Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 161804
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1204 PM CST TUE DEC 16 2014

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND WEDNESDAY
ISSUED AT 424 AM CST TUE DEC 16 2014

PCPN TRENDS AND TYPES...SNOWFALL AMOUNTS AND FOG TRENDS ARE THE MAIN
FCST CONCERNS.

AN UPPER LEVEL LOW AND SURFACE LOW PRESSURE WERE MOVG STEADILY
EAST ACROSS NORTHERN IL EARLY THIS MORNING...AND PRODUCING
WIDESPREAD PCPN ACROSS THE FORECAST AREA. DEVELOPING NORTH WINDS AT
THE SURFACE WERE PULLING COLDER AIR INTO NC WI...CAUSING RAIN TO
MIX WITH OR CHANGE OVER TO SNOW. WIDESPREAD RAIN AND FOG WAS
OCCURRING ACROSS THE REST OF GRB CWA...WITH SOME DENSE FOG IN
EASTERN WI DUE TO LINGERING MOISTURE AND LIGHT EAST FLOW OFF LAKE
MICHIGAN.

WELL-DEFINED DEFORMATION ZONE ASSOCIATED WITH THE NORTHERN IL UPPER
LOW WILL GRADUALLY PULL OUT OF NE WI EARLY THIS AFTERNOON. THE RAIN/
SNOW LINE WILL PROGRESS STEADILY SE THIS MORNING...REACHING THE
MANITOWOC AREA BY EARLY AFTERNOON. THERE WILL LIKELY BE A PERIOD
OF RAIN/SLEET/SNOW BEFORE THE COMEPLETE CHANGEOVER OCCURS.
SNOWFALL AMOUNTS OF 1 TO 3 INCHES ARE POSSIBLE OVER NC/FAR NE WI
BY EVG...WITH THE HIGHEST AMOUNTS NEAR THE UPPER PENINSULA BORDER.
ONLY A DUSTING TO A HALF INCH IS EXPECTED ACROSS MUCH OF C/EC WI.

ANOTHER DEFORMATION ZONE IS EXPECTED TO REFORM OVER NORTHERN WI
TONIGHT INTO WEDNESDAY AS SECOND UPPER LOW OVER MN SHIFTS SE INTO
CENTRAL WI AND GRADUALLY SHEARS OUT. THIS SYSTEM...COMBINED WITH
SOME MID-LEVEL FRONTOGENETIC FORCING AND PERSISTENT LAKE ENHANCEMENT
DUE TO COLD NNW WINDS OFF LAKE SUPERIOR...WILL BRING ANOTHER
COUPLE INCHES ACROSS THE FAR NORTH...WITH AS MUCH AS ANOTHER 4
INCHES IN NW VILAS COUNTY.

GIVEN THAT THE SNOW ACCUMS OVER FAR NORTHERN WI WILL OCCUR OVER AN
EXTENDED PERIOD OF TIME...DO NOT PLAN TO ISSUE ANY WINTER WEATHER
HEADLINES AT THIS TIME. HOWEVER...WE WILL NEED TO MONITOR LAKE-
EFFECT TRENDS FOR VILAS COUNTY FROM THIS AFTERNOON THROUGH WEDS
MORNING. FOR NOW...WILL HIGHLIGHT TRAVEL IMPACTS IN THE HAZARDOUS
WEATHER OUTLOOK AND A SPECIAL WEATHER STATEMENT.

HAVE EXTENDED THE DENSE FOG ADVISORY ALONG THE LAKESHORE AND OVER
LAKE MICHIGAN UNTIL 9 AM. IMPROVEMENT SHOULD OCCUR QUICKLY ONCE
NORTH WINDS INCREASE AND DRIER AIR ARRIVES DURING THE MID-MORNING
PERIOD.

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY
ISSUED AT 424 AM CST TUE DEC 16 2014

THE LATEST GFS AND ECMWF ENSEMBLE MEANS INDICATE SPLIT FLOW ACROSS
NORTH AMERICA THROUGH THIS WEEKEND...BEFORE A MORE TYPICAL PATTERN
FOR THIS TIME OF THE YEAR EMERGES EARLY NEXT WEEK.  AS A
RESULT...CONDITIONS FOR MUCH OF THIS PERIOD ARE EXPECTED TO BE
SEASONABLE AND QUIET.  ALTHOUGH MASS FIELDS BEGIN TO DIVERGE LATE IN
THE WEEK...WILL USE A BLEND OF THE GFS AND ECMWF FOR MUCH OF THIS
FORECAST.

WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...SHOULD SEE PLENTY OF CLOUD
COVER WEDNESDAY EVENING DUE TO SHARP CYCLONIC FLOW IN THE LOW LEVELS
AND UNSTABLE FLOW OFF LAKE SUPERIOR.  DRY AIR ABOVE A LOWERING
INVERSION DOES PUSH SOUTH LATE IN THE NIGHT...BUT SHOULD NOT BE
ENOUGH TO SCOUR OUT THE LOW CLOUDS.  WILL KEEP MOSTLY CLOUDY WORDING
IN THE FORECAST FOR MUCH OF THE NIGHT.  POLAR HIGH PRESSURE THEN
MOVES INTO THE REGION FOR THURSDAY.  WEAKENING FLOW OFF LAKE
SUPERIOR SHOULD LEAD TO CLEARING SKIES THROUGH THE DAY.  HIGH TEMPS
WILL BE SEASONABLE IN THE MIDDLE TO UPPER 20S.  HIGH PRESSURE WILL
HANG AROUND THE REGION THURSDAY NIGHT.  MAY SEE A LITTLE MORE HIGH
CLOUDS OVERHEAD...BUT OTHERWISE...MAINLY CLEAR AND QUIET.

REST OF THE FORECAST...A WEAK UPPER CIRCULATION WILL BE SLOWLY
MOVING ACROSS THE REGION FRIDAY THROUGH SUNDAY.  THOUGH THERE WILL
LIKELY BE PERIODS OF BROKEN MID AND HIGH CLOUDS...LINGERING LOW
LEVEL ANTICYCLONIC FLOW WILL KEEP PLENTY OF DRY AIR AROUND...WHICH
SHOULD BE ENOUGH TO KEEP THE AREA DRY.  BUT IF PRECIP WERE TO
OCCUR...ANYTHING THAT FALLS WOULD BE LIGHT.  BETTER CHANCES OF
PRECIP WILL OCCUR EARLY NEXT WEEK AHEAD OF A DIGGING NORTHERN STREAM
TROUGH.  TEMPERATURES WILL BE SLOWLY RISING THIS WEEKEND.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1204 PM CST TUE DEC 16 2014

MVFR CONDITIONS WITH SNOW SHOWERS EXPECTED OVER MOST
OF THE AREA INTO THE EVENING HOURS. LOCAL IFR POSSIBLE. SNOW
SHOWERS WILL DIMINISH OVERNIGHT EXCEPT NORTH OF RHINELANDER WHERE
LAKE EFFECT SNOW SHOWERS WILL CONTINUE INTO WEDNESDAY. D25/ARV AND
LNL ARE THE MAIN AIRPORTS AFFECTED. OTHERWISE MAINLY MVFR CEILINGS
AND VFR VIS WEDNESDAY.
&&

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

$$

SHORT TERM.....KIECKBUSCH
LONG TERM......MPC
AVIATION.......RDM





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