Winter Storm in Michigan, December 19, 2004

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
953 PM EST SAT DEC 18 2004

.UPDATE...

FOCUS IS ON LAKE EFFECT SNOW EVOLUTION FROM LAKE HURON, AND EVEN
SAGINAW BAY, INTO THE THUMB OVERNIGHT AND SUNDAY.

A MODEST BURST OF SNOW SHOWERS WILL ACCOMPANY A STRONG COLD FRONT AS
IT MOVES THROUGH THE REST OF SE MICHIGAN THIS EVENING. THIS WILL GO
ALONG WITH GENERALLY LIGHT SNOW THAT HAS BEEN IN PROGRESS AHEAD OF
THE FRONT, ASSOCIATED WITH A WEAK UPPER WAVE MOVING THROUGH OHIO.
ALL OF THIS ACTIVITY WILL EXIT TO OUR SOUTH AND EAST WITH THE FRONT
RIGHT AROUND MIDNIGHT.

AFTER THAT, FULL ATTENTION TURNS TO LAKE EFFECT SNOW THAT WILL START
TO RAMP UP ABOUT THE SAME TIME, OR SHORTLY AFTER MIDNIGHT. LAKE TO
850 MB INSTABILITY WILL BE EXTREME AS TEMPERATURES DROP TO ABOUT
-22C BY 4 AM WITH LAKE DELTA-T IN THE MID TO UPPER 20S. FORECAST
SOUNDINGS FROM THE ETA SHOW INVERSION HEIGHT/EQUILIBRIUM LEVEL
AVERAGING ABOUT 7000 FEET BY THEN AS WELL. THE BIG WILD CARD WILL BE
WHERE THE DOMINANT BAND SETS UP AND WHERE IT WILL MOVE IN THE FACE
OF A STRONG NORTH TO NORTHWEST FLOW. THIS WILL BE MONITORED BY
SATELLITE AS THE MID LEVEL CLOUDS STRIP AWAY DURING THE EARLY
MORNING HOURS.

OUR GOING FORECAST PACKAGE LOOKS GOOD WITH THE NORTHEAST PORTION OF
HURON COUNTY EXPECTED TO ENCOUNTER MULTIPLE MINOR BANDS OF LAKE
EFFECT, IF NOT THE DOMINANT BAND, OVERNIGHT AND ON SUNDAY. THE ONLY
ADJUSTMENT WILL BE TO RAISE ACCUMULATIONS INTO THE 1 TO 3 INCH RANGE
IN TUSCOLA COUNTY TO ACCOUNT FOR AN ACTIVE SAGINAW BAY.
&&

.AVIATION...

SNOW WILL ACCOMPANY MVFR CLOUDS AND VISIBILITY FOR A FEW HOURS THIS
EVENING, BUT THIS WILL GET SCOURED OUT AFTER THE COLD FRONT MOVES
THROUGH THE AREA AND THE WIND TURNS MORE FROM THE NORTH.

A GUSTY NORTH WIND AND COLD TEMPERATURES WILL BE THE STORY FROM THE
LATE OVERNIGHT HOURS THROUGH SUNDAY, BUT WITH VFR CONDITIONS
OTHERWISE.
&&

.SHORT TERM...

UPPER LEVEL TROUGH AXIS WILL PUSH SOUTHEAST ACROSS MICHIGAN
OVERNIGHT...USHERING IN THE COLDEST AIR OF THE SEASON. ELONGATED
SURFACE LOW STRETCHES FROM NORTHERN QUEBEC TO NORTHERN MICHIGAN. THE
LEADING SURFACE TROUGH ACCOMPANIED BY SNOW SHOWERS WILL MOVE ACROSS
THE AREA BY EARLY THIS EVENING WITH A STRONGER COLD PUSH COMING WITH
THE SECONDARY TROUGH THAT WILL MOVE ACROSS SOUTHEAST MICHIGAN BY
MIDNIGHT. THE BACK EDGE OF A DENSE CLOUD DECK CAN CURRENTLY BE SEEN
DRAPING ACROSS NORTHERN WISCONSIN AND LAKE SUPERIOR. THIS BACK EDGE
INDICATING HOW QUICKLY THE MOISTURE WILL MOVE OUT OF THE AREA BEHIND
THE FRONT WITH SKIES STARTING TO CLEAR BY MORNING. BITTERLY COLD
ARCTIC AIR WILL SLIDE INTO THE AREA BEHIND THE FRONT TONIGHT WITH
850 MB TEMPS DROPPING FROM -4C TO -24C BY SUNDAY MORNING.

