Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 031655
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1255 PM EDT TUE MAY 3 2016

.AVIATION...

THE REST OF THE AFTERNOON WILL BE HIGHLIGHTED WITH DIURNAL CU
ABOVE 5000 FEET AND LIGHT WEST WINDS. TONIGHT WILL HAVE INCREASING
CLOUDS FROM NORTH TO SOUTH AHEAD OF THE NEXT SYSTEM AS THEY LOWER
TO AROUND 3000-5000 FEET. ALL INDICATIONS OF THE NEXT SYSTEM
WRAPPING UP OVER SOUTH CENTRAL LOWER MICHIGAN. THIS WILL KEEP THE
NORTHERN TAF SITES OF FNT AND MBS IN LOWER CEILINGS AND
VISIBILITIES WITH A STEADY RAIN ON WEDNESDAY MORNING. EXPECT MVFR
TO NEAR IFR CEILINGS AND VISIBILITIES FOR THESE TWO SITES. A MORE
OPTIMISTIC FORECAST IS LIKELY FOR THE MORNING FOR THE METRO
DETROIT TAFS AS IT WILL TAKE MORE TIME FOR THE DEEPER AND LOW
LEVEL MOISTURE TO MOVE OVER THE AREA.

FOR DTW...JUST HIGHER BASED...ABOVE 5000 FEET...BROKEN CEILING
DIURNAL CUMULUS FOR THE REST OF THE AFTERNOON. THE FIRST HALF OF
THE NIGHT SHOULD HAVE JUST SCATTERED CLOUDS...BEFORE SOME
ALTOCUMULUS AROUND 8000 FEET MOVES IN FROM 07Z TO 14Z.

//DTW THRESHOLD PROBABILITIES...

* NONE

&&

.PREV DISCUSSION...ISSUED 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.

&&

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

$$

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


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