Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 190351
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1151 PM EDT FRI JUL 18 2014


.AVIATION...

//DISCUSSION...

CEILINGS WILL LOWER TO LOW VFR SHORTLY AFTER SUNRISE AS LOW PRESSURE
LIFTS ACROSS THE SOUTHERN GREAT LAKES. DETROIT METRO IS STILL
FORECAST TO BE ON THE WESTERN FRINGE OF THE RAIN SHIELD...THE EDGE
OF WHICH IS CURRENTLY LOCATED OVER NW OHIO. EVEN IF THE BULK OF THIS
ACTIVITY REMAINS EAST OF THE AREA, SOME NW EXPANSION OF COVERAGE IS
EXPECTED DUE TO DIURNAL HEATING. EXPECTATIONS FOR COVERAGE STILL
WARRANT JUST A TEMPO GROUP. HOWEVER, IF SOME SOME WESTWARD
DEVELOPMENT IS OBSERVED WITHIN THE NEXT FEW HOURS, PRECIP MAY MOVE
IN A BIT EARLIER WITH A LITTLE BETTER COVERAGE. CEILINGS ARE
GENERALLY EXPECTED TO BE LOW VFR, BUT COULD FALL INTO THE HIGH MVFR
RANGE. WINDS WILL REMAIN ON THE LIGHT SIDE OUT OF THE EAST.


//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CIGS BELOW 5KFT.

&&

.PREV DISCUSSION...ISSUED 352 PM EDT FRI JUL 18 2014

SHORT TERM... REST OF TODAY THROUGH TONIGHT

A LARGE EXPANSE OF SURFACE HIGH PRESSURE OVER THE GREAT LAKES WILL
FINISH OFF THE AFTERNOON WITH DRY AND PLEASANT WEATHER THAT WILL
LAST THROUGH MOST OF TONIGHT. MAX TEMPS IN THE UPPER 70S MOST
LOCATIONS REMAIN A CATEGORY BELOW NORMAL BUT CONTINUE THE WARMING
TREND THAT STARTED YESTERDAY COMING OFF THE WELL BELOW NORMAL
READINGS FROM EARLIER IN THE WEEK. THICKENING HIGH CLOUDS OVER TOP
OF FAIR WEATHER CUMULUS LIKELY PREVENTED SURFACE HEATING THAT WOULD
HAVE BROUGHT MORE THAN ONE OR TWO LOCATIONS TO 80 OR HIGHER.

THE SURFACE HIGH WILL BECOME CENTERED OVER THE NEW ENGLAND STATES
TONIGHT AS THE NEXT LOW PRESSURE SYSTEM MOVES INTO THE OHIO VALLEY
FROM THE TENNESSEE VALLEY. THIS SYSTEM WILL BRING CONTINUED
THICKENING AND LOWERING CLOUDS DURING THE NIGHT WHICH WILL KEEP MIN
TEMPS ON THE MILD SIDE OF GUIDANCE AND CERTAINLY WARMER THAN THE
LAST FEW NIGHTS.

THE BULK CLOUD...TEMPERATURE...AND WIND FEATURES COMBINE FOR BENIGN
CONDITIONS THROUGH THE NIGHT WITH THE PROSPECTS FOR RAIN THE MORE
DELICATE PART OF THE FORECAST MOSTLY IN TERMS OF TIMING. SO FAR
DURING THE DAY...MEASURABLE RAIN APPEARS ON OR SLIGHTLY AHEAD OF
MODEL SCHEDULE NEARLY REACHING THE DAYTON TO COLUMBUS AREA BY MID
AFTERNOON. THIS IS WHERE THE LEADING EDGE OF MID LEVEL MOISTURE
TRANSPORT IS COMBINING WITH MODERATE MID LEVEL SHORT WAVE FORCING
AND UPPER JET SUPPORT. MODEL SOLUTIONS THEN DEPICT THE WAVE SLIDING
TO A POSITION NEARLY OVER TOLEDO BY 12Z. THE NORTHWARD DIRECTED
MOISTURE TRANSPORT AND DYNAMIC FORCING IS EXPECTED TO PRODUCE A
RAPID MOISTENING OF THE PROFILE OVER THE EASTERN TIER OF COUNTIES IN
SE MICHIGAN SOUTH OF PORT HURON. THIS IS WHERE THE BEST CHANCE OF
RAIN WILL OCCUR BEFORE SUNRISE SATURDAY MORNING...BUT UNCERTAINTY IN
THE TIMING OF SATURATION FAVORS A CHANCE POP OVER ANYTHING MORE
AGGRESSIVE FOR NOW.

