Lake-Effect Snow in Michigan, January 27 to 28, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
1110 AM EST SAT JAN 27 2007

.UPDATE...WEST NORTHWEST FLOW LAKE ENHANCED SNOWS RAPIDLY INCREASING
IN COVERAGE AND INTENSITY OVER THE AREA AS MID LEVEL SHORTWAVE...AND
ASSOCIATED POCKET OF MODERATE -DIVQ...APPROACH THE AREA. AT THE
SURFACE...ELONGATED AREA OF LOW PRESSURE EXTENDS FROM NEAR BUFFALO
NEW YORK UP THROUGH EASTERN LAKE SUPERIOR. MONTREAL RIVER CANADA
RADAR SHOWING BEST CONVERGENCE ASSOCIATED WITH THIS LOW/SURFACE
TROUGH REMAINING NORTH OF EASTERN UPPER AT THIS TIME. FORECAST
CONCERNS REMAIN LAKE SNOW CHANCES AND AMOUNTS FOR THIS AFTERNOON.

OVERALL LAKE EFFECT PARAMETERS PRETTY DECENT WITH 12Z GREEN BAY
SOUNDING SHOWING NEARLY 7KFT INVERSION LEVEL AND MODEL GUIDANCE
SHOWING 850MB-700MB MOISTURE VALUES OF >80 PERCENT. ONE LIMITING
FACTOR...AT LEAST EARLY ON...REMAINS OVER WATER INSTABILITY WITH
GREEN BAY SOUNDING SHOWING 850MB TEMPERATURES OF ONLY
-8C...PRODUCING A CORRESPONDING DELTA T VALUE OF 10C. HOWEVER...CAA
CONTINUES WITH APPROACH OF SHORTWAVE WITH LATEST RUC GUIDANCE
SUGGESTING 16Z 850MB TEMPERATURES OF -11C OVER NORTHERN LAKE
MICHIGAN AND -11C TO -13C OVER EASTERN LAKE SUPERIOR. THIS MATCHES
NICELY WITH RECENT RADAR RETURNS SEEN ON LOCAL RADARS. SYNOPTIC
SUPPORT ONLY INCREASES DURING THE AFTERNOON AS AFOREMENTIONED
SHORTWAVE ROTATES OVER NORTHERN MICHIGAN. INVERSION LEVELS BECOME
NEARLY NON EXISTENT (ACTUALLY AT TROPOPAUSE LEVEL OF 18KT) AND MID
LEVEL MOISTURE REMAINS ABUNDANT. STILL...INSTABILITY LEVELS REMAIN
MARGINAL WITH 850MB TEMPERATURES ONLY SLOWLY FALLING TO AROUND -12C
TO -14C BY AFTERNOON. THIS SHOULD HELP LIMIT INTENSITY OF SNOW
SHOWERS. EARLY FORECAST OF UP TO 3 INCHES NEAR THE LAKE SUPERIOR
SHORELINE AND AN INCH OR TWO OVER FAVORED WEST NORTHWEST FLOW AREAS
OF THE NORTHERN LOWER APPEARS ON TARGET. HOWEVER...WILL CLOSELY
MONITOR ENHANCED CONVERGENT ZONE THAT IS EXPECTED TO DROP INTO THE
EASTERN U.P. AS SURFACE TROUGH ROTATES DOWN WITH PASSAGE OF
SHORTWAVE. IF BANDS CAN STAY FOCUSED LONG ENOUGH ALONG THIS FEATURE
SNOWFALL AMOUNTS WILL LIKELY NEED TO BE INCREASED FOR PORTIONS OF
CHIPPEWA COUNTY. OTHERWISE...ONLY SIGNIFICANT CHANGE FROM MORNING
FORECAST WAS TO BUMP UP COVERAGE TO SCATTERED AND NUMEROUS OVER
EASTERN SECTIONS OF THE FORECAST AREA BASED OFF RADAR RETURNS.

