FXUS63 KDTX 061104
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
604 AM EST SUN DEC 6 2009
.AVIATION...
SATELLITE TRENDS SHOW A SCT DECK OF STRATO CU...BASED MAINLY AROUND
4500 FT...CONTINUEING TO ERODE ACROSS SOUTHEAST MICHIGAN WITH
SLIGHTLY WARMER AND DRIER LOW LEVEL AIR ADVECTING IN FROM THE
SOUTHWEST. BOTH COVERAGE AND CEILING HEIGHTS ARE EXPECTED TO BE MORE
VARIABLE AT FNT AND MBS WITH CONTINUED MOISTURE INFLUENCE FROM LAKE
MICHIGAN. WHILE AN IMPROVEMENT IN CONDITIONS IS NOW ONGOING AT THESE
TWO SITES...WATER VAPOR IMAGERY SHOWS A WEAK SHORT WAVE OVER IOWA.
THIS WAVE IS EXPECTED TO ENHANCE CLOUDS AND FLURRIES OFF LAKE
MICHIGAN...WITH CONVERGENCE FOCUSED NEAR FNT AND MBS...EVENTUALLY
BECOMING ORIENTED MORE OVER MBS DURING THIS AFTERNOON. THIS SUGGEST
SOME FLURRIES AND POSSIBLE MVFR CEILINGS WILL BE POSSIBLE AT MBS
THROUGH A GOOD PORTION OF THE DAY.
ANOTHER LOW PRESSURE SYSTEM WILL BRING THE CHANCE FOR SNOW SHOWERS
TO SOUTHEAST MICHIGAN TONIGHT. THE BEST CHANCE WILL BE ACROSS
KMBS...SO WILL CARRY A PREVAILING GROUP FOR SNOW AT THIS SITE. THE
REST OF THE SITES WILL HAVE A LOW ENOUGH OF A CHANCE TO LEAVE OUT OF
THE TAFS AT THIS POINT.
&&
.PREV DISCUSSION...ISSUED 445 AM EST SUN DEC 6 2009
SHORT TERM...TODAY
WEAK SHORTWAVES EMBEDDED IN THE FAST WESTERLY FLOW...ALONG WITH
MOISTURE ENHANCEMENT FROM THE GREAT LAKES WILL BRING A CONTINUED
CHANCE OF FLURRIES NORTH OF INTERSTATE 69 TODAY. THE FLURRIES WILL
NOT AMOUNT TO MUCH...WITH NO ACCUMULATION EXPECTED AS WARMER 850 MB
TEMPERATURES LEAD TO LOWER DELTA T VALUES. TEMPERATURES WILL REBOUND
TODAY AS 850 MB TEMPS WARM SEVERAL DEGREES FROM THE MID TEENS BELOW
ZERO YESTERDAY TO -7 TO -9 DURING THE DAY TODAY. AS A RESULT
TEMPERATURES SHOULD CLIMB INTO THE 30S ACROSS SOUTHEAST MICHIGAN
THIS AFTERNOON.
