Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 271656 CCA
AFDDTX

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1256 PM EDT SAT JUN 27 2015

.AVIATION...

NORTHWEST QUADRANT OF THE MATURE CYCLONE AFFECTING THE REGION IS
CURRENTLY REDEFINING WHERE THE BEST OVERLAP IN MOISTURE AND
FORCING WILL PERSIST THROUGH THE LATE AFTERNOON AND EVENING HOURS.
EXPECTATION IS FOR THE BEST FORCING TO RESIDE NEAR KFNT - WITH
MORE PERIODIC RAIN FOR THE DETROIT AREA TERMINALS.
REGARDLESS...LOWER CEILINGS WILL PERSIST IN SOME FASHION THROUGH
MUCH OF THE TERMINAL FORECAST PERIOD. GUSTY NORTHEAST TO NORTH
WINDS WILL ALSO PLAGUE THE AREA PRIOR TO MIDNIGHT...WITH GUSTS
APPROACHING 30 KNOTS.

FOR DTW...CEILINGS WILL HOVER SLIGHTLY ABOVE 1KFT UNTIL THE NEXT
BATCH OF RAIN WASHES ACROSS - AFTER WHICH A PROLONGED PERIOD OF SUB-
1KFT CEILINGS IS EXPECTED. RAINFALL MAY TEMPORARILY LOWER
VISIBILITIES BELOW 3SM - BUT NOT VERY CERTAIN.  LIKEWISE...COULD
ALSO BE A STRAY LIGHTNING STRIKE.

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CEILINGS BELOW 5000 FEET THROUGH 16Z SUNDAY.
* LOW IN A THUNDERSTORM AFFECTING THE NEAR TERMINAL AIRSPACE.

&&

.PREV DISCUSSION...ISSUED 1049 AM EDT SAT JUN 27 2015

UPDATE...

MATURING MID-LATITUDE CYCLONE CONTINUES TO DEEPEN OVER THE
SOUTHERN GREAT LAKES REGION. MID-LEVEL DEFORMATION AXIS WAS ABLE
TO CENTRIFUGE TO AN IMPRESSIVE RADIUS FROM THE STORM CENTER -
REACHING MOST OF SOUTHWEST LOWER MICHIGAN. RECENT SATELLITE AND
RADAR IMAGERY LENDS SUPPORT FOR THE NOTION OF THE DEFORMATION
FORCING REFOCUSING SOUTHEAST MICHIGAN CLOSER TO SYSTEM CENTROID.
APPEARS INNER TROWAL WALL REPLACEMENT ON THE 700MB SURFACE IS
OCCURRING ALONG A DETROIT TO DEFIANCE LINE...CLOSER TO THE OVERLAP
WITH THE 850MB DEFORMATION SIGNATURE...AND SHOULD CARVE OUT THE
NEW AXIS OF FORCING WHILE SURGING NORTHWARD. THIS PROCESS WILL PUT
AN END TO THE LIGHTENING OF THE RAINFALL CURRENTLY EVIDENT OVER
MUCH OF SOUTHEAST MICHIGAN. MEANWHILE...THE WARM CONVEYOR BELT
SURGE IS PARALLELING US/CANADIAN BORDER - MAINLY ON THE CANADIAN
SIDE - SPARING THE AREA FROM THE GREATEST PRECIPITATION RATES.
ADDITIONAL RAIN ACCUMULATIONS WILL APPROACH AN INCH...WITH LOCALLY
HIGHER AMOUNTS IF PERIODIC CONVECTION CAN SPROUT IN THE
DEFORMATION CORRIDOR.

GUSTY NORTHEAST WINDS WILL CONTINUE TO INCREASE IN STRENGTH
THROUGH THE AFTERNOON AS THE LOW CENTER DEEPENS AND PASSES
SOUTHEAST OF THE AREA. OPTED TO TOSS LAKE ST CLAIR SHORELINE INTO
THE LAKESHORE FLOOD WARNING...OBSERVATIONS ARE APPROACHING LEVELS
THAT TYPICALLY CAUSE MINOR INNUDATION ISSUES.

