Winter Storm in Michigan, January 30 to 31, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
345 AM EST WED JAN 30 2002

SHORT TERM DISCUSSION...
WILL CONTINUE BOTH THE WINTER WEATHER ADVISORY THIS MORNING IN THE
FAR SOUTH AND THE WINTER STORM WATCH TONIGHT THROUGH THURSDAY NIGHT
FOR THE WHOLE AREA.

SCENARIO IS GOING ABOUT AS PLANNED...ALTHOUGH THE MODELS ARE
TRENDING FURTHER SOUTH IN THE PROGRESSION OF THE ARCTIC BOUNDARY
INTO KENTUCKY...AND FURTHER SOUTH WITH THE NORTHWARD PROGRESSION OF
THE WARN FRONT TONIGHT AND THURSDAY. ALSO...AS IS TYPICAL WITH
SYSTEMS LIFTING OUT THE SOUTHWEST UNITED STATES...A SLOWING TREND IS
NOTED. THE ONSET OF THE PRECIPITATION MAY BE A BIT LATER THAN WAS
EXPECTED WITH LAST NIGHTS RUN OF THE MODELS. FORECAST CONCERNS ARE
OBVIOUSLY HEADLINE RELATED...AND AS STATED ABOVE...WILL BE KEEPING
THE STATUS QUO IN CARRYING THE SECOND PERIOD AND BEYOND WATCH. DAY
SHIFT TODAY WILL BE DECIDING WHAT AREAS MAY NEED ANY WARNINGS AND
ADVISORIES.

IN TERMS OF MODEL OF CHOICE...WILL BE RUNNING WITH THE ETA THROUGH
THURSDAY NIGHT...BUT AGAIN IT IS SLOWER AND FURTHER SOUTH. AVN LOOKS
TO BE RUSHING THE SURFACE LOW TOO FAR EAST TOO QUICKLY GIVEN THE
UPPER WAVE IS STILL QUITE A WAYS TO ITS WEST.

FOR TODAY...SWATH OF PRECIPITATION IS HEADING FOR SOUTHERN LOWER
MICHIGAN OUT OF ILLINOIS. THIS IS ASSOCIATED WITH SOME UPPER
DIVERGENCE IN THE RIGHT READ QUAD OF A STRONG JET STREAK AND SOME
LOWER LEVEL FRONTOGENESIS. COULD SEE AND INCH OR TWO ACROSS THE
SOUTHERN TIER OF COUNTIES...POSSIBLY MIXING WITH SLEET. MODEL
SOUNDINGS ARE NOT SHOWING A BIG THREAT FOR FREEZING RAIN THIS
MORNING...SO WILL KEEP IT SNOW AND SLEET. WILL KEEP THE MENTION OF A
WINTER WEATHER ADVISORY FOR THIS MORNING. THE PRECIPITATION WILL END
TOWARDS MIDDAY AS THE FRONTAL BOUNDARY SINKS FURTHER SOUTH AND SOME
DRIER LOW LEVEL AIR WORKS IN ON NORTHEAST WINDS. ACROSS THE CENTRAL
AND NORTH...IT LOOKS TO BE MORE OF A FLURRIES/ PATCHY FREEZING
DRIZZLE TYPE OF DAY AGAIN...AND WILL TREND THE FORECAST THAT WAY.
THE -10 C ISOTHERM REMAINS UNSATURATED FOR A PORTION OF THE DAY SO
ICE WILL NOT BE INTRODUCED INTO THE CLOUD TO AID IN THE FORMATION OF
SNOW FLAKES. HIGHS SHOULD RANGE FROM 25 TO 30 NORTH AND THE LOWER
30S SOUTH.

TONIGHT...MAIN BATCH OF ISENTROPIC LIFT WORKS THROUGH. THE LIFT IS
NOT AS IMPRESSIVE AS THE 00Z MODEL RUN LAST NIGHT. THE FLOW IS MORE
ACROSS THE ISENTROPIC SURFACES AS OPPOSED TO DIRECTLY UP THEM. SNOW
WILL BREAK OUT IN THE SOUTH DURING THE EVENING AND GRADUALLY LIFT
NORTHWARD THROUGH THE FORECAST AREA. BY DAYBREAK HEAVIEST TOTALS
WILL BE IN THE SOUTH OBVIOUSLY AS IT WILL HAVE BEEN SNOWING THERE
LONGER. ANTICIPATE TOTALS OF 3-6 INCHES IN THE SOUTH IN LINE WITH
THE GOING FORECAST AND 2-4 INCHES NORTH. 12 HOUR ETA LIQUID
EQUIVALENT
TOTALS WOULD INDICATE POSSIBLY HIGHER AMOUNTS IN THE SOUTH...MAYBE
SOME 7-8 INCH TOTALS. RIGHT READ QUAD DIVERGENCE OF THE 200KT JET
MAX TO OUR NORTH IS IMPRESSIVE WITH THE BULLSEYE OVER SW LWR MI. IT
SHOULD SNOW QUITE HARD IN THE 06Z-12Z TIME FRAME...WITH INCH AN HOUR
SNOWS POSSIBLE. AT THIS POINT THOUGH WILL KEEP IT 3-6 INCHES. LOWS
PER THE GOING FORECAST SHOULD BE IN THE 20S.

