Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KDTX 270131
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
931 PM EDT FRI JUN 26 2015

.UPDATE...

THE BAND OF RAIN STRETCHING FROM METRO CHICAGO INTO NW OHIO IS
BEING DRIVEN BY MID LEVEL DEFORMATION TO THE NORTH OF A LEAD
SHORT WAVE IMPULSE CURRENTLY TRACKING FROM WRN IL INTO INDIANA.
THE NORTHERN EDGE OF THIS RAIN HAS CROSSED THE MI BORDER INTO
LENAWEE AND MONROE COUNTIES. MEANWHILE...LOW LEVEL DRY AIR
ADVECTION HAS BEEN ONGOING ACROSS SE MI UNDER THE NE SFC WINDS. IT
IS APPARENT FROM THE RADAR LOOP THAT THIS DRY AIR HAS BEEN
ERODING THE NORTHERN EDGE OF THE RAIN SHIELD. ADDITIONAL UPSTREAM
SHORT WAVE IMPULSES WILL HOWEVER FORCE THIS LEAD IMPULSE TOWARD
THE NE OVERNIGHT...LIFTING THE MID LEVEL FRONTAL BOUNDARY TO THE
NORTH. THE NET RESULT WILL BE A GRADUAL NORTHWARD EXPANSION OF THE
LIGHT RAIN INTO ANN ARBOR AND METRO DETROIT DURING THE OVERNIGHT.

INTENSIFICATION OF THIS MID LEVEL FORCING WILL OCCUR ON SATURDAY
AS THE SHORT WAVE NOW DROPPING ACROSS MN PHASES WITH THIS LEAD
IMPULSE OVER THE OHIO VALLEY. THIS WILL DRIVE THE MID LEVEL
DEFORMATION AND DEEP MOIST AXIS INTO SE MI. THE SURFACE LOW NOW
LOCATED OVER SOUTH CENTRAL INDIANA WILL IN TURN DEEPEN AS IT
TRACKS INTO OHIO SATURDAY. THE CURRENT FORECAST TONIGHT INTO
SATURDAY CONTINUES TO LOOK REASONABLE BASED ON LATEST
OBSERVATIONAL TRENDS. AN EVENING UPDATE WILL BE ISSUED SIMPLY TO
MAKE SOME MINOR ADJUSTMENTS TO TIMING OF THE RAIN TONIGHT AND
RAISE OVERNIGHT MINS A COUPLE DEGREES BASED ON CURRENT TEMPS AND
THE EXTENSIVE MID/HIGH CLOUDS NOW BLANKETING SRN MI.

&&

.AVIATION...ISSUED 706 PM EDT FRI JUN 26 2015

A DEVELOPING LOW PRESSURE SYSTEM OVER THE OHIO VALLEY IS FORECAST TO
DEEPEN ACROSS OHIO ON SATURDAY. A TIGHTENING PRESSURE GRADIENT TO
THE NORTHWEST OF THIS LOW WILL LEAD TO STRENGTHENING N-NE WINDS
ACROSS THE TERMINALS DURING THE MORNING...WITH GUSTS POSSIBLY
TOPPING 30 KNOTS SAT AFTERNOON. THIS SYSTEM WILL SPREAD RAIN ACROSS
THE REGION /MAINLY FROM FNT SOUTH/ DURING THE COURSE OF THE OVERNIGHT
INTO THE EARLY MORNING HOURS. THE RAIN WILL PERSIST THROUGH THE DAY
SAT.

FOR DTW...ONGOING E-NE LOW LEVEL WINDS HAVE BEEN ADVECTING DRIER AIR
IN THE LOW LEVELS ACROSS METRO DETROIT. THIS HAS ACTUALLY BEEN
ERODING THE 4-5K FT CLOUDS LINGERING ACROSS THE REGION.
THUS...EXPECT AS THE RAIN MOVES IN OVERNIGHT...CIGS WILL BE RATHER
HIGH BASED /ABOVE 6K FT/. PERSISTENT RAIN AND LOW LEVEL MOISTURE
ADVECTION WILL HOWEVER LEAD TO A RAPID LOWERING OF THE CLOUD BASES
TOWARD DAYBREAK SAT.

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CEILINGS FALLING BELOW 5000 FT AFTER 08Z.

* LOW IN THUNDERSTORMS ON SATURDAY.

