Frost Advisory 6, NWS Detroit, MI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
904 PM EDT SUN OCT 7 2012

.UPDATE...

STRONG SUBSIDENCE BEHIND DEPARTING UPPER WAVE HELPING TO
AGRESSIVELY BREAK UP/CLEAR THE CLOUDS OVER LOWER MICHIGAN...AND
WITH DEW PTS CRASHING INTO THE 20S ACROSS WESTERN LOWER
MICHIGAN...DECIDED TO TWEAK MINS DOWN SLIGHTLY.
SUBSEQUENTLY...WILL ISSUE A FROST ADVISORY FOR WAYNE/MORNOE
COUNTIES...TO GO ALONG WITH THE FREEZE WARNING FOR THE REMAINDER
OF SOUTHEAST MICHIGAN.

&&

.AVIATION...ISSUED 649 PM EDT SUN OCT 7 2012

//DISCUSSION...

LATEST SATELLITE TRENDS SUPPORTS A PARTIAL CLEARING TREND THIS
EVENING...AS THE BACK EDGE OF THE CLOUDS OVER LAKE MICHIGAN IS
ALONG THE MICHIGAN SHORELINE...WITH BREAKS ALSO DEVELOPING OVER
LOWER MICHIGAN. STILL...WITH INCREASING SOUTHWEST FLOW (925-850
MB) TOMORROW MORNING...A NARROW BATCH OF LOW VFR CLOUDS COULD
IMPACT MBS...OTHERWISE THE OTHER TAF SITES LOOK CEILING FREE.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE CEILING BELOW 5000 FT WILL SCATTER OUT TOWARD
MIDNIGHT.

&&

.PREV DISCUSSION...ISSUED 328 PM EDT SUN OCT 7 2012

SHORT TERM...THIS EVENING AND TONIGHT

THE EXIT OF THE OHIO RIVER VORTICITY ANOMALY ALONG WITH THE
ASSOCIATED NEGATIVE INFLECTION POINT IN THE UPPER LEVEL JET
STRUCTURE WILL CAUSE THE LOWER TROPOSPHERIC LAKE EFFECT SHOWERS TO
RIP AWAY FROM THE SOUTHERN BASIN OF LAKE MICHIGAN AND FLUSH THROUGH
THE SOUTHERN CWA THIS EVENING. THE PRIOR DISCUSSION TALKED ABOUT THE
CONVECTIVELY INDUCED MESOSCALE LOW PRESSURE CIRCULATION AND THE
FEATURE CERTAINLY DID ARISE TO FRUITION...BEST SEEN IN MORNING
VISIBLE IMAGERY. THIS CIRCULATION WILL BE SHEARED APART GOING
FORWARD...REPRESENTED AS AN OPEN WAVE FEATURE NEAR THE SURFACE AS IT
SLIDES THROUGH THE M59 TO I 96 CORRIDORS. THIS SPECIFIC FORCING WILL
MAKE SHOWERS LIKELY PRIOR TO 03Z GENERALLY ALONG AND SOUTH OF M59.
WAS DETAILED IN HIKING POPS UPWARD CONSIDERABLY FOR A NARROW
CORRIDOR. THE LACK OF INSTABILITY THAT IS COMMONPLACE DURING THE
SUMMER JUST HIGHLIGHTS THAT WE ARE IN A DIFFERENT REGIME. SO WHILE
RADAR MAY BE NOISY THIS AFTERNOON/EVENING...DRY AIR IN THE LOWER
TROPOSPHERE WILL MAKE IT MORE DIFFICULT TO MEASURE ON THE FRIDGES OF
THE PRECIPITATION BAND EVIDENT ON RADAR.

OPAQUE ALTOSTRATUS THAT WAS UPSTREAM EARLIER ACROSS SOUTHERN
WISCONSIN/NORTHERN ILLINOIS SIGNALS THAT A FAIR AMOUNT OF SATURATION
AND CLOUD MATERIAL WILL NEED TO BE WORKED THROUGH SOUTHERN MICHIGAN
AS WELL. HAVE GONE WITH A PESSIMISTIC FORECAST AGAIN PERTAINING TO
CLOUDS. MODELS AGAIN BECOME LEAN WITH AMOUNT OF SATURATION AND CLOUD
POTENTIAL FOR THE DURATION OF THE OVERNIGHT...BUT IT GOES WITHOUT
SAYING THAT CONFIDENCE IS LOW ON WHETHER OR NOT CLOUDS WILL ERODE
COMPLETELY. 06Z/12Z INITIALIZATIONS SHOW THAT THE AMOUNT OF
SHORTWAVE RIDGING THAT WAS FORECASTED FOR LAST NIGHT WAS WAY WAY
OVERDONE IN YESTERDAYS SOLUTIONS. FEEL CONFIDENT THAT THERE IS A
LITTLE MORE MEAT TO THE SHORTWAVE RIDGE/WEAKNESS THAT IS SET TO PASS
THROUGH TONIGHT. THEREFORE...CLOUDS SHOULD LESSEN THE LATTER HALF OF
THE NIGHT WILL ALL OF THE AVAILABLE GUIDANCE SUGGESTING THAT SKIES
WILL CLEAR COMPLETELY. THUS...WILL FORECAST LOWS AGAIN TO FALL NEAR
THE FREEZING MARK IN MANY AREAS AND ISSUE A FREEZE WARNING FOR ALL
AREAS EXCEPT WAYNE AND MONROE COUNTIES.

