Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 020358
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1158 PM EDT WED APR 1 2015

.AVIATION...

VFR CONDITIONS WILL REMAIN IN PLACE THROUGH THE EARLY MORNING HOURS.
THE NORTHWARD EXPANSION OF WARMER AIR UNDER FIRM SOUTHERLY FLOW WILL
PROVIDE SOME POCKETS OF CIRRUS AT TIMES.  THE INCREASING WIND FIELD
OFF THE SURFACE WILL BE SUPPORTIVE OF LOW LEVEL WIND SHEAR THROUGH
THIS TIME.  ONSET OF DIURNAL MIXING WILL INTRODUCE A GUST COMPONENT
BY LATE MORNING...SOME PEAK GUSTS INTO THE 25 TO 30 KNOT RANGE BY
AFTERNOON.  INCREASING POTENTIAL FOR SHOWER DEVELOPMENT FROM LATE
MORNING ONWARD ON THURSDAY...GREATEST COVERAGE AND INTENSITY
CENTERED DURING THE MID AND LATE AFTERNOON HOURS.  A PERIOD OF
MVFR/IFR CONDITIONS IN MODERATE TO BRIEFLY HEAVY RAINFALL WILL BE
POSSIBLE DURING THIS TIME.  WEAK INSTABILITY MAY SUPPORT SOME
EMBEDDED THUNDERSTORMS...ALTHOUGH TOO EARLY TO SPECIFICALLY MENTION
GIVEN UNCERTAINTY IN COVERAGE/DURATION AND LOCATION.

FOR DTW...FAVORABLE ENVIRONMENT EXISTS FOR LOW LEVEL WIND SHEAR
DEVELOPMENT THROUGH MID MORNING.  A FEW LIGHT SHOWERS AROUND 15Z-20Z
AS CEILINGS BEGIN TO LOWER.  RAINFALL WILL INCREASE IN COVERAGE AND
INTENSITY 20Z-00Z...POSSIBLY CONTAINING THUNDER.  CONFIDENCE IN
COVERAGE OF THUNDERSTORMS TOO LOW TO INCLUDE AT THIS TIME.

//DTW THRESHOLD PROBABILITIES...

* LOW FOR CEILING AOB 5000 FEET THURSDAY MORNING...HIGH THURSDAY
  AFTERNOON.

* LOW THAT THUNDERSTORMS WILL OCCUR THURSDAY AFTERNOON AND EARLY
  EVENING.

&&

.PREV DISCUSSION...ISSUED 316 PM EDT WED APR 1 2015

SHORT TERM... THROUGH TONIGHT

A RESIDUAL TROUGH DRAPED ACROSS SOUTHERN MI LEAD TO CHAOTIC
WIND/THERMAL PATTERNS THROUGH THE EARLY AFTERNOON. TEMPERATURES
NORTH OF A LINE FROM ABOUT LANSING TO PONTIAC WERE SLOW TO RISE
THROUGH THE MORNING WITH WINDS STAYING LIGHT AND VARIABLE. RECENT
OBS SHOW THIS TROUGH HAS ALMOST COMPLETELY FILLED AS TEMPS ARE NOW
JUMPING INTO THE 50S ACROSS MOST OF SOUTHERN MI AS SOUTHERLY WINDS
HAVE FINALLY SPREAD NORTHWARD INTO MID MI. THE EXCEPTION IS THE
SHORELINE ALONG LAKE HURON WHICH HAVE KEPT A SE FLOW OFF THE LAKES
HOLDING TEMPS SUB 40.

HEADING INTO THIS EVENING...A WARM FRONT TO OUR WEST WILL EXTEND
INTO THE REGION AS IT LIFTS NORTHWARD. THIS FRONT SHOULD BE THROUGH
MBS AROUND 06Z. A STOUT 50 KNOT LL JET BETWEEN 900-950MB WILL
INITIATE A PERIOD OF DECENT WAA IN THE LAYER WHICH WILL THEN RESULT
IN A STEEP INVERSION AS BL COOLS. THE SW GRADIENT WILL INCREASE
OVERNIGHT AS THE WARM SECTOR MOVES INTO SOUTHERN MI. WINDS WILL
INCREASE OVERNIGHT WHILE BECOMING SOUTHWESTERLY BUT THE DECOUPLED BL
WILL PREVENT MIXING INTO THE LL JET. THE COLUMN IS PRETTY DRY WITH
ONLY AROUND A HALF INCH OF PWAT AHEAD OF THE WARM FRONT. THIS WILL
LEAD TO A DRY FRONTAL PASSAGE WITH THE PRECIP REMAINING TO THE NORTH
TIED CLOSER TO THE PARENT LOW AND THE PRESSURE FALLS AND FORCING
JUST AHEAD OF IT. MID LEVEL MOISTURE ADVECTION AND ISENTROPIC ASCENT
ALONG THE FRONT WILL INCREASE THE MID CLOUD PRESENCE MAINLY ACROSS
MID MI THROUGH THE NIGHT. THERMALLY...THE FRONT WILL LIKELY LEAD TO
A NON-TYPICAL NOCTURNAL COOLING TREND WITH LOWEST TEMPS OCCURRING
EARLY IN THE NIGHT WITH STEADY WARMING TOWARD MORNING AS WAA
INCREASES AND CLOUDS MOVE IN. THIS SHOULD HOLD LOW TEMPS IN THE 40S
FOR MOST INTERIOR LOCATIONS...WITH THOSE LOCATIONS ALONG THE
SHORELINE DIPPING INTO THE UPPER 30S.

