Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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119
FXUS63 KDTX 291809
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
209 PM EDT FRI APR 29 2016


.AVIATION...

RAIN SHOWERS WILL CONTINUE TO EXIT EAST THIS AFTERNOON AS LOW
PRESSURE PULLS EAST OF THE AREA. DRIER FLOW FROM THE NORTHEAST HAS
BEEN ERODING LOW CLOUDS OVER THE DETROIT-AREA TERMINALS...WHILE MVFR
CEILINGS REMAIN NEAR PTK AND FNT. ALL DATA CONTINUES TO SUPPORT
CEILINGS SLOWLY LIFTING THROUGH THE AFTERNOON...PUTTING ALL SITES IN
VFR BY 20Z. SUBSIDENCE MOVING IN BEHIND THE EXITING UPPER WAVE
TONIGHT SHOULD ALLOW LOW CLOUDS TO SCATTER OUT. WINDS WILL REMAIN
OUT OF THE NORTHEAST TODAY...WITH SPEEDS AT OR BELOW 10 KNOTS. LIGHT
WINDS ARE EXPECTED OVERNIGHT BUT DEGREE OF CLEARING IS NOT EXPECTED
TO BE GREAT ENOUGH TO PROMOTE FOG OR BR DEVELOPMENT.

FOR DTW...DRY NORTHEAST FLOW SHOULD ALLOW CEILING TO RISE TO 3000
FEET OR ABOVE THROUGH THE LATE AFTERNOON. THIS DRIER AIR SHOULD
PREVENT LOW CEILINGS OVER THE WEST SIDE OF THE STATE FROM SPREADING
INTO THE AREA. NORTH WINDS WILL GRADUALLY SHIFT TO THE NORTHEAST
THROUGH THE LATE AFTERNOON...AND THEN FINALLY TO THE EAST BY LATE
THIS EVENING AS SPEEDS WEAKEN TO 5 KTS OR LESS.

//DTW THRESHOLD PROBABILITIES...

* HIGH FOR CEILINGS AT OR BELOW 5000 FEET THROUGH 00Z. MEDIUM
  OVERNIGHT.

&&

.PREV DISCUSSION...ISSUED 346 AM EDT FRI APR 29 2016

DISCUSSION...

SE MICHIGAN POSITIONED EARLY THIS MORNING UNDER WEAK DEFORMATION
EXTENDING FROM A CLOSED MID LEVEL CIRCULATION ANCHORED JUST
UPSTREAM.  THIS PERTURBED MID LEVEL FIELD SUSTAINING SOME POCKETS OF
LIGHT SHOWERS...ABOVE A LOW LEVEL PROFILE CHARACTERIZED AS
SEASONABLY COOL UNDER PERSISTENT NORTHEAST FLOW.  A COOL AND
UNSETTLED PATTERN WILL HOLD TODAY...REINFORCED BY THE EASTWARD
EJECTION OF THE AFORMENTIONED UPPER LOW THROUGH MID AFTERNOON. SOLID
INCREASE IN DCVA AND CONVERGENCE ACCOMPANYING THIS FEATURE...WITH A
NOTED SPIKE IN MID LEVEL LAPSE RATES BENEATH THE ASSOCIATED MID
LEVEL COLD POOL.  AN ADDITIONAL DIURNAL CONTRIBUTION WILL
SUBSEQUENTLY SUPPORT AN INCREASE IN SHOWER COVERAGE FROM MID MORNING
INTO EARLY AFTERNOON.  LATEST HI RES GUIDANCE PROJECTS A SLIGHTLY
GREATER RESPONSE ACROSS THE HEART OF THE FORECAST AREA /BETWEEN I-69
AND I-94/...STRONGER SIGNAL OF CONVERGENCE ALIGNING ACROSS THIS
CORRIDOR.  PRECIPITATION AND CORRESPONDING HIGHER CLOUD COVERAGE
WILL AGAIN ACT TO RESTRICT THE DIURNAL TEMPERATURE RESPONSE OF AN
ALREADY COOL RESIDENT THERMAL PROFILE /850 MB TEMPS NEAR FREEZING/.
HIGHS LARGELY IN THE LOWER 50S.

