Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 171203
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
603 AM CST WED DEC 17 2014

UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND THURSDAY
ISSUED AT 329 AM CST WED DEC 17 2014

SNOWFALL TRENDS AND AMOUNTS ACROSS FAR NORTHERN WI TODAY...AND CLOUD
TRENDS AND TEMPERATURES THROUGH THE PERIOD...ARE THE MAIN FCST CONCERNS.

AN UPPER LEVEL LOW WAS SHIFTING EAST THROUGH CENTRAL WI EARLY THIS
MORNING. AN ASSOCIATED DEFORMATION ZONE WAS PIVOTING AND BECOMING
ORIENTED WEST TO EAST ACROSS FAR NORTHERN WI. STEADY SNOW WAS OCCURRING
OVER FAR NE WI...AND WAS GRADUALLY FILLING BACK IN OVER NC WI...WHERE
CONDITIONS WERE ALSO FAVORABLE FOR LAKE ENHANCEMENT.

UPPER LEVEL FORCING WILL SHIFT EAST THIS MORNING...WITH THE DEFORMATION
ZONE GRADUALLY WEAKENING AS IT SLOWLY SAGS SOUTH. ANOTHER 1 TO 2 INCHES
OF ADDITIONAL SNOW IS POSSIBLE OVER FAR NORTHERN WI BEFORE IT TAPERS
OFF THIS AFTERNOON. SLIGHTLY HIGHER AMOUNTS ARE POSSIBLE OVER NW VILAS
COUNTY DUE TO LAKE EFFECT...SO WILL KEEP THE WINTER WX ADVSY GOING THERE
UNTIL NOON. SNOW WILL TAPER OFF TO FLURRIES DURING THE LATE AFTERNOON
AND EVENING AS THE WEAKENING DEFORMATION ZONE EXITS AND LAKE EFFECT
CONDITIONS BECOME MORE UNFAVORABLE (WINDS TURN NNE...INSTABILITY
WEAKENS DUE TO WAA AND MUCH DRIER AIR ARRIVES). A SIGNIFICANT SURGE
OF DRIER AIR SHOULD BRING AT LEAST PARTIAL CLEARING FROM NORTH TO
SOUTH DURING THE LATE EVG AND OVERNIGHT. PARTLY CLOUDY SKIES SHOULD
PREVAIL ON THURSDAY AS HIGH PRESSURE BUILDS INTO THE WSTRN GREAT
LAKES.

USED A BLEND OF THE BETTER PERFORMING GUIDANCE SETS FOR TEMPS OVER
THE NEXT COUPLE DAYS...WITH SOME DOWNWARD ADJUSTMENTS OVER NORTHERN
WI TONIGHT DUE TO NEW SNOW COVER AND CLEARING.

.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY
ISSUED AT 329 AM CST WED DEC 17 2014

THE LATEST GFS AND ECMWF ENSEMBLE MEAN INDICATES THAT SPLIT FLOW
WILL TRANSITION TO A MORE TYPICAL RIDGE IN THE WEST AND TROUGH IN
THE EAST PATTERN BY EARLY NEXT WEEK.  UNTIL THIS OCCURS...EXPECT
RELATIVELY QUIET AND SEASONABLE WEATHER.  THERE IS SUBSTANTIAL
SPREAD IN THE MEDIUM RANGE MODELS BY 00Z TUESDAY SO WILL HAVE TO
TAKE A GENERAL MODEL COMPROMISE EARLY NEXT WEEK.  OTHERWISE...WILL
RELY ON THE ECMWF.

THURSDAY NIGHT THROUGH FRIDAY NIGHT...HIGH PRESSURE WILL BE MOVING
ACROSS THE REGION THURSDAY NIGHT AND FRIDAY BEFORE MOVING INTO
EASTERN CANADA ON FRIDAY NIGHT.  LIGHT WINDS WITHIN THE HIGH WILL
SUPPORT GOING BELOW GUIDANCE FOR TEMPERATURES THURSDAY NIGHT...BUT
SOME UNCERTAINTY IN REGARDS TO HOW THICK CIRRUS WILL BE.  WILL STAY
CONSERVATIVE AWAY FROM THE COLD SPOTS WHERE DID DROP TEMPS A COUPLE
DEGREES.  THE CIRRUS WILL TEMPORARILY THIN OUT ON FRIDAY WHICH
SHOULD LEAD TO A BRIEF PERIOD OF MOSTLY CLEAR SKIES.  BUT THEN WILL
SEE CLOUDS INCREASE AGAIN LATE FRIDAY AFTERNOON INTO FRIDAY NIGHT
AHEAD OF A PACIFIC SHORTWAVE TROUGH.  PROGGED SOUNDINGS START TO
LOOK SATURATED BY LATE FRIDAY NIGHT...BUT WILL KEEP PRECIP OUT OF
THE FORECAST AS THE MID-LEVEL DRY WEDGE STILL LOOKS SUFFICIENT TO
THWART PRECIP.

REST OF THE FORECAST...THE SHORTWAVE WILL SLOWLY MOVE ACROSS THE
REGION SATURDAY INTO SATURDAY NIGHT. PROGGED SOUNDINGS CONTINUE TO
SATURATE AND WOULD NOT BE SURPRISED TO SEE LIGHT SNOW.  WILL MENTION
TO LATER SHIFTS.  ANY LIGHT SNOW WILL EXIT LATE SATURDAY NIGHT BUT
SOUTHERLY FLOW LOOKS TO KEEP LOW STRATUS AROUND.  BETTER CHANCES OF
PRECIP THEN ARRIVE SUNDAY NIGHT AHEAD OF A DIGGING SHORTWAVE
TROUGH.  PRECIP CHANCES CONTINUE TO IMPROVE INTO MONDAY THOUGH
ENOUGH WARM AIR AROUND COULD LEAD TO A MIX OF RAIN AND SNOW OVER
CENTRAL AND NORTHEAST WISCONSIN. PRECIP TO CONTINUE INTO TUESDAY.
&&

.AVIATION...FOR 12Z TAF ISSUANCE
ISSUED AT 550 AM CST WED DEC 17 2014

AN UPPER LEVEL DISTURBANCE WILL BRING LIGHT SNOW TO FAR NORTHERN WI
TODAY...WITH FLURRIES FARTHER SOUTH. THE SNOW WILL GRADUALLY TAPER
OFF DURING THE AFTERNOON. MUCH OF THE FORECAST AREA WILL HAVE MVFR
CONDITIONS THROUGH THE DAY AND EVENING...THOUGH SOME SPOTTY IFR
VSBYS ARE POSSIBLE IN VILAS COUNTY DUE TO HEAVIER LAKE EFFECT SNOW
SHOWERS THIS MORNING. PARTIAL CLEARING IS EXPECTED TO PROGRESS
FROM NORTH TO SOUTH DURING THE LATE EVENING AND OVERNIGHT HOURS...
BUT CONFIDENCE IN THIS TREND IS ONLY MODERATE AT THIS TIME.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL NOON CST TODAY FOR WIZ005.
&&

$$

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






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