FXUS63 KDTX 090921
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
421 AM EST WED DEC 9 2009
.SHORT TERM...TODAY
A DEEPENING LOW PRESSURE SYSTEM ACROSS CENTRAL ILLINOIS WILL QUICKLY
MOVE NORTHEAST TO NORTHERN LAKE HURON BY THIS AFTERNOON. A
SIGNIFICANT DRY SLOT SHOWS ON WATER VAPOR IS MAKING ITS WAY INTO
SOUTHEAST MICHIGAN...WHICH IS HIGHLIGHTED BY THE BACK EDGE OF THE
HIGHEST REFLECTIVITIES MOVING INTO SOUTHERN MICHIGAN. THE DRY SLOT
WILL PROVIDE A PERIOD OF LOWER PRECIP CHANCES AS MUCH OF THE
MOISTURE IS STRIPPED OUT OF THE MIDDLE LAYERS. THE STRIPPED OUT
MOISTURE AND WARMER TEMPERATURES WILL CONTINUE TO CHANGEOVER FROM
SNOW TO RAIN EARLY THIS MORNING WITH THE SOUTHERN HALF OF THE CWA
ALREADY AT ALL RAIN AT ISSUANCE. WITH THE DRIER AIR...WARMER
TEMPERATURES AND THE SLOW CHANGEOVER TO RAIN THE HEADLINES WILL
EXPIRE AT THEIR DESIGNATED TIMES FROM SOUTH TO NORTH AS THE IMPACT
FROM HEAVY SNOW AND MIXED WINTERY PRECIPITATION DECREASES EARLY THIS
MORNING.
AS THE LOW HEADS OFF TOWARDS NORTHERN LAKE HURON THIS AFTERNOON COLD
AIR WILL ADVECT BACK INTO THE AREA CHANGING THE RAIN BACK OVER TO
SNOW FROM NORTH TO SOUTH. DESPITE THE CHANGEOVER FROM RAIN TO SNOW
THE BEST MOISTURE FROM THIS SYSTEM WILL BE OUT OF THE CENTRAL GREAT
LAKES...WITH ONLY LIGHT ACCUMULATIONS EXPECTED THIS AFTERNOON.
AS THE LOW PASSES TO THE WEST...THE HEART OF THE DRY SLOT WILL MOVE
INTO THE CWA AROUND NOON AS STRONG ISENTROPIC DESCENT AND A VERY
TIGHT PRESSURE GRADIENT BRING EXTREMELY WINDY CONDITIONS TO THE AREA
TODAY. THE STRONG DESCENT WILL BRING STRONG 925 MB WINDS TO THE
SURFACE AS SOUTHWEST WINDS OF 45 TO 55 KNOTS AT THIS LEVEL ALONG AND
SOUTH OF M-59 WARRANTS A HIGH WIND WARNING WHERE THE PREVIOUS WATCH
WAS ISSUED. A BIT FURTHER NORTH OF M-59...925 WINDS WILL BE A BIT
LIGHTER AT 35 TO 40 KNOTS...WHICH WILL PROBABLY NOT MEET HIGH WIND
WARNING CRITERIA BUT WILL CERTAINLY BE HIGH ENOUGH FOR A WIND
ADVISORY. THEREFORE WILL ISSUE THIS HEADLINE JUST NORTH OF THE HIGH
WIND WARNING. THE ONE EXCEPTION WILL BE THE SAGINAW VALLEY WHICH
WILL BE CLOSE ENOUGH TO THE TRACK OF THE LOW FOR A LIGHTER PRESSURE
GRADIENT AND FAR ENOUGH NORTHWEST TO NOT BENEFIT AS MUCH FROM THE
ISENTROPIC DESCENT AND DRY SLOT FURTHER SOUTH. WITH THE LESS
FAVORABLE CONDITIONS WILL OPT TO LEAVE THE 3 COUNTIES ENCOMPASSING
THE SAGINAW VALLEY OUT OF THE WIND HEADLINES.
