Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 051754
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
154 PM EDT TUE MAY 5 2015


.AVIATION...

THE MATURE MCS AND INITIAL SURGE OF DEEP MOISTURE IS CURRENTLY
TRACKING THROUGH SOUTHEASTERN MICHIGAN THIS AFTERNOON. LATEST DATA
SUGGESTS A CONTINUED POTENTIAL FOR SHOWERS AND THUNDERSTORMS OVER
MUCH OF THE AREA THROUGH AT LEAST THE EARLY EVENING HOURS. A
DEVELOPING WARM FRONT IS THEN EXPECTED TO SLOWLY ORGANIZE OVER
SECTIONS OF SEMICH TONIGHT. UNCERTAINTY EXISTS TO EXACTLY WHERE THIS
BOUNDARY WILL STALL OUT FOR A TIME...BUT LATEST INDICATIONS ARE
SUGGESTING THE NORTHERN DETROIT METRO AREA THROUGH THE I 69 CORRDOR.
IT IS ALONG THIS BOUNDARY THAT A POTENTIAL EXISTS FOR
CONTINUED...LONG DURATION RAIN OVERNIGHT. FOCUSED THIS RAIN MENTION
AT THE KPTK/KFNT FOR THIS TAF ISSUANCE...WILL CONTINUE TO MONITOR
THE NEED FOR THE SOUTHERN TAF SITES. THE OTHER IMPORTANT ISSUE FOR
TONIGHT WILL BE THE POTENTIAL FOR IFR/LIFR CIGS ALONG AND TO THE
SOUTH OF THE DEVELOPING FRONTAL BOUNDARY. WENT MORE AGGRESSIVE WITH
IFR/LIFR CIGS SOUTH.

FOR DTW...RAIN POTENTIAL WILL NOW SHIFT TO MORE SHOWER CHARACTER AS
THE INITIAL MATURE MCS SHIFTS NORTHWARD THROUGH THE CWA. WILL NEED
TO MONITOR PORTIONS OF NORTHERN ILLINOIS/INDIANA WHERE ADDITIONAL
SHOWER AND THUNDERSTORM DEVELOPMENT IS FORECASTED TO TAKE PLACE. IT
REMAINS POSSIBLE THIS ACTIVITY WHILE MOVING EASTWARD COULD IMPACT
PORTIONS OF FAR SOUTHERN MICHIGAN...INCLUDING THE METRO TERMINAL.
OTHERWISE TONIGHT...EXPECTATIONS AT THIS TIME ARE FOR THE WARM FRONT
TO SET UP NORTH OF THE TERMINAL...FOCUSING BEST LONG DURATION RAINS
CHANCES NORTH. LIFR CIGS TONIGHT AND TOMORROW MORNING.


//DTW THRESHOLD PROBABILITIES...

* HIGH FOR CEILING BELOW 5000 FT TONIGHT.

* LOW FOR THUNDERSTORMS THIS EVENING AND TONIGHT

* LOW FOR CIGS TO FALL BELOW 200 FEET.

&&

.PREV DISCUSSION...ISSUED 1034 AM EDT TUE MAY 5 2015

UPDATE...

THE DETAILED FORECAST REASONING PROVIDED IN THE EARLY MORNING
DISCUSSION WAS WELL DONE AND REMAINS VALID.

