Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 010400
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1200 AM EDT MON SEP 1 2014


.AVIATION...

WITH LIGHT WINDS OF UNDER 5 KNOTS EXPECTED OVERNIGHT AND PLENTY OF
RESIDUAL LOW LEVEL MOISTURE...EXPECT FOG TO DEVELOP LATE TONIGHT AND
PERSIST INTO MONDAY MORNING. SOME PATCHES OF IFR STRATUS WILL MOST
LIKELY ACCOMPANY THIS FOG AT TIMES. THIS LOW LEVEL MOISTURE WILL
ERODE BY MID/LATE MORNING WITH SHRA/TSRA CHANCES THEN INCREASING BY
LATE AFTERNOON/EVENING AS A SHORTWAVE TROUGH PROGRESSES INTO THE
GREAT LAKES. TIMING/COVERAGE OF THIS ACTIVITY REMAINS DIFFICULT TO
FORECAST AND WILL LEAVE A SEVERAL HOUR PROB30 GROUP TO DENOTE THE
POTENTIAL FOR THUNDER.

//DISCUSSION...

//DTW THRESHOLD THREATS...

* LOW CONFIDENCE IN CEILINGS BELOW 5000 FEET LATE TONIGHT INTO
MONDAY MORNING.

* LOW CONFIDENCE IN THUNDERSTORM TIMING AND COVERAGE LATE MONDAY.

&&

.PREV DISCUSSION...ISSUED 341 PM EDT SUN AUG 31 2014

SHORT TERM...THROUGH TONIGHT

UPPER WAVE HAS MOVED FROM NORTHERN MICHIGAN INTO GEORGIAN BAY AND
EASTERN ONTARIO THIS AFTERNOON...WITH SURFACE LOW PRESSURE NOW
CENTERED OVER WESTERN QUEBEC. SATELLITE AND SURFACE OBSERVATIONS
THIS MORNING WERE INDICATIVE OF A WEAK COLD FRONT SETTLING DOWN INTO
CENTRAL LOWER MICHIGAN (MORE LOWER CLOUDS...WEST-NORTHWEST WIND
SHIFT) EARLY TODAY...BUT THIS HAS SINCE WASHED OUT AS
EXPECTED...WITH SATELLITE IMAGERY NOT REALLY SHOWING SIGNS OF ANY
ENHANCED CONVERGENCE OVER SOUTHEAST MICHIGAN NOW. TRENDS IN
SATELLITE AND RADAR SUPPORT MODEL IDEA OF THE THETA-E RIDGE TRAILING
YESTERDAYS SYSTEM CONTINUING TO SHIFT SOUTH AND EAST OF THE AREA
THIS AFTERNOON. CLOUDS HAVE BEEN SLOWLY BREAKING/ERODING THROUGH THE
DAY AS DRIER AIR IN THE MID LEVELS SEEN ON WATER VAPOR IMAGERY MIXES
DOWN. AN ISOLATED SHOWER OR THUNDERSTORM STILL REMAINS POSSIBLE
TODAY SOUTH OF I-69 BEFORE SHORTWAVE RIDGING TAKES HOLD THIS
EVENING...BUT COVERAGE IS EXPECTED TO REMAIN LOW. JUST ABOUT EVERY
MODEL RANGING FROM HI-RES TO GLOBAL CONTINUES TO SHOW LIMITED
CONVECTION FIRING OVER SOUTHEAST MICHIGAN THIS AFTERNOON. GFS/NAM
SOUNDINGS WERE A LITTLE UNDERDONE WITH THEIR INITIALIZATION OF THE
CAP ON THE KDTX SOUNDING AT 12Z THIS MORNING. WHILE SPC
MESO-ANALYSIS SHOWS ABOUT 1500 J/KG OF CAPE FROM I-69
SOUTH...SUSPECT THE MID-LEVEL CAP IS A LITTLE MORE HEALTHY THAT
MODELS SUGGEST BASED ON VISUAL AND SATELLITE TRENDS. THERE WAS
HOWEVER A STORM THAT DEVELOPED ALONG THE LAKE BREEZE BOUNDARY OVER
SOUTHWEST LOWER JUST BEFORE 3 PM...AND THIS DOES SUGGEST SOME
INSTABILITY COULD BE TAPPED INTO...AND SUPPORTS LEAVING SOME LOW
MENTION OF POPS IN THE FORECAST.

DIURNALLY ENHANCED CU FIELD WILL ERODE OVERNIGHT AS HEATING CEASES
AND SUBSIDENCE FROM SHORTWAVE RIDGING ENCOMPASSES THE AREA. NEARLY
CALM WINDS OVERNIGHT AND MOSTLY CLEAR SKIES WILL PROMOTE FAVORABLE
RADIATIONAL COOLING OVERNIGHT. ATMOSPHERE WILL STILL REMAIN WARM AND
HUMID HOWEVER...WITH DEWPOINTS REMAINING WELL IN THE 60S. EXPECT TO
SEE SOME FOG DEVELOP AFTER MIDNIGHT...WITH POTENTIAL FOR SOME DENSE
FOG TO DEVELOP TOWARDS SUNRISE. WILL HAVE TO MONITOR TRENDS
OVERNIGHT. MINS SHOULD REMAIN MILD IN THE 60S.