THIS EVENING EXPECT SNOW SHOWERS TO MOVE ACROSS THE AREA WITH UP TO
AN INCH POSSIBLE NORTH OF I-69 IN AN AREA OF BETTER LIFT. THIS IS
SUPPORTED BY A WEAK SHORTWAVE MOVING NORTHEAST ACROSS MICHIGAN SHOWN
ON WATER VAPOR AHEAD OF THE STRONGER TROUGH PUSHING DOWN FROM THE
NORTHWEST. SYSTEM IS STILL SOMEWHAT STARVED FOR MOISTURE BUT THE
BEST PERIOD OF OMEGA WILL BE EARLY THIS EVENING AS THIS WAVE MOVES
BY. AN AREA OF BETTER FRONTOGENETICAL FORCING WILL BE TO THE
NORTHEAST OF OUR CWA WHERE THE SHORTWAVE INTERACTS BETTER WITH THE
SURFACE FRONT.

MAIN FORECAST QUESTION FOR TONIGHT IS WHERE THE LAKE EFFECT BAND
WILL SET UP OFF OF SOUTHERN LAKE HURON. THERE IS HIGH CONFIDENCE
THAT A BAND WILL SET UP WITH ALMOST 1000 J/KG OF LAKE INDUCED CAPE
AND 26 DEGREE TEMPERATURE DIFFERENCE FROM THE LAKE SURFACE TO
850MB...BUT THE EXACT LOCATION IS NOT QUITE AS SIMPLE. LOOKS LIKE
BEST CONVERGENCE WILL BE JUST NORTH OF THE THUMB ORIENTED TOWARDS
SOUTHERN ONTARIO. HURON COUNTY MAY START TO SEE SOME LAKE EFFECT BY
2 AM AND WILL CONTINUE THROUGH AT LEAST NOON ON SUNDAY...WITH LESSER
AMOUNTS INTO THE AFTERNOON. 700MB TROUGH AXIS MOVES EAST OF THE
THUMB BY AROUND 15Z ON SUNDAY ENABLING THE STEERING FLOW THROUGH
ABOUT 15000 FEET TO BE NORTHERLY. THIS WOULD PROVIDE A MORE
FAVORABLE FLOW FOR THE BANDS TO SET UP OVER SANILAC AND POSSIBLY ST
CLAIR COUNTIES. WILL ISSUE LAKE EFFECT SNOW WARNING FOR HURON COUNTY
WITH LAKE EFFECT SNOW ADVISORY FOR NORTHEASTERN SANILAC. THESE BANDS
WILL BE NARROW WITH SNOW AMOUNTS DECREASING GREATLY AS YOU HEAD
INLAND. FLOW LOOKING UNFAVORABLE TO SEE MUCH LAKE ENHANCEMENT SOUTH
OF PORT SANILAC BUT WILL HAVE TO WAIT UNTIL MORNING TO KNOW FOR
SURE.

WINDS WILL BE STRONG TONIGHT WITH GUSTS TO 30 MPH OVER THE LAND WITH
EVEN STRONGER GUSTS OVER AREAS ADJACENT TO LAKE HURON. WIND CHILLS
WILL DROP BELOW ZERO BY SUNDAY MORNING WITH SOME AREAS DIPPING BELOW
-10. THESE STRONG WINDS WILL CAUSE BLOWING SNOW TO REDUCE
VISIBILITIES BELOW A MILE ALONG THE SHORE IN HURON COUNTY AS LAKE
EFFECT SNOW BEGINS.

&&

.LONG TERM...

SURFACE RIDGE BUILDS OVERHEAD SUNDAY NIGHT AND SHOULD PRETTY MUCH
KILL OFF SNOWFALL NEAR LAKE HURON AS LOW LEVEL WINDS BECOME
SOUTHWEST...THEN VIGOROUS WARM ADVECTION PATTERN SETS UP AHEAD OF
TUESDAY COLD FRONT. PREFER SLOWER GFS FOR TIMING OF COLD FRONT...AS
HAS BEEN MORE CONSISTENT RUN TO RUN AND ALSO CONSISTENT WITH SLOWER
PROGRESSION OF UPSTREAM MID LEVEL TROUGH. AT 500 MB...SHORTWAVE
RIDGE DEVELOPING OVERHEAD SUNDAY NIGHT...THEN GIVING WAY TO RATHER
BROAD SCALE LOWERING OF HEIGHTS FROM THE PLAINS TO GREAT LAKES.

SHORT RESPITE FROM SNOW ENDING BY MONDAY AS STRONG WARM ADVECTION
PATTERN/ISENTROPIC LIFT AS AT 280 K SETS UP...WITH ASSOCIATED GOOD
850 TO 500 MB QVECTOR CONVERGENCE MONDAY INTO MONDAY NIGHT...AS WELL
AS MODEST TOTAL FRONTOGENESIS. 700 MB OMEGA LIFT BEEFING UP AGAIN
MONDAY BY AFTERNOON...THEN MODEST THROUGH TUESDAY. DEEPER MOISTURE
RETURNS MONDAY TO ALSO SUPPORT SNOW CHANCES...THEN LESSENS TUESDAY.
WILL CONTINUE THE EARLY SUNDAY NIGHT MENTION OF RESIDUAL SNOW
SHOWERS NEAR LAKE HURON AND GO LIKELY POPS MONDAY ALL
COUNTIES...OTHERWISE MINIMAL CHANGE TO EXISTING FORECASTS SUNDAY
NIGHT/MONDAY.

