Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 140404
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1104 PM CDT SUN APR 13 2014

UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE

.UPDATE...
ISSUED AT 835 PM CDT SUN APR 13 2014

PER COORDINATION WITH MARQUETTE...ENOUGH CONCERN ACROSS OUR FAR
NORTHEAST COUNTIES TO WARRANT A WINTER WEATHER HEADLINE. COMMA
HEAD EXPECTED TO PIVOT ACROSS THE AREA OVERNIGHT. COLDER AND DRIER
AIR FILTERING IN FROM THE NORTH BASED ON OBSERVATIONS ACROSS THE
FAR NORTH OVER THE LAST HOUR OR TWO. ONCE HEAVIER PRECIPITATION
ARRIVES LATER THIS EVENING...RAIN SHOULD CHANGE OVER FAIRLY
QUICKLY IN THIS PORTION OF THE STATE. SOME QUESTIONS LINGER ABOUT
SOUTHERN MARINETTE AND SOUTHERN OCONTO COUNTIES DUE TO LOWER
ELEVATION AND SLOWER CHANGE OVER TO SNOW...BUT DECIDED TO INCLUDE
THEM IN THE ADVISORY AS WELL SINCE IT WOULD IMPACT THE MORNING
COMMUTE. TEMPERATURES WERE FAIRLY WARM TODAY... THUS THE GROUND
TEMPERATURES ABOVE FREEZING MAY HAMPER SOME ACCUMULATION AT THE
ONSET OF THE EVENT.

MEANWHILE...FLOOD WATCH CONTINUES FOR WAUSHARA...WINNEBAGO...CALUMET
AND MANITOWOC COUNTIES. SHOULD GET AROUND AN INCH IN THE WATCH AREA...
BUT PRECIPITATION IS STEADIER THAN THE LAST NIGHTS TRAINING THUNDERSTORMS.
COULD STILL BE SOME URBAN STREET FLOODING IN A FEW SPOTS...BUT MAIN
CONCERN WILL BE RISING WATERS IN DITCHES...CREEKS AND STREAMS. WILL
CONTINUE WITH THE FLOOD WATCH THROUGH THE OVERNIGHT HOURS.
&&

.SHORT TERM...TONIGHT AND MONDAY
ISSUED AT 325 PM CDT SUN APR 13 2014

FORECAST CONCERNS AGAIN ON PCPN TYPE AND AMOUNTS. SHORT WAVE OVER
CENTRAL PLAINS LIFTING NORTHEAST...TO PASS THROUGH STATE LATE
TONIGHT. SURFACE WARM FRONT OVER NORTHERN IL AT 19Z WITH
TIGHTENING 850 BAROCLINIC ZONE OVER STATE. CONVECTION ATTM TIED TO
SURFACE FRONT AND SOUTH WHERE LLVJ FOCUSED.

LARGE AREA OF PCPN SLOWLY MAKING ITS WAY NORTH THROUGH SOUTHERN
WI...INCREASING RETURNS ALSO SEEN OVER NORTHWEST PORTION OF
STATE WHERE MODELS INDICATE INCREASING FGEN FORCING. SOME QUESTION
ON WHEN PCPN WILL CHANGE OVER. SURFACE TEMPS/DEW POINTS WARMER
THAN WHAT MODELS WOULD INDICATE. HAVE STAYED WITH A 0Z TO 3Z
PERIOD FOR NORTHWEST...AND 6 TO 9Z PERIOD SOUTHEAST. CONCERNS ON
SNOW AMOUNTS...WITH NAM SUGGESTING ADVISORY LEVEL GIVEN STRONG
DYNAMICS...THOUGH SNOW GROWTH REGION IS LIMITED. HAVE GONE WITH A
1 TO 3 INCH AMOUNT OVER THE CWA.  LATER SHIFT WILL NEED TO MONITOR.

MAIN TROF PASSES THROUGH MONDAY...ENDING PCPN FOR THE AFTN...WITH
BREEZY COOL CONDITIONS EXPECTED REMAINDER OF DAY.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY
ISSUED AT 325 PM CDT SUN APR 13 2014

TRANSITIONAL AND PROGRESSIVE PATTERN NEXT FEW DAYS AS UPPER FLOW
GOES FROM NW TO ZONAL THEN MORE SW AS ENERGY APPROACHES FROM THE
PLAINS. WHAT THIS MEANS IS SEVERAL CHANCES FOR PRECIPITATION.
WITH COLDER THAN NORMAL TEMPS THRU MUCH OF PERIOD...SOME OF THAT
MAY FALL AS SNOW...ESPECIALLY ACROSS THE NORTH.

