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000
FXUS63 KMQT 092146
AFDMQT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
446 PM EST TUE FEB 9 2010

.SYNOPSIS...

WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A STRONG SHORTWAVE MOVING
FROM MO INTO THE LWR OHIO VALLEY. MINOR SHORTWAVE PIVOTING N ACROSS
LWR MI AHEAD OF SYSTEM IS HELPING TO BRING NRN FRINGE OF DEEPER
MOISTURE INTO THE UPPER GREAT LAKES. WITH THAT...SOME -SN HAS BEEN
OCCURRING ACROSS MUCH OF THE FCST AREA THIS AFTN ALTHOUGH DRY ERLY
FLOW HAS MAINTAINED DRY WEATHER OVER THE E THIRD TO HALF OF UPPER
MI. ACROSS NCNTRL UPPER MI...KMQT RADAR IMAGERY HAS SHOWN A TYPICAL
PATTERN OF INCREASING HIGHER RETURNS OVER THE HIGHER TERRAIN MOST
PERPENDICULAR TO THE MEAN NERLY BOUNDARY LAYER FLOW.
&&

.SHORT TERM /TONIGHT AND WED/...

MAIN FORCING ASSOCIATED WITH SYSTEM MOVING INTO THE OHIO VALLEY WILL
PASS S OF THE AREA TONIGHT...BUT QVECTOR PROGS DO SHOW SOME WEAK
DEEP LAYER FORCING. SINCE CAA IS MINIMAL (850MB TEMPS DROP ABOUT 1C
TO AROUND -12C)...THERE PROBABLY WON`T BE MUCH CHANGE IN LAKE
ENHANCEMENT FROM WHAT IS ONGOING CURRENTLY PER KMQT RADAR IMAGERY.
HOWEVER...WINDS WILL BACK TO AN IDEAL N TO NNE DIRECTION FOR TERRAIN
ENHANCEMENT OVER NCNTRL AND FAR WRN UPPER MI. SO...HEAVIER SNOW WILL
REALIGN OVER THE HIGHER TERRAIN. NAM/GFS CROSS SECTIONS SHOW
VERTICAL MOTION MOSTLY DUE TO UPSLOPING WITH BULK OF ASCENT
OCCURRING BELOW THE DENDRITIC SNOW GROWTH ZONE. THUS...SNOW TO WATER
RATIOS WILL BE ON THE LOW-SIDE...PROBABLY IN THE RANGE OF A 10-15 TO
1 RATIO. GIVEN THE RECENT UPTICK IN SNOW INTENSITY ACROSS MARQUETTE
COUNTY AND THE EXPECTATION OF CONDITIONS REMAINING FAIRLY STEADY
STATE THRU THE NIGHT...WILL ISSUE A WINTER WX ADVY FOR MARQUETTE
COUNTY THRU WED MORNING. OPTED FOR WINTER WX ADVY INSTEAD OF LES
ADVY DUE TO LOWER SNOW TO WATER RATIOS (WETTER SNOW WHICH IS MORE
HAZARDOUS FOR DRIVING). ALSO...SNOW WON`T LIKELY HAVE MUCH BANDING
GIVEN THE MARGINAL OVERWATER INSTABILITY FOR PURE LES. SINCE
UPSLOPING INTO THE HIGHER TERRAIN WILL PROVIDE MOST IF NOT ALL THE
FORCING FOR INCREASED SNOW RATES...HIGHER REFLECTIVITIES (HEAVIER
SNOW) WILL BE PEGGED IN THE HIGHER TERRAIN THRU THE NIGHT. FOR
NOW...PUT HIGH END ACCUMULATIONS AROUND 5 INCHES FOR THE TONIGHT
PERIOD FROM THE HURON MOUNTAINS TO ISHPEMING/NEGAUNEE AND SKANDIA.
TOTALS BY LATE WED MORNING MAY APPROACH 8 INCHES IN THOSE AREAS. IN
ALGER COUNTY...WIND FLOW WON`T BE AS FAVORABLE FOR STEADY/HEAVIER
SNOW UNTIL OVERNIGHT. SHORTER DURATION SHOULD KEEP AMOUNTS UNDER
ADVY CRITERIA THERE. OUT W (GOGEBIC/ONTONAGON)...DEEPER MOISTURE
PULLS OUT OVERNIGHT...SO ACCUMULATIONS THERE SHOULD ALSO FALL SHORT
OF ADVY. HOWEVER...WILL NEED TO MONITOR TENDS CLOSELY DURING THE
EVENING. AWAY FROM THE LAKE...-SN WILL DIMINISH THRU THE NIGHT WITH
LITTLE IN THE WAY OF ACCUMULATION.