A MATURE MCS AND COMPLEX OF SHORTWAVE ENERGY SUPPORTED BY RIGHT
ENTRANCE REGION DYNAMICS ALOFT IS CURRENTLY LIFTING INTO
SOUTHEASTERN MICHIGAN THIS MORNING. SURFACE PRECIPITATION REPORTS
SUPPORT LIGHT TO MODERATE RAIN OCCURRING WITHIN THE
FORWARD...WARM AIR ADVECTION QUADRANTS OF THE MCS. WITH THE RAIN
MOVING IN...SOUTHEASTERN MICHIGAN CAN EXPECT CATEGORICAL/PERIODS
OF RAIN THROUGHOUT THE AFTERNOON HOURS. FORECAST UNCERTAINTY FOR
THE SHORT TERM PERIOD CENTERS ON WHEN EXACTLY SYNOPTIC
SUPPORT/RAIN WILL END OVER THE AREA. LATEST NAM AND RAP ARE REALLY
PAINTING DIFFERENT PICTURES. NAM SUGGESTS SUBSIDENCE IN THE WAKE
OF THIS MCS...MAY BRING A QUIET PERIOD EARLY THIS EVENING...WHILE
THE RAP DRAGS OUT THE DURATION OF THIS CATEGORICAL RAIN INTO THE
EVENING. THERE REMAINS A WINDOW OF OPPORTUNITY FOR SOME THUNDER
CHANCES LATE THIS AFTERNOON...POST 20Z. THOSE CHANCES APPEAR TO
HINGE ON THE LIKELIHOOD OF THE NAM SOLUTION VERIFYING. NEGLIGIBLE
CONVECTIVE INSTABILITY YIELDS NO SUPPORT FOR SEVERE THUNDERSTORM
POTENTIAL.

PREV DISCUSSION...ISSUED 355 AM EDT TUE MAY 5 2015

SHORT TERM... TODAY AND TONIGHT

A WET 24 HOUR PERIOD IS SETTING UP OVER SOUTHERN LOWER MICHIGAN
TODAY THROUGH TONIGHT. THE TRI CITIES AND NORTHERN THUMB MAY ESCAPE
THE BULK OF THE RAINFALL TODAY BUT THE REST OF SE MICHIGAN STANDS TO
PICK UP A PROLONGED PERIOD OF SHOWERS AND THUNDERSTORMS. THE SURFACE
FRONT WILL REMAIN SOUTH OF THE OHIO BORDER THROUGH THE PERIOD SO
THUNDERSTORMS WILL BE THE ELEVATED VARIETY AND MAINLY CONTRIBUTE TO
LOCALLY HEAVY DOWNPOURS. RAINFALL TOTALS LOCALLY AROUND 1 INCH WILL
BE POSSIBLE BY SUNRISE WEDNESDAY.

