National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KDTX 221436
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1036 AM EDT WED MAY 22 2013

.UPDATE...

-- Changed Discussion --
OVERCAST CONDITIONS ACROSS THE REGION HAVE LIMITED HEATING AND
DESTABILIZATION EARLY TODAY...BUT THERE ARE STILL SEVERAL OTHER
FACTORS TO KEEP SEVERE WEATHER MENTION IN THE FORECAST TODAY.
VISIBLE SATELLITE AND SFC OBS SHOW THE COLD FRONT AS A SHARP
CLEARING LINE AND DROP IN DEWPOINTS ROUGHLY ALONG THE MISSISSIPPI
RIVER FROM WI TO TN. EAST OF THE FRONT FROM ORD TO CVG THERE IS
ANOTHER CLEARING FEATURE THAT IS NEAR THE LOCATION OF A VORTICITY
MAXIMUM/SHORTWAVE ENERGY THAT IS BEING EJECTED NORTHEAST FROM THE
LOWER MS VALLEY. LOCAL HI-RES MODELS AND 12Z NAM SHOWING INITIATION
IN THE SE MI AREA AROUND 18-19Z AHEAD OF THE COLD FRONT/TRIPLE POINT
WITH SEVERE THREATS COMING TO AN END BY 00Z. ONE CAVEAT TO THAT IS
POSSIBLE ADDL CONVECTION IN THE SAGINAW VALLEY WHERE THE TRAILING
SFC LOW WILL BE CO-LOCATED WITH ANOTHER SHORTWAVE AND WOULD HAVE
BETTER UPPER LEVEL DIVERGENCE DUE TO JET ORIENTATION.

SMALL ADJUSTMENTS WERE MADE TO LOWER MAX TEMPS AND ALSO OVERNIGHT
POPS AS THE ENVIRONMENT WILL BE RECOVERING BEFORE NEXT FROPA
EARLY THURS.
-- End Changed Discussion --

&&

.AVIATION...
-- Changed Discussion --
ISSUED 727 AM EDT WED MAY 22 2013

//DISCUSSION...

SCATTERED SHOWERS WILL AFFECT THE TAF SITES EARLY THIS MORNING...AS
EVIDENCED BY RADAR REFLECTIVITY. ALTHOUGH A FEW RUMBLES OF THUNDER
ARE POSSIBLE...THEIR COVERAGE EARLY THIS MORNING IS TOO ISOLATED TO
PUT IN THE TAFS. MORE WIDESPREAD SHOWERS AND THUNDERSTORMS ARE
EXPECTED TO ARRIVE LATER THIS MORNING AND INTO THE AFTERNOON AS AN
UPPER LEVEL SHORT WAVE LIFTS INTO THE REGION FROM THE SOUTHWEST.
CONSIDERABLE UNCERTAINTY EXITS AT THIS TIME WITH RESPECT TO BOTH
TIMING AND COVERAGE OF THUNDERSTORMS THIS AFTERNOON. HOWEVER THERE
IS ENOUGH CONFIDENCE TO PLACE A TEMPO GROUP IN MOST OF THE TAF SITES
THIS AFTERNOON REPRESENTING THE BEST WINDOW FOR THUNDERSTORMS.
FURTHER NORTH AT MBS THUNDERSTORM PROBABILITIES ARE LOWER DUE TO
LOWER INSTABILITY VALUES...THEREFORE WILL CONTINUE TO LEAVE THUNDER
OUT. LATER TONIGHT THERE SHOULD BE A BREAK IN THE SHOWER ACTIVITY AS
THE SHORTWAVE TRACKS EAST...HOWEVER RAIN IS EXPECTED TO CONTINUE AT
MBS AS THE WARM FRONT STARTS TO SINK SOUTH AS A COLD FRONT OVER THE
SAGINAW VALLEY.

FOR DTW...SCATTERED SHOWERS ARE EXPECTED TO TRANSITION TO MORE
WIDESPREAD ACTIVITY LATER THIS MORNING WITH THUNDERSTORMS POSSIBLE
LATER THIS AFTERNOON AND INTO THE EVENING HOURS. BEST CHANCE FOR
THUNDER IS IN THE 17-21Z TIME FRAME...HOWEVER THUNDER IS POSSIBLE
PRETTY MUCH ALL DAY.

//DTW THRESHOLD THREATS...

