Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 301733
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
133 PM EDT SAT APR 30 2016


.AVIATION...

HIGH CLOUDS AND VFR CONDITIONS WILL START OUT THE 18Z TAF PERIOD
BEFORE A LOW PRESSURE SYSTEM TRACKING THROUGH THE OHIO VALLEY BRINGS
A DETERIORATION IN CEILINGS/VIS AS RAIN MOVES INTO THE AREA. RAIN
SHIELD STRETCHING FROM SOUTHWEST MICHIGAN DOWN THROUGH NORTHWEST
OHIO IS ADVANCING TOWARDS THE AREA NOW...AND IS EXPECTED TO SPILL
INTO THE TERMINALS DURING THE 20-23Z TIMEFRAME. DRY FEED OF LOW-
LEVEL FLOW FROM THE EAST WILL INITIALLY KEEP CEILINGS/VIS AT VFR AS
RAIN BEGINS. BETTER FORCING AND MOISTURE ARRIVING AROUND 00Z WILL
THEN QUICKLY DROP CONDITIONS TO LOW-END MVFR AND IFR BY MID-EVENING.
RAIN WILL BE HEAVIER NEAR THE DETROIT-AREA TERMINALS WHERE A LITTLE
MORE INSTABILITY WILL RESIDE...AND EXPECT TO SEE A FEW DIPS TO LIFR
DURING THE LATE EVENING AND VERY EARLY MORNING ON SUNDAY. RAIN WILL
LIFT NORTH AND EAST OF THE AREA OVERNIGHT...BY ABOUT 08Z FOR MOST
LOCATIONS. A FEW SHOWERS WILL LINGER THROUGH EARLY
SUNDAY...ESPECIALLY AT MBS.


FOR DTW...LATEST MODEL FORECAST GUIDANCE AND EXTRAPOLATION FROM
UPSTREAM RADAR SUPPORTS RAIN BEGINNING AT DTW BETWEEN 20-21Z...WITH
HEAVIER RAINFALL AND MVFR/IFR CEILINGS ARRIVING AFTER 00Z TONIGHT.
CEILINGS WILL INITIALLY BE VFR AS RAIN BEGINS AS DRY AIR IN THE LOW-
LEVELS MUST FIRST BE OVERCOME. A PERIOD OF STRONGER FORCING AND
INSTABILITY TONIGHT...ROUGHLY BETWEEN 02Z AND 05Z...MAY DROP
CONDITIONS TO LIFR IN HEAVIER SHOWERS. THUNDERSTORM POTENTIAL IS
LOW...BUT NOT ZERO.


//DTW THRESHOLD PROBABILITIES...

* MEDIUM FOR CIGS AOB 5KFT BY 22Z...HIGH AFTER 00Z.

* LOW FOR A THUNDERSTORM TO IMPACT DTW TONIGHT.

&&

.PREV DISCUSSION...ISSUED 352 AM EDT SAT APR 30 2016

DISCUSSION...

TODAY...INCREASINGLY FAVORABLE ENVIRONMENT FOR A SOLID RAINFALL
EVENT LOCALLY HEADING INTO TONIGHT CURRENTLY IN THE EARLY STAGES OF
DEVELOPMENT JUST UPSTREAM.  WATER VAPOR DISPLAYING A CLEAR SIGNAL OF
DEEP LAYER NORTHWARD MOISTURE TRANSPORT LODGED WITHIN THE ATTENDANT
STRENGTHENING MID LEVEL SOUTHWESTERLIES IMMEDIATELY DOWNSTREAM OF
THE CLOSED LOW/HEIGHT FALLS NOW LIFTING INTO THE CENTRAL PLAINS.  A
CLASSIC APPEARING SETUP AT THE FRONT END...PRECEDED BY A PERIOD OF
BRIEF SHORTWAVE RIDGING THAT WILL SWEEP ACROSS SE MICHIGAN TODAY.
RAPID ADVANCEMENT OF HIGH CLOUD COMBINED WITH PESKY LINGERING
STRATUS WILL LEAVE A SHRINKING WINDOW FOR CLEAR SKY EARLY TODAY.
MODEST RECOVERY TO THE LOW LEVEL THERMAL PROFILE GIVEN THE GENERAL
UPWARD INCREASE IN MEAN THICKNESSES AND SOME ADDED INSOLATION
POTENTIAL /PARTICULARLY NORTH/.  CONTINUED LOW LEVEL EASTERLY FLOW
WILL MAINTAIN A NEUTRAL ADVECTIVE COMPONENT...NETTING A SOMEWHAT
LIMITED OVERALL RESPONSE. WITH THAT...STILL LOOKING FOR HIGHS UPPER
50S/AROUND 60 MOST LOCALES.