&&
.LONG TERM...TONIGHT THROUGH TUESDAY
BIG STORY: COLD AIR AND GUSTY WINDS WILL PRODUCE A PROLONGED PERIOD
WITH WIND CHILLS IN THE SINGLE DIGITS TO SLIGHTLY BELOW ZERO TONIGHT
THROUGH SATURDAY MORNING. LAKE EFFECT SNOW SHOWERS WILL ALSO BE
POSSIBLE THROUGH FRIDAY...WITH ACCUMULATIONS OF A FEW INCHES
POSSIBLE.
STORY OVERNIGHT WILL BE A CONTINUATION OF COLD AIR ADVECTION AND
WINDY CONDITIONS BEHIND THE FRONT. WIND HEADLINES WILL CONTINUE
UNTIL 4 AM AS TIGHT SURFACE PRESSURE GRADIENT...ISENTROPIC
DESCENT...AND GOOD THERMAL SUPPORT CONTINUE TO MIX HIGHER GUSTS DOWN
TO THE SURFACE. IT DOES LOOK LIKE THERE WILL BE A LULL IN ACTIVITY
DURING THE EARLY MORNING AS THE LOW LIFTS AWAY...BEFORE WINDS BEGIN
TO INCREASE AGAIN BY LATE MORNING AND AFTERNOON. ALTHOUGH THE AREA
OF STRONG SURFACE LOW PRESSURE WILL HAVE LIFTED NORTHEAST INTO
QUEBEC...A STRONG DOME OF HIGH PRESSURE BUILDING TO OUR SOUTHWEST
WILL ACTUALLY REINTENSIFY THE PRESSURE GRADIENT BEHIND THE DEPARTING
SYSTEM. IT IS POSSIBLE WE MAY NEED ANTIHERO SET OF WIND HEADLINES
FOR TOMORROW AFTERNOON...ESPECIALLY GIVEN CONTINUED THERMAL SUPPORT
FROM COLD AIR ADVECTION. MODELS HOLD THE TIGHT PRESSURE GRADIENT
OVER THE CENTRAL GREAT LAKES THROUGH THURSDAY NIGHT AND INTO THE
FIRST HALF OF FRIDAY...AS BOTH THE LOW TO OUR NORTHEAST AND THE HIGH
TO OUR SOUTHWEST SHIFT EAST TOGETHER. CHILLY TEMPERATURES WILL
SETTLE INTO THE REGION TONIGHT WITH LITTLE RECOVERY EXPECTED FOR
DAYTIME HIGHS ON THURSDAY. BOTH LOWS TONIGHT AND HIGHS ON THURSDAY
WILL BE FROM THE MID TEENS TO LOW 20S. COLD TEMPERATURES WILL
CONTINUE THROUGH FRIDAY...WITH CHILLY MORNING LOWS RANGING FROM 8-14
AND HIGHS ONLY IN THE LOW 20S.
STRONG WESTERLY FLOW ACROSS LAKE MICHIGAN WITH LAKE TO H850 DELTA T
VALUES STARTING AT 17 C AND FALLING TO 27 C BY THURSDAY
AFTERNOON...ALONG WITH A FAIRLY DEEP SATURATED LAYER AND GOOD
LOW/MID LEVEL LAPSE RATES WILL ALL SUPPORT LAKE EFFECT SNOW FROM
TONIGHT THROUGH FRIDAY. ALTHOUGH THE WHOLE FORECAST AREA WILL SEE
CHANCES FOR THESE SHOWERS...MODEL WIND CONVERGENCE FIELDS SHOW
SUPPORT FOR ADDITIONAL BANDING STRETCHING MAINLY FROM I-69 DOWN TO
THE OHIO BORDER DURING THIS PERIOD. ACCUMULATIONS OF A FEW INCHES
OVERALL ARE POSSIBLE SOUTH OF I-69.
HIGH PRESSURE WILL BUILD OVER THE REGION FRIDAY NIGHT AND
SATURDAY...WITH LIGHTER WINDS AND A MORE SOUTHERLY COMPONENT HELPING
LAKE EFFECT SNOW SHOWERS END ACROSS SOUTHEAST MICHIGAN. DRIER
AIRMASS AND DEEP LAYER SUBSIDENCE MAY ALLOW THE SUN TO PEAK OUT AS
WELL. TEMPERATURES WILL REMAIN COLD AND BELOW NORMAL...BUT SHOULD
MODERATE SEVERAL DEGREES FROM FRIDAY UNDER VERY WEAK WARM AIR
ADVECTION.
