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000
FXUS63 KGRB 160336
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1036 PM CDT TUE APR 15 2014

UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE

.UPDATE...
ISSUED AT 823 PM CDT TUE APR 15 2014

PER COORDINATION WITH WFO LA CROSSE...DECIDED TO ISSUE WINTER WEATHER
ADVISORY FOR MARATHON COUNTY DUE TO SNOW EXPECTED FOR THE MORNING
COMMUTE TO WORK. SNOW TOTALS ACROSS THIS COUNTY SHOULD BE IN THE 2
TO 4 INCH RANGE...HIGHEST TOTALS OVER THE NORTH BY LATE MORNING.
STARTED THE ADVISORY AT 7 AM INSTEAD OF 10 AM AS NARROW BAND OF
SNOW SHOULD WORK INTO MARATHON COUNTY AROUND 12Z...THEN GRADUALLY
SHIFT NORTH AND EAST DURING THE MORNING. DECIDED TO END THE
ADVISORY FOR MARATHON COUNTY AT 15Z THURSDAY. HOWEVER...A LULL IN
THE HEAVIER PRECIPITATION AND TEMPERATURES A FEW DEGREES ABOVE FREEZING
MAY MINIMIZE THE IMPACTS OF ANY SNOW WEDNESDAY AFTERNOON INTO WEDNESDAY
EVENING. IN MATTER OF FACT...THE PRECIPITATION MAY CHANGE OVER TO
RAIN IN MARATHON COUNTY. MIDNIGHT/DAY SHIFT CAN ANALYZE TO SEE IF THE
ADVISORY FOR MARATHON COUNTY MAY BE CANCELLED EARLY.

MADE SOME ADJUSTMENTS TO PRECIPITATION CHANCES LATE TONIGHT/WEDNESDAY
MORNING...AND TO QPF/SNOWFALL GRIDS. NEW GRIDS/ZONES/WINTER WEATHER
PRODUCT OUT SHORTLY.
&&

.SYNOPSIS...
ISSUED AT 326 PM CDT TUE APR 15 2014

MORE SNOW FOR THE NORTH THE NEXT COUPLE DAYS...BUT MODERATING
TEMPERATURES NEXT WEEK.

UPR TROF POSN OVER THE CENTRAL CONUS WL BE RE-ENERGIZED BY
PACIFIC SHRTWV HEADING IN FROM THE WEST. THE TREND LATER IN THE
FCST PERIOD WL BE TOWARD A LOWER AMPLITUDE MORE PROGRESSIVE
PATTERN. BACKING UPR FLOW AHEAD OF THE RE-AMPLIFYING UPR TROF
COMBINED WITH CYCLONE WORKG EWD FM THE PLAINS WL BRING A SIG SNOW
TO NRN WI THE NEXT COUPLE DAYS. AFTER THAT...THERE WL BE ANOTHER
CHC OF PCPN DURING THE WEEKEND. PCPN AMNTS WL PROBABLY END UP AOA
NORMAL ACRS THE NRN PART OF THE AREA...AND AOB NORMAL ACRS THE S.
TEMPERATURES WL START OUT WELL BELOW NORMAL...BUT SHOULD MODERATE
DURING THE MIDDLE TO LATTER PART OF THE PERIOD.
&&

.SHORT TERM...TONIGHT AND WEDNESDAY
ISSUED AT 326 PM CDT TUE APR 15 2014

MAIN ISSUE THIS PERIOD...WHAT TO DO WITH HEADLINES. HAVE TRENDED
TOWARDS A BLEND OF THE ECMWF AND GEM WHICH FEATURE SLIGHTLY SLOWER
AND COOLER PICTURE WITH INCOMING SYSTEM. NOT TOO OVERLY DIFFERENT
THAN WHAT PREVIOUS FORECAST HAD GOING.

UPPER TROF EXITING THE REGION TODAY...PLENTY OF CU AND LIGHT SNOW
SHOWERS...FLURRIES DEVELOPED OVER CWA WITH COLD AIR ALOFT.
ACTIVITY ENDING FROM WEST TO EAST WITH PERIOD OF CLEAR SKIES
EXPECTED TONIGHT BEFORE CLOUDS FROM NEXT SYSTEM MOVE IN. LOOK FOR
LATE AFTN HIGH TEMPS...WITH SIG DROP AS SUN GOES DOWN GIVEN LIGHT
WINDS AND DEW POINTS IN THE SINGLE DIGITS TO MID TEENS.

WAVE MOVING THROUGH PACIFIC NORTHWEST WILL DEEPEN AS DROPS INTO
PLAINS. ASSOCIATED SURFACE LOW TO MOVE INTO CENTRAL PLAINS...THAN
SHIFT NORTHEAST INTO SOUTHERN MN LATE WED AFTN. SIG DYNAMICS WITH
SYSTEM VIA RRQ OF AN UPPER LEVEL JET MOVING THROUGH CANADA...H8 WAA ON
THE NOSE OF A 50 KT LLJ AND INCREASING MID-LEVEL FRONTOGENETIC
FORCING TO BRING AN EXTENDED PERIOD OF STRONG LIFT FOCUSED OVER
NORTHERN WISCONSIN. DOES INTERSECT BEST SNOW GROWTH
REGION...THOUGH HAVE SOME CONCERNS ON MOISTURE GIVEN SOURCE
REGION. ALTHOUGH THE AIR MASS WILL BE COLD ENOUGH FOR SNOW OVER
THE ENTIRE FORECAST AREA EARLY IN THE DAY...THE RAIN/SNOW LINE IS
EXPECTED TO STEADILY SHIFT NORTH DURING THE DAY. HOW FAR NORTH IS
STILL IN QUESTION BETWEEN MODELS. BELIEVE ALL SNOW WHERE WATCH
CURRENTLY IN PLACE...THUS WILL UPGRADE TO WARNING. FURTHER SOUTH
WENT WITH ADVISORY AS TOTALS WILL BE MORE AFFECTED BY WARM LAYER.
LATER SHIFT MAY NEED TO UPGRADE IF COOLER TEMPS WIN OUT. LIGHT
SNOW EXPECTED TO START JUST BEFORE 12Z OVER THE WEST...WITH MUCH
OF HEAVIER SNOW STARTING BY MID MORNING. NO CHANGE TO TIMES ON
WARNING NEEDED.

