Marine Thunderstorm Wind in Lake St. Clair, June 18, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
238 PM EDT WED JUN 18 2014

.SHORT TERM...THIS AFTERNOON AND TONIGHT

QLCS WITH EMBEDDED BOWING STRUCTURES FED BY DEEP LAYER MEAN WESTERLY
FLOW OF 40 TO 50 KTS AND INTENSE LEADING UPDRAFTS LOCATED ALONG THE
BUOYANCY GRADIENT NEAR THE MICHIGAN/INDIANA BORDER WILL PROGRESS
THROUGH THE AREA DURING THE MID-AFTERNOON HOURS. THE PRIMARY THREAT
REMAINS WIND, BUT LARGE HAIL TO AN INCH IN DIAMETER, PARTICULARLY IN
ADVANCE OF THE LINE/ACROSS THE SOUTHERN PORTION OF THE WATCH AREA
WILL BE POSSIBLE. HEAVY RAIN AND LOCALIZED FLOODING WILL BE A
CONCERN PARTICULARLY GIVEN 1-2" THAT FELL ALONG/SOUTH OF THE
I-96/696 CORRIDOR EARLIER TODAY.

IN THE WAKE OF THIS AFTERNOON'S THUNDERSTORMS, THE CONVECTIVELY
ENHANCED SHORTWAVE EVIDENT OVER WISCONSIN WILL GRADUALLY PROPAGATE
SOUTHEASTWARD INTO THE LOWER PENINSULA. THIS WILL SUPPORT CONTINUING
A CHANCE OF SHOWERS THROUGH ABOUT MIDNIGHT. A FEW EMBEDDED
THUNDERSTORMS WILL BE POSSIBLE DEPENDING ON WHAT REMAINS OF THE
INSTABILITY RESERVOIR OVER SOUTHEAST MICHIGAN IN THE WAKE OF THE
QLCS, BUT WIDESPREAD THUNDERSTORMS ARE NOT EXPECTED.

BUILDING UPPER RIDGE WILL TAKE HOLD BY LATE TONIGHT ALLOWING A
SURFACE RIDGE ASSOCIATED WITH HIGH PRESSURE CENTERED NEAR JAMES BAY
TO EXTEND INTO SEMI BY MORNING. LIGHT NORTHEAST FLOW OFF OF LAKE
HURON COMBINED WITH AN ABUNDANCE OF BOUNDARY LAYER MOISTURE MAY LEAD
TO SOME LIGHT FOG/LOW CLOUDS TOWARD MORNING HELPING LOWS REMAIN ON
THE WARM SIDE...WELL INTO THE 60S.

&&

.LONG TERM...

UPPER LEVEL NORTHWEST CONFLUENT FLOW IN BEHIND OUR DEPARTING
MCV...WITH INCREASING LOW LEVEL ANTICYCLONIC/EASTERLY FLOW TOMORROW
EMITTING FROM STRONG SURFACE HIGH OVER ONTARIO/JAMES BAY SHOULD
RESULT IN DRY WEATHER TOMORROW...AS WELL AS NOTICEABLY LESS HUMID
CONDITIONS. UPPER LEVEL RIDGE AXIS WILL THEN BE IN PLACE TOMORROW
NIGHT...BUT WILL BE FLATTENING AS UPPER LEVEL ENERGY EJECTS OUT OF
THE CENTRAL/NORTHERN PLAINS. WHETHER THE MOISTURE
ADVECTION/WEAKENING 850-700 MB THETA-E RIDGE/MODEST HEIGHT FALLS ON
FRIDAY WILL BE ENOUGH TO SUPPORT SHOWERS/THUNDERSTORM ACTIVITY
REMAINS SOMEWHAT QUESTIONABLE...AS THERE IS A TIGHT
MOISTURE/STABILITY/SHOWALTER GRADIENT IN PLACE. ALTHOUGH...MARINE
INFLUENCE WILL LIKELY ONLY ENHANCE THE GRADIENT/LOW LEVEL
CONVERGENCE ACROSS WESTERN AREAS...ADDING SOME CONFIDENCE THERE WILL
BE SHOWERS/POSSIBLE THUNDERSTORMS DEVELOPING ALONG/WEST OF U.S.
23...WHERE LOW LIKELY POPS WILL BE CARRIED. LINGERING BUT WEAKENING
MOISTURE AXIS INTO FRIDAY EVENING/NIGHT...WITH WANING INSTABILITY
SUPPORTS JUST CHANCE POPS. RENEWED MODEST SUBSIDENCE ON SATURDAY AS
UPPER LEVEL RIDGE BUILDS INTO THE CENTRAL GREAT LAKES OVER THE
WEEKEND...WHICH IS EXPECTED TO LEAD TO DRY (SLIGHT CHANCE) AND
PLEASANT DAY.