* MEDIUM CONFIDENCE IN TIMING AND COVERAGE OF THUNDERSTORMS THIS
  AFTERNOON.
-- End Changed Discussion --

&&

.PREV DISCUSSION...ISSUED 337 AM EDT WED MAY 22 2013

SHORT TERM...TODAY AND TONIGHT

THE LARGE MID LEVEL CLOSED OFF LOW THAT HAS BEEN PARKED OVER THE
NORTHERN PLAINS WILL MAKE ITS WAY EAST TODAY AND TONIGHT. THE LOW
WILL BEGIN TO MERGE WITH A LARGER AREA OF LOW PRESSURE OVER HUDSON
BAY AND TRANSITION FROM A CLOSED OFF LOW TO A POSITIVELY TILTED
TROUGH AS IT MAKES ITS WAY TOWARD THE WESTERN GREAT LAKES
TODAY...AND EVENTUALLY OVER THE CENTRAL GREAT LAKES TONIGHT. BEFORE
THE LOW TRACKS OVER THE CENTRAL GREAT LAKES...A PIECE OF SHORTWAVE
ENERGY CURRENTLY SPINNING OVER EASTERN OKLAHOMA WILL LIFT NORTHEAST
THROUGH THE CENTRAL GREAT LAKES THIS AFTERNOON. THIS SHORTWAVE WILL
TRACK THROUGH AS THE JET STREAM LIFTS NORTH...PUTTING SOUTHEAST
MICHIGAN IN THE RIGHT ENTRANCE REGION PRODUCING UPPER LEVEL
DIVERGENCE. SOUTHEAST MICHIGAN WILL REMAIN IN THE WARM SECTOR
TODAY...AS MUCAPE VALUES CLIMB TO 1000 TO 1500 J/KG. IN ADDITION TO
THE INSTABILITY...BULK SHEAR VALUES AROUND 40 KNOTS  WILL LEAD TO AN
INCREASED THREAT FOR DAMAGING WINDS AND LARGE HAIL. ACROSS THE FAR
SOUTHEASTERN CWA...TURNING IN THE LOWEST LEVELS OF THE ATMOSPHERE
WILL LEAD TO AN ENHANCED THREAT FOR ISOLATED TORNADOES DEEPER IN THE
WARM SECTOR WITH 0-1 KM BULK SHEAR VALUES OF 25 KNOTS AND 200 J/KG
OF 0-3 KM CAPE. OVERALL THE SEVERE WEATHER THREAT TODAY LOOKS A BIT
BETTER THAN YESTERDAY GIVEN THE DYNAMICS INVOLVED WITH THE MAIN
CONVECTIVE MODE EXPECTED TO BE SEVERAL ROUNDS OF MESOSCALE
CONVECTIVE SYSTEMS TRACKING THROUGH THE CENTRAL GREAT LAKES THIS
AFTERNOON AND INTO THE EVENING HOURS. THE AREA REMAINS IN THE SLIGHT
RISK FOR SEVERE WEATHER PER THE SPC SWODY1 DISCUSSION WHICH LOOKS
SOLID GIVEN THE ABOVE FACTORS.

WITH THE AREA STILL IN THE WARM SECTOR...HIGH TEMPERATURES ARE
EXPECTED TO HIT 80 OR BETTER SOUTH OF M-59...WITH MID TO UPPER 70S
ACROSS THE NORTH WITH MORE CLOUD COVER AND CLOSER PROXIMITY TO THE
WARM FRONT.

THE THREAT FOR SHOWERS AND THUNDERSTORMS CONTINUES OVERNIGHT AS THE
AFOREMENTIONED TROUGH APPROACHES THE CENTRAL GREAT LAKES AND THE
SURFACE LOW TRACKS ALONG THE WARM FRONT...TURNING IT INTO A COLD
FRONT AS IT SLOWLY SINKS SOUTH. WITH THE LOSS OF INSTABILITY AND
SUPPORT FROM THE JET STREAM...SEVERE WEATHER THREAT WILL DIMINISH
MARKEDLY AFTER MIDNIGHT...WITH SHOWERS AND ISOLATED THUNDERSTORMS
EXPECTED LATE TONIGHT. WITH THE COLD FRONT DRAPED OVER THE CENTER OF
THE CWA...LOWS WILL RANGE FROM AROUND 50 ACROSS THE NORTH TO AROUND
60 ACROSS THE FAR SOUTH...SOUTH OF THE COLD FRONT. RAIN CHANCES WILL
MAINLY BE ALONG AND BEHIND THE FRONT...WITH THE BEST CHANCES ACROSS
THE NORTH AND A DIMINISHED CHANCE LATE TONIGHT ACROSS THE SOUTHERN
CWA AHEAD OF THE COLD FRONT.

LONG TERM...THURSDAY THROUGH TUESDAY

BY THURSDAY MORNING...THE CUTOFF LOW THAT SAT OVER THE NORTHERN
PLAINS FOR THE LAST SEVERAL DAYS WILL GET ABSORBED BY A NORTHERN
STREAM TROUGH DIGGING SOUTHWARD THROUGH MANITOBA/ONTARIO. A COLD
FRONT WILL PASS THROUGH LOWER MI THURSDAY AFTERNOON THEN THE UPPER
LEVEL TROUGH AXIS WILL PASS THROUGH MI THURSDAY EVENING RIGHT BEHIND
A STRONGER COLD FRONT. THIS FRONT WILL USHER IN A MUCH COLDER AND
DRIER AIRMASS AS A LARGE AND STRONG CANADIAN SFC HIGH PRESSURE
SYSTEM BUILDS SOUTHWARD THROUGH THE GREAT LAKES AND TOWARD THE EAST
COAST. THIS WILL PUT AN END TO THE PRECIP CHANCES FOR SE MI FOR A
WHILE...AT LEAST THROUGH THE HOLIDAY WEEKEND.