SNOW NEAR THE LAKE WILL WIND DOWN W TO E WED AS DEEPER MOISTURE
EXITS. WITH MARGINAL OVERWATER INSTABILITY FOR LES...IT`S QUITE
POSSIBLE SNOW MAY END COMPLETELY WITH DEPARTURE OF DEEPER MOISTURE.
FOR NOW...DROPPED POPS MUCH MORE SHARPLY IN THE AFTN COMPARED TO
PREVIOUS FCST TO BEGIN TRENDING FCST IN A DRIER DIRECTION.

.LONG TERM...WEDNESDAY NIGHT AND LATER PERIODS.

A MID LEVEL LOW OVER CENTRAL CANADA WILL DEEPEN OVER NORTHEAST
SASKATCHEWAN WEDNESDAY NIGHT...AS THE RIDGE BUILDS OVER THE PACIFIC
COAST AND THE LONG WAVE TROUGH DEEPENS OVER THE WESTERN ATLANTIC. A
WEAK SHORTWAVE WILL SHIFT OVER THE WESTERN U.P. THE SURFACE RIDGE
WILL STRETCH FROM HUDSON BAY SOUTH THROUGH THE MISSISSIPPI RIVER
VALLEY AND A SURFACE LOW OVER MID ATLANTIC STATES. THIS WILL KEEP A
NORTHERLY FLOW ACROSS LAKE SUPERIOR. SOME MOIST AIR WRAPPING AROUND
THE ATLANTIC LOW WILL REACH INTO LAKE SUPERIOR. THIS WOULD SUGGEST
LES DOWNWIND OF LAKE SUPERIOR. HOWEVER...THE BASE OF THE LOWEST
INVERSION WILL BE AROUND 925MB...13K FEET...OVER LAKE SUPERIOR AND
THE DELTA-T`S WILL BE MARGINAL. THE LOW INVERSION WILL POINT TO
LIMITED LES AS WELL.

THE SURFACE RIDGE WILL PUSH INTO WISCONSIN AND WESTERN LAKE SUPERIOR
ON THURSDAY. THIS WILL TEND TO DIMINISH THE FLOW OVER LAKE SUPERIOR.
TEMPERATURES WILL STILL BE COLD ENOUGH TO PRODUCE SOME LAKE EFFECT
SNOW. LOW INVERSIONS WILL PERSIST AND THE MOIST AIR WILL SHIFT EAST.
THUS WILL STILL CALL FOR A LIMITED LES.

THE SURFACE RIDGE WILL SHIFT OVER THE FORECAST AREA THURSDAY NIGHT
AND FRIDAY. THE DELTA-T`S WILL BE VERY MARGINAL. THE LIGHT LES WILL OCCUR
EARLY. AS THE WINDS DIMINISH TO CALM...THE LES WILL CONTINUE TO
TAPER OFF.

THE MID LEVEL RIDGE OVER ALBERTA WILL MIGRATE SLOWLY INTO
SASKATCHEWAN ON SATURDAY. THE CLOSED LOW OVER NORTHEAST NORTH DAKOTA
WILL SETTLE SOUTHEAST TO THE QUAD CITIES AREA. THE SURFACE RIDGE
WILL SETTLE OUT OF CENTRAL CANADA INTO THE DAKOTAS. THIS WILL DRAW
COLD CANADIAN AIR INTO THE FORECAST AREA. THE AIR MASS WILL BE
FAIRLY DRY SO LES WILL BE POSSIBLE...BUT LIMITED ACCUMULATION.