WIDESPREAD SHOWERS AND THUNDERSTORMS ARE ALREADY UNDERWAY OVER THE
MIDWEST AND WILL SPREAD TO THE NORTH AND EAST DURING THE REST OF THE
MORNING. THIS AREA OF CONVECTION ORIGINATED ALONG THE FRONT OVER THE
CENTRAL PLAINS DURING PEAK HEATING YESTERDAY AND HAS SINCE GROWN
LARGE ENOUGH AND PERSISTENT ENOUGH TO SUPPORT MCV DEVELOPMENT ALOFT
AND AN AREA OF SURFACE PRESSURE FALLS OVER IOWA AND MISSOURI. THE
WAVE IS JUST STRONG ENOUGH TO SUPPORT A WEAK LOW LEVEL JET FUELING
ACTIVITY OVER NORTHERN ILLINOIS WHICH WILL CONTINUE TO DEVELOP INTO
SOUTHERN LOWER MICHIGAN AS THE LOW TO MID LEVELS OF THE FRONT
STRENGTHEN WITH TIME. CONVECTIVE DEBRIS IN SATELLITE IMAGERY SHOWS
THE ENTRANCE REGION OF A 120 KNOT UPPER JET ANALYZED IN MODEL DATA
AT 250 MB. THIS FEATURE IS POSITIONED FAVORABLY OVER THE GREAT LAKES
TO GENERATE STRONG FRONTOGENESIS THROUGH TODAY WHILE THE LARGE SCALE
FRONTAL POSITION REMAINS STATIONARY AND THEN DRIFTS SLOWLY NORTHWARD
TONIGHT. CROSS SECTIONS OF MODEL DATA FROM THE POSITION OF THE
SURFACE FRONT EXTENDING NORTHWARD TO THE UPPER JET AXIS SHOW THE
STEEPEST PORTION OF THE AGEOSTROPHIC CIRCULATION SETTING UP THROUGH
CENTRAL SECTIONS OF OUR AREA BY AFTERNOON THROUGH THIS EVENING. DEEP
CONVECTIVE INSTABILITY ABOVE THE FRONTAL SURFACE COMBINED WITH
PRECIPITABLE WATER RISING TO ABOUT 1.25 INCHES WILL ENSURE
WIDESPREAD COVERAGE OF SHOWERS WITH EMBEDDED THUNDERSTORMS. LOCALLY
HEAVY RAINFALL WILL ALSO BE POSSIBLE DUE TO THE PERSISTENCE OF THIS
TEXTBOOK UPPER JET ENHANCED FRONTAL CIRCULATION AND THE CONVECTIVE
NATURE OF THE PRECIPITATION PATTERN. SO THEN WHAT COULD GO WRONG IN
THIS FORECAST? THE POTENTIAL FOR SURFACE BASED CONVECTION OVER
INDIANA AND OHIO...COMBINED WITH THE TENDENCY FOR ELEVATED
INSTABILITY TO BECOME LESS EFFECTIVE DURING THE DAY...COULD LEAD TO
A WEAKENING TREND IN THE PATTERN OVER SE MICHIGAN DURING THE
AFTERNOON INTO THIS EVENING. SHOULD THIS OCCUR...IT WOULD DO MORE TO
REDUCE THE POTENTIAL FOR HEAVY RAINFALL IN OUR AREA AND POSSIBLY
ALTER THE LOCATION OF THE MOST PERSISTENT SHOWERS AND OVERALL QPF...
BUT MOST AREAS WILL SEE A LENGTHY PERIOD OF RAIN AS THE MORNING RAMP
UP WOULD CARRY OVER INTO THE AFTERNOON JUST BASED ON INERTIA.

PROGRESSION OF THE UPPER LEVEL RIDGE AND THE ENTRANCE REGION OF THE
UPPER JET WILL NUDGE THE MID LEVEL FRONTAL ZONE TO THE NORTH AND
EAST OVERNIGHT. THIS WILL BRING THE TRI CITIES AND NORTHERN THUMB
MORE INTO THE PATTERN OF REMAINING SHOWERS AND WILL BE THE FAVORED
LOCATION FOR ANY NOCTURNAL REDEVELOPMENT. THE AXIS OF LIKELY POPS
OVER SE MICHIGAN IS PLACED ALONG THE 850 MB THETA-E GRADIENT WHICH
IS WELL AGREED UPON BY THE 00Z MODEL CYCLE AND IS THE MOST FAVORED
LOCATION FOR RENEWED DEVELOPMENT OF NOCTURNAL ELEVATED INSTABILITY
AND SUPPORT FOR SHOWERS THROUGH SUNRISE WEDNESDAY.

LONG TERM...WEDNESDAY THROUGH MONDAY

SE MICHIGAN WILL RESIDE ALONG THE IMMEDIATE DOWNSTREAM SIDE OF AN
ELONGATING UPPER RIDGE ON WEDNESDAY.  THE RESULTING WEAKLY SHEARED
WEST-NORTHWEST FLOW WILL SUSTAIN A PERTURBED 850-925 MB FRONTAL ZONE
ACROSS THE REGION.  MODELS TRENDING SLIGHTLY STRONGER WITH THE
ASCENT/CONVERGENCE THROUGH THIS LAYER...SUGGESTING THE EXISTING
FRONTAL SLOPE WILL POTENTIALLY BE MORE ACTIVE.  THIS WILL SUPPORT
THE INCLUSION OF A LOWER END POP.  GREATER POTENTIAL FOR SHOWER
PRODUCTION DURING THE MORNING PERIOD...BEFORE BOTH THE MOISTURE
QUALITY AND AVAILABLE FORCING DIMINISHES AS THE INBOUND UPPER RIDGE
MAKES BETTER INROADS.  SUBSTANTIAL CLOUD COVER WITHIN PERSISTENT LOW
LEVEL EASTERLY FLOW WILL CAP THE DIURNAL TEMPERATURE RESPONSE TO
SOME DEGREE...REGARDLESS OF SHOWER COVERAGE.  ABSENT OF A LARGER AND
PERSISTENT COVERAGE OF SHOWERS TO DISRUPT THE HEATING CYCLE...
EXISTING THERMAL PROFILE WILL SUPPORT HIGHS GENERALLY WITHIN THE MID
AND UPPER 60S RANGE.