ON THURSDAY...THE BURST OF ISENTROPIC LIFT SNOW WILL TAPER OFF AND
IT APPEARS NOW THERE WILL BE A LULL BEFORE ADDITIONAL PRECIPITATION
WORKS BACK IN THURSDAY NIGHT WITH THE MAIN UPPER WAVE. GIVEN THE
FURTHER SOUTH SOLUTION OF THE MODELS...SYNOPTIC SCALE FREEZING RAIN
APPEARS LESS OF A THREAT ON THURSDAY IN OUR CWA. WILL FEATURE MAINLY
SNOW NORTH AND CENTRAL AND SNOW...POSSIBLY MIXING WITH SLEET AND
SOME FREEZING RAIN IN THE SOUTH. ETA IS INDICATING SOME DRYING OF
THE MID LEVELS WHICH WOULD TAKE THE -10 C ISOTHERM UNSATURATED ONCE
AGAIN YIELDING FREEZING DRIZZLE/RAIN. THIS LOOKS A LITTLE SUSPECT AT
THIS POINT AND WILL RUN WITH THE ABOVE THINKING. FEEL SNOW TOTALS
WILL BE FAIRLY UNIMPRESSIVE ON THURSDAY AND WILL JUST MENTION
ADDITIONAL ACCUMULATIONS LIKELY. BEST CHANCE OF SNOW ON THURSDAY
WILL BE WHAT LINGERS INTO THE MORNING.

MAIN UPPER WAVE LIFTS TOWARD THE WESTERN GREAT LAKES THURSDAY
NIGHT...WITH ANOTHER BURST OF PRETTY IMPRESSIVE ISENTROPIC LIFT.
WITH DPVA SPREADING IN...UPPER DIVERGENCE INCREASING ONCE AGAIN
AFTER A LULL DURING THE DAY ON THURSDAY AND 4-6 G/KG SPECIFIC
HUMIDITY ON THE 295K SURFACE FEEL THE ETA LIQUID PRECIPITATION IS
UNDERDONE. FEEL TOTALS AGAIN WILL APPROACH/EXCEED WARNING CRITERIA
OF 6 INCHES IN 12 HOURS. SO...GIVEN THE SNOW OF TONIGHT...LASTING
INTO THE MORNING ON THURSDAY...THEN REDEVELOPING THURSDAY NIGHT FEEL
THE WATCH IS GOOD. THE MIX FINALLY COMES INTO PLAY IN THE SOUTH
THURSDAY NIGHT AS WELL...WHEN THE ICING THREAT WILL PROBABLY BE THE
GREATEST ALONG THE I-94 CORRIDOR.

DUKESHERER

EXTENDED FORECAST DISCUSSION...
ON FRIDAY THE SFC LOW WILL GRADUALLY MOVE EAST AND A PERIOD OF
DEFORMATION ZONE SNOWFALL FOLLOWED BY LAKE EFFECT SNOW SHOWERS ARE A
GOOD BET BEHIND IT. TIME HEIGHT RH PROGS OFF 00Z AVN GUIDANCE
CONTINUE TO SHOW DECENT LOW LEVEL MOISTURE FROM AROUND 800 MB DOWN
TO THE SURFACE. CAA WILL CAUSE 850 MB TEMPS TO FALL TO AROUND -13 C
IN THE AFTERNOON... SETTING UP DELTA T/S IN THE MID TEENS. THE WIND
PROFILE WITH HEIGHT WILL BE UNIDIRECTIONAL OUT OF THE WEST
NORTHWEST. LIGHT ACCUMULATIONS ARE CERTAINLY POSSIBLE BUT IT IS TOO
EARLY TO TRY AND NAIL DOWN SPECIFICS. THE SURFACE HIGH PRESSURE
RIDGE
WILL BEGIN TO MOVE IN FROM THE WEST FRIDAY NIGHT... BRINGING AN END
TO THE SNOW SHOWERS. THE RIDGE WILL MOVE ACROSS OUR REGION SATURDAY
AS WAA BEGINS IN ADVANCE OF THE NEXT SYSTEM FOR SUNDAY. WE WILL KEEP
MOSTLY CLOUDY WORDING GOING SATURDAY IN ANTICIPATION OF A GOOD DEAL
OF MID/HIGH CLOUD COVER. THE WEAK SURFACE LOW WILL MOVE ACROSS
THE LAKE SUPERIOR REGION SUNDAY AND PULL A COLD FRONT THROUGH...
WHICH WILL BRING MORE SNOW SHOWERS AND SCATTERED LAKE EFFECT SNOW
SHOWERS BEHIND IT. FOR EARLY NEXT WEEK OUR LATEST ECMWF AND CANADIAN
GUIDANCE SUGGESTS SEASONABLY COLD WEATHER WILL CONTINUE MONDAY
BEFORE ANOTHER HIGH PRESSURE RIDGE BUILDS IN TUESDAY.

LAURENS

.GRR...WINTER WEATHER ADVISORY INTERSTATE 94 CORRIDOR THIS MORNING.

WINTER STORM WATCH TONIGHT THROUGH THURSDAY NIGHT FOR THE
ENTIRE FORECAST AREA.