Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 240408
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1008 PM CST TUE DEC 23 2014

UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE

.UPDATE...
ISSUED AT 840 PM CST TUE DEC 23 2014

JUST SOME LINGERING LGT PCPN ACRS THE FCST AREA EARLY THIS
EVENING. KGRB 88D STILL HAD AN AREA OF RETURNS LIFG NEWD TO THE W
OF THE FOX VALLEY...PROBABLY JUST SOME SPRINKLES. OTHERWISE...SFC
OBS INDICATED MAINLY PATCHY DZ/FZDZ...WITH SOME FLURRIES IN THE N.

MODEL FCST SOUNDINGS SHOW MID-LVL DRY AIR TO REMAIN IN PLACE
THROUGH THE NGT AND INTO TOMORROW MORNING...SUGGESTING JUST
DZ/FZDZ AS PCPN TYPE. BUT CARRIED FLURRIES IN THE FCST FOR N-C
ANYWAY AS STLT HAS A LITTLE COLDER CLD TOPS THERE.

A SMALL PORTION OF THE FCST AREA FM ABOUT MFI/ISW ENEWD TOWARD
WAUSAUKEE HAS PRETTY GOOD CONDITIONS FOR FOG THIS EVENING. THAT
AREA GOT ENOUGH SNOW IN THE PAST 24 HRS TO HAVE SNOW-COVERED
GROUND. WINDS IN THAT AREA ARE LGT AS THAT IS ALONG THE TRACK OF
ELONGATED AREA OF SFC LOW PRESSURE DRIFTING SLOWLY NEWD ACRS THE
AREA. IT/S ALSO AN AREA WHERE SFC DWPTS HAVE CREPT AOA FZG. PLAN
TO CONT TO HANDLE WITH AN SPS...AND WL LIKELY RE-ISSUE THE CURRENT
SPS TO COVER THE SITN INTO THE EARLY MORNING HOURS.

FINALLY...STILL KEENLY WATCHING HOW THE LATEST GUIDANCE IS
HANDLING THE SECONDARY CYCLONE THAT WL LIFT NWD ALONG THE
BAROCLINIC ZONE IN THE NEXT 24-36 HRS. THE NAM HAS SEEMINGLY
SETTLED IN ON A TRACK THAT KEEPS THE PCPN JUST TO OUR E. HAVE ALSO
BEEN WATCHING THE ENDING OF THE HOURLY RAP RUNS...AND THE PAST FEW
OF THOSE GRAZED THE LAKESHORE TOMORROW AFTN/EVENING...AND EVEN
BROUGHT PCPN BACK INTO THE ERN FOX VALLEY AT TIMES.

THE REAL PROBLEM WE/VE HAD DEALING WITH THIS SYSTEM ACTUALLY
ISN/T SO MUCH THE TRACK OF THE CYCLONE. THAT HAS CERTAINLY BEEN
CHAOTIC ON THE NUMERICAL GUIDANCE...BUT WITH A TYPICAL
CYCLONE...THE ENVELOPE OF SOLUTIONS OUT THERE NOW WOULD ALLOW FOR
DECENT CONFIDENCE IN POPS AND A BALLPARK ESTIMATE OF
PCPN/SNOW. THE REAL PROBLEM HAS BEEN THE VERY NARROW/COMPRESSED
DEFORMATION ZONE ON THE WRN FLANK OF THE CYCLONE. THAT SEEMS TO BE
THE RESULT OF HAVING A FAIRLY SMALL CYCLONE...AND THE INTERACTION
OF THE CYCLONE WITH UPSTREAM ENERGY DRIVING EWD ACRS THE NRN
PLAINS. THAT ENERGY WL IMPINGE ON THE DEFORMATION ZONE ON THE WRN
FLANK OF THE CYCLONE...SO THE WIDTH OF THE PCPN W OF THE STORM
CENTER IS UNUSUALLY NARROW. IN ANY CASE...CURRENT FCST SEEMS TO
HAVE THINGS HANDLED FAIRLY WELL...WITH CHC POPS ERN FOX VALLEY AND
SOME LIKELY POPS RIGHT AT THE LAKESHORE. NO SIG CHGS TO THAT THIS
EVENING.