EMERGING WEAK MID LEVEL SUBSIDENCE AND GENERAL DRYING THROUGH THE
COLUMN WILL SUPPORT A CLEARING TREND TONIGHT IN THE WAKE OF THIS
SYSTEM.  A PERSISTENT LIGHT NORTHEAST LOW LEVEL GRADIENT WILL CAP
THE OVERALL RADIATIONAL COOLING RESPONSE...BUT OVERALL MAGNITUDE OF
THE EXISTING COLDER PROFILE WILL STILL BRING LOWS SATURDAY MORNING
INTO THE 30S NEARLY ALL LOCALES.  SOME POCKETS OF FROST NOT OUT OF
THE QUESTION /PARTICULARLY IN THE THUMB/...BUT AGAIN THE GRADIENT
WILL BE A LIMITING FACTOR.  GIVEN THIS AND THE FACT THAT THE GROWING
SEASON IS STILL LAGGING ACROSS THE TRI-CITIES AND THUMB...WHERE
FROST WOULD BE MORE LIKELY...WILL REFRAIN FROM A MENTION AT THIS
STAGE.

GENERAL SURFACE RIDGING AND CORRESPONDING DRY LOW LEVEL EASTERLY
FLOW...TUCKED BENEATH WEAKLY CONFLUENT MID LEVEL WESTERLIES...WILL
PRESENT A BENIGN PERIOD OF WEATHER FOR SATURDAY.  SOME OF EARLY DAY
SUN BEFORE HIGH CLOUDS THICKEN IN ADVANCE OF THE NEXT SYSTEM.
INCREASING THICKNESSES AND THE ADDED INSOLATION WILL BRING DAYTIME
TEMPERATURES INTO THE 55 TO 60 DEGREE RANGE.

SHORTWAVE ENERGY PIVOTING THRU THE PERIPHERY OF A CLOSED LOW PARKED
OVER THE CENTRAL PLAINS WILL ELICIT A SOLID LOW/MID LEVEL RESPONSE
IMMEDIATELY DOWNSTREAM EARLY THIS WEEKEND...THIS PROCESS TARGETING
SE MICHIGAN BY SATURDAY EVENING/NIGHT.  THE REGION WILL RECEIVE A
GLANCING SHOT OF THE ATTENDANT NORTHEAST SURGING MOISTURE PLUME /PW
NEAR 1 INCH/ BACKED BY A FORMIDABLE LOW LEVEL JET ARCING THROUGH THE
MIDWEST AND STRENGTHENING ISENTROPIC ASCENT.  UPGLIDE ALONG THE
ISENTROPIC SURFACE WILL DRIVE THE EARLY STAGES OF THE EFFECTIVE
RAINFALL AXIS EARLY SATURDAY NIGHT...BEFORE A TRANSITION TOWARD MID
LEVEL DEFORMATION NORTH OF THE SURFACE LOW RACING THROUGH THE OHIO
VALLEY.  SOME UNCERTAINTY YET ON THE NORTHWARD EXTENT OF THE BOTH
THE BETTER FORCING AND DEEPER MOISTURE...BUT CERTAINLY GROWING
CONFIDENCE ON WITNESSING A SOLID PERIOD OF RAIN ACROSS AT LEAST THE
SOUTHERN HALF SATURDAY NIGHT.  CORRESPONDING NUDGE UPWARD IN POPS
ACROSS THIS CORRIDOR.

SHOWERS MAY REMAIN PREVALENT THROUGH EARLY SUNDAY AS LINGERING
DEFORMATION SLOWLY RELEASES EASTWARD.   REGARDLESS...TEMPERATURES
LIKELY TO TAKE STEP BACK FROM THOSE NOTED SATURDAY...UNDER RENEWED
COOLER NORTHEAST FLOW AND PLENTY OF RESIDUAL CLOUDINESS.  THE
SUPPRESSED UPPER HEIGHTS AS MID LEVEL TROUGHING EASES THROUGH WILL
CONTRIBUTE TO THE COOLER TREND.  READINGS SUNDAY BROADLY
DISTRIBUTED IN THE 50S.

MARINE...

LIGHT TO MODERATE BREEZE EXPECTED THROUGH MIDDAY SATURDAY. A WEAK
LOW LIFTING THROUGH THE OHIO RIVER VALLEY WILL THEN PROVIDE SEVERAL
HOURS OF MODERATE TO FRESH ONSHORE FLOW LATE SATURDAY THROUGH
SUNDAY. THE PROLONGED PERIOD OF ONSHORE FLOW WILL LIKELY NECESSITATE
SMALL CRAFT ADVISORIES FOR ELEVATED WAVE CONDITIONS FOR THE
NEARSHORE WATERS OF LAKE HURON DURING THIS TIME.

&&

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

$$

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


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



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