AT THE START OF THE PERIOD TEMPERATURES ARE EXPECTED TO BE MUCH
BELOW NORMAL FOR THIS TIME OF YEAR IN NORTHWEST FLOW ALOFT. THERE
WILL BE A MODERATION AS UPPER FLOW BACKS AND BECOMES MORE ZONAL
AND THEN SOUTHWEST.

SUBTLE SHORTWV RIDGING AND SURFACE HIGH BRINGS ONE DECENT WEATHER
DAY THIS WEEK ON TUESDAY...THOUGH TEMPS WILL BE AROUND 15 DEG
COLDER THAN NORM.

FIRST ROUND OF PRECIP DURING THIS PERIOD APPROACHES WED AS UPPER
SHORTWV ENERGY AND SURFACE REFLECTION/FRONT MOVES ESE TOWARD
STATE. FORECAST FOR THIS SYSTEM A BLEND OF 13/12Z MODELS WHICH IS
VERY CLOSE TO PREVIOUS FORECAST. HAVE INCREASED POPS GIVEN
SLIGHTLY BETTER MODEL AGREEMENT...WITH BEST CHANCE ACROSS THE
NORTH. COLD ENOUGH FOR SNOW/MIX...ESP AT NIGHT. AN INCH OR TWO NOT
OUT OF THE QUESTION IN THE NORTH.

ASSOCIATED SFC FRONTAL BOUNDARY HANGS UP ACROSS WESTERN GREAT
LAKES AND IS FOCUS FOR ADDITIONAL PRECIP AS SURFACE LOW DEVELOPS
AHEAD OF DEEPER UPPER WAVE MOVING OUT OF PLAINS. CONSIDERABLE
DIFFERENCES BETWEEN 13/12Z GFS AND ECMWF BY THE TIME THE SYSTEM
MOVES ACROSS STATE FRIDAY. WILL CONTINUE WITH HIGHEST POPS ON
FRIDAY WITH THIS SYSTEM AND MIX ACROSS THE NORTH AND MAINLY RAIN
IN THE SOUTH PART OF FORECAST AREA.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1101 PM CDT SUN APR 13 2014

RAIN WAS NOW BEGINNING TO CHANGE TO SNOW ACROSS THE NORTH THIS
EVENING. THE PRECIPITATION WILL CHANGE FROM RAIN TO SNOW OVER THE
REMAINDER OF THE AREA OVERNIGHT...REACHING KGRB/KATW AROUND 09Z
AND KMTW AROUND 11Z. THE SNOW WILL GRADUALLY END BY MID MORNING
ACROSS THE ENTIRE REGION. IFR/MVFR CIGS WILL IMPROVE TO VFR
CONDITIONS MONDAY AFTERNOON.

&&

.MARINE...
ISSUED AT 325 PM CDT SUN APR 13 2014

SMALL CRAFT ADVISORY IN EFFECT BUT POTENTIAL FOR SHORT
PERIOD OF GALE FORCE GUSTS POSSIBLE AFTER MIDNIGHT WITH STRONG
NORTH NORTHEAST WINDS AND PRESSURE COUPLET PASSING THROUGH.
LOCALIZED GALE GUSTS ALSO POSSIBLE THROUGH DEATHS DOOR AS WINDS
SHIFT TO NORTHWEST.
&&

.HYDROLOGY...
ISSUED AT 325 PM CDT SUN APR 13 2014

WILL LET FLOOD WATCH CONTINUE...FLASH FLOOD GUIDANCE IS VERY LOW
1 INCH/6 HOURS OVER MOST OF WATCH AREA. PCPN SLOWER IN MAKING
PROGRESS NORTH...SOMEWHAT DUE TO DRIER AIR ALOFT FOLLOWING
YESTERDAYS WAVE. MODELS CONTINUE TO SUGGEST QPF AMOUNTS OF 1 TO
1.5 INCHES WORKING NORTH INTO FLOOD WATCH AREA THIS EVENING AND
TONIGHT. CONVECTION TIED TO FRONT WHICH IS FURTHER SOUTH THAN
YESTERDAY...SO EXPECT HEAVY QPF TO BE MORE WIDESPREAD AND NOT AS
LOCALIZED.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH UNTIL 7 AM CDT MONDAY FOR WIZ045-048>050.

WINTER WEATHER ADVISORY UNTIL 10 AM CDT MONDAY FOR WIZ013-020-
021-073-074.

WINTER WEATHER ADVISORY UNTIL 7 AM CDT MONDAY FOR WIZ011-012-019.
&&

$$

UPDATE.........ECKBERG
SHORT TERM.....TE
LONG TERM......JKL
AVIATION.......ECKBERG
MARINE.........TE
HYDROLOGY......TE






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