Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 040359
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1159 PM EDT SUN MAY 3 2015


.AVIATION...

WIDELY SCATTERED SHOWERS WILL WORK INTO KMBS/KFNT LATE TONIGHT INTO
MONDAY MORNING IN ADVANCE OF APPROACHING SHORTWAVE AND COLD FRONT.
THIS ACTIVITY WILL LIKELY FADE IN THE DIURNAL CONVECTIVE MINIMUM
PORTION OF THE DAY AS IT OUTRUNS ANY UPPER SUPPORT. ADDITIONAL SHRAS
AND PERHAPS A FEW TSRAS WILL REDEVELOP BY MIDDAY INTO LATE AFTERNOON
AND EARLY EVENING AS THE COLD FRONT ITSELF PROGRESSES INTO THE AREA.
THIS WILL OCCUR FIRST KMBS/KFNT AND THEN SHIFT SOUTHWARD THROUGH THE
REST OF THE AREA 20Z-22Z AND BEYOND UNTIL THE COLD FRONT CLEARS THE
TAF SITES IN THE EVENING AND PRECIPITATION CHANCES WANE.

FOR DTW...COLD FRONT WILL MOVE INTO AREA LATE IN THE FORECAST AFTER
00Z MONDAY...BUT PREFRONTAL TROUGH WILL BRING SCT SHRAS TO THE TAF
SITE BY AFTERNOON. WHILE A TSRA OR TWO ARE POSSIBLE...CONFIDENCE
REMAINS LOW GIVEN WEAK/MODEST INSTABILITY. VFR CIGS WILL GIVE WAY TO
OCCASIONAL MVFR WITH THIS ACTIVITY...BUT RETURN TO VFR AFTER 02Z AS
FROPA OCCURS AND THE FRONT THEN SINKS SOUTH OF THE AREA.

//DTW THRESHOLD PROBABILITIES...

* MEDIUM FOR CIGS AOB 5000FT MONDAY AFTERNOON AND EVENING.

* LOW FOR TSRAS MONDAY AFTERNOON.

&&

.PREV DISCUSSION...ISSUED 341 PM EDT SUN MAY 3 2015

SHORT TERM...THROUGH TONIGHT

HIGH PRESSURE IS HOLDING ON OVER SE MI WHILE THE APPROACHING UPPER
LEVEL TROUGH CURRENTLY RESIDES OVER THE MN/WI SOUTHWEST INTO THE
CENTRAL PLAINS. CIRRUS DEBRIS HAS BEEN A BIT THINNER THAN
ANTICIPATED WHILE THE SW WINDS HAVE BEEN SOLIDLY GUSTING TO 20-25
KNOTS WHICH HAS LEAD TO RH VALUES FALLING INTO THE UPPER 20 PERCENT
RANGE ACROSS THE AREA. THIS COMBINED WITH THE CIRRUS HAS HELPED MAKE
IT DIFFICULT FOR A MORE WIDESPREAD CU FIELD TO DEVELOP.
REGARDLESS...STRONG WAA CAUSED TEMPS TO SOAR QUICKLY INTO THE UPPER
70S TO LOW 80S OVER SOUTHERN MI BUT INCREASING CLOUD COVER WILL HELP
MODERATE THAT THE REST OF THE EVENING.

THE TROUGH...EXTENDING SOUTHWARD OUT OF THE PARENT LOW IN ONTARIO...
WILL CONTINUE TO SLIDE EASTWARD WHILE ENERGY RIDES NE ALONG IT INTO
ONTARIO THROUGH THE OVERNIGHT. THE COLD FRONT WILL NOT REACH SE MI
TIL AFTER 12Z BUT PREFRONTAL ACTIVITY IN A REGION OF HIGHER THETA E
AND A SHEARED RIBBON OF VORTICITY WILL REACH THE AREA BETWEEN 06-12Z
EARLY MONDAY MORNING. THIS WILL WARRANT A CHANCE OF SHOWERS AND
THUNDERSTORMS OVER THE NORTH AND WEST PORTIONS OF THE CWA. MODELS
ADVERTISE SEVERAL MID LEVEL SHORTWAVES TRAVELING IN THE WEAK
WESTERLY MIDLEVEL FLOW AROUND THE RIDGE CENTERED TO THE SE. THE
FIRST OF WHICH IS CURRENTLY PRODUCING A COMPACT AREA OF CONVECTION
OVER THE CHICAGO AREA. IT IS EXPECTED TO TRACK EAST THEN START
TURNING SE AS THE VORT MAX WEAKENS TONIGHT THUS HAVE KEPT THE
SOUTHERN COUNTIES DRY THOUGH THERE MAY BE SOME THICKER CLOUD DEBRIS
FOR A BIT LATER THIS EVENING AS A RESULT OF IT.

ANY THUNDERSTORMS THAT DO DEVELOP WITHIN THE AREA OF SHOWERS LATE
TONIGHT ARE NOT EXPECTED TO BE SEVERE AS SHEAR WILL BE
WEAK...GENERALLY LESS THAT 20 KNOTS...FORCING WILL BE MINIMAL. CAPE
VALUES WILL ONLY BE AROUND 100 J/KG THIS FAR AHEAD OF THE FRONT. THE
UPPER LEVEL JET WILL BE WELL TO THE NORTH OVER ONTARIO AND THE LL
JET LOSES ITS ORGANIZATION WHILE PIVOTING MORE WEST TO EAST AS IT
DRIFTS FROM WI OVER LAKE MI THROUGH THE NIGHT. SO NOT A LOT TO WORK
WITH TONIGHT AHEAD OF THE FRONT.

