561
FXUS63 KDTX 212352
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
752 PM EDT TUE MAY 21 2019
AVIATION
DOWNSTREAM RESPONSE TO DYNAMIC UPPER LEVEL LOW PRESSURE OVER CENTRAL
U.S. WILL FORCE GEOPOTENTIAL HEIGHT RISES AND SIGNIFICANT WARM AIR
ADVECTION EVENT OVER SOUTHEAST MICHIGAN THE NEXT 12 TO 18 HOURS.
EFFICIENCY TO SYSTEM RELATIVE ISENTROPIC ASCENT IS NOT IMPRESSIVE
AND WILL RELY UPON FORCED, TANGIBLE INCREASE IN LOW TO MIDLEVEL
THETA E CONTENT TO GENERATE PRECIPITATION. MID TO HIGH CLOUD DURING
THE OVERNIGHT WITH THE POTENTIAL FOR SHOWER ACTIVITY IN THE 12-17Z
TIME WINDOW FOR SOUTHEAST MICHIGAN. THIS BETTER POTENTIAL WILL COME
WITH A RIBBON OF DEEPER MIDLEVEL MOISTURE. LOWER CONFIDENCE EXISTS
WITH WHAT SORT OF COVERAGE WILL EXIST WITHIN THIS MOISTURE PLUME AS
SOME MODEL GUIDANCE SHOWS LACK OF MOISTURE DEPTH WITH A VERY QUICK
ONSET TO ACTIVE MIDLEVEL SUBSIDENCE. BOUNDARY LAYER CLOUD IS
ANTICIPATED WEDNESDAY AFTERNOON IN THE WAKE OF THE PASSING SHORTWAVE
ENERGY. A WELL MIXED SOUTHEASTERLY WIND IS EXPECTED FOR MUCH OF THE
DAY WEDNESDAY.
FOR DTW...SHOWERS ARE POSSIBLE IN THE 13-16Z TIMEFRAME WEDNESDAY AT
DTW WITH CIGS IN THE 2500 TO 5000 FT AGL LAYER.
DTW THRESHOLD PROBABILITIES
* LOW CONFIDENCE IN THUNDERSTORMS WEDNESDAY.
* MEDIUM CONFIDENCE IN CIGS AOB 5000 FEET LATE WEDNESDAY MORNING,
OTHERWISE LOW FOR WEDNESDAY.
PREV DISCUSSION
ISSUED AT 312 PM EDT TUE MAY 21 2019
DISCUSSION...
A REGION OF LIGHT RAIN ALONG THE MI/IN/OH BORDER REGION IS
ASSOCIATED WITH A NARROW MID LEVEL FRONTAL ZONE. THIS FRONT HAS BEEN
WEAKENING AS A RESULT OF MID LEVEL HEIGHT RISES ASSOCIATED WITH A
SHARPENING OF THE MID LEVEL RIDGE AXIS NOW BUILDING OVER LOWER MI.
THE RESULTANT RAIN SHOULD IN TURN CONTINUE TO DIMINISH. OTHERWISE,
SFC HIGH PRESSURE WILL SLOWLY EXIT THE REGION TO THE EAST DURING THE
NIGHT AS THE MID LEVEL RIDGE AXIS SLIDES INTO THE ERN GREAT LAKES.
DESPITE THE ABUNDANCE OF LOW LEVEL DRY AIR THROUGH MUCH OF THE
NIGHT, AMPLE MID/HIGH LEVEL CLOUDS STREAMING IN FROM THE SOUTHWEST
AND AN INCREASING SOUTHEAST GRADIENT THROUGH THE NIGHT WILL LIMIT
NIGHTTIME RADIATIONAL COOLING, LEADING TO A LITTLE WARMER NIGHT IN
COMPARISON TO LAST NIGHT; MINS IN THE 40S.
THE DEPARTING SFC HIGH AND SFC LOW LIFTING NORTHWARD ACROSS THE
PLAINS LATE TONIGHT/WED MORNING WILL INCREASE THE SOUTHEAST GRADIENT
ACROSS THE EASTERN LAKES. THE LOW LEVEL AIRMASS LOOKS TO BE COLD
ENOUGH TO SUPPORT SLIGHTLY UNSTABLE CONDITIONS ACROSS LAKES ST CLAIR
AND ERIE, SUPPORTING GUSTY SE WINDS FOR A PERIOD WED. THIS AND GIVEN
THE HIGH LAKE LEVELS WILL AGAIN RAISE FLOODING CONCERNS ALONG THE
LAKES ST CLAIR AND ERIE SHORELINES.
AS THE UPPER LOW NOW CHURNING OVER THE CENTRAL PLAINS LIFTS INTO
SOUTH DAKOTA BY WED MORNING, A 60+ KNOT LOW LEVEL JET WILL DRIVE A
PLUME OF DEEP LAYER MOISTURE AND MODEST ELEVATED INSTABILITY INTO
WESTERN LOWER MI TOWARD 09 TO 12Z WED MORNING. THE REMNANT MID LEVEL
THETA E PUSH/ELEVATED INSTABILITY AXIS WILL BE DRIVEN ACROSS SE MI
WED MORNING (LINGERING IN THE THUMB INTO EARLY AFTERNOON), POSSIBLY
AIDED BY CONVECTIVELY ENHANCED SHORT WAVE IMPULSES. THERE IS SOME
CONCERN THAT WITH THE BETTER DYNAMIC SUPPORT RESIDING NORTHWEST OF
THE AREA AND HIGHER INSTABILITY ACROSS INDIANA, COVERAGE OF
CONVECTION MAY SUBSTANTIALLY DECREASE OVER SE MI WED MORNING, SO
CHANCE TYPE POPS WILL SUFFICE ATTM. LOW LEVEL SW FLOW WILL DRIVE A
SFC WARM FRONT NORTHWARD INTO SE MI DURING THE DAY WEDNESDAY,
EVENTUALLY REPLACING THE COOL MARINE MODIFIED AIR WITH A WARMER MORE
SUMMER-LIKE AIRMASS. MODEL SOUNDINGS SUGGEST STRONG MID LEVEL
CAPPING TAKING HOLD FAIRLY QUICKLY IN THE WARM SECTOR. THE EXCEPTION
IS ALONG THE FAR EAST FROM MONROE UP THROUGH PORT HURON WHERE THERE
APPEARS TO BE A SHORT WINDOW OF OPPORTUNITY OF DECENT INSTABILITY
BEFORE CAPPING TAKES HOLD.