LONG TERM...

CONVECTIVELY INDUCED SHORTWAVE CURRENTLY SPAWNING CONVECTION IN
SOUTHWEST MISSOURI WILL LIFT NORTH OVERNIGHT AS DEEPER SOUTHWEST
FLOW SPREADS ACROSS THE CENTRAL CONUS AND GREAT LAKES. ARRIVAL WILL
BE ROUGHLY COINCIDENT WITH THE LOW-LEVEL WARM FRONT AND IS EXPECTED
TO SUPPORT AT LEAST A PARTIAL COVERAGE OF SHOWERS THROUGH MID-
MORNING. A RUMBLE OF THUNDER IS NOT OUT OF THE QUESTION AS MORNING
SHOWERS WILL BE MOST LIKELY REMAIN TIED TO THE LEAD EDGE OF THE
MOISTURE TRANSPORT AXIS.

GENERAL AGREEMENT AMONG NAM/GFS/ECMWF THAT STRONG RIGHT ENTRANCE
DYANMICS JUXTAPOSED WITHIN THE FAVORABLE REGION FOR SUPERGEOSTROPHIC
ACCELERATION AND DIVERGENCE ALOFT WILL OCCUR INVOF NORTHERN LOWER
MICHIGAN. CROSS-SECTION ANALYSIS REVEALS A STRONG TILTING COMPONENT
RESULTING IN A CONSIDERABLE FGEN RESPONSE ALOFT WHILE THE BAROCLINIC
ZONE BELOW 850MB REMAINS ESSENTIALLY STATIONARY, TENDING ONLY TO
CONTRACT WITH TIME, 15-21Z. THE STRONGEST RESPONSE IS PROGGED BY THE
NAM/GFS TO ALIGN ROUGHLY ALONG A MUSKEGON TO SAGINAW VALLEY LINE
WHILE THE ECMWF IS SLIGHTLY FURTHER SOUTH AND EAST, A NOD TOWARD THE
POTENTIAL FOR A MORE PROGRESSIVE OUTCOME.

H85-H7 WIND MAX IS FORECAST IS FORECAST BY THE 12Z NAM TO EMERGE OUT
OF ILLINOIS AND SPREAD NORTH INTO CENTRAL LOWER FACILITATING
EXCELLENT BOUNDARY LAYER MOISTURE TRANSPORT ALONG THE FRONTAL ZONE.
WITH H85 DEWPOINTS NEARING 10C AND DEVELOPING LOW DENSITY CAPE, THE
STAGE IS SET FOR MODERATE TO PERHAPS LOCALLY HEAVY RAINFALL WITH A
BIT OF EMBEDDED THUNDER PERSISTING THROUGH MIDDAY WITHIN THE
AFOREMENTIONED FAVORED AXIS. THE PROGRESSIVE NATURE OF THE UPEPR
FLOW AND RELATIVELY SHALLOW (<10KFT) WARM CLOUD LAYER WILL SEEMINGLY
PREVENT ANY THREAT OF A FORMIDABLE HEAVY RAIN EPISODE.

APPROACHING CONVECTIVELY ENHANCED SHORTWAVE WITH ORIGINS OVER THE
PLAINS WILL THEN RACE ACROSS MI DURING THE AFTN, FORCING THE FRONT
THROUGH THE STATE BY EVENING AS JET SUPPORT RAPIDLY PEELS NORTHEAST.
CONFIDENCE IS MODERATELY HIGH IN A BAND OF 0.4-0.6" QPF BEFORE THE
FRONT ACCELERATES SOUTHEAST, BUT WOULD NOT BE TERRIBLY SURPRISED TO
SEE LOCALLY HIGHER AMOUNTS. IT IS HERE THAT IT IS WORTH NOTING THE
SLIGHTLY MORE PROGRESSIVE NATURE OF THE ECMWF WHICH WOULD RESULT
FAVOR A MORE SMOOTHED QPF FIELD AND A LOWER POTENTIAL MAXIMA. IN
GENERAL, EXPECT LOWER TOTALS FURTHER SOUTH AND EAST GIVEN DECREASING
FORCING AND FORWARD-ACCELERATING COLD FRONT, THOUGH 0-3KM MUCAPE
NEAR 500 J/KG MAY BE SUFFICIENT TO PRODUCE A COUPLE OF THUNDERSTORMS
CAPABLE OF PRODUCING BRIEF HEAVY DOWNPOURS BY AFTERNOON. HIGH
TEMPERATURES IN ADVANCE OF THE FRONT AND AHEAD OF ANY MORE
PERSISTENT SHOWERS/TSTORMS WILL PUSH UPPER 60S/70 DEGREES AS WINDS
GUST 25 TO 30 KTS.