MORE ABOUT NEXT WEEK...
MODELS SHOW PRETTY GOOD CONSENSUS IN CARVING OUT HIGH AMPLITUDE MID
LEVEL TROUGH OVER THE PLAINS MONDAY...THEN GRADUAL EASTWARD
PROGRESSION. MEDIUM RANGE MODELS ARE TRENDING SLOWER WITH THIS
PROGRESSION OF MID LEVEL TROUGH...AS TROUGH STEEPENS IN RESPONSE TO
SERIES OF JET SEGMENTS PLUNGING SOUTHWARD ON BACK SIDE OF TROUGH.
06Z GFS NOTICEABLY SLOWER WITH PROGRESSION COMPARED TO 00Z
OPERATIONAL RUN. SOME MODELS...SUCH AS DGEX...EVEN CLOSE OFF THIS
LOW LATE NEXT WEEK SOUTH OF GREAT LAKES. AT THE SURFACE...NEXT
CLIPPER RIDES SOUTHEAST TO VICINITY OF NORTHERN GREAT LAKES REGION
TUESDAY...THEN ENTIRE LOW/TROUGH SLOWS ITS EASTWARD PROGRESSION IN
RESPONSE TO STEEPENING TROUGH ALOFT...WITH WAVE OR WAVES MOVING UP
FROM GULF COAST AREA ALONG FRONT...INCREASINGLY INDICATED SO
TRACKING WEST OF THE APPALACHIANS...THOUGH MODELS AT THIS POINT
QUITE DIVERSE AS TO TIMING. MODELS TENDING TO KEEP LOW LEVEL
CYCLONIC FLOW ON BACK SIDE OF THIS TROUGH BACK ACROSS AREA FRIDAY
AND PERHAPS INTO SATURDAY...WITH HIGH PRESSURE THEN GRADUALLY
PUSHING IN FROM THE WEST. ANTICIPATE NOT GOING QUITE AS LOW WITH
TEMPERATURES MUCH OF NEXT WEEK...AS GUIDANCE TEMPERATURES ARE A FAIR
BIT MORE MODERATE THAN YESTERDAY AND UPPER TROUGH PROGRESSION
DELAYED. HOWEVER...ANY MORE THAN EXPECTED CLEARING COULD RAISE HAVOC
WITH ESPECIALLY NIGHTTIME TEMPERATURES.

&&

.AVIATION...ISSUED 100 PM EST

A BAND OF SNOW SHOWERS WILL SPREAD EAST ACROSS THE AREA THROUGH
EARLY AFTERNOON DROPPING VISIBILITIES TO IFR CONDITIONS. BEHIND THIS
BAND...CEILINGS WILL DROP...WITH AIRPORTS MAINLY NORTH OF I-69
APPROACHING IFR CONDITIONS. AS A SURFACE TROUGH CURRENTLY ALONG THE
EASTERN EDGE OF LAKE MICHIGAN MOVES EAST ACROSS THE AREA LATE THIS
AFTERNOON...EXPECT WINDS TO INCREASE AS THEY SHIFT AROUND TO THE
WEST. DRIER AIR BEHIND THIS TROUGH WILL HELP CONDITIONS IMPROVE
ACROSS THE SOUTHERN PORTION OF THE CWA BRIEFLY BEFORE CONDITIONS
WORSEN AREA WIDE THIS EVENING. SNOW SHOWERS WILL BEGIN OUT AHEAD OF
THE FRONT WITH STRONG WINDS OUT OF THE NORTHWEST TONIGHT.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
.MI...
LAKE EFFECT SNOW WARNING...HURON...LATE TONIGHT AND SUNDAY.
LAKE EFFECT SNOW ADVISORY...SANILAC...LATE TONIGHT AND SUNDAY.
.LAKE HURON...GALE WARNING...ALL WATERS...OVERNIGHT AND SUNDAY
MORNING.
.LAKE ST CLAIR...GALE WARNING...OVERNIGHT AND SUNDAY MORNING.
.MI WATERS LAKE ERIE...GALE WARNING...OVERNIGHT AND SUNDAY MORNING.