THE MID LEVEL LOW WILL SHIFT THROUGH THE OHIO RIVER VALLEY AND ON TO
THE MID ATLANTIC STATES SATURDAY NIGHT AND SUNDAY. WHILE THE SURFACE
RIDGE EXTENDS SOUTH THROUGH THE CENTRAL AND SOUTHERN PLAINS. THIS
WILL PRODUCE SOME LES DOWNWIND OF LAKE SUPERIOR. CONDITIONS STILL
APPEAR TO BE FAIRLY DRY...SO LES WILL BE LIMITED.
&&

.AVIATION /FOR THE 18Z TAFS/...

UPPER MI IS ON THE FRINGE OF STORM SYSTEM ROLLING INTO THE OHIO
VALLEY. DEEPER MOISTURE ON THE NRN FLANK OF THIS SYSTEM WILL AID
SNOW DEVELOPMENT OFF LAKE SUPERIOR THRU MUCH OF THE FCST PERIOD. AT
KCMX...THERE WILL BE IFR CONDITIONS FOR A WHILE DURING THE AFTN
UNTIL SLIGHTLY DRIER LOW-LEVEL AIR FROM THE NE AND N CAN WORK INTO
THE AREA. OTHERWISE...MVFR CONDITIONS SHOULD DOMINATE FOR THE MOST
PART AS NERLY FLOW BACKING NRLY IS TYPICALLY NOT THE FAVORABLE
DIRECTION FOR HEAVIER SNOW OFF THE LAKE OR LOW CIGS AT KCMX.

AT KSAW...NE FLOW BACKING NNE TO N WILL BE IDEAL FOR TERRAIN
ENHANCED SNOW OFF THE LAKE. IFR CONDITIONS SHOULD DOMINATE FOR THE
MOST PART. THERE MAY BE SOME PERIODS OF MVFR AND POTENTIALLY LIFR.
IF ANY PERIODS OF LIFR OCCUR...THEY WILL MOST LIKELY HAPPEN TONIGHT
WHEN WINDS WILL BE MOST FAVORABLE FOR UPSLOPING TERRAIN ENHANCEMENT.
&&

.MARINE /FOR THE 4 PM LAKE SUPERIOR ISSUANCE/...

AS LOW PRESSURE PASSES SOUTH OF THE GREAT LAKES...NE TO N WINDS WILL
INCREASE TO 30 KNOTS OVER MUCH OF LAKE SUPERIOR TONIGHT. MAY SEE
SOME GALE FORCE GUSTS OVER PORTIONS OF CNTRL/ERN LAKE SUPERIOR. WITH
LACK OF CAA...NOT EXPECTING THE NEED FOR A GALE WARNING. WINDS WILL
DIMINISH W TO E WED/WED NIGHT. WINDS WILL BE MAINLY UNDER 20KT THU
THRU SAT. LOW PRES DIVING SE TO THE S OF LAKE SUPERIOR OVER THE
WEEKEND WILL BRING INCREASING WINDS AGAIN FOR SUN.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
  WINTER WEATHER ADVISORY UNTIL NOON EST WEDNESDAY FOR MIZ005.

LAKE SUPERIOR...
  HEAVY FREEZING SPRAY WARNING FROM 1 AM TO 1 PM EST WEDNESDAY FOR
     LSZ265>267.

  HEAVY FREEZING SPRAY WARNING UNTIL 1 PM EST /NOON CST/ WEDNESDAY
     FOR LSZ162-263-264.

LAKE MICHIGAN...
NONE.
&&

$$

SYNOPSIS...ROLFSON
SHORT TERM...ROLFSON
LONG TERM...DLG
AVIATION...ROLFSON
MARINE...ROLFSON