Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 211721
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1121 AM CST SUN DEC 21 2014

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND MONDAY
ISSUED AT 401 AM CST SUN DEC 21 2014

PCPN TRENDS/TYPE AND SNOWFALL AMOUNTS ARE THE MAIN FCST CONCERNS.

SOUTHERLY RETURN FLOW WAS INCREASING ACROSS THE REGION EARLY THIS
MORNING...BUT MOISTURE WAS STILL TOO SHALLOW FOR ANY SIGNIFICANT
PCPN. A FEW FLURRIES WERE REPORTED IN NC WI...AND ALSO SUSPECT
THAT SOME PATCHY FREEZING DRIZZLE WAS OCCURRING. WIDESPREAD
OVERCAST CONDITIONS COVERED THE FORECAST AREA...AND TEMPERATURES
WERE IN THE 25 TO 30 RANGE.

A LOW-LEVEL JET IS EXPECTED TO GRADUALLY STRENGTHEN TO 30-40 KTS
TODAY...RESULTING IN INCREASING WAA/ISENT LIFT DURING THE LATE
MORNING AND AFTERNOON. PATCHY FLURRIES/FZDZ WILL START TO MIX WITH
LIGHT SNOW AS THE MORNING PROGRESSES...THEN CHANGE OVER TO ALL
SNOW AS DEEPER SATURATION AND STRONGER LIFT OCCURS THIS AFTERNOON.
HAVE INCREASED POPS TO CATEGORICAL OVER NC/FAR NE WI LATE THIS
AFTERNOON...WITH SNOW ACCUMS AROUND AN INCH ANTICIPATED THERE. QPF
AND SNOWFALL AMOUNTS WILL TAPER OFF QUICKLY FARTHER SE. HIGH TEMPS
WILL BE IN THE LOWER TO MIDDLE 30S.

STEADY LIGHT SNOW (AND CATEGORICAL POPS) WILL CONTINUE THROUGH
THE EVG ACROSS NC/FAR NE WI...WITH JUST PATCHY LIGHT SNOW OVER THE
SE PART OF THE CWA. ANOTHER INCH OR TWO OF SNOW ACCUMULATION IS
EXPECTED OVER THE NORTHWOODS. A DRY SLOT WILL WORK ITS WAY INTO
THE REGION LATE TONIGHT INTO EARLY MONDAY...WHICH WILL CAUSE SNOW
TO DECREASE AND MIX WITH FREEZING DRIZZLE...AS ICE CRYSTALS GET
STRIPPED OUT OF THE MID-LEVELS. PCPN WILL INCREASE AGAIN BY MONDAY
AFTERNOON...AS AN UPPER LOW MOVES INTO NW IOWA AND A S/W TROF
LIFTS NORTH INTO WI. PCPN SHOULD BE MAINLY SNOW ACROSS NC/FAR
NE WI...WITH A RAIN/SNOW MIX CHANGING TO RAIN FARTHER SE. LOW
TEMPS TONIGHT ARE EXPECTED TO BE AROUND 30 DEGREES...WITH HIGHS
ON MONDAY IN THE 30S.

.LONG TERM...MONDAY NIGHT THROUGH SATURDAY
ISSUED AT 401 AM CST SUN DEC 21 2014

THE LATEST GFS AND ECMWF ENSEMBLE MEANS HAVE BECOME MORE CONSISTENT
WITH THE TRACK OF A DEEPENING CYCLONE DURING THE MIDDLE OF THE
UPCOMING WEEK.  THIS TRACK WOULD TAKE INTENSIFYING LOW FROM
SOUTHWEST LOWER MICHIGAN TO ROUGHLY SAULT STE MARIE.  HOWEVER...THE
00Z GFS AND ECMWF NOW SHOWS FLATTER UPSTREAM FLOW...AND CONSEQUENTLY
TAKES THE LOW ON A WEAKER AND MORE EAST HEADING...THEREBY MISSING
THE REGION COMPLETELY. THIS IS A NEW DEVELOPMENT...BUT UNTIL THE
ENSEMBLE MEANS SHOW THIS SHIFT...PLAN ON KEEPING CONTINUITY AS MUCH
AS POSSIBLE.  WILL THEREFORE RELY ON THE ENSEMBLE MEANS FOR MUCH OF
THIS FORECAST AFTER 12Z WED.

