806
FXUS63 KDTX 152313
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
713 PM EDT MON JUL 15 2019
AVIATION
THE WARM FRONT, EXTENDING NW-SE ACROSS LOWER MICHIGAN MOVES INTO
CANADA DURING THE EVENING AND TAKES THUNDERSTORMS OUT OF THE AREA.
THAT LEAVES VFR IN PLACE AT THE TERMINALS WITH LIGHT SW WIND THROUGH
EARLY TUESDAY MORNING. CLEAR SKY DEVELOPING BY LATE EVENING SHOWS AN
INCREASE OF HIGH CLOUDS LATE AS THE NORTHERN FRINGE OF BARRY
REMNANTS MOVE IN FROM THE SOUTH. LIGHT SHOWERS REACH DTW FIRST
AROUND NOON TUESDAY AND SPREAD NORTHWARD TOWARD FNT DURING THE
AFTERNOON. THERE IS ALSO A GRADUAL LOWERING OF CEILING TOWARD ENTRY
LEVEL MVFR WHICH IS INDICATED IN OBSERVATIONS TODAY MOVING INTO THE
OHIO VALLEY. AFTERNOON TIMING BRINGS DURATION INTO QUESTION AND THE
FORECAST WILL TIE RESTRICTION TO SHOWERS FOR NOW. TIMING AND
COVERAGE OF ANY THUNDERSTORMS WOULD BE LATE IN THE DAY WITH
INSTABILITY IN QUESTION DUE TO THE EARLIER CLOUDS AND SHOWERS.
PREFER TO SAVE THE MENTION OF STORMS FOR EVALUATION IN LATER
UPDATES.
FOR DTW... THUNDERSTORMS EXIT EAST OF DTW TO START THE FORECAST LEAVING
VFR UNDER DECREASING CLOUDS THROUGH MIDNIGHT WITH LIGHT SW WIND.
HIGH CLOUDS INCREASE LATE AND LOWER TOWARD 5000 FT TUESDAY MORNING
LEADING TO A CHANCE OF VFR SHOWERS.
DTW THRESHOLD PROBABILITIES
* MODERATE FOR CEILING 5000 FT OR LESS TUESDAY.
* LOW FOR THUNDERSTORMS LATE TUESDAY.
PREV DISCUSSION
ISSUED AT 322 PM EDT MON JUL 15 2019
DISCUSSION...
CONVECTION HAS FIRED AS EXPECTED, WITH LATEST SPC MESOSCALE ANALYSIS
INDICATING MLCAPES 1000-1500 J/KG ON THE WESTERN FRINGE OF THE CWA,
WITH EFFECTIVE BUILD SHEAR ABOVE 30 KNOTS GENERALLY NORTH OF I-69.
AN ISOLATED MARGINALLY SEVERE THUNDERSTORM OR TWO REMAINS POSSIBLE
THROUGH THE BULK OF DAYLIGHT HOURS, BUT WEAK MID LEVEL LAPSE RATES
SUGGESTS OTHERWISE WITH JUST TORRENTIAL DOWNPOURS DUE TO THE
TROPICAL NATURE OF THE AIRMASS. SUBSIDENCE/MODEST DRYING OUT AT THE
700 MB LEVEL BEHIND THE MID/UPPER WAVE EXITING LAKE HURON IS
EXPECTED TO PRODUCE A DRY LATE EVENING INTO THE EARLY MORNING HOURS
OF TUESDAY.
REMNANT CIRCULATION/MOISTURE OF BARRY OVER THE LOW-MID MISSISSIPPI
RIVER VALLEY BEING SHEARED OFF TO THE NORTHEAST AND NORTHERN FRINGE
LOOKS TO CLIP SOUTHEAST MICHIGAN TOMORROW, AS THE CLOSED 500 MB LOW
OPENS UP. PW VALUES EXCEEDING 2 INCHES SOUTH OF I-69 WITH 700 MB DEW
PTS PUSHING 7 C AND POSSIBLY EVEN 8 C, RECORD TERRITORY FOR MID JULY
AROUND HERE. THE MAIN MOISTURE SURGE IS ACTUALLY GOING TO OCCUR
AROUND 12Z TUESDAY WHEN NOSE OF THE 800-700 MB JET CROSSES JUST
ACROSS THE SOUTHERN MICHIGAN BORDER. STRONGER WINDS THEN ARE SHUNTED
OFF TO THE EAST DURING TUESDAY, WITH 0-6 KM BULK SHEAR GENERALLY
UNDER 20 KNOTS. THUS, NO SEVERE WEATHER IS EXPECTED WITH THE WEAK
INSTABILITY/MID LEVEL LAPSE RATES. ONCE AGAIN, TORRENTIAL RAINFALL
WILL BE THE MAIN HAZARD AND SHOULD NOT TAKE MUCH TO SET OFF DIURNAL
ENHANCED SHOWERS AND EMBEDDED THUNDERSTORMS (SEE ARW), LINGERING
INTO THE EARLY EVENING. WITH ACTIVITY/CLOUDS ALREADY ARRIVING TO
START THE DAY, TEMPERATURES LIKELY HOLDING IN THE 80S, WITH TRI-
CITIES AND NORTHERN THUMB REGION LIKELY SEEING THE WARMEST TEMPS.