THURSDAY LOOKS TO START OFF WET WITH A DRYING/COOLING TREND THROUGH
THE DAY AS THE FIRST COLD FRONT DROPS THROUGH THE STATE. SHOWERS
WILL PERSIST THROUGH THE EVENING AS MODELS IN GOOD AGREEMENT WITH A
BAND OF HIGHER THETA E WRAPPING AROUND THE ELONGATED SFC LOW OVER
SOUTHERN ONTARIO/QUEBEC. THERE IS A SMALL RISK OF THUNDERSTORMS FOR
EXTREME SOUTHERN MI JUST SOUTH OF THE COLD FRONT AS MODELS CONTINUE
TO INDICATE SOME INSTABILITY ALONG THE FRONT. FOR THE MOST PART WE
WILL SHOWERS WITH A CHANCE OF THUNDER THROUGH THE MORNING...THEN
AFTER THE FROPA SHOWERS WILL TAPER OFF THROUGH THE LATE EVENING FROM
NW TO SE AS THE SECOND COLD FRONT DROPS THROUGH. PWATS WILL DROP
FROM ABOUT 1.1 INCHES THURSDAY MORNING TO 0.25 INCHES FRIDAY
MORNING. LIKEWISE...850MB TEMPS WILL DROP FROM AROUND +10C TO AROUND
0C FOR THE SAME PERIODS. THURSDAYS HIGH TEMPS WILL OCCUR EARLY IN
THE DAY AHEAD OF THE FIRST COLD FRONT. TEMPS WILL FALL THROUGH THE
REST OF THE DAY AND NIGHT. CLOUDS SHOULD CLEAR OUT FAIRLY QUICKLY
AFTER MIDNIGHT THURSDAY NIGHT ALLOWING TEMPS TO DROP OFF INTO THE
UPPER 30S.

FOR FRIDAY AND BEYOND THE STORY BECOMES DRY AND COOL WITH A SLIGHT
WARMING TREND. FRIDAY NIGHT WILL AGAIN BE FAIRLY COOL...DIPPING DOWN
TO AROUND 40 WITH HIGHS ONLY AROUND 60. BUT AS TROUGHS SET UP OVER
BOTH COASTS...AMPLIFICATION OF A RIDGE ACROSS THE CENTRAL CONUS WILL
LEAD TO HEIGHTS BUILDING SLOWLY THROUGH THE WEEKEND. MODEL SOLUTIONS
START TO STRAY FROM EACH OTHER EARLY NEXT WEEK IN HOW THEY WANT TO
HANDLE THE NEXT SYSTEM BUT CONFIDENCE IS PRETTY GOOD THAT THE STRONG
SFC RIDGE WILL KEEP THE WARM FRONT TO OUR SOUTH AND KEEP US DRY
UNTIL TUESDAY.

MARINE...

MODEST SOUTHERLY WINDS WILL REMAIN IN PLACE TODAY AND TONIGHT AS A
LOW PRESSURE SYSTEM SLOWLY LIFTS EAST OUT OF THE UPPER MIDWEST. A
WARM AND UNSTABLE ENVIRONMENT WILL BRING A CHANCE OF THUNDERSTORMS
DURING THIS TIME. LINGERING DENSE FOG IS EXPECTED ACROSS NORTHERN
LAKE HURON EARLY THIS MORNING...BEFORE MIXING OUT. EXPANDED THE
DENSE FOG ADVISORY A SEGMENT SOUTH GIVEN LAND AND SHIP OBSERVATIONS
ACROSS THE NORTHERN LAKE HURON REGION. WINDS WILL SHIFT TO THE NORTH
ACROSS ALL WATERS BY THURSDAY MORNING...AS THE LOW AND TRAILING COLD
FRONT PUSH OFF TO THE EAST. THESE CONDITIONS WILL PUSH WINDS AND
WAVES CLOSE TO SMALL CRAFT CRITERIA ON THURSDAY OVER LAKE HURON.
DESPITE THE PROXIMITY TO HEADLINE CRITERIA...WILL HOLD OFF ON
HEADLINES FOR THURSDAY AT THIS TIME. HIGH PRESSURE WILL BUILD IN
ACROSS THE GREAT LAKES ON FRIDAY...BRINGING QUIET WEATHER AND
COOLER TEMPERATURES TO THE REGION.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
-- End Changed Discussion --

&&

$$

UPDATE.......MM
AVIATION.....KURIMSKI
SHORT TERM...KURIMSKI
LONG TERM....DRK
MARINE.......KURIMSKI


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