&&

.PREV DISCUSSION...ISSUED 401 PM EDT FRI JUN 26 2015

SHORT TERM...TONIGHT

SHORT WAVE DROPPING SOUTHEAST OUT OF THE UPPER MIDWEST IS
SPINNING UP SURFACE LOW OVER CENTRAL ILLINOIS THIS AFTERNOON. THIS
WAVE WILL SWING DOWN TO THEN LIFT NORTHEAST THROUGH THE OHIO
VALLEY. SURFACE LOW WILL RAPIDLY DEEPEN OVER NIGHT AS IT TRACKS
ACROSS CENTRAL INDIANA THEN LIFT NORTHEASTWARD TOWARDS CLEVELAND
AS WAVE BECOMES NEGATIVELY TILTED AND BEGINS TO CLOSE OVER WESTERN
LAKE ERIE. RAIN SHIELD NOW OCCURRING OVER INDIANA WILL LIFT
NORTHWARD TOWARD THE FORECAST AREA TONIGHT. NORTHEAST FLOW WILL
INCREASE OVERNIGHT AS LOW DEEPENS. THIS WILL DRAW IN DRIER AIR IN
THE LOWER LEVELS WHICH SHOULD HELP SLOW THE ADVANCEMENT OF RAIN
SHIELD. GFS/EURO EXPAND THE RAIN RAPIDLY AFTER MIDNIGHT AND ALLOW
MEASURABLE RAIN TO REACH AS FAR NORTH AS I69 BY 12 SAT WHILE NAM
REACHES I96 CORRIDOR. WITH SUCH A STRONG NORTHEAST FLOW DEVELOPING
OVERNIGHT WOULD SIDE MORE TOWARDS NAM AND THINKING RADAR MAY SHOW
RETURNS FURTHER NORTH BUT DRIER SHOULD HOLD IT TO MOSTLY VIRGA
NORTH OF M59. VERY STABLE ENVIRONMENT WITH JUST STRONG ISENTROPIC
LIFT. NOT EXPECTING ANY THUNDER OVERNIGHT.

ANOTHER COOL NIGHT WITH FLOW COMING FROM CANADA.  LOWS AGAIN WILL
BELOW NORMAL WITH LOWS LOW 50S THUMB TO AROUND 60 OHIO BORDER.

LONG TERM...

PSEUDO TROPICAL MOISTURE (700 MB DEW PTS OF 6 C...850 MB DEW PTS OF
14 C) OVER MISSOURI ADVANCING EAST-NORTHEAST INTO THE OHIO
VALLEY...AS STRONG UPPER WAVE RESIDES OVER THE MIDWEST. A SECOND
STRONG UPPER WAVE/PV ANOMALY WAS DROPPING SOUTH FROM
MINNESOTA...WHICH WILL RESULT IN PHASED SOLUTION/DEEPENING LOW
PRESSURE SYSTEM WORKING THROUGH THE EASTERN GREAT LAKES ON SATURDAY.
THE QUESTION IS HOW STRONG (00/12Z EURO INDICATING 14-15 MB DROP IN
24 HRS FROM 18Z FRIDAY-18Z SATURDAY)...AND WHICH LAYER WILL BE MOST
ACTIVE...AS WE WILL BE RELYING ON THE STRONG 700 MB FGEN/MID LEVEL
DEFORMATION CLIPPING EASTERN HALF OF THE CWA. AS NOTED
BEFORE..PLENTY OF MOISTURE AT 700 MB LEVEL...WITH AT LEAST 2 C
ADVECTING INTO SOUTHEAST MICHIGAN. 5 C MOISTURE AXIS WILL NOT BE TOO
FAR AWAY EITHER...AND WITH STRONG EASTERLY FLOW AT THAT
LEVEL....SEEMS REASONABLE A LONGER DURATION HEAVY RAIN IS POSSIBLE.
THE SAVING GRACE COULD BE IF THE 850 MB ZONE IS MORE ACTIVE...AND
LOWER BASED INSTABILITY/CONVECTION MAINTAINS THE HEAVIEST RAIN SOUTH
AND EAST OF SOUTHEAST MICHIGAN...ALONG THE LINES OF THE 12Z NAM/GFS.
CONFIDENCE IS NOT HIGH IN ENOUGH IN THESE SOLUTIONS VERBATIM...SEE
12Z REGIONAL GEM/EURO. HOWEVER...EVEN WITH FORECASTED 1-2 INCHES OF
RAINFALL ACROSS FAR EASTERN SECTIONS...(WITH THE LACK OF
INSTABILITY/CONVECTION/THUNDERSTORMS EXPECTED OVER SOUTHEAST
MICHIGAN AND PW VALUES IN THE 1 TO 1.35 INCH RANGE...FLASH FLOODING
DOES NOT SEEM LIKE A BIG CONCERN WITH 6 HR FLOOD GUIDANCE AT OR
ABOVE 2 INCHES FOR JUST ABOUT ALL OF SOUTHEAST MICHIGAN. THIS LOOKS
TO BE A SLOWER RESPONSE/ADVISORY TYPE FLOODING...AND WILL EVEN FORGO
FLOOD WATCH...AS EVEN THE 12Z EURO SEEMS TO BE SUFFERING FROM
CONVECTIVE FEEDBACK...AS THE FORECASTED 4 INCH QPF BULLSEYES JUST
SOUTH OF WEST LAFAYETTE INDIANA THIS AFTERNOON (18-00Z). LOOKS
OVERDONE AND SEEMS TO CARRY THROUGH INTO TOMORROW...RESULTING IN A
POTENTIALLY SLIGHTLY OVER DEEPENED SOLUTION.