LATEST EURO INDICATED PSEUDO ZONAL FLOW ACROSS THE NORTHERN CONUS
INTO FIRST PART OF THE WORK WEEK...MAKING FOR DIFFICULT TIMING
ISSUES WITH SUBTLE SHORTWAVES...AND SUNDAY THROUGH TUESDAY WILL BE
CARRYING GENERIC CHANCE POPS WITH PRETTY GOOD MOISTURE RETURN (12 C
DEW PT AT 850 MB) COMING UP FROM THE PLAINS/MISSISSIPPI RIVER
VALLEY. NO GREAT OPPORTUNITY TO DEVIATE MUCH FROM NEAR NORMAL
TEMPERATURES...EXCEPT BELOW NORMAL BY WEDNESDAY AS STRONG NORTHERN
STREAM TROUGH MOVING THROUGH TUESDAY/WEDNESDAY DELIVERS COOLER
CANADIAN (POSSIBLE ARCTIC ORIGIN) AIRMASS.

&&

.MARINE...

SHOWERS AND THUNDERSTORMS WILL COME TO AN END THIS EVENING...AS
FRONTAL BOUNDARY SINKS SOUTH INTO THE OHIO VALLEY. HIGH PRESSURE
WILL BUILD INTO THE CENTRAL GREAT LAKES TONIGHT INTO
TOMORROW...INCREASING THE EASTERLY FLOW...BUT REMAINING UNDER 20
KNOTS FOR THE MOST PART. A LITTLE CONCERNED THE CHANNELING NORTHEAST
WINDS OVER SAGINAW BAY COULD BRIEFLY HIT 25 KNOTS...WITH WAVES
BUILDING UP AROUND 4 FEET...BUT HELD OFF ON SMALL CRAFT ADVISORY FOR
NOW DUE TO JUST ENOUGH LOW LEVEL STABILITY. HIGH PRESSURE WILL TRY
TO HOLD FOR FRIDAY...LEADING TO LIGHT EASTERLY WINDS
CONTINUING...BUT RAIN AND POSSIBLE THUNDERSTORMS ARE EXPECTED TO
OVERSPREAD PARTS OF THE AREA AS SURGE OF MOISTURE TAKES PLACE. DRY
WEATHER SHOULD RETURN SATURDAY AS HIGH PRESSURE REASSERTS
ITSELF...WITH LIGHT WINDS AND LOW WAVES MAKING FOR IDEAL BOATING
CONDITIONS.

&&

.AVIATION...ISSUED 1221 PM EDT WED JUN 18 2014

//DISCUSSION...

VARIABLE, BUT PREDOMINANTLY VFR, CONDITIONS AND LIGHT SOUTH WINDS
WILL BE THE RULE IN THE VERY NEAR TERM AS A CONVECTIVE COMPLEX
GATHERS OVER THE WEST SIDE OF THE STATE. THUNDERSTORMS PRESENTLY
OVER EASTERN LAKE MICHIGAN ARE EXPECTED TO HOLD TOGETHER AND REACH
SOUTHEAST MICHIGAN AROUND 19Z, SUPPORTING A PREVAILING MENTION OF
TSRA AT ALL TAF SITES DURING THE MID/LATE AFTERNOON. WILL ATTEMPT TO
DEFINE THE FORECAST PEAK INTENSITY PERIOD WITH A BRIEF TEMPO GROUP
FEATURING FURTHER REDUCED VSBY/GUSTS. THE STORMS MAY CARRY A SEVERE
POTENTIAL BY THIS TIME...MAINLY FOR THE DETROIT AREA TAF SITES. HIGH
PRESSURE WILL BRING TRANQUIL CONDITIONS BY TONIGHT, BUT MOIST
NORTHEAST FLOW OFF OF LAKE HURON COMBINED WITH REMNANT MOISTURE FROM
TODAY'S RAINFALL WILL PRESENT POTENTIAL FOR LIGHT FOG/MVFR CLOUD
COVER TOWARD MORNING.

FOR DTW...THUNDERSTORMS WILL APPROACH FROM THE WEST DURING THE
18Z-19Z PERIOD AND ARE FORECAST TO DIRECTLY IMPACT THE AIRFIELD
DURING THE 19Z-20Z

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE THAT THUNDERSTORMS WILL IMPACT KDTW AIRSPACE AFTER
19Z.

* MEDIUM CONFIDENCE IN CEILINGS AOB 5KFT OUTSIDE OF T-STORMS

&&

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

&&

SHORT TERM...JVC
LONG TERM....SF
MARINE.......SF
AVIATION.....JVC

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1045 AM EDT WED JUN 18 2014

MIZ047>049-053>055-060>063-068>070-075-076-082-083-191445-
MIDLAND-BAY-HURON-SAGINAW-TUSCOLA-SANILAC-SHIAWASSEE-GENESEE-LAPEER-
ST. CLAIR-LIVINGSTON-OAKLAND-MACOMB-WASHTENAW-WAYNE-LENAWEE-MONROE-
1045 AM EDT WED JUN 18 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST
MICHIGAN.