REASONABLE AGREEMENT AMONGST MODELS WITH AN UPPER LEVEL DISTURBANCE
COMING OUT OF THE CENTRAL PLAINS AND TRACKING THROUGH LOWER MICHIGAN
ON WEDNESDAY, HELPING TO KICK REMNANT OPEN 500 MB TROUGH OF BARRY
OFF TO THE EAST. STILL A LOT OF MOISTURE TO WORK (PW VALUES AROUND 2
INCHES/700 MB DEW PTS STILL AOA 5 C) WITH TO GENERATE SHOWERS AND
THUNDERSTORMS, AS MLCAPES PUSH ABOVE 1000 J/KG AND POTENTIALLY UP TO
2000 J/KG, DEPENDING ON TIMING AND STRENGTH OF THE DISTURBANCE.
LOCALIZED ENHANCEMENT OF 0-6 KM BULK SHEAR REACHING AROUND 30 KNOTS
(PROBABLY ALONG/NORTH M-46 ONCE AGAIN PER NAM) COULD SUPPORT AN
ISOLATED SEVERE THREAT, BUT MID LEVEL LAPSE RATES STILL LOOK TO BE
WEAK (UNDER 6 C/KM). 850 MB TEMPS AROUND 18 C, SUPPORTIVE OF MAXES
AROUND 90 DEGREES, BUT WITH SHOWERS AND THUNDERSTORMS AROUND AND
MOIST LOW LEVELS (SURFACE DEW PTS AOA 70 DEGREES), PROBABLY GOING TO
HOLD TEMPS MORE IN THE 85-90 DEGREE RANGE.
HEAT WILL INCREASE AT THE END OF THE WEEK AS AN UPPER LEVEL RIDGE
SETS UP OVER THE CENTRAL PLAINS BEFORE EXPANDING EASTWARD ALLOWING
THE 591DAM TO MOVE INTO SOUTHERN MI ON FRIDAY AND SATURDAY. BOTH OF
THOSE DAYS WILL HAVE HIGHS IN THE MID 90'S (POSSIBLY UPPER 90'S IN
DETROIT ITSELF) WITH DEWPOINTS IN THE MID 70'S GIVING HEAT INDEX
VALUES WELL INTO THE 100'S. LOWS THURSDAY NIGHT ON WILL ONLY GET
DOWN INTO THE MID 70'S.
A LOW BEGINS TO DEVELOP OVER THE NORTHERN PLAINS THURSDAY MORNING
AND MOVES OVER THE UPPER PENINSULA THURSDAY NIGHT. THIS SYSTEM PULLS
HOTTER MUGGIER AIR INTO SE MI HELPING TO CREATE THOSE MID-90'S ON
FRIDAY AND SATURDAY. THERE WILL BE A MODERATE CHANCE OF RAIN
THURSDAY NIGHT THROUGH FRIDAY WITH THIS SYSTEM'S PASSAGE. A WEAK MID-
LEVEL DISTURBANCE LOOKS TO MOVE FROM WISCONSIN INTO SE MI SATURDAY
AFTERNOON WITH COULD BRING A CHANCE OF SCATTERED SHOWERS AND
THUNDERSTORMS.
MARINE...
PREVAILING LATE DAY SOUTHEASTERLY WINDS WILL INCREASE MODESTLY WHILE
GRADUALLY VEERING TO SOUTHWEST OVERNIGHT AS A WARM FRONT LIFTS
THROUGH THE REGION. A 10 TO 20 KNOT SOUTHWEST WIND WILL REMAIN IN
PLACE THROUGH TUESDAY. STRONGEST WINDS LIKELY NOTED ACROSS SAGINAW
BAY DURING THIS TIME, WHERE CONDITIONS MAY NEAR ADVISORY LEVELS FOR
SMALL CRAFT. SOUTHWEST WINDS WILL DIMINISH TUESDAY NIGHT AS THE
GRADIENT EASES. WINDS WILL THEN TURN LIGHT AND VARIABLE FOR
WEDNESDAY. INCREASINGLY MOIST AND UNSTABLE AIR ACROSS THE REGION
OVER THE NEXT COUPLE DAYS WILL LEAD TO INCREASING CHANCES FOR
THUNDERSTORMS.
HYDROLOGY...
A WARM FRONT WILL LIFT ACROSS SOUTHEAST MICHIGAN DURING THE
AFTERNOON AND EVENING HOURS. THIS FRONTAL PASSAGE TIMED FAVORABLY
WITH DIURNAL DESTABILIZATION WILL PROVIDE THE FOCUS FOR A SCATTERED
COVERAGE OF SHOWERS AND THUNDERSTORMS DURING THIS TIME. ANY
THUNDERSTORM ACTIVITY WILL BRING THE POTENTIAL FOR LOCALIZED HEAVY
RAINFALL, WITH AMOUNTS IN EXCESS OF AN INCH POSSIBLE. THERE WILL
AGAIN BE A CHANCE FOR SHOWERS AND THUNDERSTORMS BOTH TUESDAY AND
WEDNESDAY, PARTICULARLY DURING THE AFTERNOON AND EVENING HOURS, AS
TROPICAL MOISTURE ASSOCIATED WITH REMNANTS OF BARRY ENTER THE
REGION. POTENTIAL EXISTS FOR LOCALLY INTENSE RAINFALL RATES TO
DEVELOP WITHIN ANY ACTIVITY GIVEN THE HIGH MOISTURE CONTENT. THIS
COULD LEAD TO POOR DRAINAGE FLOODING OF SUSCEPTIBLE LOW LYING AND
URBAN AREAS.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY FROM 8 AM TO 6 PM EDT TUESDAY FOR LHZ421-422.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
AVIATION.....BT
DISCUSSION...SF/KDK
MARINE.......MR
HYDROLOGY....MR
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