TONIGHT...WELL DEFINED MOISTURE AXIS LOCKED ALONG AN EMERGING STRONG
WING OF MID LEVEL ISENTROPIC ASCENT/WAA EXPECTED TO RAPIDLY ADVANCE
INTO SE MICHIGAN AFTER 20Z.  AN ADDITIONAL CONTRIBUTION OF DCVA AND
CONVERGENCE AS SHORTWAVE ENERGY AND LOW LEVEL JET FORCING IMPINGE ON
THE REGION WILL CONTRIBUTE TO AN EXPANSIVE REGION OF RAINFALL
LIFTING ACROSS ALL LOCALES THIS EVENING/TONIGHT.  00Z NAM/ARR/NMM
MODEL SUITE POINT TOWARD A POTENTIALLY MORE DYNAMIC RESPONSE
OVERNIGHT INTO EARLY SUNDAY...PORTIONS OF SE MICHIGAN BECOMING
FAVORABLY POSITIONED BENEATH A STRENGTHENING 850-700 MB FRONTAL ZONE
AND DEFORMATION AXIS.  DIMINISHED STABILITY THROUGH THIS LAYER WILL
ADD A CONVECTIVE ELEMENT AND THE POTENTIAL FOR A PERIOD OF MODERATE
TO LOCALLY HEAVY RAINFALL.  INSTABILITY NOT ENOUGH TO INCLUDE A
THUNDER MENTION...BUT RAINFALL AMOUNTS IN EXCESS OF HALF AN INCH
CERTAINLY IN PLAY.

SUNDAY AND SUNDAY NIGHT...MID LEVEL FORCING/DEFORMATION MAY BE SLOW
TO VACATE THE REGION EARLY SUNDAY...PARTICULARLY OVER
NORTHERN/EASTERN SECTIONS AS THE PARENT SURFACE AND MID LEVEL
CIRCULATIONS SLOWLY EXIT INTO ONTARIO. THIS WILL MAINTAIN THE CHANCE
FOR SHOWERS TO LINGER THROUGH THE FIRST HALF OF THE DAY.  SUBSTANTIAL
RESIDUAL MOIST LOW LEVEL ENVIRONMENT WILL ENSURE CONSIDERABLE
CLOUDINESS HOLDS ALL LOCALES...WITH POST-SYSTEM NORTHWEST FLOW AGAIN
RESULTING IN BELOW NORMAL TEMPERATURES. AFTERNOON READINGS REACHING
INTO THE 50S REMAIN ON TARGET.  GREATER FORECAST UNCERTAINTY YET IN
THE SUNDAY NIGHT PERIOD...MODEL GUIDANCE PROVIDING A MIXED SIGNAL ON
THE EVENTUAL TRACK OF THE AFOREMENTIONED CENTRAL PLAINS CLOSED LOW
EJECTING THROUGH THE OHIO VALLEY/SOUTHERN MICHIGAN DURING THIS TIME
WINDOW.  POTENTIAL FOR STRONGER DCVA WITHIN THE NORTHERN PERIPHERY
OF THIS WAVE TO PROVIDE AT LEAST A CHANCE FOR ADDITIONAL SHOWER
DEVELOPMENT...POSITIONING YIELDING A GREATER POSSIBILITY SOUTH OF
THE M-59 CORRIDOR.

EARLY NEXT WEEK...BROADER LONGWAVE TROUGHING LEFT IN THE WAKE OF THE
ACTIVE WEEKEND PATTERN. INCREASING DRY AIR ADVECTION INTO MONDAY
WILL FAVOR A STEADY CLEARING TREND...THE ADDED INSOLATION POTENTIAL
BOOSTING HIGHS BACK TOWARD THE LOWER 60S. MODERATING TREND CONTINUES
INTO TUESDAY UNDER GENERAL SUBSIDENCE AND WEAK RIDGING. TEMPERATURES
BACK IN THE VICINITY OF NORMAL FOR EARLY MAY /MID 60S/.

MARINE...

MODERATE NORTHEASTERLY ONSHORE FLOW WILL BECOME FRESH AT TIMES LATE
TONIGHT THROUGH SUNDAY AS LOW PRESSURE PASSES SOUTH OF THE AREA.
WINDS WILL GUST TO SMALL CRAFT ADVISORY CRITERIA DURING THIS TIME
WHILE PERSISTENT ONSHORE FLOW ALLOWS SIGNIFICANT WAVE HEIGHTS TO
BECOME ELEVATED IN THE NEARSHORE ZONES OF LAKE HURON. A SMALL CRAFT
ADVISORY HAS BEEN ISSUED ACCORDINGLY. MODERATE NORTHWEST WIND WILL
FILL IN IN THE WAKE OF THE LOW EARLY NEXT WEEK.

HYDROLOGY...

LOW PRESSURE LIFTING THROUGH THE OHIO VALLEY WILL PRODUCE WIDESPREAD
RAIN TONIGHT. WIDESPREAD AMOUNTS OF AROUND ONE HALF OF AN INCH ARE
ANTICIPATED WITH LOCATIONS SOUTH OF THE I-69 CORRIDOR SEEING UP TO
THREE QUARTERS OF AN INCH. THE FAVORED TIME PERIOD FOR THE HEAVIEST
RAIN IS BETWEEN 10 PM AND 5 AM LOCAL TIME. IT SHOULD BE NOTED
THAT,DEPENDING ON HOW LONG DEFORMATION FORCING LINGERS INTO EARLY
SUNDAY, THERE MAY BE AN OPPORTUNITY FOR AN ADDITIONAL FEW TENTHS OF
AN INCH THROUGH LATE SUN MORNING.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY FROM 5 AM TO 8 PM EDT SUNDAY FOR LHZ421-422-
     441>443.

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

$$

AVIATION.....HLO
DISCUSSION...MR
MARINE.......JVC
HYDROLOGY....JVC


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


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