RESIDENT 850MB THERMAL FIELD WILL COOL BACK INTO THE LOW SINGLE
DIGITS BY FRIDAY MORNING AS THE THETA-E AXIS FOLDS SOUTH AND EAST
LATE THURSDAY INTO THURSDAY NIGHT. BAROCLINIC ZONE ASSOCIATED WITH
THE APPROACHING TROUGH WILL THEN SLIDE THROUGH ON FRIDAY,
SUBSTANTIALLY COOLING THE COLUMN BY LATE FRIDAY EVENING. TRAILING
ENERGY ALONG THE NORTHERN PERIPHERY OF AN EMERGING JET STREAK WILL
FORCE A FRONTAL WAVE TO DEVELOP ALONG THIS BOUNDARY. STRONG COUPLING
OF THE UPPER JET STRUCTURE IS PROGGED BY THE ECMWF, WITH PEAK DEEP
LAYER FORCING TRANSITING LOWER MICHIGAN ROUGHLY 18-00Z. TAKEN AT
FACE VALUE, ECMWF SUGGESTS THE COLUMN WILL BE COLD ENOUGH FOR ALL
SNOW WITH THE EXCEPTION OF THE NEAR-SURFACE LAYER. LIGHT
ACCUMULATION OF AN INCH OR TWO IS STILL IN PLAY NORTH AND WEST OF
THE I-69 CORRIDOR, BUT SURFACE DEWPOINTS SOLIDLY ABOVE FREEZING CAST
DOUBT ELSEWHERE. NO SIGNIFICANT CHANGES NEEDED TO THIS PORTION OF
THE FORECAST.

THE WEEKEND WILL START OFF DRY AS HIGH PRESSURE NUDGES INTO THE
REGION ON SATURDAY. INCREASING CLOUDS ARE EXPECTED THROUGH SATURDAY
AS THE NEXT SYSTEM APPROACHES THE GREAT LAKES REGION. THIS SYSTEM
WILL BRING RAIN AND SNOW SHOWERS TO SOUTHEAST MICHIGAN THROUGH
SUNDAY. LOW TEMPERATURES ON SATURDAY NIGHT WILL BE IN THE UPPER 20S
TO LOW 30S WITH TEMPERATURES QUICKLY RISING AFTER SUNRISE INTO THE
MID 40S BY SUNDAY AFTERNOON. THEREFORE...THE BEST CHANCE FOR ANY
SNOW WILL BE SATURDAY NIGHT AND MAINLY NORTH OF THE M-59
CORRIDOR...HOWEVER... NO ACCUMULATION IS EXPECTED AT THIS TIME. THE
NEXT MAJOR LOW PRESSURE SYSTEM ARRIVES EARLY NEXT WEEK. THERE IS
UNCERTAINTY ABOUT THE TRACK AND TIMING OF THIS SYSTEM THOUGH...WITH
SOME MODELS BRINGING IN THIS SYSTEM BY MONDAY MORNING AND OTHERS NOT
BRINGING IT IN UNTIL MONDAY NIGHT. THEREFORE...DID NOT FEEL
CONFIDENT ABOUT ADDING ANYTHING MORE THAN CHANCE POPS TO THE
FORECAST FROM MONDAY THROUGH NEXT WEDNESDAY.

MARINE...

MODERATE TO FRESH SOUTHERLY FLOW WILL DOMINATE THROUGH THURSDAY
AFTERNOON RESULTING IN MODEST WAVE GROWTH OVER THE OPEN WATERS OF
LAKE HURON. THE STABLE SOUTH BREEZE WILL...HOWEVER...SIGNIFICANTLY
LIMIT WIND GUST POTENTIAL. THUNDERSTORMS WILL BE POSSIBLE THROUGHOUT
THE DAY WITH THE BEST CHANCE FROM CENTRAL LAKE HURON SOUTHWARD.
AFTER A BRIEF REPRIEVE OF WINDS THURSDAY NIGHT...COLDER AIR WILL
SPREAD ACROSS THE WATERS FRIDAY INTO FRIDAY NIGHT. FRESH NORTHWEST
WINDS WILL DEVELOP LATE FRIDAY MORNING INTO FRIDAY AFTERNOON WITH
GUSTS TO NEAR-GALES POSSIBLE OVER LAKE HURON AND THE EXPOSED
NEARSHORE WATERS OF THE THUMB.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

AVIATION.....MR
SHORT TERM...DRK
LONG TERM....JVC/RK
MARINE.......JVC


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