Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 030754
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
354 AM EDT TUE MAY 3 2016

.DISCUSSION...

STRONG NORTH-SOUTH TEMPERATURE GRADIENT OVER THE CWA THIS MORNING AS
CLEARING ACROSS THE NORTH HAS ALLOWED TEMPERATURES TO FALL INTO THE
LOW 30S. SLOW PROGRESS OF THE SURFACE RIDGE AXIS HAS ALLOWED STRATUS
TO HANG ON INTO THE EARLY MORNING HOURS SUPPORTING TEMPERATURES IN
THE UPPER 40S SHORTLY BEFORE SUNRISE. WATER VAPOR IMAGERY REVEALS
THE POTENT SHORTWAVE AGGRESSIVELY DIGGING SOUTH INTO NORTHWEST
ONTARIO. ASSOCIATED PRESSURE FALLS WILL GIVE THE RESIDENT RIDGE AXIS
THE NECESSARY SOUTHWARD PUSH TO CLEAR STRATUS FROM OUR SOUTHERN
COUNTIES EARLY THIS MORNING YIELDING HIGH CONFIDENCE IN FULL SUN FOR
THE FIRST HALF OF THE DAY. WITH THE THERMAL TROUGH JUST BARELY EAST
OF THE STATE, FULL INSOLATION WILL EFFECTIVELY FACILITATE SUBSTANTIAL
DIURNAL BOUNDARY LAYER GROWTH. DRY ADIABATIC LAPSE RATES UP TO AT
LEAST 6KFT WILL SUPPORT HIGH TEMPERATURES IN THE MID TO UPPER 60S
AREAWIDE. SUFFICIENT MID-LEVEL MOISTURE WILL BE PRESENT DURING PEAK
HEATING TO SUPPORT DEVELOPMENT OF A FAIRLY WIDESPREAD CU DECK BY
AFTERNOON.

INCREASING SOUTHWEST GRADIENT IN ADVANCE OF THE AFOREMENTIONED WAVE
WILL LIMIT OVERNIGHT LOWS TO AROUND 50 DEGREES. MODEL CONSENSUS IS
STRONG THAT CONVERGENT/LINEAR FORCING ASSOCIATED WITH THE
TROUGH/DEEP TROPOSPHERIC FRONT WILL SUPPORT A BAND OF RAIN
TRANSITING THE AREA LATE TONIGHT. SCATTERED LEAD ACTIVITY WILL BE
POSSIBLE AS ISENTROPIC ASCENT RAMPS UP FROM SOUTH TO NORTH MAINLY
AFTER 06Z.

THE CHARACTER OF RAIN ON WEDNESDAY IS STILL VERY MUCH IN QUESTION,
ALTHOUGH THERE HAS BEEN NOTABLE SOLUTION CONVERGENCE AMONG THE
EC/NAM/GEM INDICATING PROLONGED DEFORMATION FORCING BENEATH THE COLD
UPPER LOW. STEEP MID-LEVEL LAPSE RATES WILL SUPPORT AT LEAST A
COUPLE HUNDRED J/KG CAPE WITHIN ROBUST AND PERSISTENT DEFORMATION. 0-
3KM MUCAPE IN THE NAM OF 1500 J/KG IS UNREASONABLY HIGH BUT IT DOES
SERVE AS A WINDOW INTO A HIGHER INSTABILITY SCENARIO WHICH WOULD BE
A SOLID SHARS EVENT OVER A PORTION OF THE CWA. THE LIMITED CAPE IN
THE EC THE RESULTS IN A STRAIGHT DEFORMATION RAIN SCENARIO WEDNESDAY
AFTERNOON AND WEDNESDAY NIGHT. GIVEN THE STEEP LAPSE RATES, A MIDDLE-
GROUND SCENARIO BETWEEN THE TWO SOLUTIONS IS CERTAINLY PLAUSIBLE.
GAUGING WEDNESDAY AFTERNOON/EVENING INSTABILITY POTENTIAL AS THE
SPATIAL FOOTPRINT OF DEFORMATION FORCING AROUND THE CLOSED LOW WILL
BE A KEY FOCUS OF SUBSEQUENT FORECAST SHIFTS. FOR NOW...AN AREAWIDE
QPF OF AROUND ONE HALF INCH WILL SUFFICE.

&&

.MARINE...

A LIGHT AND VARIABLE WIND WILL EXIST TODAY IN ADVANCE OF A COLD
FRONT. THIS COLD FRONT SHIFTS THROUGH ALL WATERWAYS LATE TONIGHT AND
EARLY WEDNESDAY.  WINDS WILL BECOME NORTHWESTERLY AND STRENGTHEN
WITH THIS FRONTAL PASSAGE BY LATE WEDNESDAY. STRONGEST WINDS ACROSS
NORTHERN AND CENTRAL SECTIONS OF LAKE HURON...WHERE A PERIOD OF
WINDS AROUND 25 KNOTS APPEARS LIKELY.  THE ONSHORE FLOW WILL LEAD TO
A PERIOD OF ELEVATED WAVE CONDITIONS ALONG THE THUMB WEDNESDAY
NIGHT.  HIGH PRESSURE WILL THEN BRING TRANQUIL MARINE CONDITIONS FOR
THE LATE WEEK PERIOD.

&&

.HYDROLOGY...

THE NEXT ROUND OF RAINFALL ARRIVES LATE TONIGHT AND WILL CONTINUE
THROUGH WEDNESDAY AS A STORM SYSTEM TRACKS THROUGH THE REGION.  AT
THIS TIME...RAINFALL TOTALS RANGING FROM ONE QUARTER TO ONE HALF AN
INCH ARE EXPECTED BEFORE THE RAIN TAPERS OFF EARLY WEDNESDAY NIGHT.
THE POTENTIAL DOES EXIST FOR LOCALIZED HIGHER AMOUNTS...PERHAPS
UPWARDS OF ONE INCH...SHOULD THIS STORM SYSTEM EXIT AT A SLOWER
PACE.

&&

.AVIATION...ISSUED 1223 AM EDT TUE MAY 3 2016

PERSISTENT UPPER RIDGING OVER EASTERN NORTH AMERICA WILL MAINTAIN A
RATHER SLUGGISH TREND TO DRY AIR ADVECTION AND EROSION OF
STRATUS/STRATOCU/ALTOSTRATUS. THERE HAS BEEN SLOW SOUTHERN MOVEMENT
TO THE EDGE OF THE CLOUD DECK THE PAST FEW HOURS...BUT SUSPECT THAT
SKC/SCT CIRRUS WILL DEVELOP EITHER BY 6Z OR AN HOUR OR TWO AFTER AT
THE START OF THE PERIOD. A WEAK PRESSURE GRADIENT HAS ALREADY LED TO
A VARIABLE WIND FIELD IN MANY AREAS...SHALLOW FOG WILL ALSO BE A
POSSIBILITY FOR MANY AREAS LATER TONIGHT. THE PERSISTENT TROUGH AND
HIGHER AMBIENT MOISTURE WILL LEAD TO CUMULUS DEVELOPMENT AT 4000-
5000 KFT AGL DURING THE LATE MORNING AND EARLY AFTERNOON.

//DTW THRESHOLD PROBABILITIES...

* HIGH CONFIDENCE ABOVE 5000 FT AGL CIGS AT THE START OF THE PERIOD.
  LOW CONFIDENCE FOR PERIOD OF 5000 FOOT CEILINGS TOMORROW AFTERNOON
  (BKN CIGS ABOVE 5000 FT AGL).

&&

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

$$

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


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