Small Craft Advisory 10, NWS Detroit, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
346 AM EDT TUE APR 19 2011

.SHORT TERM...TODAY AND TONIGHT

THE 06Z SURFACE ANALYSIS SHOWS LOW PRESSURE OVER THE OKLAHOMA
PANHANDLE WITH A STATIONARY FRONT EXTENDING ACROSS THE OHIO VALLEY.
MEANWHILE...STRONG HIGH PRESSURE IS ANCHORED OVER THE NORTHERN GREAT
LAKES. NORTHEASTERLY FLOW ASSOCIATED WITH THIS HIGH HAS ADVECTED
COLD AIR INTO THE NORTHERN OHIO VALLEY...CREATING A VERY STRONG LOW
LEVEL THERMAL GRADIENT ALONG THE SURFACE FRONT DRAPED TO THE SOUTH.
THE 00Z MODEL SUITE ARE IN REASONABLE AGREEMENT IN SHOWING THE MID
LEVEL SHORT WAVE ENERGY NOW OVER THE CENTRAL ROCKIES LIFTING INTO
THE UPPER MIDWEST TODAY...ALLOWING THE SURFACE LOW TO TRACK INTO
CENTRAL ILLINOIS BY EVENING. THE MID LEVEL TROUGH IS THEN FORECAST
TO TRACK INTO THE WESTERN GREAT LAKES TONIGHT...SENDING THE
ASSOCIATED SURFACE LOW ACROSS METRO DETROIT OVERNIGHT.

FAIRLY WIDESPREAD CONVECTION ACROSS IL/IN/OH IS ASSOCIATED WITH
CONVERGENCE ALONG THE NOSE OF THE 850MB JET. THE BULK OF THIS
FORCING WILL SLIDE EAST EARLY THIS MORNING AS THE LOW LEVEL INFLOW
VEERS. REGIONAL RADAR IMAGERY DOES SUGGEST SOME SHOWERS ON THE
NORTHERN EDGE OF THIS CONVECTION LIKELY IMPACTING LOCALS SOUTH OF
THE I 94 CORRIDOR EARLY THIS MORNING. A SECOND BAND OF LIGHT PRECIP
HAS BEEN OCCURRING FROM SOUTH DAKOTA ALL THE WAY INTO SOUTHERN
MICHIGAN...ASSOCIATED WITH WEAK FORCING ALONG THE 700MB FRONT. MODEL
SOLUTIONS INDICATE THIS FORCING REMAINING VERY WEAK OVER SOUTHERN
MI...WHICH HAS BEEN VERIFYING WELL AS FEW SITES HAVE REPORTED PRECIP
WITH THIS FEATURE OVER THE LAST COUPLE OF HOURS. THE STRENGTH OF THE
CONVECTION TO OUR SOUTH IS LIKELY HINDERING BETTER DEVELOPMENT ALONG
THIS 700MB FRONT. SO PRECIP CHANCES NORTH OF I 94 ACTUALLY LOOK
FAIRLY SLIM THIS MORNING.

THE 850MB FRONT IS FORECAST TO LIFT NORTH INTO FAR SOUTHERN MI BY
EVENING AS LOW LEVEL SWRLY FLOW INCREASES ACROSS THE LOWER OHIO
VALLEY. AN UPPER JET CORE TO THE NORTHEAST OF THE REGION IS ALSO
FORECAST TO STRENGTHEN THIS AFTERNOON. MODEL CROSS SECTIONS INDICATE
THE AGEOSTROPHIC RESPONSE TO THIS WILL LEAD TO STRONG ISENTROPIC
ASCENT OVER SE MI ALONG AND NORTH OF THE 850MB FRONT...ESPECIALLY
LATE THIS AFTERNOON INTO THE EVENING. MOISTURE WILL CERTAINLY NOT BE
A PROBLEM BY EVENING AS 850MB DEWPOINTS RISE TO +12C ACROSS THE FAR
SOUTH IN THE EVENING. SO EXPECT WIDESPREAD RAIN TO DEVELOP DURING
THE COURSE OF THE AFTERNOON. ENOUGH COOL AND DRY AIR WILL LIKELY BE
LINGERING OVER THE SAGINAW VALLEY AND THUMB TO WHERE SOME SNOW IS
STILL POSSIBLE AT THE ONSET OF PRECIP. STRENGTHENING NORTHEASTERLY
WINDS AT THE SURFACE ALONG WITH WET BULB COOLING WITH THE ONSET OF
PRECIP WILL INSURE YET ANOTHER CHILLY MID APRIL DAY. THE CURRENT
FORECAST HIGHS ONLY IN THE LOW 40S STILL SEEMS REASONABLE. THE
INCREASING WINDS WILL ALSO CREATE A BIT OF A WIND CHILL.