LONG TERM...MONDAY THROUGH NEXT SATURDAY

AFTER A QUIET START TO LABOR DAY...THINGS LOOK TO TAKE A TURN FOR
THE WORSE DURING THE AFTERNOON AND EVENING HOURS ACROSS SOUTHEAST
MICHIGAN. THE DYNAMICS CERTAINLY SET THE STAGE FOR A POSSIBLE SEVERE
EVENT WITH A 120 KNOT 250 MB JET STREAM DEVELOPING OVER THE NORTH
CENTRAL GREAT LAKES TO THE EAST OF AN UPPER LEVEL TROUGH...WITH
PLENTY OF UPPER LEVEL DIVERGENCE OVER SOUTHERN LOWER MICHIGAN MONDAY
AFTERNOON AND EVENING. IN ADDITION A FAIRLY IMPRESSIVE PIECE OF
SHORTWAVE ENERGY WILL TRACK THROUGH THE CENTRAL GREAT LAKES DURING
THIS PERIOD...WHICH CAN CURRENTLY BE SEEN EMERGING OUT OVER THE
CENTRAL PLAINS THIS AFTERNOON. AT 850 MB AN IMPRESSIVE 40 KNOT LOW
LEVEL JET DEVELOPS OVER THE CENTRAL GREAT LAKES. A SURFACE LOW WILL
TRACK THROUGH SOUTHERN CANADA...BRINGING A COLD FRONT THROUGH THE
CENTRAL GREAT LAKES MONDAY NIGHT. WITH DAYTIME HIGHS GETTING INTO
THE MID 80S...SB CAPE VALUES ARE EXPECTED TO GET TO AROUND 2000 J/KG
DURING PEAK HEATING WITH 0-6 KM BULK SHEAR VALUES OF 30 TO 35 KNOTS.

DESPITE THE GOOD DYNAMICS...IMPRESSIVE INSTABILITY AND SHEAR THERE
ARE SOME CONCERNS REGARDING THE SEVERE POTENTIAL ON LABOR DAY.
MAINLY THE MID LEVEL LAPSE RATES BEING LESS THAN IDEAL DURING MUCH
OF THE AFTERNOON WITH A FAIRLY UNIDIRECTIONAL WIND PROFILE. HOWEVER
THE ENVIRONMENT IS FAR FROM HOSTILE...THEREFORE EVEN IF WE ARE
UNABLE TO GENERATE SURFACE BASED CONVECTION ON OUR OWN...THERE IS
THE POSSIBILITY OF AN MCS TO TRACK THROUGH WHICH WOULD BE MOVING
INTO THIS UNSTABLE ENVIRONMENT. THEREFORE INHERITED LIKELY POPS
STILL LOOK REASONABLE GIVEN THE ABOVE CONCERNS. SEVERE WEATHER WISE
THE UNIDIRECTIONAL WIND PROFILE LENDS ITSELF TO LINE SEGMENTS...WITH
DAMAGING WINDS BEING THE MAIN THREAT AS FREEZING LEVELS OF 13-14K FT
DO NOT LEND THEMSELVES TO MUCH IN THE WAY OF HAIL. THE UPGRADE TO
SLIGHT RISK IN THE DAY 2 SPC OUTLOOK LOOKS SOLID BASED ON THIS
EVIDENCE. THERE WILL BE A LOT OF MOISTURE AS PWATS APPROACH 2 INCHES
WITH A DEEP LAYER OF MOISTURE AND LONG SKINNY CAPES. THIS MAY CAUSE
HEAVY RAIN AND LOCALIZED FLOODING WITH THE STRONGEST STORMS THAT
TRACK THROUGH MONDAY AFTERNOON AND EVENING.

THE COLD FRONT ITSELF WILL PASS THROUGH EARLY ON TUESDAY...TAKING
THE SHOWER AND THUNDERSTORM ACTIVITY EAST OF THE AREA BY THE
AFTERNOON HOURS. BEHIND THE FRONT HIGH PRESSURE WILL BUILD IN ACROSS
THE SOUTHERN GREAT LAKES AS MID LEVEL RIDGING USHERS IN A QUIET
PERIOD ACROSS SOUTHEAST MICHIGAN FROM TUESDAY AFTERNOON AND NIGHT.

AS HIGH PRESSURE SLIDES TO THE EAST ON WEDNESDAY...A DYNAMICALLY
EVOLVING LOW PRESSURE SYSTEM WILL BE FORMING IN THE CENTRAL US. AN
OPEN 500 MB WAVE AND STRONG VORTICITY ANOMALY WILL PUSH ACROSS THE
COUNTRY AND HELP STRENGTHEN LOW PRESSURE. THIS LOW WILL DRAG A COLD
FRONT ACROSS MICHIGAN ON FRIDAY...WHICH WILL BE THE MAIN
WEATHER-MAKER FOR THE EXTENDED PERIOD. WARM FRONTAL CONVECTIVE
ACTIVITY IS POSSIBLE THURSDAY BEFORE THE COLD FRONT ROLLS THROUGH ON
FRIDAY.

MARINE...

MARINE CONDITIONS WILL CONTINUE TO BE FAVORABLE DURING THE OVERNIGHT
HOURS. LABOR DAY WILL THEN START OUT PLEASANT BUT WILL LIKELY BECOME
STORMY WITH SOME SEVERE WEATHER POTENTIAL DURING THE AFTERNOON
THROUGH MONDAY NIGHT AS A COLD FRONT MOVES THROUGH LAKE HURON AND
LOWER MICHIGAN. HIGH PRESSURE WILL BUILD INTO THE REGION BEHIND THIS
FRONT ON TUESDAY...WHICH WILL REMAIN IN CONTROL OF THE WEATHER
THROUGH THURSDAY.

&&

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

&&

$$

AVIATION.....DG
SHORT TERM...HLO
LONG TERM....KURIMSKI/MM
MARINE.......KURIMSKI


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





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