Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 210452
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1052 PM CST SAT DEC 20 2014

UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND SUNDAY
ISSUED AT 234 PM CST SAT DEC 20 2014

FOR HI PRES NEARBY...A LOT OF NUISANCE WEATHER TO DEAL WITH OVER
THE NEXT 24 HOURS. MAIN CONCERN FOR TNGT TO BE WHETHER PATCHY
FREEZING DRIZZLE WL BE ABLE TO DEVELOP AFTER MIDNGT. MAIN ISSUE
FOR SUNDAY TO BE WHEN TO TRANSITION THIS FREEZING DRIZZLE TO
EITHER SNOW OR A RAIN/SNOW MIX AS DEEPER MOISTURE ARRIVES AND
TEMPS BEGIN TO WARM.

PLENTY OF LOW-LEVEL MOISTURE IS FCST TO LINGER BEHIND A DEPARTED
SHORTWAVE TROF TNGT. A MILD FLOW OF PACIFIC AIR TO TRAVERSE THE
CONUS LATER TNGT WITH THE LEADING EDGE OF THIS MILDER AIR ALOFT
PUSHING INTO WI. THIS INCREASE IN WAA...COMBINED WITH NO ICE
WITHIN THE COLUMN...COULD LEAD TO A ROUND OF PATCHY DRIZZLE ACROSS
MOST OF NE WI AFTER MIDNGT. EVEN IF THE FREEZING DRIZZLE DOES NOT
MATERIALIZE...PATCHY FOG AND SUB-FREEZING TEMPS MAY PRODUCE
SLIPPERY ROAD CONDITIONS. MIN TEMPS TO GENERALLY RESIDE IN THE
LOWER TO MIDDLE 20S.

SOUTHERLY WINDS ALOFT BEGIN TO INCREASE ON SUNDAY AHEAD OF THE
NEXT PACIFIC SYSTEM DIVING SE INTO THE NRN/CNTRL PLAINS. THE WAA
WL CONT ACROSS THE WRN GREAT LAKES AND AS DEEPER MOISTURE BEGINS
TO OVERSPREAD NE WI...ANY FREEZING DRIZZLE WOULD CHANGE MAINLY TO
LIGHT SNOW BY SUNDAY AFTERNOON. THERE COULD BE SOME RAIN MIXING IN
WITH THE SNOW OVER SRN PARTS OF THE FCST AREA LATE IN THE DAY AS
SFC TEMPS WARM INTO THE MID TO UPR 30S. OTHERWISE...SNOW
ACCUMULATIONS ARE FCST TO BE ON THE LIGHT SIDE WITH THE HIGHEST
AMOUNTS RUNNING FROM CNTRL TO FAR NE WI WHERE ONE-HALF TO ONE INCH
OF NEW SNOW IS EXPECTED.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY
ISSUED AT 234 PM CST SAT DEC 20 2014

ACTIVE WEATHER PATTERN ON THE TABLE FOR MUCH OF NEXT WEEK. MEDIUM
RANGE MODEL SOLUTIONS HAVE VARIED THE LAST FEW RUNS BUT MAY HAVE
FOCUSED A BIT BETTER ON A SOLUTION TO WORK WITH FOR AT LEAST
THROUGH EARLY WEDNESDAY.

PROGS CONTINUE TO DEVELOP AND SLOWLY DEEPEN AN UPPER LOW OVER THE
NORTHERN PLAINS THROUGH TUESDAY BEFORE TRACKING NORTHEAST INTO THE
WESTERN LAKE SUPERIOR REGION TUESDAY NIGHT. OF NOTED CHANGES FROM
PREVIOUS RUNS IS THE MORE WESTERN TRACK AND NOT AS DEEP OF A 500
MB LOW THROUGH TUESDAY.  UNDER THIS SCENARIO...MODEL OUTPUT
APPEARS TO BE A LONGER DURATION WAA AND LIGHT PCPN EVENT SUNDAY
NIGHT INTO MONDAY. MOST LIKELY TIME FOR HIGHER WATER EQUIVALENT
AMOUNTS APPEAR TO BE LATER MONDAY INTO TUESDAY MORNING WITH THE
STRONGEST PERIOD OF WAA AHEAD OF THE DRY SLOT...BUT BY THEN
FORECAST SOUNDINGS INDICATE A MIX WITH MOSTLY RAIN EAST CENTRAL
WISCONSIN AND MAINLY SNOW NC WI. AN ADVISORY HEADLINE WILL BE
POSSIBLE WITH THIS WAA SURGE LATE MONDAY INTO TUESDAY MORNING. ALL
MODELS APPEAR SIMILAR WITH THE EXCEPTION OF THE SLOWER TIMING OF
THE ECMWF. THERE IS ALSO A POTENTIAL OF AN WEAKER ADVISORY EVENT
FOR LATE SUNDAY INTO MONDAY MORNING IF THE MIX CONTAINS A BIT MORE
ZR AND TEMPS STRUGGLE TO CLIMB ABOVE 32 FOR SOME LOCATIONS. IT
COULD COINCIDE WITH THE MONDAY MORNING COMMUTE. SURFACE DEWPOINTS
RISE INTO THE UPPER 20S TO LOWER 30S ON MONDAY TO FOCUS THE BEST
TIME OF ZR EARLY PART OF MONDAY.

