000
FXUS63 KGRB 012349
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
549 PM CST SUN DEC 1 2013

UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND MONDAY
ISSUED AT 220 PM CST SUN DEC 1 2013

SEVERAL FORECAST ISSUES THIS PERIOD INCLUDING SOUTHERN EXTENT OF
LOW CLOUDS OVERNIGHT...WHETHER LAKE EFFECT SNOW SHOWERS AFFECT
DOOR COUNTY...AND TIMING OF NEXT SYNOPTIC-SCALE SYSTEM.

WEAK LOW-LEVEL WAA TONIGHT AS WINDS BECOME SW-W. AS A RESULT
WOULD EXPECT THE LOW CLOUDS TO STICK AROUND OVER MUCH OF THE
AREA. DIURNAL CU THAT FORMED ALONG SOUTHERN EXTENT OF LOW CLOUDS
MAY DISSIPATE BUT HIGHER CLOUDS UPSTREAM MOVING IN.

REPEATED RUNS OF HRRR AND OTHER SHORT-TERM MODELS INDICATE SOME
LAKE EFFECT SNOW SHOWERS ASSOCIATED WITH POSSIBLE MESOVORTEX OVER
NORTH-CENTRAL LK MICHIGAN TONIGHT WHICH COULD CLIP DOOR COUNTY.
DELTA-T`S ARE MARGINAL BUT WILL CONTINUE WITH SMALL CHANCE OF
SNOW SHOWERS OR FLURRIES IN NORTHERN DOOR. MIN TEMPS SHOULD DROP
INTO THE 20S MOST AREAS AWAY FROM LK MICHIGAN.

ON MONDAY...WAA INCREASES AS NEXT SYSTEM APPROACHES FROM THE
WEST. SOME LIGHT SNOW OR FLURRIES EXPECTED TO MOVE INTO AT LEAST
THE WESTERN HALF OF THE AREA BY LATE AFTERNOON. STILL SOME
QUESTION AS TO HOW FAST SYSTEM BEGINS TO AFFECT AREA...SO WILL
CONTINUE TO USE MODEL BLEND WHICH RESULTS IN TIMING SIMILAR TO
PREVIOUS FORECAST. HIGH TEMP FORECAST A BLEND OF BEST PERFORMING
MOS GUIDANCE WHICH IS NOT FAR OFF FROM PREVIOUS FORECAST.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY
ISSUED AT 220 PM CST SUN DEC 1 2013

A VERY CHALLENGING FORECAST PERIOD THROUGH MID WEEK DUE TO
TIMING ISSUES WITH A DEVELOPING STORM SYSTEM AND PCPN TYPE. THE
POTENTIAL EXISTS FOR WINTER HEADLINES OVER NORTH CENTRAL WISCONSIN
FOR MAINLY SNOW.

STARTING MONDAY NIGHT...NAM AND GFS CONTINUE TO REMAIN A BIT QUICKER
WITH SPREADING THE BAND OF SNOW OVER THE AREA FASTER WITH THE WARM
AIR ADVECTION. OLD ECMWF IS ABOUT 12 HOURS SLOWER WHILE THE GEM
WAS THE AVERAGE. LATEST ECMWF IS CLOSER TO THE GEM TIME WITH THE
INITIAL WAA TOWARD MONDAY NIGHT.

AVAILABLE FORECAST SOUNDINGS DO INDICATE SNOW AT THE START FOR
THE PCPN TYPE WITH AROUND AN INCH OR TWO OF ACCUMULATION BY
TUESDAY MORNING...WITH THE 2 INCH AMOUNTS TOWARD CENTRAL AND NORTH
CENTRAL AND POINTS NORTHWEST. THE AIR COLUMN LIKELY WILL REMAIN
COLD ENOUGH FOR SNOW FOR ANOTHER 2 INCHES ACROSS THE NORTH. ITS
POSSIBLE AN ADVISORY WILL BE NEEDED FOR NORTH CENTRAL AND PARTS OF
FAR NORTHEAST WISCONSIN FOR THIS INITIAL BAND. SNOW AMOUNTS APPEAR
TO DIMINISH DUE TO CONTINUED WAA AND PCPN CHANGING TO RAIN OR A
RAIN SNOW MIX. THE NAM FORECAST SOUNDING FOR RHI CHANGES THE SN
OVER BRIEFLY ZR THEN RAIN TUESDAY NIGHT THEN BACK TO SNOW LATE.
WITH FROST DEPTHS A FEW INCHES DEEP OVER MANY LOCATIONS DUE TO THE
COLD LATER HALF OF NOVEMBER...POTENTIAL OF BRIEF PERIOD ICY ROADS
DUE TO ZR AND COLD GROUND. NOT CONFIDENT OF THE ZR AT THIS TIME
BUT IF THIS BECOMES MORE OF A THREAT...WINTER WEATHER ADVISORIES
MAY BE NEEDED FOR THAT ELEMENT ALONE TOWARD TUESDAY AS WELL.

BLEND OF MEDIUM RANGE MODELS WITH THE H850 LOW TRACKS SUGGESTS THE
SYSTEM PCPN/SNOW TO REMAIN NORTHWEST OF THE AREA BUT CLOSE ENOUGH
TO PRODUCE ANOTHER INCH OR TWO OVER NORTH CENTRAL WISCONSIN. AT
THIS TIME...UP TO 6 INCHES OF SNOW POSSIBLE OVER PARTS OF NORTH
CENTRAL WISCONSIN FROM MONDAY NIGHT INTO WEDNESDAY MORNING. BUT
DUE TO THE SNOW AMOUNTS WILL BE SPREAD OVER A 36-48 PERIOD...NO
WATCH ISSUED AT THIS TIME. ANTICIPATE A LONG DURATION ADVISORY OR
TWO SHORTER WINTER ADVISORIES MAY BE NEEDED TO HANDLE THE SNOW
ACCUMULATION AND OR MIX CLOSER TO THE EVENT.

BITTERLY COLD ARCTIC AIR WILL THEN POUR INTO THE ARE IN THE WAKE
OF THE SYSTEM. WITH NEED TO HAVE A HEALTHY NORTH TO SOUTH GRADIENT
IN TEMPS LATER IN THE WEEK DUE TO THE COLDER TEMPERATURES OVER
THE ANTICIPATED SNOW COVER OVER NORTH CENTRAL WISCONSIN TO
PROBABLY LITTLE OR NO SNOW OVER CENTRAL AND EAST CENTRAL
WISCONSIN. WINDS APPEAR TO WESTERLY FOR SIGNIFICANT LAKE EFFECT
SNOWS TO REACH FAR NORTH CENTRAL WISCONSIN DURING THE ARTIC SURGE.

MEDIUM RANGE RUNS BEGIN TO DEVELOP RETURN FLOW PCPN AGAIN LATE
NEXT WEEKEND AND FOR THE START OF THE NEXT WEEK...WILL KEEP THE
FORECAST DRY THROUGH NEXT WEEKEND FOR NOW.
&&

.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 546 PM CST SUN DEC 1 2013

WITH GENERALLY WEAK/DIFFUSE PATTERN ACRS THE RGN...LOW CLDS EXPECTED TO
LINGER THROUGH TOMORROW.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....JKL
LONG TERM......TDH
AVIATION.......SKOWRONSKI