Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 170929
AFDGRB

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

FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST 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 06Z TAF ISSUANCE
ISSUED AT 1146 PM CST TUE DEC 16 2014

SNOW SHOWERS WERE ON THEIR WAY OUT OF FAR NORTHEAST WISCONSIN AT
TAF ISSUANCE TIME. THEY SHOULD EXIT BY AROUND 09Z OR 10Z...BUT
LAKE EFFECT SNOW SHOWERS WILL CONTINUE ACROSS NORTH CENTRAL
WISCONSIN THROUGH WEDNESDAY MORNING.

THERE WERE AREAS OF VFR CIGS ACROSS PARTS OF EAST CENTRAL
WISCONSIN AT 05Z...BUT UPSTREAM CIGS WERE MAINLY MVFR SO HAVE
GENERALLY KEPT THEM THAT WAY OVERNIGHT. VSBYS WERE VFR EXCEPT IN
THE LOCATIONS THAT HAD SNOW WHERE THEY WERE MVFR AND IFR. THE
LAKE EFFECT SNOW SHOWERS SHOULD WIND DOWN BY 18Z WEDNESDAY.

MODELS INDICATED QUITE A BIT OF LOW LEVEL MOISTURE HANGING AROUND
THROUGH WEDNESDAY EVENING...BUT HAVE CIGS RISING DURING THE DAY TO
VFR IN MOST LOCATIONS DURING THE AFTERNOON. HAVE CLOUDS SCATTERING
OUT AROUND 03Z THURSDAY.
&&

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

$$

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






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