MODEL CONSENSUS IS FOR THE SURFACE LOW TO DEEPEN TO AROUND 1000 MB
(STILL -2 TO -3 STANDARDIZED ANOMALY FOR LATE JUNE) AS IT LIFTS INTO
NORTHEAST OHIO LATE IN THE DAY. 925 MB WINDS ARE FORECASTED TO REACH
50 KNOTS...BUT PRECIPITATION DRAG ISSUES AND NEUTRAL STABILITY
PROFILES EXPECTED TO HOLD WINDS TOPPING OUT AROUND 40 MPH. WILL
HAVE TO KEEP CLOSE ON EYE LAKE ERIE/DETROIT RIVER WATER LEVELS FOR
POSSIBLE FLOODING...BUT SUSPECT WITH WINDS STARTING OUT FROM THE
NORTHEAST AND SHIFTING MORE DUE NORTHERLY BY EARLY SATURDAY
EVENING SUSPECT IT WILL BE BIGGER ISSUE FOR LUCAS COUNTY IN OHIO.
NONE-THE-LESS...WITH LAKE ERIE WATER LEVELS RUNNING SO
HIGH...FELT COASTAL FLOOD WATCH WAS WARRANTED.

SLOWLY DRYING OUT SATURDAY NIGHT INTO EARLY SUNDAY AS ANOTHER UPPER
LEVEL SHORTWAVE TROUGH DROPPING SOUTHEAST FROM SOUTH CENTRAL CANADA
WILL ACT AS THE KICKER...WITH RIDGING/BUILDING HEIGHTS ON SUNDAY
ALLOWING FOR DRY FORECAST WITH TEMPS RISING CLOSE INTO UPPER 70S TO
NEAR 80 DEGREES AS 850 MB TEMPS SNEAK JUST ABOVE 10 C.

12Z GLOBAL MODELS AND GEFS MEMBERS IN FAIRLY GOOD AGREEMENT WITH
LARGE SCALE FEATURES NEXT WEEK. LONGWAVE TROUGH OVER THE GREAT LAKES
MONDAY/TUESDAY WILL TRANSLATE EASTWARD TRANSITIONING TO NORTHWEST
UPPER FLOW AND SURFACE HIGH PRESSURE WEDNESDAY ONWARD. ENOUGH MODEL
AGREEMENT IN A DIGGING SHORTWAVE TROUGH FOR MONDAY TO MAINTAIN
CHC/LIKELY POPS. LINGERING LOW CHANCE POPS FOR TUESDAY WITH A DRYING
TREND WEDNESDAY INTO LATE WEEK. TEMPS EXPECTED TO REMAIN ON THE LOW
SIDE OF NORMAL.

MARINE...

A STRONG AND DYNAMIC LOW PRESSURE SYSTEM IS FORECASTED TO TRACK
ACROSS THE EASTERN OHIO RIVER VALLEY ON SATURDAY BEFORE LIFTING
NORTHWARD INTO THE EASTERN GREAT LAKES SATURDAY NIGHT. MODEL
GUIDANCE CONTINUES TO SUGGEST NORTHEAST GALES FOR LAKE ST CLAIR AND
LAKE ERIE DURING SATURDAY...AND HAVE UPGRADED TO GALE WARNING. GALES
REMAIN POSSIBLE ACROSS FAR SOUTHERN LAKE HURON...BUT NOT UNTIL VERY
LATE IN THE DAY ON SATURDAY AND INTO SATURDAY EVENING...AND WILL
MAINTAIN THE GALE WATCH...STARTING AT 4 PM HOWEVER. RAIN
SHOWERS/PRECIPITATION DRAG ISSUES AND JUST ENOUGH NEAR WATER
STABILITY IS EXPECTED TO LIMIT THE WINDS TO LOWER END GALES...BUT
POTENTIAL IS FOR HIGHER WINDS THAN FORECASTED.

DIMINISHING WINDS LATE SATURDAY NIGHT INTO SUNDAY AS A WEAK SURFACE
RIDGE WILL PASS THROUGH THE REGION  WITH THE LOW LIFTING AWAY FROM
SOUTHEASTERN MICHIGAN.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...LAKESHORE FLOOD WATCH FROM 7 AM EDT SATURDAY THROUGH SATURDAY
     EVENING FOR MIZ083.

LAKE HURON...GALE WATCH FROM SATURDAY AFTERNOON THROUGH LATE SATURDAY NIGHT FOR
     LHZ443-464.

LAKE ST CLAIR...GALE WARNING FROM 8 AM SATURDAY TO 4 AM EDT SUNDAY FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...GALE WARNING FROM 8 AM SATURDAY TO 4 AM EDT SUNDAY FOR LEZ444.

&&

$$

UPDATE.......SC
AVIATION.....SC
SHORT TERM...DRC
LONG TERM....SF/DT
MARINE.......SF


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


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.