Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 302311
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
711 PM EDT SAT AUG 30 2014


.AVIATION...

//DISCUSSION...

SCT-BKN CONVECTION WILL CONTINUE TO SHIFT SOUTHWEST TO NORTHEAST
THROUGH THE NORTHERN CWA THIS EVENING ALONG A SURFACE TROUGH. THIS
ACTIVITY WILL GRADUALLY PROGRESS INTO THE SOUTHERN TERMINALS LATER
THIS EVENING INTO THE OVERNIGHT HOURS AS THIS BOUNDARY SETTLES TO
THE SOUTHEAST. COVERAGE MAY EVEN INCREASE...OR AT LEAST REMAIN
FAIRLY STEADY STATE AS LIFT/FORCING FROM A SHORTWAVE RIDING INTO
AREA ALONG THIS BOUNDARY OFFSET THE LOSS OF DAYTIME INSTABILITY.
ONCE SHRAS/TSRAS FADE IN/AROUND MIDNIGHT TO 2 AM...MVFR STRATUS AND
EVENTUALLY BR WILL OVERSPREAD THE AREA AS LOW LEVEL MOISTURE CONTENT
REMAINS ELEVATED.

FOR DTW...SCT SHRAS/TSRAS WILL WORK INTO THE AREA IN THE 01Z-03Z
TIME FRAME AND PERSIST IN THE VICINITY UNTIL 04Z-06Z OR SO.

//DTW THRESHOLD THREATS...

* MEDIUM CONFIDENCE OF CEILINGS AOB 5000 FEET OVERNIGHT INTO SUNDAY.

* MEDIUM CONFIDENCE IN TIMING THE ONSET OF THUNDERSTORMS DURING THE
  EVENING WITH LOWER CONFIDENCE IN THE END TIME OVERNIGHT.

&&

.PREV DISCUSSION...ISSUED 349 PM EDT SAT AUG 30 2014

SHORT TERM...THIS AFTERNOON AND TONIGHT

DESPITE ABUNDANT CLOUD COVER FOR MUCH OF THE DAY...TEMPERATURES HAVE
SLOWLY RISEN TO AROUND 80 ACROSS MUCH OF THE AREA...WITH A FEW LOW
80S ACROSS EXTREME SOUTHEAST MICHIGAN. THE ATMOSPHERE HAS BECOME
QUITE JUICY...AS EVIDENCED BY DEW POINTS AROUND 70 DEGREES AND THE
18Z KDTX RAOB SHOWING A PWAT OF 1.81 INCHES. IN ADDITION THE 18Z
SOUNDING SHOWS QUITE A BIT OF INSTABILITY WITH SB CAPES OF 1820 J/KG
AND GOOD SHEAR WITH 0-3 KM SRH OF 121 M2/S2. THESE INGREDIENTS
CERTAINLY SET THE STAGE FOR POSSIBLE SEVERE WEATHER LATER THIS
AFTERNOON INTO THIS EVENING...WITH DYNAMIC BOW ECHOES AND MINI
SUPERCELLS BEING THE MAIN THREAT. SEVERE WEATHER WOULD MAINLY BE IN
THE FORM OF WIND DAMAGE AS HIGH FREEZING LEVELS OF 14K FT DO NOT
HOLD MUCH PROMISE FOR HAIL.  IN ADDITION THE HIGH AMOUNT OF WATER
AND LONG SKINNY CAPE INDICATES HEAVY RAIN IS A CONCERN AS WELL AS AN
ISOLATED TORNADO GIVEN THE LOW LEVEL WIND SHEAR AND LOW LCL HEIGHTS
OF 3K FT.  HOWEVER THE 18Z SOUNDING DOES SHOW SOME CONCERNS WITH A
LAYER OF WARM AIR BETWEEN 850 AND 900 MB AND LESS THAN STELLAR MID
LEVEL LAPSE RATES BETWEEN 700 AND 500 MB. STORMS ARE STARTING TO
FIRE UPSTREAM WITH THE 850-700 MB THETA-E SURGE AND A SHORTWAVE
TRACKING THROUGH THE CENTRAL GREAT LAKES...HOWEVER THEY ARE NOT VERY
ROBUST AS THE SHORTWAVE SEEMS TO BE STRUNG OUT AND NOT PACKING MUCH
OF A PUNCH. WILL HAVE TO WATCH VERY CLOSELY TO SEE IF THE EXPECTED
THETA-E SURGE ACROSS THE WESTERN CWA AROUND 21Z IS SUFFICIENT TO
PRODUCE THUNDERSTORMS ACROSS THE AREA AS THE SHORTWAVE CONTINUES TO
TRACK EASTWARD LATE THIS AFTERNOON AND EARLY THIS EVENING.