LONG TERM...TONIGHT THROUGH SATURDAY
THE UPPER WAVE EVIDENT ON WATER VAPOR PUSHING ACROSS NORTHERN
ARIZONA WILL RACE NORTHEAST AND INTO THE SOUTHERN GREAT LAKES BY
MONDAY. THIS WILL PUSH A SURFACE LOW ACROSS LOWER MICHIGAN..AS IT
RIDES ALONG A LOOSE FRONTAL BOUNDARY THAT WILL STALL THIS
EVENING...LYING FROM CENTRAL IOWA TO ACROSS CENTRAL LAKE HURON. AS
THE LOW APPROACHES...THE FRONT SHOULD CONTRACT AND LIFT FURTHER
NORTHWARD INTO NORTHERN LOWER MICHIGAN AND LAKE HURON. EXPECT THE
HEAVIEST SWATH OF SNOW TO THEREFORE FALL IN A NARROW BAND JUST TO
THE NORTH OF THE FORECAST AREA AND OVER LAKE HURON...AS THIS
BOUNDARY PROVIDES THE BEST FOCUS FOR PRECIPITATION. THIS IDEA IS
SUPPORTED BY THE GFS/EURO/GEM. HAVE DROPPED SNOW ACCUMULATIONS
OVERALL...WITH TOP AMOUNTS OF BETWEEN 1 AND 2 INCHES BRUSHING THE
NORTHERN PORTIONS OF BAY AND MIDLAND COUNTIES...QUICKLY TAPERING
DOWN BELOW ONE INCH AS YOU HEAD SOUTHWARD TOWARDS I-69. SNOW SHOWERS
ARE STILL EXPECTED ACROSS ALL OF SOUTHEAST MICHIGAN LATE TONIGHT AND
TOMORROW AS THE PASSAGE OF THE SURFACE LOW...UPPER WAVE...AND LEFT
EXIT REGION FORCING COINCIDE.
AFTER A QUIET DAY UNDER SURFACE HIGH PRESSURE ON TUESDAY...ATTENTION
TURNS TO A MUCH STRONGER STORM SYSTEM THAT WILL IMPACT THE AREA
TUESDAY NIGHT THROUGH THURSDAY. MODELS REMAIN IN SOLID AGREEMENT
WITH PUSHING A STRONG LOW PRESSURE SYSTEM UP ACROSS THE GREAT LAKES
ON WEDNESDAY AS THE UPPER TROUGH OVER THE PACNW COAST ZIPS ACROSS
THE COUNTRY IN FAST WESTERLY FLOW. THERE REMAINS A GREAT DEAL OF
SPREAD WITH REGARD TO WHERE THE CENTER OF THIS SYSTEM WILL TRACK AS
IT LIFTS ACROSS MICHIGAN...HOWEVER THE 00Z MODEL SUITE OVERALL HAS
TRENDED TO THE NORTHWEST WITH THE TRACK...LENDING MORE CONFIDENCE TO
SOME WARMER AIR NOSING IN LATE TUESDAY NIGHT/WEDNESDAY. 00Z LOW
CENTER TRACKS RANGED FROM TOLEDO (UKMET) TO TRAVERSE CITY (WRF
HEMI)...WITH THE EURO LIFTING THE SYSTEM ACROSS HOUGHTON LAKE...THE
GEM/6Z NAM LIFTING IT ACROSS SAGINAW BAY AND THE GFS TAKING THE
CENTER ACROSS FLINT.
WITH COLD AIR ALREADY IN PLACE AT THE ONSET OF PRECIPITATION TUESDAY
NIGHT...EXPECT SNOW TO SPREAD INTO THE AREA AS ISENTROPIC ASCENT AND
FRONTOGENETICAL FORCING INCREASE WITHIN THE DEFORMATION ZONE
(ESPECIALLY AFTER 1 AM) AND AS A COUPLED JET STRUCTURE MOVES IN
OVERHEAD. CURRENT FORECAST CALLS FOR BETWEEN 2 AND 4 INCHES OF SNOW
OVERNIGHT...WITH THE LIGHTEST OF THESE AMOUNTS TOWARDS THE OHIO
BORDER AS RAIN MIXES IN LATE. TAKING INTO ACCOUNT THE LATEST
TRACKS OF THE GFS/EURO/GEM/NAM...HAVE ACCOUNTED FOR A CHANGEOVER TO
ALL RAIN FROM 12-21Z ON WEDNESDAY SOUTH OF M-59...WITH AT LEAST A
CHANCE MENTION OF A RAIN/SNOW MIX NORTH OF THERE. 00Z MODELS OVERALL
ARE ALL WARMER...WITH EVEN THE COLD-END-OF-THE-GUIDANCE-ENVELOPE GFS
SHOWING A CHANGE TO RAIN AS FAR NORTH AS FLINT. IF THE OVERALL TRACK
CONTINUES TO SHIFT NORTHWEST (AS IT COULD WITH A DEEPER
SYSTEM)...FUTURE FORECAST PACKAGES WOULD HAVE TO SHIFT THE RAIN/SNOW
LINE FURTHER TO THE NORTHWEST AND DECREASE SNOW AMOUNTS. WHILE THE
SYSTEM IS LOOKING WARMER...WE ARE BY NO MEANS OUT OF THE WOODS YET.