LONG TERM...SATURDAY THROUGH NEXT FRIDAY

WATER VAPOR IMAGERY HAS SHOWN THE UPPER SHORTWAVE OVER SOUTHERN
INDIANA STRENGTHENING TODAY AS IT LIFTS NORTHEAST. THIS HAS OCCURRED
AS THE WAVE BECOME PLACED IN THE RIGHT ENTRANCE REGION OF A JET
STREAK LIFTING THROUGH THE EASTERN HALF OF THE CONUS...AND AGREES
WELL WITH 18.00Z AND 12Z MODEL FORECASTS THAT HAD THIS SYSTEM
DEEPENING. WITH A DEEPER SYSTEM EXPECTED...CONCUR WITH RECENT MODEL
TRENDS OVER THE PAST 24 HOURS WHICH SHIFTED THE TRACK MORE TO THE
NORTH AND WEST...AND NOW TRACK THE CENTER OF THE MID-LEVEL
CIRCULATION ACROSS EXTREME SOUTHEAST MICHIGAN. GOOD DEFORMATION ON
THE NORTHWEST FLANK OF THE SYSTEM...UP THROUGH 700MB...LOOKS TO
GLIDE ACROSS SOUTHEAST MICHIGAN TOMORROW MORNING AND AFTERNOON. THIS
COMBINED WITH A DECENT PUSH OF MOISTURE FROM THE SOUTH AND EAST (PW
VALUES UP TO 1.4 INCHES OVER THE EASTERN HALF OF THE FORECAST AREA)
AS A SOUTHEASTERLY LOW-LEVEL JET DEVELOPS OVER EASTERN ONTARIO AND
LAKE HURON WARRANT A FURTHER INCREASE IN PRECIPITATION CHANCES FOR
TOMORROW. HIGHEST CHANCES...NOW RANGING FROM LIKELY TO CATEGORICAL
POPS...REMAIN ROUGHLY EAST OF A LINE FROM ANN ARBOR TO HARBOR BEACH.
WE SHOULD SEE A FAIRLY GOOD COVERAGE OF RAIN SHOWERS IN THIS
AREA...WHERE THE DEFORMATION COINCIDES WITH MID-LEVEL PVA...MODEST
LOW-MID LEVEL INSTABILITY...AND GOOD MOISTURE ADVECTION. THUNDER
CHANCES REMAIN FAIRLY LOW WITH SB CAPE VALUES ONLY TOPPING OUT
AROUND 500 J/KG...BUT DID INCLUDE AT LEAST SOME MENTION OF THUNDER.
CLOUDS AND RAIN WILL HOLD BACK TEMPERATURES TOMORROW...KEPT LOW/MID
70S FOR HIGHS OVER MOST OF THE AREA...WITH NEAR 80 OVER THE SAGINAW
VALLEY WHERE DRIER WEATHER AND LESS CLOUDS ARE EXPECTED. RAIN WILL
BEGIN TO TAPER OFF FROM SOUTH TO NORTH DURING THE AFTERNOON AS THE
SYSTEM LIFTS WEST-NORTHWEST INTO ONTARIO. MOSTLY DRY WEATHER IS THEN
EXPECTED OVERNIGHT.

THE LARGE DOME OF SURFACE HIGH PRESSURE OFF THE NEW ENGLAND COAST
WILL THEN EXPAND BACK INTO THE GREAT LAKES SUNDAY. DESPITE
OCCASIONAL MODEL RUNS KICKING OUT SOME QPF OVER THE AREA...FORECAST
SOUNDINGS LOOK FAIRLY DRY AND SHOW A FAIRLY HEALTHY MID-LEVEL CAP
DURING THE AFTERNOON. THIS JUSTIFIES A DRY FORECAST WITH JUST SOME
CU DEVELOPING WITH MOISTURE LEFT OVER BEHIND THE UPPER LOW. MAX
TEMPERATURES WILL WARM INTO LOW 80S SUNDAY AFTERNOON AS H850
TEMPERATURES BEGIN A SLOW CLIMB EXPECTED TO LAST INTO MID-WEEK.

EXTENDED FORECAST...MONDAY THROUGH THURSDAY...TEMPERATURES WILL BE
ON THE RISE TO BEGIN THE WORK WEEK. WARM TEMPS WILL PEAK ON TUESDAY
WITH HIGHS IN THE MID TO UPPER 80S. IT IS A RELATIVELY SHORT LIVED
HEATWAVE OF SORTS...AS TEMPS FALL BACK INTO THE MID 70`S BY THE END
OF THE WEEK...HOWEVER...THE SOUTHERLY FLOW THAT BRINGS IN THE WARMER
TEMPERATURES WILL ALSO USHER IN MOISTURE. THIS SHOULD TRIGGER A MORE
ACTIVE WEATHER SITUATION BEGINNING MID-WEEK.

MARINE...

A WEAK LOW PRESSURE SYSTEM WILL TRACK ACROSS FAR SOUTHEAST MICHIGAN
SATURDAY. THIS WILL BRING A GOOD CHANCE FOR RAIN TO SOUTHERN LAKE
HURON...LAKE ST CLAIR...AND LAKE ERIE. RAIN SHOWERS WILL MOVE INTO
THE SOUTHERN GREAT LAKES LATE TONIGHT...THEN SPREAD NORTHWARD ON
SATURDAY. A FEW THUNDERSTORMS MAY BECOME EMBEDDED WITHIN THESE
SHOWERS...BUT ARE NOT EXPECTED TO BECOME STRONG OR SEVERE. THE LOW
WILL EXIT INTO ONTARIO BY SATURDAY EVENING...ALLOWING HIGH
PRESSURE CENTERED OFF THE NEW ENGLAND COAST TO EXPAND BACK OVER
THE AREA FOR SUNDAY AND MONDAY. WINDS ARE EXPECTED TO REMAIN
FAIRLY LIGHT THROUGH MONDAY.

&&

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

&&

$$

AVIATION.....JVC
SHORT TERM...BT
LONG TERM....HLO/DE
MARINE.......HLO


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