IF THIS INITIAL SURGE DOES NOT MATERIALIZE A SHORTWAVE WILL TRACK
THROUGH NORTHERN LOWER MICHIGAN DURING THE OVERNIGHT HOURS...WHICH
WILL SUSTAIN ONGOING CONVECTION OR FIRE ELEVATED CONVECTION IF IT IS
NOT ALREADY ONGOING ACROSS THE AREA. ALTHOUGH PEAK HEATING WILL BE
OVER...HEAVY RAIN AND SOME WIND DAMAGE ARE POSSIBLE WITH THE
CONVECTION OVERNIGHT AS THE HI-RES RUNS DEPICT A LINE OF STORMS
TRACKING THROUGH OVERNIGHT.

LONG TERM... SUNDAY THROUGH NEXT FRIDAY

LOW PRESSURE WILL TRACK NORTH OF LAKE HURON TONIGHT AND INTO QUEBEC
BY MID-AFTERNOON SUNDAY. A COLD FRONT WILL DROP SOUTH DOWN THE
BACKSIDE OF THE SYSTEM...HOWEVER MODELS DIFFER WITH HOW FAR THIS
BOUNDARY PENETRATES INTO LOWER MICHIGAN. GFS/EURO DROP THE FRONT
INTO NORTHERN/CENTRAL LOWER MICHIGAN DURING THE EARLY PART OF THE
DAY...BEFORE LIFTING IT BACK NORTHWARD DURING THE EVENING AND
OVERNIGHT. 12Z NAM IS A LITTLE MORE AGRESSIVE WITH THE SOUTHWARD
PUSH...DROPPING THE FRONT DOWN INTO SOUTHEAST MICHIGAN BY
AFTERNOON/EVENING BEFORE IT LIFTS NORTHWARD OVERNIGHT. WITH THE NAM
BEING A LITTLE DEEPER WITH THE SURFACE LOW THAN THE OTHER
MODELS...WILL FAVOR THE GFS/EURO.

WEAKER COLD FRONT NOW WORKING ACROSS MICHIGAN WILL SETTLE TO OUR
SOUTH AND EAST BY 12Z SUN. THIS WILL ALLOW TEMPS TO COOL SLIGHTLY
FOR TOMORROW...HOWEVER DEWPOINTS WILL REMAIN HIGH AND WILL MAINTAIN
HEAT INDEX VALUES IN THE MID AND UPPER 80S. CONVECTIVE FORECAST FOR
TOMORROW IS TRICKY...WITH LINGERING MOISTURE AND INSTABILITY
FIGHTING DRIER AIR AND SUBSIDENCE WORKING IN AS SHORTWAVE RIDGING
BUILDS ALOFT. BEST POTENTIAL WILL BE SOUTH OF THE I-69 CORRIDOR
WHERE THE THETA-E RIDGE THAT SETTLED IN TODAY WILL STILL BE PRESENT
INTO THE AFTERNOON. MODEL FORECAST SOUNDINGS CONTINUE TO SHOW A
MODESTLY FAVORABLE ENVIRONMENT FOR A FEW STORMS TO FORM IN THIS
AREA...BUT WILL KEEP POPS LOW GIVEN POTENTIAL FOR A CAPPING
INVERSION TO DEVELOP UNDER THE UPPER RIDGE IN THE LATTER PART OF THE
AFTERNOON.

UPPER ENERGY OFF THE BRITISH COLUMBIA COAST WILL DIVE
INLAND...FORMING A BROAD TROUGH OVER THE CENTRAL CONUS BY MONDAY.
MODEL SHOW A COLD FRONT WITH SEVERAL AREAS OF LOW PRESSURE ALIGNED
ALONG IT STRETCHING FROM NORTHERN ONTARIO DOWN THROUGH THE SOUTHERN
PLAINS. THIS FRONT IS EXPECTED TO MOVE ACROSS SOUTHEAST MICHIGAN
MONDAY NIGHT...WITH THE LARGEST AREA OF SURFACE LOW PRESSURE PASSING
TO OUR NORTH OVER ONTARIO. PLUME OF WARMER AIR AND GULF MOISTURE
(MODEL PW VALUES BACK UP TO NEAR 2.0 INCHES) WILL SURGE BACK UP INTO
THE AREA LABOR DAY AHEAD OF THE UPPER TROUGH...ALLOWING A THETA-E
RIDGE TO EXTEND BACK INTO MICHIGAN. WARM FRONT IS EXPECTED TO LIFT
UP ACROSS SOUTHEAST MICHIGAN DURING THE AFTERNOON...PROVIDING AN
INITIAL CHANCE FOR SHOWERS AND THUNDERSTORMS TO DEVELOP BEFORE THE
COLD FRONT AND SURFACE TROUGH APPROACH FOR THE EVENING/OVERNIGHT.
HIGHEST PROBABILITIES FOR THUNDERSTORMS AND SEVERE WEATHER DURING
THE DAY WILL BE TO OUR WEST (SOUTHERN WISCONSIN/NORTHERN
ILLINOIS/LAKE MICHIGAN) WHERE 50-60 KNOT LOW-LEVEL JET...BEST
MID-LEVEL HEIGHTS FALLS...AND RIGHT ENTRANCE REGION FORCING WILL
COINCIDE WITH THE EASTWARD ADVANCING COLD FRONT. THIS ACTIVITY WOULD
THEN WORK ACROSS DURING THE EVENING. SEVERE POTENTIAL WILL DEPEND ON
HOW MUCH DAYTIME HEATING AND INSTABILITY ARE STILL AROUND WHEN IT
WORKS ACROSS. ATMOSPHERE OUT AHEAD OF ANY INCOMING STORMS FROM THE
WEST WILL BE WARM AND HUMID WITH TEMPS IN THE MID 80S AND DEWPOINTS
BACK UP NEAR 70...SUPPORT CAPE VALUES AROUND 2500 J/KG THROUGH 00Z.