.DAY ONE...TODAY AND TONIGHT

SCATTERED TO NUMEROUS THUNDERSTORMS ARE EXPECTED THIS AFTERNOON AND
EVENING AS A CONVECTIVE COMPLEX APPROACHES FROM THE WEST. THERE IS A
CHANCE OF SEVERE WEATHER FROM I-69 SOUTHWARD WITH THESE
STORMS...WITH THE GREATEST RISK TOWARD THE OHIO BORDER. THE
STRONGEST STORMS WILL BE CAPABLE OF PRODUCING WIND GUSTS TO 70 MPH
AND HAIL GREATER THAN ONE INCH IN DIAMETER. THERE IS ALSO A RISK
OF ISOLATED TORNADOES. STORM MOTION WILL BE TO THE EAST AT 40 MPH.
ANY STORM THAT DEVELOPS WILL ALSO BE CAPABLE OF PRODUCING FREQUENT
CLOUD TO GROUND LIGHTNING AND INTENSE RAINFALL...WITH LOCALIZED
FLOODING POSSIBLE.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THERE IS A CHANCE OF THUNDERSTORMS SOUTH OF INTERSTATE 69
THURSDAY. A CHANCE OF THUNDERSTORMS WILL REMAIN IN THE FORECAST
FRIDAY THROUGH SUNDAY FOR ALL OF SOUTHEAST MICHIGAN.

.SPOTTER INFORMATION STATEMENT...
DISPATCHERS...PLEASE NOTIFY YOUR EMERGENCY MANAGERS IMMEDIATELY.
SPOTTER ACTIVATION MAY BE NEEDED TODAY.

LCZ422-423-460-LEZ444-LHZ361>363-421-422-441>443-462>464-191445-
ST. CLAIR RIVER-DETROIT RIVER-LAKE ST. CLAIR-
MICHIGAN WATERS OF LAKE ERIE FROM DETROIT RIVER TO NORTH CAPE MI-
LAKE HURON FROM 5NM EAST OF MACKINAC BRIDGE TO PRESQUE ISLE LT
BEYOND 5 NM OFF SHORE-
LAKE HURON FROM PRESQUE ISLE LIGHT TO STURGEON POINT MI BEYOND 5NM
OFF SHORE-
LAKE HURON FROM STURGEON POINT TO ALABASTER MI BEYOND 5NM OFF SHORE-
OUTER SAGINAW BAY SW OF ALABASTER TO PORT AUSTIN MI TO INNER SAGINAW
BAY-INNER SAGINAW BAY SW OF POINT AU GRES TO BAY PORT MI-
PORT AUSTIN TO HARBOR BEACH MI-HARBOR BEACH TO PORT SANILAC MI-
PORT SANILAC TO PORT HURON MI-
LAKE HURON FROM PORT AUSTIN TO HARBOR BEACH BEYOND 5NM OFF SHORE-
LAKE HURON FROM HARBOR BEACH TO PORT SANILAC BEYOND 5NM OFF SHORE-
LAKE HURON FROM PORT SANILAC TO PORT HURON BEYOND 5NM OFF SHORE-
1045 AM EDT WED JUN 18 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF LAKE ERIE...LAKE
HURON AND LAKE ST CLAIR.

.DAY ONE...TODAY AND TONIGHT

SCATTERED TO NUMEROUS THUNDERSTORMS ARE EXPECTED THIS AFTERNOON AND
EVENING AS A CONVECTIVE COMPLEX APPROACHES FROM THE WEST. THERE IS A
CHANCE OF SEVERE WEATHER FOR LAKE ERIE AND LAKE ST CLAIR. THE
STRONGEST STORMS WILL BE CAPABLE OF PRODUCING WIND GUSTS TO 60 KNOTS
AND HAIL GREATER THAN ONE INCH IN DIAMETER. THERE IS ALSO A RISK
OF ISOLATED WATERSPOUTS. STORM MOTION WILL BE TO THE EAST AT 35
KNOTS. ANY STORM THAT DEVELOPS WILL ALSO BE CAPABLE OF PRODUCING
FREQUENT CLOUD TO GROUND LIGHTNING AND INTENSE RAINFALL.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THERE IS A CHANCE OF THUNDERSTORMS FOR LAKE ERIE THURSDAY. A
CHANCE OF THUNDERSTORMS WILL REMAIN IN THE FORECAST FRIDAY THROUGH
SUNDAY FOR ALL MARINE AREAS.

DT

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

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