PREV DISCUSSION...ISSUED 426 AM EDT SAT JUN 27 2015

SHORT TERM...TODAY AND TONIGHT

UPPER WAVE DROPPING THROUGH THE WESTERN GREAT LAKES IS LOOKING MUCH
BETTER DEFINED ON WATER VAPOR IMAGERY THAN COMPARED TO 24 HOURS AGO.
THIS RESPONSE WAS EXPECTED...AS THE PATTERN AMPLIFIED WITH RIDGES
BUILDING OVER BOTH THE WESTERN U.S. AND OFF THE ATLANTIC COAST. THE
SYSTEM SHOULD INTENSIFY FURTHER TODAY AS THIS PROCESS
CONTINUES...AND AS THE WAVE ENCOUNTERS A COUPLED JET STRUCTURE AS IT
SLIDES INTO THE SOUTHERN GREAT LAKES. THIS WILL SUPPORT A DEEPENING
SURFACE LOW TODAY AND TONIGHT AS IT TRACKS ACROSS OHIO. THIS SYSTEM
WILL BRING A LOT OF RAIN AND WIND TO THE AREA...PRESENTING POTENTIAL
FOR LAKESHORE FLOODING AND EVEN SOME LOW-END AREAL FLOODING IF WE
CAN GET ENOUGH RAIN TO FOCUS OVER THE SAME AREA. TOTAL RAINFALL
THROUGH TONIGHT OF BETWEEN 1 AND 2 INCHES IS EXPECTED TO OCCUR IN A
SOUTHWEST TO NORTHEAST ORIENTATED SWATH...GENERALLY STRETCHING
SOUTHEAST OF A HOWELL TO PORT SANILAC LINE. IT SHOULD BE NOTED THAT
THE SAGINAW VALLEY AND EVEN PORTIONS OF THE FAR NORTHERN THUMB WILL
BE ON THE NORTHERN PERIPHERY OF THE RAIN SHIELD AND MORE UNDER THE
INFLUENCE OF DRY NORTHEASTERLY FLOW. THESE AREAS WILL ACTUALLY SEE
LITTLE TO NO RAINFALL.

LOWER PORTIONS OF THE FRONTAL SLOPE LOOK TO REMAIN SOUTH OF THE
FORECAST AREA PER LATEST MODEL GUIDANCE. THIS WILL LEAVE SOUTHEAST
MICHIGAN POSITIONED WITH A BROAD AREA OF DEFORMATION AND ALONG THE
700MB FRONTAL SLOPE. CURRENT RADAR IMAGERY SUPPORTS THIS IDEA...WITH
RAIN SPREADING BACK FROM SOUTHEAST MICHIGAN DOWN THROUGH NORTHERN
INDIANA. MID-LEVEL FGEN IS EXPECTED TO RAMP UP THIS
AFTERNOON...ESPECIALLY AT 700MB. THIS SHOULD ALLOW FOR SOME
ENHANCEMENT TO THE RAIN OVER THE AREA...ESPECIALLY OVER THE FAR
EASTERN PORTION OF THE FORECAST AREA. NAM SHOWS BEST AREA OF MID-
LEVEL FGEN ORIENTATED WEST TO EAST NEAR THE OHIO BORDER THIS MORNING
BEFORE IT PIVOTS NORTHWARD...BECOMING ORIENTATED SOUTHWEST TO
NORTHEAST...SOUTH OF THAT ROUGH HOWELL TO PORT SANILAC LINE
MENTIONED ABOVE DURING THE AFTERNOON AND VERY EARLY EVENING. RAIN
WILL TAPER OFF FROM WEST TO EAST OVERNIGHT...BUT ONLY GRADUALLY
GIVEN SLOW TRACK OF THE LOW AWAY FROM THE AREA AS IT IS BLOCKED A
BIT BY RIDGING TO THE EAST. WITH MAX RAINFALL EXPECTED TO REMAIN
UNDER TWO INCHES (HIGHER AMOUNTS ONLY IN LOCALIZED AREAS)...WILL
FOREGO ISSUANCE OF AN AREAL FLOOD WATCH. ANY FLOODING THAT OCCURS IS
EXPECTED TO BE MORE OF THE NUISANCE VARIETY AND BETTER HANDLED WITH
ADVISORIES.

TIGHT GRADIENT WILL SUPPORT BREEZY/WINDY CONDITIONS TODAY.
PRECIPITATION DRAG ADDS SOME UNCERTAINTY WITH HOW MUCH OF A STRONG
CORE OF 45-50 KNOT WINDS BETWEEN 925-700MB WE MAY BE ABLE TO MIX
INTO AFTER COOLER AIR ALOFT STARTS TO ARRIVE BY THE VERY LATE
AFTERNOON AND EVENING...STEEPENING LAPSE RATES AND INCREASING THE
DEPTH OF THE MIXED LAYER. HIGHEST LIKELIHOOD LOOK TO BE FOR GUSTS IN
THE 35 TO 40 MPH RANGE SOUTH OF THE I-69 CORRIDOR...BUT POTENTIAL
FOR HIGHER GUSTS IS THERE...ESPECIALLY IF WE SEE BREAKS IN THE RAIN.

THE STRONG EAST TO NORTHEAST WINDS WILL BE MORE PRONOUNCED OVER THE
MARINE AREAS...WITH FLOW ACROSS THE LENGTH OF LAKE ERIE EXPECTED TO
PUSH WATER LEVELS UP TO AROUND 7 FEET ABOVE CHART DATUM NEAR TOLEDO
BY THIS AFTERNOON. THIS IS EXPECTED TO CAUSE SOME FLOODING ISSUES
ALONG THE LAKESHORE...ESPECIALLY FROM TOLEDO BEACH SOUTHWARD GIVEN
THE NORTHERLY COMPONENT TO THE WIND. A LAKESHORE FLOOD WARNING IS
NOW IN EFFECT FOR THE SHORELINE OF MONROE COUNTY. WATER LEVELS
FURTHER NORTH TOWARDS THE MOUTH OF THE DETROIT RIVER ARE A BIT MORE
UNCERTAIN GIVEN THIS NORTHERLY COMPONENT...AND CONFIDENCE IS NOT
HIGH ENOUGH TO ISSUE ANY FLOOD PRODUCTS THERE. STRONGEST WINDS ARE
NOT EXPECTED UNTIL LATER IN THE DAY...AND THIS WILL PROVIDE US AN
OPPORTUNITY TO MONITOR LEVELS THROUGHOUT THE DAY.