UPPER RIDGE STEADILY BUILDS INTO LOWER MICHIGAN WEDNESDAY NIGHT...
580 DM AT 500 MB MARKING THE RIDGE AXIS CENTERING OVERHEAD BY EARLY
THURSDAY MORNING.  THIS PROGRESSION WILL SEND SE MICHIGAN INTO THE
WARM SECTOR BY THURSDAY...SOLID DEPTH TO THE EMERGING SOUTHWEST FLOW
CONTINUING TO POINT TOWARD HIGHS MAKING A RUN INTO THE LOWER 80S.
DRY/STABLE PROFILE STILL INFLUENCED BY EXITING UPPER RIDGING WILL
RESULT IN LITTLE MORE THAN A STANDARD DIURNAL CU FIELD.

CLOSED LOW CURRENTLY PARKED OVER THE DESERT SOUTHWEST WILL LIFT
NORTHEAST THROUGH THE LATTER HALF OF THE WEEK...EVENTUALLY SHEARING
OVER THE TOP OF THE UPPER RIDGE STAGNATING ALONG THE EAST COAST.
THIS LOWERING HEIGHT FIELD WILL BEGIN TO EASE AN ATTENDANT FRONTAL
BOUNDARY EASTWARD WITHIN THE FRIDAY AND SATURDAY WINDOW.  GENERAL
TIMING ACROSS THE MODEL SPECTRUM SUGGESTS FRIDAY WILL REMAIN
CHARACTERED BY THE PRE-FRONTAL WARM SECTOR...WITH ANY POSSIBLE LATE
DAY/EVENING CONVECTIVE CHANCES ARRIVING TOO LATE TO DISRUPT ANOTHER
DAY WITH HIGHS IN THE 80S.  POTENTIAL IS THERE FOR AN ACTIVE PERIOD
HEADING INTO THE UPCOMING WEEKEND...FRONTAL BOUNDARY EVENTUALLY
ALIGNING OVER OR NEAR THE REGION FOR AN EXTENDED TIME AS THE AXIS
BECOMES PARALLEL TO THE MEAN FLOW.  THIS PATTERN WOULD SHAVE A FEW
DEGREE OFF PROSPECTIVE HIGHS THIS WEEKEND RELATIVE TO THE
THU/FRI WARMTH...STILL NEAR TO ABOVE NORMAL THROUGH THIS TIME.

MARINE...

SHOWERY CONDITIONS WITH THE CHANCE OF THUNDERSTORMS WILL EXIST UNDER
PERSIST EAST TO NORTHEAST FLOW OVER THE SOUTHERN LAKE HURON BASIN
AND POINTS SOUTHWARD THROUGH TONIGHT.  FAVORABLE MARINE CONDITIONS
ACROSS NORTHERN LAKE HURON DURING THIS TIME AS HIGH PRESSURE BUILDS
INTO THE REGION.  MODEST WAVE AND WIND CONDITIONS THROUGH THE
MIDWEEK PERIOD AS HIGH PRESSURE SUSTAINS A WEAK GRADIENT.

&&

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

$$

AVIATION.....CB
UPDATE.......CB
SHORT TERM...BT
LONG TERM....MR
MARINE.......MR


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AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).


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