STORM TOTALS RIGHT NOW RANGE BETWEEN 2 AND 7 INCHES (SOUTHEAST TO
NORTHWEST ACROSS THE FORECAST AREA)...BUT THESE ARE CONSERVATIVE
WITH TAKING THE WARM AIR FULLY INTO ACCOUNT. (GFS WAS STILL TAKEN
STRONGLY INTO ACCOUNT SINCE IT WAS MORE CONSERVATIVE WITH DEEPENING
THE LOW.) WFR HEMI SOLUTION ACROSS TVC WOULD BE ALL RAIN...WITH THE
EURO/NAM/GEM NOW LOOKING MUCH LEANER ON SNOW ACCUMULATIONS AS WELL.
WILL HOPE FOR ADDITIONAL CLARITY WITH THE 12Z SUITE.
ALL PRECIPITATION WILL CHANGE BACK TO SNOW BY WEDNESDAY EVENING AS A
POWERFUL COLD FRONT SWEEPS WEST TO EAST ACROSS MICHIGAN. EXPECT
PRECIPITATION TO CONTINUE IN WRAP AROUND MOISTURE/TROWAL ON THE
BACKSIDE OF THE SYSTEM...WITH LAKE EFFECT CONTRIBUTIONS AS WELL. BIG
STORY ON THURSDAY WILL BE COLD AND WINDY CONDITIONS WITH NUMEROUS
SNOW SHOWERS CONTINUING. HAVE DROPPED HIGHS INTO THE 20S GIVEN
STRONG COLD AIR ADVECTION.
THE END OF THE WEEK LOOKS TO BRING A CONTINUATION OF COLD
TEMPERATURES WITH OCCASIONAL LIGHT SNOW SHOWERS AS NORTHWEST FLOW
CONTINUES OVER THE GREAT LAKES.
MARINE...
SOUTHWEST WINDS WILL INCREASE TODAY AS A WEAK SURFACE TROUGH PASSES
TO THE NORTH. THE INCREASED WINDS AND LONG FETCH WILL BRING WAVES
BACK UP TO SMALL CRAFT ADVISORY CRITERIA ACROSS THE SAGINAW BAY TO
THE TIP OF THE THUMB. GIVEN THE HIGH WINDS ALREADY ACROSS SAGINAW
BAY WILL HOIST THE SMALL CRAFT ADVISORIES IMMEDIATELY ACROSS THESE
AREAS AND INCLUDE THE PORT AUSTIN TO HARBOR BEACH NEARSHORE ZONE
WITH HIGH WAVES ACROSS THE TIP OF THE THUMB.
THERE IS A WEAKER AREA OF LOW PRESSURE PASSING THROUGH THE AREA ON
MONDAY...BUT FLOW WILL BE RATHER WEAK WITH THIS FEATURE. THE NEXT
GALE POTENTIAL WILL BE FOR TUESDAY NIGHT RIGHT INTO THURSDAY AS A
VERY STRONG STORM DEEPENS OVER THE LAKES REGION.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...
SMALL CRAFT ADVISORY...SAGINAW BAY AND THE NEARSHORE WATERS FROM
PORT AUSTIN TO HARBOR BEACH...UNTIL 7 PM SUNDAY.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....KURIMSKI
SHORT TERM...KURIMSKI
LONG TERM....HLO
MARINE.......KURIMSKI
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AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