WILL CONTINUE TO ANALYZE INCOMING DATA THIS AFTERNOON FOR A
POSSIBLE UPGRADE TO AN ADVISORY OR WARNING FOR THOSE AREAS UNDER THE
LAKE EFFECT SNOW WATCH TONIGHT AND SUNDAY.

MSB

&&

.PREV DISCUSSION...ISSUED AT 437 AM EST SAT JAN 27 2007

SFC WAVE SLOWLY SLIDING THROUGH THE WESTERN GREAT LAKES THIS
MORNING...WITH A SECONDARY COLD FRONT AND THE LEADING EDGE OF
SUBSTANTIALLY COLDER AIR TRAILING THROUGH THE UPPER MIDWEST/NRN
PLAINS. WATER VAPOR IMAGERY REVEALING SHORT WAVE COMING RIGHT BEHIND
PUSHING ACROSS LAKE SUPERIOR ATTM. 00Z UPPER AIR PLOTS REVEALING
UPPER JET STREAK OVER BUFFALO LAST EVENING WHILE SECOND JET CORE
ACROSS CENTRAL MN. CAN INFER WEAK JET COUPLING/UPPER DIVERGENCE
ACROSS NRN MICHIGAN LAST EVENING...WHICH WITH COMBINED WITH LOW
LEVEL CONVERGENCE ALONG THE SFC WAVE...MAY HAVE HELPED SPAWN OUR
LITTLE FREEZING DRIZZLE STORM DURING MID-LATE EVENING HOURS. FZDZ
HAD DIMINISHED AROUND MIDNIGHT ACROSS THE REGION...BUT HAVE SEEN
ANOTHER FLARE UP ON KAPX RADAR AND HERE AT THE OFFICE OVERNIGHT
(ALBEIT NOT NEARLY AS WIDESPREAD AND HEAVY AS LAST EVENING).

INITIAL FORECAST CONCERN REVOLVES AROUND ONGOING WINTER WEATHER
ADVISORY GOOD THROUGH 8 AM (COVERING FZDZ). THEN...ATTENTION TURNS
TO A LAKE EFFECT EVENT LATER TODAY THROUGH SUNDAY AND HEADLINE
POSSIBILITIES.

TODAY...FIRST OFF WILL NEED TO ADDRESS ONGOING WSW. AS MENTIONED
ABOVE...ANOTHER LIGHT FLARE UP OF -FZDZ MATERIALIZED OVERNIGHT
PRIMARILY ACROSS THE HIGHER TERRAIN (AS USUAL) PER RADAR DATA AND
SFC OBS. BUT LATEST RADAR TREND SUGGESTING -FZDZ AGAIN DWINDLING AND
THINK WE CAN GET AWAY WITH CANCELLING THE WSW WITH MORNING ZONE
ISSUANCE. ATTENTION THEN TURNS TO PRECIP AND LAKE EFFECT POTENTIAL
FOR THE REST OF TODAY. DECENT MID LEVEL SHORT WAVE AND SHOT OF QG
UPWARD FORCING FORECAST TO SLIDE THROUGH NRN MICHIGAN DURING THE
AFTERNOON HOURS. MEANWHILE...SFC LOW SLIDES OFF TO THE EAST BUT WITH
A VERY SHARP LOW LEVEL TROUGH HANGING BACK ACROSS LAKE HURON AND
INTO EASTERN LAKE SUPERIOR. STRONG LOW LEVEL CONVERGENCE ALONG THIS
TROUGH COUPLED WITH QG UPWARD FORCING MOVING THROUGH/GRADUALLY
INCREASING OVER LAKE INSTABILITY (DELTA T/S INCREASING THROUGH THE
TEENS)/AND ERODING INVERSION HEIGHTS WILL FOCUS BEST LAKE EFFECT
SNOW SHOWERS ALONG THE NORTH SHORE OF THE UPPER PENINSULA FROM
WHITEFISH POINT WESTWARD THIS AFTERNOON. BUT WITH THE MODEST
LAKE-850 MB DELTA T/S WILL KEEP ACCUMULATIONS UNDER 3 INCHES FOR THE
DAY GREATEST AMOUNTS FOCUSED AROUND WHITEFISH POINT. ACROSS NRN
LOWER MICHIGAN...LOW LEVEL FLOW NOW TURNING INTO THE NW AND WILL
PERSIST THROUGH THE DAY. WITH ARRIVAL OF UPSTREAM WAVE/ ASSOCIATED
DEEPER MOISTURE/AND ERODING INVERSION HEIGHTS...EXPECT SNOW SHOWERS
TO INCREASE ACROSS THE REGION DURING THE AFTERNOON (CATEGORICAL POPS
IN NW LOWER AND ALONG THE PRESQUE ISLE SHORELINE. BUT AGAIN...WITH
ONLY MODEST LAKE INSTABILITY WILL KEEP ACCUMULATIONS IN THE 1 TO 2
INCH RANGE IN THE FAVORED AREAS.