&&

KAHL/DWD/BT

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
500 PM EST SAT DEC 18 2004

CORRECTED TONIGHT PORTION OF THIRD SEGMENT

MIZ049-055-191000-
HURON MI-SANILAC MI-
INCLUDING THE CITIES OF...BAD AXE AND SANDUSKY
500 PM EST SAT DEC 18 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR HURON AND SANILAC COUNTIES

.DAY ONE...TONIGHT

A LAKE EFFECT SNOW WARNING IS IN EFFECT FOR HURON COUNTY...AND A
LAKE EFFECT SNOW ADVISORY IS IN EFFECT FOR SANILAC COUNTY...BOTH FOR
OVERNIGHT TONIGHT THROUGH SUNDAY. PLEASE SEE THE LATEST URGENT
WINTER WEATHER MESSAGE FOR DETAILS.

.DAY TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

ANOTHER LOW PRESSURE SYSTEM WILL MOVE THROUGH THE AREA ON MONDAY AND
MONDAY NIGHT. SNOW ACCUMULATION OF 1 TO 3 INCHES IS POSSIBLE DURING
THIS TIME.

NO HAZARDOUS WEATHER IS EXPECTED AFTER MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT PLANNED...BUT SNOWFALL REPORTS FROM
SPOTTERS WILL BE NEEDED OVERNIGHT AND ON SUNDAY.

MIZ047-048-053-054-191000-
BAY MI-MIDLAND MI-SAGINAW MI-TUSCOLA MI-
INCLUDING THE CITIES OF...BAY CITY...CARO...MIDLAND AND SAGINAW
500 PM EST SAT DEC 18 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE SAGINAW VALLEY.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAY TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

ANOTHER LOW PRESSURE SYSTEM WILL MOVE THROUGH THE AREA ON MONDAY AND
MONDAY NIGHT. SNOW ACCUMULATION OF 1 TO 3 INCHES IS POSSIBLE DURING
THIS TIME.

NO HAZARDOUS WEATHER IS EXPECTED AFTER MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT PLANNED.

MIZ060>063-068>070-075-076-082-083-191000-
GENESEE MI-LAPEER MI-LENAWEE MI-LIVINGSTON MI-MACOMB MI-MONROE MI-
OAKLAND MI-SHIAWASSEE MI-ST. CLAIR MI-WASHTENAW MI-WAYNE MI-
INCLUDING THE CITIES OF...ADRIAN...ANN ARBOR...DOWNTOWN DETROIT...
FLINT...HOWELL...LAPEER...MONROE...MOUNT CLEMENS...OWOSSO...
PONTIAC AND PORT HURON
500 PM EST SAT DEC 18 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST MICHIGAN...SOUTH OF
THE TRI CITIES AND THUMB...INCLUDING FLINT...PORT HURON AND DETROIT.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAY TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

ANOTHER LOW PRESSURE SYSTEM WILL MOVE THROUGH THE AREA ON MONDAY AND
MONDAY NIGHT. SNOW ACCUMULATION OF 1 TO 2 INCHES IS POSSIBLE DURING
THIS TIME...MAINLY MONDAY NIGHT.

NO HAZARDOUS WEATHER IS EXPECTED AFTER MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT PLANNED.

LCZ422-423-460-LEZ444-LHZ421-422-441>443-462>464-191000-
INNER SAGINAW BAY FROM POINT AU GRES TO BAY PORT-LAKE ST. CLAIR-
MICHIGAN WATERS OF LAKE ERIE-
NEARSHORE WATERS OF LAKE HURON FORM PORT SANILAC TO PORT HURON-
NEARSHORE WATERS OF LAKE HURON FROM HARBOR BEACH TO PORT SANILAC-
NEARSHORE WATERS OF LAKE HURON FROM PORT AUSTIN TO HARBOR BEACH-
OUTER SAGINAW BAY-THE DETROIT RIVER-
THE OPEN WATERS OF LAKE HURON FROM HARBOR BEACH TO PORT SANILAC-
THE OPEN WATERS OF LAKE HURON FROM PORT AUSTIN TO HARBOR BEACH-
THE OPEN WATERS OF LAKE HURON FROM PORT SANILAC TO PORT HURON-
THE ST. CLAIR RIVER-
500 PM EST SAT DEC 18 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR LAKE HURON...SAGINAW BAY...
LAKE ST. CLAIR...THE MICHIGAN WATERS OF LAKE ERIE...AND THE
CONNECTING RIVERS.

.DAY ONE...TONIGHT

A GALE WARNING IS IN EFFECT OVERNIGHT FOR ALL WATERS. PLEASE SEE THE
LATEST MARINE FORECASTS FOR DETAILS.

.DAY TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

A GALE WARNING IS IN EFFECT SUNDAY MORNING FOR ALL WATERS. PLEASE
SEE THE LATEST MARINE FORECASTS FOR DETAILS.

HAZARDOUS WEATHER IS NOT EXPECTED AFTER SUNDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT PLANNED.

BT