CLOUDS AND RAIN WILL KEEP TEMPERATURES COOL TODAY...IN THE 60S FOR
MOST OF THE AREA. DRIER WEATHER OVER THE SAGINAW VALLEY WILL HOWEVER
ALLOW THEM TO POP UP INTO THE LOW 70S.

LONG TERM...SUNDAY THROUGH FRIDAY

PERSISTENT DEEP CYCLONIC FLOW WILL REMAIN IN PLACE FOR A SIZABLE
PORTION OF SUNDAY WITH THE CLOSED CIRCULATION REMAINING AT AN
IMPRESSIVE WAVELENGTH. STRATUS AND STRATOCUMULUS WILL BE VERY
SLUGGISH IN ITS EXIT FOR MUCH IF NOT ALL OF THE CWA. A FAVORABLE
STEEP LAPSE RATE POCKET BETWEEN 800-700MB SUGGESTS THOSE WESTERN
AREAS THAT CLEAR OUT DURING THE MORNING...WILL THEN HAVE A GOOD
POTENTIAL TO CU BACK UP BY MIDDAY. GEOPOTENTIAL HEIGHT REBOUND WILL
EVENTUALLY FORCE A VERY WEAK SURFACE RIDGE ACROSS LOWER MICHIGAN.
WENT RELATIVELY OPTIMISTIC OR REMAINED NEAR GUIDANCE FOR DAYTIME
HIGHS...WITH TEMPERATURES RISING INTO THE MIDDLE 70S. NOTE...STILL 6
TO 8 DEGREES BELOW SEASONAL AVERAGES. A CHANCE OF LEFTOVER SPRINKLES
OR LIGHT SHOWERS WILL EXIST BEFORE 14-15Z...PRIMARILY OVER THE THUMB
DOWN TO THE NORTHERN SUBURBS OF DETROIT.

THE NEXT SHORTWAVE IS FORECASTED TO DIVE SOUTHWARD INTO THE BASE OF
THE TROUGH ON SUNDAY. THIS ENERGY IS THEN EXPECTED TO PIVOT AND TURN
NEGATIVE TILT ACROSS SOUTHEASTERN MICHIGAN DURING THE DAY ON MONDAY.
OVERALL...THE MODELS CALL FOR A GOOD COHERENT MIDLEVEL CYCLONIC
CIRCULATION THAT WILL AUGMENT AN ALREADY FAVORABLE ENVIRONMENT FOR
WARM AIR ADVECTION ACROSS THE CENTRAL GREAT LAKES. THE SYSTEM
TRAJECTORY AND ORIENTATIONS OF THERMALS BOUNDARIES SUGGEST THAT DEEP
THETA E CONTENT WILL NEVER BE ABLE TO LIFT NORTHWARD INTO STATE. IN
FACT...OVERALL LOW NEAR SURFACE THETA E WITH SFC DEWPOINTS IN THE
50S TO NEAR 60 CONDITIONS WILL BE HARD PRESSED TO SUPPORT MUCH IN
THE WAY OF INSTABILITY. DEEP DRY AIR INITIALLY...IS EXPECTED TO
SATURATE AND LEAD TO NUMEROUS SHOWERS/RAIN LIKELY SCENARIO BY MONDAY
AFTERNOON.

MARINE...

A STRONG AND DYNAMIC LOW PRESSURE SYSTEM IS FORECASTED TO TRACK
ACROSS THE EASTERN OHIO RIVER VALLEY TODAY BEFORE LIFTING NORTHWARD
INTO THE EASTERN GREAT LAKES TONIGHT. GALE WARNINGS REMAIN IN EFFECT
FOR THE MICHIGAN WATERS OF LAKE ERIE AND LAKE ST CLAIR. LONG FETCH
NORTHEASTERLY FLOW SUPPORTS AN UPGRADE TO A GALE WARNING FOR THE
WATERS OF LAKE HURON FROM PORT SANILAC TO PORT HURON. 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...BEACH HAZARDS STATEMENT THROUGH SUNDAY MORNING FOR MIZ049-055-063-
     083.

     LAKESHORE FLOOD WARNING UNTIL 10 PM EDT THIS EVENING FOR MIZ070-076-
     083.

LAKE HURON...GALE WARNING UNTIL 4 AM EDT SUNDAY FOR LHZ443-464.

     SMALL CRAFT ADVISORY UNTIL 8 AM EDT SUNDAY FOR LHZ421-422-441-442.

LAKE ST CLAIR...GALE WARNING UNTIL 4 AM EDT SUNDAY FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...GALE WARNING UNTIL 4 AM EDT SUNDAY FOR LEZ444.

&&

$$

AVIATION.....MANN
UPDATE.......MANN
SHORT TERM...HLO
LONG TERM....CB
MARINE.......CB


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



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