WILL SEE INCREASING EAST WINDS OVER THE AREA AS LOW MOVES
EAST...WHICH MAY CAUSE ISSUES WITH BLOWING SNOW LATE IN THE DAY WED.

.LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY
ISSUED AT 326 PM CDT TUE APR 15 2014

FOCUS OF THE FCST IS ON SYSTEM TRACKING ACRS THE AREA AT THE
START OF THE LONG TERM PORTION OF THE FCST PERIOD. THE MAIN
CONCERN WITH THE SYSTEM IS MOISTURE. 12Z RAOBS FM THE PLAINS WWD
WERE QUITE DRY...AND SFC DWPTS ACRS THE ENTIRE RGN ARE DRY. THAT
SUGGESTS SIG LIFT WL NEED TO GO INTO ACHIEVING SATURATION. WITH
SUCH SYSTEMS...THE SIG PCPN IS CONFINED TO AREAS N OF THE TRACK
OF THE LOW-LEVEL CYCLONE. THE DRY AIR ALSO WL OPEN THE DOOR TO SIG
EVAPORATIVE COOLING...LIKELY LIMITING THE NWD ADVANCE OF ANY WARM
LAYER ALOFT. OF ALL THE 12Z GUIDANCE PRODUCTS...THE ECMWF FITS THE
BILL WITH THESE ASPECTS OF THE FCST THE BEST. IT HAD ONE OF THE
MOST CONSERVATIVE QPF TOTALS FOR THE EVENT...AND KEPT THE TEMPS
ALOFT COLDER THAN THE OTHER MODELS. FOR THESE REASONS...TRENDED
STRONGLY TOWARD THE 12Z ECMWF WITH THE FCST GRIDS.

AS MENTIONED YDA...THE THE TIMING OF PCPN CHCS DURING THE LATTER
PART OF THE FCST WL BE DIFFICULT GIVEN THE FLATTENING UPR FLOW.
THE CONSENSUS-BASED XTD INITIALIZATION GRIDS SEEMED REASONABLE...
SO NO SIG CHGS WERE MADE TO THEM.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1028 PM CDT TUE APR 15 2014

COMPLICATED FORECAST AS LOW PRESSURE IS EXPECTED TO MOVE ACROSS
THE REGION DURING THE NEXT 24 HOURS. COMPLICATING MATTERS IS AMOUNT
OF DRY AIR FEEDING INTO THE STORM...AND HOW THIS COLD DRY AIR WILL
AFFECT PRECIPITATION TYPES. DESPITE STRONG SOUTH WINDS...850MB
TEMPERATURES STRUGGLE TO GET TO 0C DESPITE IT BEING MID APRIL.
PRECIPITATION IS EXPECTED TO BREAK OUT LATE TONIGHT ACROSS WESTERN
WISCONSIN WHICH SHOULD WORK INTO PORTIONS OF CENTRAL WISCONSIN
AROUND 12Z. AN ACCUMULATING SNOW IS EXPECTED NORTH AND WEST OF THE
FOX VALLEY ON WEDNESDAY...WITH LITTLE OR NO SNOW OVER THE FOX VALLEY
AND LAKESHORE. THE LATEST WRF MESOSCALE (WRF12...WRF40) MODELS
NOW SHOW A BREAK IN THE HEAVIER PRECIPITATION OR A COMPLETE BREAK
EVEN ACROSS PORTIONS OF NORTHERN WISCONSIN. THIS COULD REALLY PLAY
HAVOC ON SNOW TOTALS ACROSS THE NORTH ALONG WITH TIMING OF PRECIPITATION
AND TRYING TO DETERMINE CEILINGS FOR THE 06Z TAFS. IF THERE IS A
BREAK OR LULL IN THE PRECIPITATION...IT SHOULD MOVE BACK INTO THE AREA
WEDNESDAY NIGHT. DID INCLUDE SOME LOW LEVEL WIND SHEAR WEDNESDAY
EVENING. THERE MAY BE SOME SIGNIFICANT CHANGES TO THE 12Z TAFS AFTER
MIDNIGHT PERSON TAKE A LOOK AT THE FULL SUITE OF 00Z MODEL
GUIDANCE.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 10 AM WEDNESDAY TO 10 AM CDT THURSDAY
FOR WIZ005-010>012.

WINTER WEATHER ADVISORY FROM 7 AM WEDNESDAY TO 10 AM CDT
THURSDAY FOR WIZ030.

WINTER WEATHER ADVISORY FROM 10 AM WEDNESDAY TO 10 AM CDT
THURSDAY FOR WIZ013-018-019.
&&

$$

UPDATE.........ECKBERG
SYNOPSIS.......SKOWRONSKI
SHORT TERM.....TE
LONG TERM......SKOWRONSKI
AVIATION.......ECKBERG