TONIGHT THROUGH SUNDAY...GETS EVEN MORE INTERESTING AS SECONDARY
STRONG MID LEVEL WAVE (KICKER) DROPS THROUGH THE SOUTHERN HALF OF
THE STATE HELPING TO DRAG SFC TROUGH/COLD FRONT DOWN THROUGH NRN
MICHIGAN OVERNIGHT...FOLLOWED BY SUBSTANTIALLY COLDER AIR (850 MB
TEMPS DROPPING TO -16C TO -18C BY SUNDAY) OVERSPREADING THE STATE.
ALTHOUGH STRONGEST FORCING WITH THE WAVE SLIDES ACROSS THE SRN PART
OF THE STATE...CAN ENVISION AN AREA OF SNOWFALL SLIDING SOUTHWARD
WITH THE TROUGH OVERNIGHT...WITH INTENSITIES ENHANCED BY THE LAKES
AS IT PASSES THROUGH...AND PRODUCING A QUICK 1 TO 2 INCHES FOR MUCH
OF THE AREA. LAKE ENHANCEMENT MAY ACTUALLY IMPACT BOTH THE LAKE
MICHIGAN AND LAKE HURON SHORELINES...TACKING ON ADDITIONAL AMOUNTS.
TRANSITION TO A NORTH FLOW LAKE EFFECT EVENT FOLLOWS LATE OVERNIGHT
AND THROUGH SUNDAY MORNING BEFORE SOME DRYING COMMENCES IN THE
AFTERNOON. LAKE EFFECT PARAMETERS LATE TONIGHT THROUGH SUNDAY
MORNING LOOKING GOOD FOR MOD-HEAVY LAKE EFFECT SNOW POSSIBILITIES AS
DELTA T/S INCREASE TO AROUND 20C COUPLED WITH WEAK OR NON EXISTANT
INVERSION HEIGHTS AND PLENTY OF LOW LEVEL MOISTURE AROUND. RIGHT
NOW...AREAS AROUND LEELANAU COUNTY AND GRAND TRAVERSE BAY SOUTH TO
MANISTEE LOOKING MOST FAVORED ASSUMING MODELS HAVE A GOOD HANDLE ON
THE FLOW REGIME BEHIND THE FRONT. AND COUPLED WITH THE OVERNIGHT
SNOWFALL...ACCUMULATIONS APPROACHING WARNING CRITERIA A GOOD BET BY
SUNDAY AFTERNOON IN THOSE AREAS. PROBABLY CLOSE ENOUGH TO WARRANT
ISSUING A LAKE EFFECT SNOW WATCH FOR TONIGHT THROUGH SUNDAY ALTHOUGH
LATER SHIFTS MAY OPT TO TRANSITION WATCH INTO ADVISORIES IF SHIFTING
LOW LEVEL WINDS DO NOT COOPERATE.