STRONG LOWER TROPOSPHERIC FRONTAL FORCING IN ADVANCE OF THE SURFACE
LOW AND DECREASING STABILITY ALOFT WILL LEAD TO WIDESPREAD SHOWERS
AND THUNDERSTORMS THROUGH MUCH OF THE NIGHT. HAIL WILL BE POSSIBLE
WITH SOME OF THE STORMS GIVEN THE STEEP MID LEVEL LAPSE RATES. THE
CURRENT FORECAST TRACK OF THE SURFACE LOW THROUGH METRO DETROIT
KEEPS SURFACE BASED INSTABILITY JUST SE OF MONROE COUNTY. IF THE
SURFACE LOW TRACKS A BIT FARTHER WEST...SOME RESIDUAL SURFACE BASED
INSTABILITY MAY BE ABLE TO ADVECT IN FROM NORTHERN INDIANA. GIVEN
THE STRONG DEEP LAYER SHEAR...THIS SCENARIO WOULD POSE A THREAT FOR
SEVERE WEATHER. THEREFORE SPC HAS KEPT THE SOUTHERN HALF OF THE
FORECAST AREA IN A SLIGHT RISK FOR LATE TONIGHT. WARMER AIR NEAR
THE SURFACE WILL ADVECT IN WITH THE SURFACE LOW...SO EXPECT TEMPS
WILL WARM DURING THE COURSE OF THE NIGHT.

&&

.LONG TERM...

UPPER LEVEL ENERGY/NOSE OF JET MAX QUICKLY MOVING THROUGH THE FOUR
CORNERS REGION AT THE PRESENT TIME...WITH MAIN PV ANOMALY RESIDING
OVER NORTHERN IDAHO. THIS ENERGY WILL QUICKLY HEAD EAST...WITH
CONSOLIDATION OF PV OVER THE GREAT LAKES REGION ON WEDNESDAY.

FAST MOVING LOW PRESSURE SYSTEM TO WORK THROUGH THE CENTRAL GREAT
LAKES WEDNESDAY MORNING. 00Z GEM/GFS/UKMET/NAM ALL SHOW THE LOW
EXITING EAST OF SOUTHEAST MICHIGAN BY 12Z WEDNESDAY. EXCELLENT LOW
LEVEL COLD ADVECTION TO OCCUR DURING WEDNESDAY...AS 850 MB TEMPS
SEEN STARTING OUT AROUND +10 C...FALLING INTO THE NEGATIVE MID
SINGLE NUMBERS BY THE END OF THE DAY. MODELS SHOW BASICALLY NO
DEEPENING OF THE SURFACE LOW (THE LOW LEVEL MOISTURE PLUME/850 MB
THETA-E RIDGE AXIS OUT PACES THE UPPER LEVEL SUPPORT TO THE
EAST)...THUS THE REASON FOR THE FASTER AND FARTHER EAST TRACK. IT
KNOW LOOKS DOUBTFUL DETROIT WILL GET INTO THE TRUE WARM SECTOR...AND
WILL BE CARRYING HIGHS IN THE MID 50S BEFORE TEMPERATURES BEGIN TO
FALL. TEMPERATURES WILL LIKELY REMAIN STUCK IN THE 40S ACROSS THE
NORTH THIRD OF THE CWA.

WITH THE LOW FAILING TO DEEPEN...THIS CALLS INTO QUESTION JUST HOW
STRONG THE WINDS WILL BE DURING WEDNESDAY. THE NAM IS CERTAINLY THE
STRONGEST...WITH 50 TO 55 KNOTS AT 850 MB ADVERTISED ACROSS THE
SOUTH HALF...ALONG WITH GOOD SUBSIDENCE SEEN ON THE ISENTROPIC
SURFACES DURING THE MIDDLE OF THE DAY. ALTHOUGH THE SURFACE LOW IS
NOT DEEPENING...THE SURFACE HIGH BUILDING OVER THE NORTHERN
PLAINS/MIDWEST IS...AND THERE IS A NICE 6 HR +13/-13 MB PRESSURE
COUPLET (ALSO SEEN IN THE GFS)...ALTHOUGH THE PRESSURE RISE CENTER
MOVES OVER SOUTHEAST MICHIGAN BY 18Z WEDNESDAY. BOTTOMLINE...WOULD
EXPECT WESTERLY GUSTS OF 45 TO 50 MPH OVER AT LEAST THE SOUTH HALF
OF THE CWA.

LOW LEVEL LAPSE RATES WILL BE STEEP BUT SHALLOW ON WEDNESDAY...AND
STILL THINK SOME ISOLATED TO SCATTERED ACTIVITY WILL BE TOUCHED
OFF...AS MODELS ARE USUALLY A BIT TOO LOW WITH THE INVERSION HEIGHT.