MODELS THEN SHOW A STRONG UPPER WAVE AND JET STREAK RIDING THROUGH
WESTERN CANADA...AS WEAKER SHORTWAVE ENERGY DROPS DOWN THE
CALIFORNIA COAST. AS THE RESULTANT ELONGATED TROUGH FORMED BY THESE
TWO SYSTEMS BEGINS TO PUSH EASTWARD...MODELS SPIN UP AND LIFT A
FAIRLY STRONG LOW PRESSURE SYSTEM NORTHEAST OUT AHEAD OF IT. 00Z
EURO LIFTS THIS SYSTEM UP INTO MICHIGAN ON MONDAY...WHILE THE 00Z
GFS LIFTS IT MORE INTO WISCONSIN AND MINNESOTA ON SUNDAY NIGHT.
TRACK OF THE SURFACE LOW IS STILL TOO EARLY TO DETERMINE ESPECIALLY
GIVEN THE VARIABILITY MODELS HAVE SHOWN OVER THE PAST FEW DAYS WITH
THESE TWO WAVES...BUT THIS SYSTEM COULD BE THE NEXT ONE TO WATCH.
CURRENT TRACKS TO THE NORTH AND WEST WOULD ALLOW WARMER AIR TO SURGE
UP INTO THE REGION ALONG WITH THE MOISTURE (00Z EURO/GFS SHOWS 925
TEMPS RISING ABOVE FREEZING)...BUT GIVEN THE COLD AIRMASS THAT WILL
ALREADY BE ENTRENCHED WELL TO OUR SOUTH...THIS WOULD NOT NECESSARILY
MEAN RAIN WOULD FALL. HAVE LET THE INHERITED FORECAST RIDE SINCE
THIS SOLUTION HAS JUST COME TOGETHER AND WILL MONITOR IN FUTURE RUNS.
&&
.MARINE...
LOW PRESSURE IN NORTHERN ILLINOIS AT 985 MB WILL DEEPEN TO 975 MB
OFFSHORE OF KENOSHA WISCONSIN DURING THE MORNING AND THEN MOVE INTO
NORTHERN LAKE HURON TONIGHT. EASTERLY GUSTS TO STORM FORCE REMAIN
EXPECTED OVER THE NORTH HALF OF LAKE HURON AS THE SYSTEM
APPROACHES...AND THEN OVER THE SOUTH HALF DOWN TO WESTERN LAKE ERIE
TONIGHT AS THE SYSTEM EXITS THE REGION. IN BOTH CASES, COLD AIR
BEING DRAWN OVER THE WATER WILL LEAD TO ENOUGH INSTABILITY FOR DEEP
TURBULENT MIXING OF STRONG WINDS ALOFT DOWN TO THE LAKE SURFACE.
AN ADDITIONAL MAJOR IMPACT OF THIS STORM WILL BE WAVE HEIGHTS WITH
THE ONSHORE FLOW. WAVE HEIGHTS IN EXCESS OF 22 FEET WILL BE POSSIBLE
ACROSS THE WESTERN WATERS OF LAKE HURON NORTH OF SAGINAW BAY. THERE
WILL BE A LULL IN THE WINDS AS THE LOW CENTER TRACKS THROUGH
NORTHERN PORTIONS OF THE LAKE. THIS WILL BE FOLLOWED BY A STRONG
POLAR COLD FRONT THAT WILL SLICE THROUGH SOUTHERN LAKE HURON...LAKE
ST CLAIR...AND THE MICHIGAN WATERS OF LAKE ERIE THIS AFTERNOON AND
TONIGHT. A SECONDARY TIME PERIOD FOR STORM FORCE WINDS WILL OCCUR
ALONG AND BEHIND THIS FRONT FOR SOUTHERN LAKE HURON SOUTH THROUGH
WESTERN LAKE ERIE. A PROLONGED PERIOD OF GALE FORCE WINDS ARE THEN
EXPECTED TO PERSIST THROUGH THURSDAY NIGHT AND FRIDAY.
&&
.PREV DISCUSSION...ISSUED 1218 AM EST WED DEC 9 2009
AVIATION...
