Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 190920
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
320 AM CST FRI DEC 19 2014

FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND SATURDAY
ISSUED AT 318 AM CST FRI DEC 19 2014

CLOUD TRENDS AND TEMPERATURES WILL BE THE MAIN FCST CONCERNS
THROUGH SATURDAY.

HIGH PRESSURE WAS SITUATED OVER WI EARLY THIS MORNING. SOME LAKE
ENHANCED CLOUDS HAD DRIFTED INLAND OVER FAR EASTERN WI DUE TO
WEAK ONSHORE FLOW. IN ADDITION...STRATUS CLOUDS WERE SITUATED
OVER THE FAR WSTRN PART OF THE FCST AREA...AND WERE EDGING EAST.
IN BETWEEN...SKIES WERE MOSTLY CLEAR. TEMPERATURES RANGED FROM
THE SINGLE DIGITS ABOVE AND BLO ZERO OVER NORTHERN WI...TO THE
TEENS AND LOWER 20S FARTHER SOUTH.

AN UPPER LEVEL TROF WILL PASS MAINLY NW OF THE FORECAST AREA
TODAY...SO LIGHT SNOW/FLURRIES OVER MN SHOULD BYPASS NORTH
CENTRAL WI. EXPECT LAKE ENHANCED CLOUDS TO DISSIPATE THIS
MORNING AS ONSHORE FLOW WEAKENS AND ENDS. LOW STRATUS OVER PARTS
OF NC/C WI SHOULD CONTINUE TO VERY SLOWLY SHIFT EAST...THOUGH
THE EASTERN EDGE MAY TEND TO DISSIPATE DUE TO DAYTIME MIXING.
HIGH TEMPERATURES ARE EXPECTED TO WARM INTO THE MIDDLE 20S TO
LOWER 30S.

TONIGHT...CLOUDS WILL CONTINUE TO SHIFT EAST...WITH ALL BUT
FAR EASTERN WI BECOMING MOSTLY CLOUDY TO CLOUDY. PARTLY CLOUDY
SKIES AND LIGHT WINDS IN EASTERN WI MAY LEAD TO PATCHY FOG
DEVELOPMENT. MOST PLACES SHOULD HAVE MIN TEMPS IN THE MIDDLE
TEENS TO LOWER 20S...THOUGH SINGLE DIGITS AND LOWER TEENS ARE
POSSIBLE IN FAR NE WI.

ON SATURDAY...A WEAK UPPER TROF WILL MOVE INTO THE REGION.
THOUGH MOISTURE WILL CONTINUE TO INCREASE/DEEPEN WITH TIME...
THE MOISTURE LAYERS APPEAR TO BE A BIT DISJOINTED...AND LITTLE
OR NO LIFT IS EVIDENT...SO WILL KEEP THE CURRENT DRY FCST INTACT.
HIGH TEMPERATURES SHOULD WARM INTO THE UPPER 20S TO MIDDLE 30S.

.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY
ISSUED AT 318 AM CST FRI DEC 19 2014

THE LATEST GFS AND ECMWF ENSEMBLE MEANS CONTINUE TO SHOW AN
AMPLIFYING TROUGH OVER THE WESTERN GREAT LAKES REGION DURING THE
MONDAY TO WEDNESDAY PERIOD OF NEXT WEEK.  THE MEDIUM RANGE MODELS
ARE REASONABLY CLUSTERED THIS FAR OUT...BUT SUBTLE DIFFERENCES WITH
RESPECT TO THE DEPTH AND TRACK OF THE CYCLONE LEAD TO RATHER LARGE
UNCERTAINTY WITH THE FORECAST.  THE NEW ECMWF HAS A MORE SOUTHERLY
TRACK AND IS SIGNIFICANTLY DEEPER COMPARED TO OTHER GUIDANCE WHILE
THE GEM IS FARTHER NORTH.  THE ENSEMBLE MEANS RESIDE BETWEEN THESE
TWO MODELS...WHICH IS CLOSEST TO THE GFS...BUT DO NOT WANT TO RELY
SOLELY ON THIS MODEL FOR THE DETAILS.  WILL INSTEAD BLEND THE
GFS/ECMWF FOR MUCH OF THIS FORECAST.