BACKED OFF ON POPS A LITTLE FOR THE EARLY PART OF THE DAY
MONDAY...BUT DID KEEP LIKELY POPS FOR THE WHOLE AREA DURING THE
EVENING IN CASE THE COLD POOL FROM WHATEVER CONVECTIVE COMPLEX
DEVELOPS UPSTREAM OUTRUNS THE COLD FRONT. FORECAST SOUNDINGS ARE
MOST SUPPORTIVE OF A DAMAGING WIND AND LARGE HAIL THREAT. THIS IS IN
ADDITION TO VERY HEAVY RAINFALL. THE FRONT WILL WORK ACROSS DURING
THE LATE EVENING AND OVERNIGHT...CONTINUING A THREAT FOR RAIN AND
THUNDERSTORMS. SOME OF THIS RAIN COULD AGAIN BE HEAVY.

THETA-E AXIS WILL EXIT THE AREA ON TUESDAY AS THE UPPER TROUGH AXIS
WORKS ACROSS. CHANCES FOR SHOWERS/TSTORMS WILL CONTINUE ACROSS
EASTERN MICHIGAN DURING THE DAY BEFORE ENOUGH DRY AIR WORKS IN TO
BRING DRIER WEATHER. THIS WILL BRING COOLER TEMPERATURES...WITH
HIGHS IN THE UPPER 70S TO LOW 80S.

ON WEDNESDAY ZONAL FLOW ALOFT AND SURFACE HIGH PRESSURE WILL BE IN
PLACE. INTO THE EVENING...A PV ANOMALY LOOKS TO CREATE A SURFACE
DISTURBANCE THAT WILL BRING A CHANCE FOR SHOWERS AND THUNDERSTORMS
TO THE AREA IF THE WAVE COMES TO FRUITION. A BETTER CHANCE FOR
PRECIPITATION WILL COME WHEN THE RIGHT REAR ENTRANCE REGION OF THE
JET STREAM SETS UP OVER MICHIGAN. THIS WILL SET THE STAGE FOR LOW
PRESSURE AND AN ELONGATED TROUGH TO BRING STORMS TO THE REGION IN
THE FRI TO SAT TIMEFRAME.

MARINE...

GUSTY SOUTH TO SOUTHWEST WINDS WILL CONTINUE THIS AFTERNOON AND
EVENING AHEAD OF A LOW PRESSURE SYSTEM TRACKING THROUGH NORTHERN
MICHIGAN. WIND GUSTS ARE EXPECTED TO JUST BARELY EXCEED 20
KNOTS...WITH THE LARGEST WAVE HEIGHTS OF 2 TO 4 FEET EXPECTED OVER
SAGINAW BAY WHERE A FUNNELING EFFECT EXISTS. SHOWERS AND
THUNDERSTORMS WILL ALSO BE POSSIBLE THROUGH TONIGHT AS A WEAK COLD
FRONT WORKS ACROSS THE AREA. QUIETER WEATHER IS EXPECTED ON
SUNDAY...ALTHOUGH A FEW SHOWERS AND THUNDERSTORMS WILL STILL BE
POSSIBLE. ANOTHER COLD FRONT WILL APPROACH FOR MONDAY...BRINGING
GOOD CHANCES FOR SHOWERS AND THUNDERSTORMS ONCE AGAIN...SOME OF THEM
COULD BE STRONG TO SEVERE.

&&

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

&&

$$

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


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






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