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000
FXUS63 KGRB 072116
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
316 PM CST SAT DEC 7 2013

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND SUNDAY
ISSUED AT 313 PM CST SAT DEC 7 2013

OVERALL FORECAST STILL ON TRACK FOR ANOTHER FRIGED NIGHT ACROSS
NORTHCENTRAL WISCONSIN TONIGHT...THEN A DECENT ACCUMULATING SNOW
FOR THE ENTIRE FORECAST AREA SUNDAY AND SUNDAY NIGHT. MADE
GENERALLY MINOR ADJUSTEMTS TO PREVIOUS FORECAST WITH RESPECT TO
START TIME OF SNOW AND AND SNOW AMOUNTS. ISSUED ANOTHER WIND CHILL
ADVISORY FOR TONIGHT ACROSS THE FAR NORTH AND A WINTER WEATHER
ADVISORY FOR SNOW FOR THE ENTIRE FORECAST AREA STARTING MID MORNING
SUNDAY ACROSS CENTRAL WISCONSIN AND LATE SUNDAY AFTERNOON ACROSS
THE FAR NORTHEAST PORTION OF THE FORECAST AREA.

STORM SYSTEM OF INTEREST STILL GETTING ITS ACT TOGETHER OVER THE
ROCKIES LATE THIS AFTERNOON. OVERALL SUITE OF MODEL GUIDANCE SEEMS
TO HAVE A PRETTY GOOD HANDLE ON THIS SYSTEM AS IT TRACKS ACROSS
THE PLAINS TO SOUTHERN LAKE MICHIGAN BY 06Z MONDAY. PRIMARY
FORCING WILL BE LOW-LEVEL WARM ADVECTION SUNDAY INITIALLY...FOLLOWED
BY UPPER-LEVEL QG FORCING WITH SHORTWAVE DISTURBANCE FORECAST TO
MOVE ACROSS SOUTHEAST WISCONSIN BETWEEN 00Z AND 06Z MONDAY.
ALTHOUGH NOT OVERLY IMPRESSED WITH DYNAMICS ASSOCIATED WITH THIS
SYSTEM AND THE FACT THAT IT IS RATHER PROGRESSIVE...GIVEN AMPLE
MOISTURE WITH MAX MIXING RATIOS AROUND 2 G/KG...AND MODEST
VERTICAL MOTION WITHIN FAVORABLE DENDRITIC ICE GROWTH REGION...A
HIGH-END ADVISORY FOR THE FORECAST AREA SEEMED REASONABLE.
ASSUMING ROUGHLY 18:1 SLR...3 TO 5 INCHES SEEMS LIKE A REASONABLE
SNOWFALL FORECAST TO GET THE BALL ROLLING.

SOME OF THE HIGHER RESOLUTION MESOSCALE MODELS CONTINUE TO
SUGGEST SOME SNOWBAND DEVELOPMENT OVER SOUTHERN LAKE MICHIGAN BY
15Z SUNDAY AS BOUNDAY LAYER WINDS TURN SOUTHEAST. MAJORTITY OF
THESE HIGHER RESOLUTION MODELS ADVECT THESE LAKE BANDS TOWARD THE
SHEBOYGAN TO MILWAUKEE COUNTY LAKESHORE...THEN PUSH IT NORTHWARD
TOWARD MANITOWOC COUNTY BY LATE SUNDAY AFTERNOON OR EARLY SUNDAY
EVENING. GIVEN HOW COLD THE AIRMASS IS...LES ENHANCEMENT NEEDED TO
BE CONSIDERED FOR OUR LAKESHORE COUNTIES. HOWEVER...CONFIDENCE
JUST NOT HIGH ENOUGH AT THIS POINT WITH RESPECT TO TIMING AND
LOCATION WHERE ANY LES BAND WILL IMPINGE ON THE SHORELINE...THUS
OPTED TO STICK WITH ADVISORY THERE AS WELL. DID MENTION LOCALLY
HIGHER AMOUNTS AROUND 6 INCHES FOR MANITOWOC AND KEWAUNEE
COUNTIES.

BULK OF ACCUMULATING SNOW SHOULD BE EAST OF THE FORECAST AREA BY
12Z MONDAY. IT APPEARS BOUNDARY LAYER WINDS WILL BE RATHER MODEST
DURING THE BULK OF THE SNOWFALL SO DO NOT EXPECT MUCH IN THE WAY
OF BLOWING OR DRIFTING. HOWEVER WINDS START TO PICK UP IN EARNEST
LATER MONDAY MORNING SO SOME BLOWING OF THE FLUFFLY LIGHT SNOWFALL
IS POSSIBLE THEN.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY
ISSUED AT 313 PM CST SAT DEC 7 2013