INCREASING CLOUD COVER AND AN INCREASED WIND FIELD TONIGHT WILL HELP
KEEP LOW TEMPERATURES QUITE MILD FROM ABOUT 55-60F.

LONG TERM...MONDAY THROUGH SATURDAY

MOISTURE AXIS (850-700 MB THETA-E RIDGE) WILL BE SLIDING THROUGH THE
CENTRAL GREAT LAKES TOMORROW...BUT LACK OF UPPER LEVEL FORCING (500
MB HEIGHTS ACTUALLY RISING DURING THE DAY) DRAWS CONCERN FOR
PRECIPITATION CHANCES...AS MID LEVEL FLOW BECOMES
WESTERLY...BECOMING PARALLEL WITH THE SURFACE COLD FRONT...WHICH
STILL LOOKS TO BE GETTING TIED UP AROUND THE SOUTHERN MICHIGAN
BORDER MONDAY NIGHT. THE 12Z NAM IS ADAMANT THERE WILL BE SHOWERS
AND THUNDERSTORMS TOMORROW AHEAD OF THE COLD FRONT...AS SURFACE
BASED CAPES FLARE UP TO AROUND 1500 J/KG BEFORE CONVECTIVE SCHEME
KICKS IN. HOWEVER...SURFACE/LOW LEVEL MOISTURE LOOKS TO BE OVERDONE
(FORECASTED LOWER 60 DEW PTS). IN FACT...EVEN AT THE PRESENT
TIME...NAM APPEARS TO BE A BIT OVERDONE OVER THE MIDWEST WITH LOW
LEVEL MOISTURE...AND THUS ENOUGH CONCERN TO HOLD POPS AT INHERITED
VALUE...LIKELY POPS. EVEN SO...MAJORITY OF THE DAY SHOULD BE
DRY...BUT TIMING DIFFICULTIES PRECLUDE SEPARATING MORNING/AFTERNOON
HOURS.  AIRMASS POTENTIAL IS FOR LOWER 80S TOMORROW BASED ON 850 MB
TEMPS IN THE LOWER TEENS...BUT CLOUDS AND CONVECTIVE ACTIVITY WILL
LIKELY BE SUFFICIENT HOLD MAXES IN THE MID 70S TO AROUND 80 DEGREES.

STALLED OUT FRONTAL BOUNDARY ALONG OR JUST SOUTH OF THE MICHIGAN
BORDER MONDAY NIGHT THROUGH TUESDAY NIGHT...LEADING TO GOOD LOW
LEVEL CONVERGENCE AS MOISTURE AXIS WRAPS AROUND THE LARGE BERMUDA
HIGH. SOME UPPER LEVEL IMPULSES EJECTING FROM FOUR CORNERS REGION OR
CONVECTIVE VORTS TO SUPPORT A GOOD CHANCE FOR CONVECTIVE ACTIVITY
DURING THIS TIME FRAME...RIDING ALONG THE FRONT. THUS...LIKELY POPS
TOWARD THE OHIO BORDER SEEM IN ORDER...BUT EXACT TIMING AND LOCATION
IS UNCERTAIN...AS NOCTURNAL LOW LEVEL JET WILL PROVIDE
OPPORTUNITIES...ALONG WITH PEAK HEATING/MAX INSTABILITY OF THE
AFTERNOON HOURS. BEING ON THE NORTH SIDE OF THE FRONT....LOW LEVEL
EASTERLY FLOW WILL KEEP TEMPS IN CHECK...HOLDING IN THE LOW/MID 60S
ON TUESDAY...WITH THE POTENTIAL TO BE EVEN BIT COOLER IF GOOD
COVERAGE OF SHOWER ACTIVITY DOES IN FACT MATERIALIZE.

FRONTAL BOUNDARY WILL LIFT NORTHWARD THROUGH THE LOCAL AREA WED/WED
NIGHT AS A WARM FRONT. A FEW SHOWERS CANNOT BE RULED OUT BUT THIS
PROCESS LOOKS TO BE MOSTLY DRY WITH NO UPPER SUPPORT FOR FORCING.
DEEPER LOW/MIDLEVEL SOUTHERLY FLOW DEVELOPS THURSDAY/FRIDAY BOOSTING
LOW-LEVEL TEMPS AND MOISTURE AGAIN. NO TRIGGER FOR PRECIPITATION
EVIDENT UNTIL FRIDAY WHEN THE UPPER RIDGE BEGINS TO BREAK DOWN.
CHANCE POPS FOR FRIDAY INTO NEXT WEEKEND.

MARINE...

MILD AIR IN PLACE OVER CENTRAL GREAT LAKES AHEAD OF A COLD
FRONT...WHICH WILL DROP SOUTH THROUGH THE REGION
TOMORROW...TRIGGERING SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS. WINDS WILL SHIFT FROM THE SOUTH-SOUTHWEST TO THE
NORTHWEST...BUT GENERALLY REMAIN UNDER 20 KNOTS. HIGH PRESSURE WILL
THEN BUILD INTO THE NORTHERN GREAT LAKES MONDAY NIGHT...LEADING TO
LIGHT WINDS TUESDAY AND WEDNESDAY.

&&

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

$$

AVIATION.....DG
SHORT TERM...DRK
LONG TERM....SF/DT
MARINE.......SF


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).


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