SATURDAY NIGHT THROUGH SUNDAY NIGHT...ONE SHORTWAVE TROUGH WILL BE
EXITING THE REGION SATURDAY NIGHT...WHILE THE NEXT WAVE MOVES EAST
ACROSS THE CENTRAL PLAINS.  ALONG WITH LIGHT SOUTHERLY FLOW...CLOUDS
ASSOCIATING WITH THE DEPARTING WAVE COMBINED WITH INCOMING CLOUDS
FROM THE NEXT SYSTEM SHOULD LEAD TO A MOSTLY CLOUDY NIGHT ACROSS THE
REGION.  STILL LOOKING AT DRY WEDGE IN THE MID-LEVELS WHICH SHOULD
KEEP THE AREA DRY.  THIS WILL CHANGE WITH THE ARRIVAL OF THE QUICK
MOVING CENTRAL PLAINS SHORTWAVE ON SUNDAY.  INCREASING ISENTROPIC
ASCENT/FGEN AND WEAK QG FORCING WILL LEAD TO AN AREA OF LIGHT SNOW
MOVING INTO THE REGION SUNDAY MORNING.  TEMPERATURES LOOK COLD
ENOUGH FOR ALL SNOW THOUGH SURFACE TEMPS AROUND 33 TO 34 SHOULD LEAD
TO MELTING ON ROADWAYS OVER EASTERN WISCONSIN.  PROGGED QPF AMOUNTS
USING A 10-12:1 RATIO WOULD GIVE A HALF INCH TO AN INCH OF
ACCUMULATION BY THE END OF SUNDAY AFTERNOON. THOUGH THE SHORTWAVE
WILL BE EXITING THE REGION EARLY IN THE EVENING...MODELS CONTINUE TO
GENERATE LIGHT PRECIP THROUGH THE NIGHT.  NOT EXACTLY CLEAR WHY AS
PROGGED SOUNDINGS SHOW MID-LEVEL DRY AIR MOVING IN AND ASCENT
WEAKENS.  WILL KEEP A SMALL CHANCE IN THE FORECAST...BUT THINK THE
MODELS ARE OVERDONE.  COULD SEE ANOTHER INCH OVER N-C WISCONSIN BY
MORNING IF MODELS ARE CORRECT.

REST OF THE FORECAST...A DIGGING SHORTWAVE ON MONDAY WILL BE
INTENSIFYING AS IT MOVES ACROSS THE CENTRAL PLAINS.  THE AMPLIFYING
FLOW ARGUES FOR A SLOWER SOLUTION SO WONDER IF MUCH OF THE DAY WILL
BE DRY...LIKE THE ECMWF SHOWS.  BUT AS THE CYCLONE TRACKS INTO THE
WESTERN GREAT LAKES MONDAY NIGHT...SHOULD SEE WIDESPREAD PRECIP MOVE
ACROSS THE REGION.  TEMPERATURE PROFILES CALL FOR ALL SNOW ACROSS
THE WEST...AND MIX OF RAIN AND SNOW ACROSS THE EAST.  THE CYCLONE
MEANDERS ABOUT MONDAY NIGHT AND TUESDAY WITH THE COLUMN GRADUALLY
COOLING.  THOUGH A MIX OF RAIN AND SNOW WILL LIKELY PERSIST INTO
TUESDAY ACROSS THE EAST...ALL AREAS COULD SEE LIGHT SNOW ON TUESDAY
NIGHT.  LIGHT SNOW WILL LIKELY CONTINUE WEDNESDAY AND WEDNESDAY
NIGHT BEFORE DRY WEATHER RETURNS ON THURSDAY.

IN GENERAL THOUGH...THIS LOOKS LIKE A SEVERAL DAY EVENT OF LIGHT
PRECIP.  NORTH-CENTRAL WISCONSIN LOOKS TO SEE THE MOST ACCUMULATING
SNOW BUT HIGH IMPACT AMOUNTS DO NOT APPEAR LIKELY AT THIS TIME.
DETAILS CAN CHANGE THOUGH...SO ANYONE WITH TRAVEL PLANS NEXT WEEK
SHOULD STAY TUNED TO THE LATEST FORECASTS.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1148 PM CST THU DEC 18 2014

CLOUD TRENDS CONTINUE TO BE THE MAJOR FORECAST CHALLENGE
THROUGHOUT THE TAF VALID PERIOD. DRIER AIR MAKING ITS WAY INTO
WISCONSIN CLEARED THE LOW CLOUDS OUT OF MOST OF THE AREA DURING
THE AFTERNOON AND EVENING HOURS. HOWEVER...MVFR CIGS RETURNED TO
MFI/Y50. NOT GOOD CONFIDENCE REGARDING THE LOW CLOUD TRENDS.
MODEL TIME/HEIGHT SECTIONS MOSTLY SHOW QUITE A BIT OF MOISTURE
BELOW ABOUT 2500FT THROUGH 06Z SATURDAY. THINK LOW CLOUDS WILL
MAKE A RETURN FROM THE SOUTHWEST BUT NOT SO SURE HOW LONG BEFORE
MVFR CIGS RETURN TO THE FAR NORTHEAST PART OF THE STATE. HAVE
AGAIN ATTEMPTED TO USE A COMBINATION OF THE LATEST TRENDS...THE
PREVIOUS FORECAST AND 00Z GUIDANCE.
&&

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

$$

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






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