LONG TERM...MONDAY THROUGH NEXT SUNDAY

LOW LEVEL SOUTHWESTERLY FLOW WILL DEVELOP ACROSS THE FORECAST AREA
ON MONDAY AND PERSIST THROUGH TUESDAY...LEADING TO A STEADY WARMING
TREND. THIS RETURN FLOW WILL BECOME ESTABLISHED OVER THE GREAT LAKES
AS THE STRONG SFC HIGH NOW OVER THE SRN PLAINS DRIFTS TO THE EAST
COAST. MEANWHILE...DEEPENING SFC LOW PRESSURE AND AN ASSOCIATED COLD
FRONT WILL MOVE FROM THE NORTHERN PLAINS INTO THE NORTHERN GREAT
LAKES ON TUES. THIS SYSTEM WILL BE IN RESPONSE TO A MID LEVEL
IMPULSE CASCADING INTO THE NRN PLAINS FROM NW CANADA. THE SOUTHWEST
FLOW IN ADVANCE OF THE FRONT WILL ADVECT FAIRLY DRY AIR INTO THE
FORECAST AREA ON MONDAY. IN LIGHT OF UPSTREAM TEMPS WHICH ARE STILL
QUITE COOL...HIGHS ON MON WILL LIKELY REACH THE MID 50S /STILL BELOW
NORMAL FOR EARLY OCTOBER/. THE GRADIENT WILL STRENGTHEN CONSIDERABLY
BY TUES...ACCELERATING THE RATE OF WARM AIR ADVECTION. THIS REMAINS
SUPPORTIVE OF DAYTIME HIGHS RISING BACK INTO THE 60S.

THE 12Z MODEL SOLUTIONS CONTINUE TO FOLLOW EARLIER TRENDS IN
SHOWING THE MID LEVEL WAVE AMPLIFYING AS IT ENTERS THE UPPER MIDWEST
/EVEN DEVELOPING A SLIGHT NEGATIVE TILT AS IT TRAVERSES LOWER MI
TUES NIGHT/. GOOD MID LEVEL HEIGHT FALLS AND UPPER JET DYNAMICS
SHOULD INVOKE A FAIRLY HEALTHY MID LEVEL FGEN RESPONSE. GIVEN THIS
WAVE ORIGINATING FROM A FAIRLY DATA SPARSE REGION...THERE REMAINS
SOME UNCERTAINTY AS TO HOW MUCH AMPLIFICATION WILL OCCUR AS IT
PUSHES ACROSS THE REGION. ALTHOUGH MODEL SOLUTIONS HAVE TRENDED MORE
PROGRESSIVE WITH THIS FEATURE...THEY REMAIN SUPPORTIVE OF LIKELY
POPS TUES NIGHT. THIS WAVE WILL REINFORCE THE LONG WAVE TROUGH
ACROSS THE ERN US ON WEDNESDAY...WITH COLD AIR /ALMOST AS COLD AS
THIS WEEKEND/ AGAIN ADVANCING ACROSS THE FORECAST AREA.

A BREAKDOWN OF THE REX BLOCK NOW OFF THE COAST OF NOAM BY MID WEEK
WILL MARK THE BEGINNING OF A LONG WAVE PATTERN CHANGE...LEADING TO
THE RETREAT OF THE EASTERN US LONG WAVE TROUGH. PRIOR TO THIS
OCCURRING...RECENT MEDIUM RANGE MODELS SUGGEST ANOTHER SHORT WAVE
IMPULSE TRACKING ACROSS THE GREAT LAKES THURS NIGHT...SENDING YET
ANOTHER COLD FRONT ACROSS THE STATE. TEMPS WILL REBOUND ON THURS
WITHIN THE SOUTHWEST FLOW IN ADVANCE OF THIS FRONT. ALTHOUGH THIS
LATE WEEK TROUGH IS NOT EXPECTED TO BE AS AMPLIFIED AS TUES NIGHTS
SYSTEM...VERY COLD LOW LEVEL AIR WILL STILL BE IN PLACE WITHIN THE
POST FRONTAL AIRMASS...BRINGING ANOTHER SURGE OF COLD AIR INTO SE MI
TO END THE WORKWEEK. A STRONG MODERATING TREND SHOULD THEN COMMENCE
NEXT WEEKEND. LARGE VARIANCE AMONG ENSEMBLE MEMBERS WITH RESPECT TO
THE PACE OF THE UPPER LOW EJECTING OUT OF THE SWRN US LEADS TO A LOW
CONFIDENCE FORECAST WITH RESPECT TO PRECIP CHANCES. ORDINARILY
MODELS TEND TO BE TOO FAST LIFTING THESE REMNANT LOWS INTO THE
CENTRAL US. THE POTENTIAL FOR A VERY STRONG ZONAL UPPER JET MAX
NOSING INTO THE PACIFIC NORTHWEST HOWEVER LEADS SOME CREDENCE TO THE
FASTER SOLUTIONS AND THUS SUPPORTS A CHANCE OF RAIN NEXT WEEKEND.