SURFACE HIGH (1030 MB) BUILDING OVER SOUTHEAST MICHIGAN ON
THURSDAY...WITH CU RULES SUGGESTING AT LEAST PARTLY CLOUDY SKIES
DEVELOPING. THINKING MAXES WILL STRUGGLE TO REACH 50 DEGREES...AS
NAM/GFS BOTH INDICATING 925 MB TEMPS ONLY MAKING IT TO ZERO TO +2 C.

NEXT FAST MOVING LOW PRESSURE SYSTEM LOOKS TO BE TRACKING THROUGH
THE CENTRAL GREAT LAKES FRIDAY NIGHT...BRINGING ANOTHER CHANCE OF
THUNDERSTORMS AND RAIN LIKELY. ONCE AGAIN...TEMPERATURES WILL BE A
CHALLENGE AS WE HEAD INTO SATURDAY...DEPENDENT ON THE ULTIMATE TRACK
OF THE LOW...WHICH LOOKS TO BE A BIT FARTHER WEST THAN TONIGHT'S
TRACK...AND WILL THUS HOLD ON TO THE SHOT AT 60 DEGREES FOR FAR
SOUTHERN AREAS.

&&

.MARINE...

THE NORTHEASTERLY PRESSURE GRADIENT WILL INCREASE THROUGH THE DAY AS
LOW PRESSURE APPROACHES FROM THE SOUTHWEST AND STRONG HIGH PRESSURE
LINGERS JUST NORTHEAST OF LAKE HURON. MODEL SOUNDINGS ACTUALLY
INDICATE ENOUGH SHALLOW COLD AIR...ESPECIALLY OVER LAKE HURON...TO
LEAD TO UNSTABLE CONDITIONS OVER THE LAKES. THE LATEST MODEL
SOLUTIONS INDICATE SHALLOW MIXING AND THE TIGHTENING GRADIENT WILL
LEAD TO GALE FORCE WINDS ACROSS LAKE HURON TONIGHT WHICH WILL PROMPT
THE ISSUANCE OF A GALE WARNING. THE NORTHEAST WINDS WILL INCREASE
ENOUGH DURING THE DAY TO WARRANT SMALL CRAFT CONDTIONS THROUGH THE
AFTERNOON ACROSS ALL MARINE AREAS. THE LOW PRESSURE SYSTEM WILL PASS
TO THE NORTHEAST OF THE REGION WEDNESDAY MORNING. STRONG WINDS ON
THE BACK SIDE OF THIS SYSTEM WILL POSE THE RISK OF LINGERING GALES
OVER THE SOUTHERN LAKE HURON BASIN AS WELL AS LAKES ST CLAIR AND
ERIE. WINDS AND WAVES WILL THEN DIMINISH WED NIGHT INTO THURSDAY AS
HIGH PRESSURE BUILDS IN FROM THE WEST.

&&

.AVIATION...ISSUED 108 AM EDT TUE APR 19 2011

DRY AIR HAS SETTLED IN THROUGH THE LOW LEVELS, CONVINCINGLY ENOUGH
ACCORDING TO SURFACE OBSERVATIONS, TO EXPECT MOSTLY VIRGA OUT OF THE
LEADING MOISTURE INDICATED ON RADAR AT PRESS TIME. THIS WILL,
HOWEVER, MARK THE BEGINNING OF THE NEXT PATTERN OF PRECIPITATION
THAT WILL MOVE INTO THE REGION. THIS IS TAKING SHAPE IN A LENGTHY
BAND ROUGHLY FROM CHICAGO ALL THE WAY WEST INTO THE CENTRAL ROCKIES
AND WILL CONTINUE TO FILL IN ALONG AND NORTH OF A FRONTAL BOUNDARY
STALLED IN THE OHIO VALLEY, EVENTUALLY SPREADING INTO LOWER MICHIGAN
AROUND BY SUNRISE. THE LATEST RUNS OF MODEL SOUNDINGS INDICATE A MIX
OF RAIN AND SNOW POSSIBLE AT THE ONSET, WHILE THE POTENTIAL FOR
SLEET LOOKS TOO BRIEF TO MENTION AT ANY ONE TERMINAL SITE.
TEMPERATURES WILL BE VERY NEAR THE FREEZING MARK, ESPECIALLY AT PTK,
AND MAY DROP JUST BELOW FOR A SHORT TIME AT PRECIPITATION ONSET. THE
RAIN PORTION OF THE RAIN/SNOW MIX, WHILE TECHNICALLY FREEZING RAIN,
IT IS NOT EXPECTED TO HAVE AN IMPACT ON OPERATIONS BEFORE THE
BOUNDARY LAYER WARMS ENOUGH FOR A TRANSITION TO ALL RAIN BY LATE
MORNING.