MONDAY NIGHT THROUGH TUESDAY NIGHT...LOW PRESSURE WILL BE MOVING
EAST INTO SOUTHWEST WISCONSIN MONDAY NIGHT AHEAD OF SHORTWAVE ENERGY
ROTATING NORTHEAST INTO THE REGION.  WITH THE APPROACH OF BETTER
FORCING...SHOULD SEE PRECIPITATION SURGE NORTHWARD THROUGH THE
NIGHT.  STILL LOOKING AT MAINLY SNOW OVER N-C WISCONSIN...A MIX
NORTH AND WEST OF THE FOX VALLEY...AND MAINLY RAIN OVER THE REST OF
THE FORECAST AREA.  THE LOW WILL MOVE NORTHEAST ON TUESDAY WHICH
WILL TRANSPORT WARMER AIR INTO N-C WISCONSIN WHERE SNOW COULD CHANGE
TO A MIX...WHILE A DRY SLOT MOVES OVERHEAD OVER EASTERN WISCONSIN.
THIS MAY LEAD TO BREAK IN THE PRECIP ACROSS THE EAST...OR A
TRANSITION TO LIGHT DRIZZLE.  ACCUMULATING SNOW WILL LIKELY OCCUR
OVER NORTH-CENTRAL WISCONSIN BEFORE THE CHANGE OVER OCCURS...THAT COULD
POTENTIALLY PROMPT AN ADVISORY.  TEMPERATURES COOL ALOFT A BIT
ACROSS CENTRAL AND NORTH-CENTRAL WISCONSIN TUESDAY NIGHT...BUT THE
DRY SLOT WILL REMAIN AN ISSUE...WHICH MEANS PRECIP WILL REMAIN
RATHER LIGHT.  NOT EXPECTING MUCH ACCUMULATIONS IF TEMPERATURES COOL
ENOUGH FOR SNOW OVER THE I39/ROUTE 51 CORRIDOR.  LATE IN THE
NIGHT...WILL BE WATCHING AN INTENSIFYING CYCLONE MOVE NORTH INTO
SOUTHERN LOWER MICHIGAN.  THE EASTERN EDGE OF THE PRECIP SHIELD FROM
THIS LOW MAY BE FELT ALONG THE LAKESHORE...BUT TEMPS LOOK WARM
ENOUGH FOR A RAIN/SNOW MIX.  FORECAST TEMPERATURES LOOK GOOD MONDAY
NIGHT AND TUESDAY...BUT RAISED LOW TEMPS TUESDAY NIGHT.

REST OF THE FORECAST...THE LOW PRESSURE WILL CONTINUE TO STRENGTHEN
AS IT HEADS TOWARDS THE SOO ON WEDNESDAY.  THIS TRACK WOULD BRING A
GLANCING BLOW TO NORTHEAST WISCONSIN...WITH SUB-ADVISORY TYPE SNOWS.  ANY
DEVIATIONS THOUGH COULD LEAD TO MUCH HIGHER TOTALS...OR NONE AT
ALL...SO UNCERTAINTY REMAINS HIGH IN ANY CASE.  BEHIND THE
LOW...EXPECT WEST WINDS TO STRENGTHEN AND BECOME GUSTY WEDNESDAY
AFTERNOON THROUGH THURSDAY...WHICH WOULD BLOW/DRIFT ANY NEW SNOW.
CHRISTMAS DAY CONTINUES TO LOOK QUIET BESIDES THE GUSTY WINDS. THEN
WILL BE WATCHING THE NEXT CHANCE OF SNOW ARRIVE ON FRIDAY.  NEXT
WEEKEND LOOKS QUIET.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1121 AM CST SUN DEC 21 2014

PLENTY OF LIFR/IFR CIGS EXPECTED OVER ALL OF THE NE WI TAF SITES
FOR THE NEXT 24 HOURS AS THE FIRST WAVE OF PCPN MOVES THROUGH THE
REGION AHEAD OF A LARGE SYSTEM ORGANIZING OVER THE PLAINS. LIGHT
SNOW WL FALL OVER THE RHI...AUW AND CWA TAF SITES THRU THE EVENING
HOURS BEFORE TAPERING OFF TO FREEZING DRIZZLE OR FLURRIES LATE
TNGT. A BREAK IN THE PCPN IS ANTICIPATED LATE TNGT INTO MON
MORNING WITH VSBYS REDUCED DUE TO PATCHY FOG. THE NEXT WAVE OF
PCPN SET TO GRADUALLY OVERSPREAD THE AREA FROM SOUTH TO NORTH MON
AFTERNOON. PCPN TYPE WL BE TRICKY AS WARMER AIR LIFTS INTO THE
STATE AND RAIN WL MIX WITH THE SNOW OR EVEN TURN TO ALL RAIN OVER
CNTRL/E-CNTRL WI. CIGS/VSBYS MAY BRIEFLY RISE INTO THE MVFR RANGE
MON MORNING BEFORE HEADED BACK DOWN TO IFR CONDITIONS MON
AFTERNOON.
&&

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

$$

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






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