WITH THE UPPER LOW SHIFTING NORTH OF THE AREA LATER TUESDAY INTO
TUESDAY NIGHT AND PERHAPS EVEN INTO WEDNESDAY...MODELS FOCUS ON A
DRY SLOT TO WORK OVER THE AREA FOR PERIOD OF REDUCED PCPN.
DEPENDING ON TEMPS...FREEZING DRIZZLE COULD STILL BE AN ISSUE
UNDER THIS DRY SLOT REGION IF THE MID LEVELS DRY OUT.

ATTENTION TURNS TO WEDNESDAY INTO THURSDAY AS SOUTHERN STREAM
ENERGY LIFTS NORTHWARD TOWARD LOWER MICHIGAN TO PHASE WITH THIS
NORTHERN STREAM LOW TO DEEPEN THE SYSTEM. WITH THE EXCEPTION OF
THE HIGHER OUTPUT PCPN FOR EASTERN WISCONSIN AS PER GFS...BLEND
OF THE GUIDANCE KEEPS THE BRUNT OF THE PRECIPITATION EAST OF THE
AREA. WILL NEED TO KEEP AN EYE OUT FOR THIS SYSTEM AS ANY SHIFT
WEST IN THE TRENDS WITH THE MODELS...AND THIS AREA WILL BE DEALING
WITH A BIT MORE SNOW.

STILL A BLUSTERY DAY EXPECTED FOR LATER WEDNESDAY INTO
THURSDAY...BUT FOR THIS MORNINGS RUN...THE DEEPENING LOW POSITION
IS A LITTLE MORE EAST AND WILL LIKELY IMPACT NORTHEAST WISCONSIN
INCLUDING THE LAKESHORE REGION.

ALTHOUGH INCONSISTENT...PROGS HAVE BEEN HINTING AT TIMES WITH
ANOTHER STORM SYSTEM TRAILING ALONG THE BAROCLINIC ZONE LAID OUT
BY THE CAA FROM THE DEPARTING STORM SYSTEM...BUT THE LATEST GFS
AND ECMWF RUNS HAVE BACKED OFF WITH THE DYNAMICS WITH THIS SYSTEM.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1051 PM CST SAT DEC 20 2014

WAA OVERNIGHT WILL BRING BOTH A LOWERING OF CIGS INTO THE IFR AND
THE DEVELOPMENT OF PATCHY FREEZING DRIZZLE OVER CENTRAL WISCONSIN WELL
AFTER MIDNIGHT. THIS WAA PATTERN WILL CONTINUE INTO SUNDAY MORNING
WITH ADDITIONAL FREEZING DRIZZLE POSSIBLE. AS THE MID-LEVELS OF
THE ATMOSPHERE SATURATE AND ICE CRYSTALS ARE INTRODUCED INTO THE
COLUMN...THE FREEZING DRIZZLE SHOULD TRANSITION MORE TO LIGHT SNOW
BY SUNDAY AFTERNOON...ESPECIALLY OVER CENTRAL AND NORTHERN
WISCONSIN. CIGS/VSBYS SHOULD GENERALLY REMAIN IN THE IFR TO MVFR
RANGE ON SUNDAY INTO SUNDAY NIGHT.
&&

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

$$

SHORT TERM.....AK
LONG TERM......TDH
AVIATION.......ESB





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