THE UPPER LEVEL LOW IS FORECAST TO DAMPEN AS IT TRAVERSES THE
NORTHERN LAKES ON THURSDAY, BUT WILL STILL DRIVE A COLD FRONT INTO
SE MI THURS MORNING. CONVECTIVE CHANCES THURS MAY ACTUALLY HINGE ON
CONVECTIVE DEVELOPMENT/PROPAGATION UPSTREAM ACROSS ILLINOIS/NRN
INDIANA AND THE POTENTIAL FOR THE NORTHERN PORTIONS OF THIS TO
IMPACT SE MI. BY THURS AFTERNOON, MODEL SOUNDINGS SUGGEST STRONG
CAPPING TAKING HOLD WITHIN THE POST FRONTAL WESTERLY FLOW. A DECENT
WESTERLY GRADIENT WILL LEAD TO WARM AND BREEZY CONDITIONS.
ANOTHER WAVE FORECAST TO LIFT FROM THE CENTRAL ROCKIES INTO THE NRN
PLAINS ON FRIDAY. THIS SYSTEM WILL LIKELY DRIVE THE SFC FRONT BACK
INTO LOWER MI AS A WARM FRONT IN THE FRIDAY TO SATURDAY TIME FRAME,
SUPPORTING ANOTHER CHANCE FOR SHOWERS AND THUNDERSTORMS. DESPITE
SOME DIFFERENCES, THE EURO SOLUTION SUGGESTS NORTHERN STREAM
TROUGHING WILL DRIVE HIGH PRESSURE INTO THE AREA BY SUNDAY AND HOLD
ITS INFLUENCE INTO EARLY NEXT WEEK, OFFERING DRY AND RELATIVELY COOL
CONDITIONS FOR THE END OF THE FORECAST PERIOD.
MARINE...
HIGH PRESSURE WILL BUILD OVER THE AREA PROVIDING LIGHT WINDS AND
SUBDUED WAVES INTO THIS EVENING. EAST TO SOUTHEAST FLOW WILL
INCREASE OVERNIGHT INTO WEDNESDAY AS THIS HIGH SHIFTS OFF TO THE
EAST AND A WARM FRONT BEGINS TO ENCROACHES FROM THE SOUTH.
HOWEVER, WIND GUSTS ARE GENERALLY EXPECTED TO STAY UNDER 25 KNOTS
ALONG THE NEARSHORE WATERS, AND SMALL CRAFT ADVISORIES ARE NOT
ANTICIPATED AT THIS TIME. WINDS BECOME SOUTH TO SOUTHWEST LATE
WEDNESDAY NIGHT AHEAD OF A COLD FRONT WHICH PASSES THROUGH ON
THURSDAY. GUSTS UP TO 25 KNOTS ARE POSSIBLE RIGHT ALONG THE
SHORELINE AREAS OF THE NEARSHORE WATERS, BUT WITH LOW LEVEL
STABILITY OVER THE OPEN WATERS WILL MAIN GUSTS GENERALLY UNDER
20 KNOTS.
HYDROLOGY...
SCATTERED SHOWERS AND A FEW THUNDERSTORMS WILL PASS THROUGH
SOUTHEAST MICHIGAN LATE TONIGHT AND WEDNESDAY MORNING AS A WARM
FRONT LIFTS NORTH. BASIN AVERAGE RAINFALL EXPECTED TO AVERAGE LESS
THAN A QUARTER OF AN INCH.
INCREASING SOUTHEAST FLOW ASSOCIATED WITH THIS WARM FRONT WILL BRING
ANOTHER PERIOD OF FLOODING CONCERNS ALONG THE SHORELINES OF LAKE ST
CLAIR AND WESTERN LAKE ERIE. THIS PERIOD OF STRONGER ONSHORE WINDS
WILL BE RATHER BRIEF AND LIMITED TO LATE TONIGHT AND WEDNESDAY
MORNING. NONE-THE-LESS, LAKESHORE FLOODING ADVISORIES HAVE BEEN
ISSUED ONCE AGAIN.
DTX WATCHES/WARNINGS/ADVISORIES
MI...LAKESHORE FLOOD ADVISORY FROM 6 AM TO 6 PM EDT WEDNESDAY FOR MIZ070-
076.
LAKESHORE FLOOD ADVISORY FROM 6 AM TO 2 PM EDT WEDNESDAY FOR MIZ083.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY FROM 4 AM TO NOON EDT WEDNESDAY FOR LEZ444.
AVIATION.....CB
DISCUSSION...SC
MARINE.......SF
HYDROLOGY....SF
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