SHOWERS ARE THEN EXPECTED TO INCREASE COVERAGE AND INTENSITY AS THE
DAY PROGRESSES. THIS, ALONG WITH THE APPROACH OF THE SURFACE LOW,
WILL LEAD TO LOWERING VISIBILITY AND CEILING IN THE DETROIT AREA AS
THE SURFACE WARM FRONT MAKES A NORTHWARD MOVE FROM THE OHIO VALLEY.
CONDITIONS NO BETTER THAN IFR ARE EXPECTED BY SUNSET WITH A TREND TO
LIFR DURING THE EVENING THROUGH THE OVERNIGHT TUESDAY NIGHT.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.

LAKE HURON...
     SMALL CRAFT ADVISORY...SAGINAW BAY AND THE NEARSHORE WATERS FROM
     PORT AUSTIN TO HARBOR BEACH...FROM 8 AM TUESDAY TO 8 PM
     TUESDAY.

     GALE WARNING...LHZ441-LHZ442-LHZ443-LHZ462-LHZ463-LHZ464...FROM 8
     PM TUESDAY TO 5 PM WEDNESDAY.

     GALE WARNING...SAGINAW BAY...FROM 8 PM TUESDAY TO 8 AM WEDNESDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM HARBOR BEACH TO PORT
     HURON...FROM NOON TUESDAY TO 8 PM TUESDAY.

     GALE WARNING...LHZ361-LHZ362-LHZ363...FROM 8 PM TUESDAY TO NOON
     WEDNESDAY.

LAKE ST CLAIR...
     GALE WATCH...FROM 8 AM WEDNESDAY TO 5 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...FROM 8 AM TUESDAY TO 8 AM WEDNESDAY.

MI WATERS OF LAKE ERIE...
     GALE WATCH...FROM 8 AM WEDNESDAY TO 5 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...FROM 8 AM TUESDAY TO 8 AM WEDNESDAY.

&&

SHORT TERM...SC
LONG TERM....SF
MARINE.......SC
AVIATION.....BT

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

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
323 PM EDT MON APR 18 2011

CORRECTED MARINE SECTION

MIZ047>049-053>055-191930-
MIDLAND-BAY-HURON-SAGINAW-TUSCOLA-SANILAC-
323 PM EDT MON APR 18 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST
MICHIGAN.

.DAY ONE...THIS AFTERNOON AND TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THE NEXT STRONG LOW PRESSURE SYSTEM WILL BRING A CHANCE OF
THUNDERSTORMS TUESDAY EVENING THROUGH WEDNESDAY MORNING. WINDY
CONDITIONS WILL EXIST ON WEDNESDAY...WITH THE POTENTIAL FOR
WESTERLY WIND GUSTS OF 45 MPH.

THE APPROACH OF ANOTHER LOW PRESSURE SYSTEM WILL BRING A CHANCE OF
THUNDERSTORMS FRIDAY NIGHT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED THROUGH TONIGHT.

MIZ060>063-068>070-075-076-082-083-191930-
SHIAWASSEE-GENESEE-LAPEER-ST. CLAIR-LIVINGSTON-OAKLAND-MACOMB-
WASHTENAW-WAYNE-LENAWEE-MONROE-
323 PM EDT MON APR 18 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHEAST
MICHIGAN.

.DAY ONE...THIS AFTERNOON AND TONIGHT

THERE IS A SMALL CHANCE OF FREEZING RAIN LATE TONIGHT.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THE NEXT STRONG LOW PRESSURE SYSTEM WILL BRING A CHANCE OF
THUNDERSTORMS TUESDAY EVENING THROUGH WEDNESDAY MORNING. WINDY
CONDITIONS WILL EXIST ON WEDNESDAY...WITH THE POTENTIAL FOR
WESTERLY WIND GUSTS OF 45 MPH.

THE APPROACH OF ANOTHER LOW PRESSURE SYSTEM WILL BRING A CHANCE OF
THUNDERSTORMS FRIDAY NIGHT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED THROUGH TONIGHT.

LCZ422-423-460-LEZ444-LHZ361>363-421-422-441>443-462>464-191930-
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-
323 PM EDT MON APR 18 2011

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

A GALE WATCH IS IN EFFECT FOR NORTHERN LAKE HURON TUESDAY NIGHT AND
ACROSS ALL MARINE AREAS ON WEDNESDAY. REFER TO THE LATEST MARINE
FORECASTS FOR DETAILS.

A CHANCE OF THUNDERSTORMS WILL EXIST TUESDAY EVENING THROUGH
WEDNESDAY MORNING...MAINLY OVER LAKE ERIE AND LAKE ST CLAIR.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED THROUGH TONIGHT.

MR

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