SNOW IS IN THE PROCESS OF MIXING WITH AND CHANGING TO RAIN IN THE
DETROIT AREA. THIS CONDITION WILL SPREAD NORTHWARD TO PONTIAC AND
FLINT DURING THE EARLY MORNING HOURS BUT EXPECT SNOW TO REMAIN THE
PRIMARY TYPE AT SAGINAW. WITH MBS AS AN EXCEPTION, THE TRANSITION
TO RAIN WILL EASE AVIATION CONDITIONS IN TERMS OF PRECIPITATION
BUT MILD AIR MOVING IN FROM THE SOUTH WILL KEEP CEILING AND
VISIBILITY IN THE IFR/LIFR RANGE AS THE LOW MOVES THROUGH CENTRAL
LOWER MICHIGAN.
THE MAIN STORY FOR THE DAYTIME HOURS WILL BE THE WIND. THE DRY
SLOT OF THIS LOW PRESSURE SYSTEM WILL REDUCE THE PRECIPITATION TO
SPOTTY LIGHT RAIN SHOWERS OR DRIZZLE DURING THE DAYLIGHT HOURS.
IMPROVEMENT IN CEILING AND VISIBILITY WILL COME AT THE EXPENSE OF
SOUTHWEST WINDS GUSTING TO 40 KNOTS WITH A FEW GUSTS NEAR 50 KNOTS
POSSIBLE AS COLD AIR SPILLS BACK INTO THE REGION. THE GUSTY
CONDITIONS WILL THEN LAST WELL INTO THE EVENING WHILE TURNING
TOWARD THE WEST. THIS WIND DIRECTION AND THE COLD AIR WILL DIRECT
SNOW SHOWERS INTO THE AREA FROM LAKE MICHIGAN, MAINLY TOWARD
PONTIAC AND FLINT.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER STORM WARNING...MIZ047-MIZ048...UNTIL 10 AM WEDNESDAY.
HIGH WIND WARNING...MIZ063-MIZ068-MIZ069-MIZ070-MIZ075-MIZ076-
MIZ082-MIZ083...FROM NOON WEDNESDAY TO 4 AM THURSDAY.
WINTER WEATHER ADVISORY...MIZ055-MIZ060-MIZ061-MIZ062...UNTIL 7 AM
WEDNESDAY.
WIND ADVISORY...MIZ049-MIZ054-MIZ055-MIZ060-MIZ061-MIZ062...FROM
NOON WEDNESDAY TO 4 AM THURSDAY.
WINTER WEATHER ADVISORY...MIZ049-MIZ053-MIZ054...UNTIL 10 AM
WEDNESDAY.
LAKE HURON...
GALE WARNING...LHZ361-LHZ362...FROM 7 PM WEDNESDAY TO 4 PM FRIDAY.
STORM WARNING...LHZ361-LHZ362...UNTIL 7 PM WEDNESDAY.
GALE WARNING...LHZ363-LHZ462-LHZ463-LHZ464...FROM 4 AM THURSDAY TO
4 PM FRIDAY.
STORM WARNING...LHZ363-LHZ421-LHZ441-LHZ442-LHZ443-LHZ462-LHZ463-
LHZ464...UNTIL 4 AM THURSDAY.
GALE WARNING...NEARSHORE WATERS FROM PORT AUSTIN TO PORT HURON
INCLUDING OUTER SAGINAW BAY...FROM 4 AM THURSDAY TO 4 AM
FRIDAY.
GALE WARNING...INNER SAGINAW BAY...UNTIL 4 AM FRIDAY.
LAKE ST CLAIR...
GALE WARNING...FROM 4 AM THURSDAY TO 4 AM FRIDAY.
STORM WARNING...UNTIL 4 AM THURSDAY.
MI WATERS OF LAKE ERIE...
GALE WARNING...FROM 4 AM THURSDAY TO 4 AM FRIDAY.
LOW WATER ADVISORY...FROM NOON WEDNESDAY TO 7 PM THURSDAY.
STORM WARNING...UNTIL 4 AM THURSDAY.
&&
$$
SHORT TERM...KURIMSKI
LONG TERM....HLO
MARINE.......KURIMSKI
AVIATION.....BT
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