MONDAY THROUGH WEDNESDAY...NO CHANGE IN THE ONGOING PATTERN THROUGH
MIDWEEK AND BEYOND. BLOCKING RIDGE PATTERN IN THE EASTERN PACIFIC
ONLY STRENGTHENS FURTHER...WHILE DOWNSTREAM LONG WAVE TROUGHING
ACROSS CENTRAL AND EASTERN NAOM DEEPENS. WITHIN THE LONG WAVE TROUGH
PATTERN...SERIES OF SHORT WAVES EXPECTED TO SLIDE THROUGH THE REGION
DURING THE UPCOMING WEEK EACH SERVING TO REINFORCE THE COLD AIR OVER
THE GREAT LAKES. IN BETWEEN SYSTEMS WITH SFC HIGH PRESSURE NOSING
INTO THE REGION...MAY GET A BIT OF A BREAK (AT LEAST FROM HEADLINES)
ON MONDAY WITH JUST CHANCY POPS FOR THE SNOW BELTS. NEXT SHORT WAVE
CURRENTLY FORECAST TO DROP THROUGH THE REGION ON TUESDAY BRINGING
MORE WIDESPREAD SNOW. POSSIBLY ANOTHER BREAK FOR WEDNESDAY BEHIND
THIS SYSTEM...BEFORE YET ANOTHER WAVE ARRIVES LATE WEDNESDAY.

ADAM

&&

.APX WATCHES/WARNINGS/ADVISORIES...LAKE EFFECT SNOW WATCH...TONIGHT
     THROUGH SUNDAY...MIZ020-025-026-031.

&&

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE GAYLORD MI
1023 AM EST SAT JAN 27 2007

LHZ345>349-361-362-LMZ323-341-342-344-345-363-LSZ321-322-MIZ008-
015>036-041-042-281100-
STRAITS OF MACKINAC-ST IGNACE TO FALSE DETOUR CHANNEL-
MACKINAC BRDG TO PRESQUE ISLE LT-PRESQUE ISLE LT TO STURGEON PT-
STURGEON PT TO ALABASTER-MICHIGAN WATERS OF NORTHERN LAKE HURON-
MICHIGAN WATERS OF CENTRAL LAKE HURON-GRAND TRAVERSE BAY-
SEUL CHOIX PT TO MACKINAC BRDG-NORWOOD TO MACKINAC BRDG-
SLEEPING BEAR PT TO GRAND TRAVERSE LT-MANISTEE TO SLEEPING BEAR PT-
MICHIGAN WATERS OF NORTHERN LAKE MICHIGAN-WHITEFISH BAY-
ST. MARYS RIVER-CHIPPEWA-MACKINAC-EMMET-CHEBOYGAN-PRESQUE ISLE-
CHARLEVOIX-LEELANAU-ANTRIM-OTSEGO-MONTMORENCY-ALPENA-BENZIE-
GRAND TRAVERSE-KALKASKA-CRAWFORD-OSCODA-ALCONA-MANISTEE-WEXFORD-
MISSAUKEE-ROSCOMMON-OGEMAW-IOSCO-GLADWIN-ARENAC-
1023 AM EST SAT JAN 27 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF LAKE HURON...LAKE
MICHIGAN...LAKE SUPERIOR...EASTERN UPPER MICHIGAN AND NORTHERN LOWER
MICHIGAN.

.DAY ONE...REST OF TODAY AND TONIGHT

ACCUMULATING SNOW IS EXPECTED TONIGHT ACROSS EASTERN UPPER AND
NORTHERN LOWER MICHIGAN...WITH HEAVY LAKE EFFECT SNOW SHOWERS
POSSIBLE AROUND THE GRAND TRAVERSE BAY AREA SOUTH TO MANISTEE. SEE
ONGOING WATCHES FOR DETAILS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

HEAVY LAKE EFFECT SNOW SHOWERS ARE POSSIBLE SUNDAY AROUND THE
GRAND TRAVERSE BAY AREA SOUTH TO MANISTEE. SEE ONGOING WATCHES FOR
DETAILS.

PERIODS OF MUCH BELOW NORMAL TEMPERATURES CAN BE EXPECTED THROUGH
NEXT WEEK AS SEVERAL COLD WAVES INVADE THE WESTERN GREAT LAKES.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS...PLEASE RELAY SNOWFALL REPORTS TO THE NATIONAL WEATHER
SERVICE IN GAYLORD.

MSB