY BELOW THE NORMAL RANGE IN THE LOWER 60S FOR
DAYTIME HIGHS THEN MODERATING INTO THE MID AND UPPER 60S BY TUESDAY.
GLOBAL MODELS ARE THEN IN REASONABLE AGREEMENT ON SOLUTIONS THAT
SHOW A STRONG COLD FRONT MOVING THROUGH THE REGION CENTERED ON THE
WEDNESDAY TIME PERIOD. THIS WILL BRING THE NEXT ROUND OF SHOWERS AND
ANOTHER COOLING TREND FOR THE SECOND HALF OF THE WEEK. THERE IS SOME
INCONSISTENCY IN THE MAGNITUDE OF THE COLD SURGE AMONG THE MODELS
BUT NONE SUGGEST CONDITIONS AS COLD AS THE CURRENT AIR MASS THAT HAS
KEPT READINGS IN THE 40S OVER THE LAST COUPLE OF DAYS. HIGH PRESSURE
IS THEN LIKELY TO FOLLOW THE WEDNESDAY FRONTAL SYSTEM FOR A DRY END
OF THE WEEK WITH A GRADUAL TEMPERATURE MODERATION.

MARINE...

THE SOUTHERN EXTENT OF A LARGE AREA OF HIGH PRESSURE CENTERED OVER
HUDSON BAY WILL KEEP FAIRLY LIGHT EAST TO NORTHEAST WINDS OVER THE
CENTRAL GREAT LAKES THROUGH SATURDAY. LOW PRESSURE TRACKING ACROSS
THE OHIO VALLEY WILL THEN TIGHTEN THE SURFACE PRESSURE GRADIENT AND
WIND SPEEDS SATURDAY NIGHT AND SUNDAY. HIGH CONFIDENCE EXISTS WITH
SPEEDS REMAINING BELOW GALE FORCE...BUT GUSTS MAY REACH AROUND 25
KNOTS. STRONGER AND PERSISTENT NORTHEAST FLOW OVER THE LENGTH OF
LAKE HURON (INCLUDING SAGINAW BAY) AND EAST FLOW OVER LAKE ERIE MAY
NECESSITATE SMALL CRAFT ADVISORIES AS WAVE HEIGHTS BUILD SATURDAY
NIGHT INTO SUNDAY. WINDS WILL TURN TO THE NORTH SUNDAY AS THE CENTER
OF LOW PRESSURE TRACKS SOUTH OF LAKE ERIE...WITH SPEEDS GRADUALLY
WEAKENING THROUGH THE AFTERNOON AND ALLOWING LARGE WAVES TO SUBSIDE.

HYDROLOGY...

LOW PRESSURE TRACKING THROUGH THE OHIO VALLEY WILL SPREAD RAIN INTO
SOUTHEAST MICHIGAN SATURDAY EVENING THROUGH SUNDAY. TOTAL RAINFALL
IS EXPECTED TO EXCEED 0.25 INCHES SOUTH OF THE I-69 CORRIDOR...WITH
CLOSER TO ONE-HALF INCH OF RAIN EXPECTED SOUTH OF I-94. MOST OF THE
RAIN WILL FALL BEFORE 500 AM SUNDAY MORNING.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...FROST ADVISORY UNTIL 8 AM EDT THIS MORNING FOR MIZ060>063-068>070.

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

$$

AVIATION.....JVC
DISCUSSION...SF/BT
MARINE.......HLO
HYDROLOGY....HLO


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



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