SYSTEM WILL BE MOVING ACROSS THE REGION SUNDAY EVENING. MANY
LITTLE THINGS TO FOCUS ON TO ENHANCE SNOW TOTALS. THE FIRST WILL
BE A 160+ KNOT JET STREAK PASSING TO THE SOUTH OF THE AREA. THE
SECOND IS SOUTHEAST FLOW OFF THE LAKE WHICH WILL ENHANCE SNOW TOTALS
NEAR THE LAKE. THERE IS ALSO WEAK 850MB WARM ADVECTION. THE LAST
FEATURE WILL BE INVERTED TROUGH(S) FROM THE SURFACE LOW INTO EASTERN
WISCONSIN THAT WILL ENHANCE CONVERGENCE. SOME DIFFERENCES NOTED IN
THE MODELS ON WHERE INVERTED TROUGH WILL SET UP. ONE MODEL HAD TWO
INVERTED TROUGHS...ONE ALONG THE LAKESHORE REGION WITH A SECOND
TROUGH EXTENDING NORTHWEST INTO CENTRAL WISCONSIN. PER COORDINATION
WITH SHORT TERM FORECASTER...DECIDED TO GO WITH A WINTER WEATHER
ADVISORY FOR TOTALS OF 2 TO 4 INCHES OVER THE FAR NORTH AND 3 TO 5
ELSEWHERE EXCEPT ALONG THE LAKE. TOTALS ALONG THE LAKE COULD REACH
OVER 6 INCHES DUE TO LAKE ENHANCEMENT. THE SNOW WILL DIMINISH FROM
SOUTHWEST TO NORTHEAST AFTER MIDNIGHT.

ON MONDAY...GUSTY WEST WINDS OF 25 TO 30 KNOTS WILL CREATE SOME BLOWING
AND DRIFTING OF THE SNOW...ESPECIALLY ACROSS NORTH-SOUTH ROADS.
TEMPERATURES WILL PROBABLY NOT BUDGE MUCH...AND MAY ACTUALLY FALL
SOME. ANOTHER CLIPPER SYSTEM WILL BRING A SMALL CHANCE OF LIGHT SNOW
LATE MONDAY NIGHT INTO TUESDAY...AND WILL BRING A REINFORCING SHOT
OF ARCTIC AIR TUESDAY AND WEDNESDAY. PRETTY GOOD BET THAT WIND CHILL
HEADLINES WILL BE NEEDED INCLUDING WIND CHILL WARNINGS IN SOME
SPOTS. ANOTHER CLIPPER SYSTEM WILL PASS TO THE SOUTH OF THE AREA
TUESDAY NIGHT...BUT SOME UNCERTAINTY IN THE TRACK OF THE SYSTEM
THIS FAR OUT. SOME MODIFICATION OF THE ARCTIC AIR IS EXPECTED THURSDAY
INTO FRIDAY AS 850MB TEMPERATURES WARM 10 C BY FRIDAY. PRETTY FAR
OUT TO SEE IF THIS WOULD PLAY OUT...BUT WILL HOPE FOR THE BEST. THE
LATEST ECMWF WILL BRINGS IN THE MILDER AIR AROUND THE 16TH OF DECEMBER.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1152 AM CST SAT DEC 7 2013

VFR CONDITIONS WILL PREVIAL AS HIGH PRESSURE DRIFTS
EASTWARD ACROSS THE FORECAST AREA TODAY AND EARLY TONIGHT. AS THE
HIGH PRESSURE SYSTEM PASSES TO THE EAST OF THE FORECAST AREA AFTER
MIDNIGHT...WINDS WILL TURN SOUTHEASTERLY WITH INCREASING WARM AIR
ADVECTION...LEADING TO GRADUAL INCREASE IN MID-LEVEL CLOUDS TOWARD
DAYBREAK.

A DEVELOPING STORM SYSTEM OVER THE PLIANS WILL THEN APPROACH THE
FORECAST AREA BY LATE SUNDAY MORNING WITH SNOW SHOWERS OR LIGHT
SNOW BREAKING OUT IN THE 15Z TO 18Z TIME FRAME OVER CENTRAL
WISCONSIN. BY 18Z...COULD SEE MVFR CIGS AND VSBYS IN LIGHT SNOW AT
THE CWA AND AUW TAF SITES. LIGHT SNOW AND MVFR CONDITIONS WILL
QUICKLY SPREAD EASTWARD ACROSS THE REMAINDER OF THE FORECAST AREA
DURING THE AFTERNOON.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM NOON SUNDAY TO 6 AM CST MONDAY FOR
WIZ005-010-011-018>021-031-037>040-045-048>050-074.

WINTER WEATHER ADVISORY FROM 9 AM SUNDAY TO 6 AM CST MONDAY FOR
WIZ030-035-036.

WIND CHILL ADVISORY UNTIL 6 AM CST SUNDAY FOR WIZ005-010>012-018-
019.

WINTER WEATHER ADVISORY FROM 3 PM SUNDAY TO 6 AM CST MONDAY FOR
WIZ012-013-022-073.
&&

$$

SHORT TERM.....ESB
LONG TERM......ECKBERG
AVIATION.......ESB