MARINE...

SOUTHWESTERLY WINDS WILL INCREASE MONDAY INTO TUESDAY IN ADVANCE OF
A STRONG COLD FRONT APPROACHING FROM THE NORTHWEST. RESIDUAL COLD
AIR OVER THE GREAT LAKES WILL LEAD TO UNSTABLE CONDITIONS THROUGH
TUESDAY MORNING...WHICH WILL PROMOTE GOOD MIXING POTENTIAL OVER THE
LAKES. RECENT MODEL SOLUTIONS INDICATE A CORE OF 35-40 KNOT WINDS
ATOP THE MIXED LAYER OVER LAKE HURON MONDAY NIGHT AND TUESDAY
MORNING. THIS WILL LEAD TO A HIGH PROBABILITY OF GALE FORCE WIND
GUSTS OVER MUCH OF THE LAKE AND HAS PROMPTED THE ISSUANCE OF A GALE
WATCH. ALTHOUGH THE SOUTHWEST WINDS WILL PERSIST THROUGH TUESDAY
AFTERNOON AND EVENING...MUCH WARMER AIR WILL ADVANCE ACROSS THE
LAKE. THE AIRMASS IS EXPECTED TO BE WARM ENOUGH TO ALLOW STABLE
CONDITIONS TO DEVELOP OVER THE WATER...THEREBY MAKING IT MORE
DIFFICULT FOR GALE FORCE WINDS TO REACH THE LAKE SURFACE. THE
PASSAGE OF THE COLD FRONT TUESDAY NIGHT WILL CAUSE THE WINDS TO VEER
TO THE NORTHWEST. ARCTIC AIR WILL THEN SPILL OVER THE REGION
WEDNESDAY. WINDS WILL CONTINUE TO BE STRONG...ALTHOUGH THE POTENTIAL
FOR GALES ON WEDNESDAY LOOK RATHER LOW AT THIS TIME. ANOTHER FRONT
IS FORECAST TO ADVANCE ACROSS THE REGION THURSDAY NIGHT. THIS SYSTEM
WILL KEEP CONDITIONS RATHER ROUGH ON THE LAKES RIGHT THROUGH THE END
OF THE WORKWEEK.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...FREEZE WARNING...MIZ047-MIZ048-MIZ049-MIZ053-MIZ054-MIZ055-MIZ060-
     MIZ061-MIZ062-MIZ063-MIZ068-MIZ069-MIZ070-MIZ075-MIZ082...FROM
     1 AM MONDAY TO 8 AM MONDAY.

     FROST ADVISORY...MIZ076-MIZ083...FROM 1 AM MONDAY TO 8 AM MONDAY.

LAKE HURON...
     GALE WATCH...LHZ361-LHZ362-LHZ363-LHZ421-LHZ422-LHZ441-LHZ442-
     LHZ443-LHZ462-LHZ463-LHZ464...FROM 8 PM MONDAY TO NOON TUESDAY.

LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

UPDATE.......SF
AVIATION.....SF
SHORT TERM...CB
LONG TERM....SC
MARINE.......SC

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
545 PM EDT SUN OCT 7 2012

MIZ047>049-053>055-060>063-068>070-075-076-082-083-080800-
MIDLAND-BAY-HURON-SAGINAW-TUSCOLA-SANILAC-SHIAWASSEE-GENESEE-LAPEER-
ST. CLAIR-LIVINGSTON-OAKLAND-MACOMB-WASHTENAW-WAYNE-LENAWEE-MONROE-
545 PM EDT SUN OCT 7 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST MICHIGAN.

.DAY ONE...TONIGHT

A FREEZE WARNING IS IN EFFECT TONIGHT FOR THE MAJORITY OF SOUTHEAST
MICHIGAN.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT.

LCZ422-423-460-LEZ444-LHZ361>363-421-422-441>443-462>464-080800-
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-
545 PM EDT SUN OCT 7 2012

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

.DAY ONE...TODAY AND TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

A GALE WATCH IS IN EFFECT FOR ALL OF LAKE HURON ON MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT.

SF

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