UPDATED GRIDS SENT ABOUT 1/2 HR AGO.

UPDATE
ISSUED AT 526 PM CST TUE DEC 23 2014

UST LGT PCPN LINGERING ACRS N-C WI...SO WL ALLOW THE ADVISORY TO
EXPIRE AT 6 PM AS SCHEDULED.
&&

.SHORT TERM...TONIGHT AND WEDNESDAY
ISSUED AT 237 PM CST TUE DEC 23 2014

MAIN FCST CONCERNS DEAL WITH THE DEMISE OF ONE SYSTEM AND ITS
ASSOCIATED SNOW TNGT AND THEN TRYING TO FIGURE OUT THE PATH OF THE
NEXT SYSTEM TOWARD THE GREAT LAKES ON WED.

THE 20Z MSAS SFC ANALYSIS SHOWED A WEAKENING AREA OF LOW PRES OVER
CNTRL WI MOVING ALONG A QUASI-STNRY BOUNDARY. THIS BOUNDARY WAS
SEPARATING WARM...MOIST AIR ON SOUTH WINDS OVER ERN WI FROM COOL...
MOIST AIR OVER WRN WI ON NORTH WINDS. RADAR MOSAIC CONTINUED TO
SHOW PCPN PIVOTING AROUND THE SFC LOW WITH MAINLY LIGHT RAIN OR
DRIZZLE OVER ERN WI AND EITHER LIGHT SNOW OR A RAIN/SNOW MIX OVER
CNTRL WI. PLAN ON CANCELING THE WINTER WX ADVY FOR ALL BUT VILAS/
ONEIDA COUNTIES WHERE SNOW INTENSITY IS LIGHT OR MIXED PCPN HAS
TAKEN OVER.

SYSTEM OVER THE GREAT LAKES REGION WL CONT TO DRIFT NE AND
STEADILY WEAKEN TNGT AS MAIN ENERGY SHIFTS TOWARD THE TN/OHIO
RIVER VALLEYS WHERE A STRENGTHENING SFC LOW TO RESIDE. FCST
SOUNDINGS INDICATE A LOSS OF MID-LEVEL SATURATION WHICH WOULD
DIMINISH ANY PCPN MAINLY TO EITHER FREEZING DRIZZLE OR DRIZZLE
DEPENDING ON SFC TEMPS. LOW-LEVELS OF THE ATMOSPHERE REMAIN
MOIST...SO PATCHY FOG TO BE A GOOD BET. ANOTHER MILD NGT ON TAP
ACROSS THE FCST AREA WITH MIN TEMPS ONLY RANGING FROM AROUND 30
DEGS N-CNTRL TO THE LWR TO MID 30S NEAR LAKE MI.

EVEN AT THIS LATE DATE...THE MODELS CONT TO STRUGGLE WITH THE
MOVEMENT OF THIS SFC LOW AS IT LIFTS N-NE INTO THE GREAT LAKES ON
WED. AN ERN TRACK (TOWARD DETROIT) PER ECMWF/GEM WOULD ESSENTIALLY
KEEP ANY SNOW POTENTIAL TO OUR EAST AND LEAVE NE WI CLOUDY WITH
ONLY A MINIMAL CHC OF ANY PCPN. A WRN TRACK (TOWARD CNTRL SECTIONS
OF LWR MI) PER NAM/GFS WOULD BRING THE THREAT OF MEASURABLE SNOW
TO ERN WI. THE FINAL SOLUTION MAY NOT BE KNOWN UNTIL THE SFC LOW
ACTUALLY DEVELOPS OVER THE OZARKS AND MAKES IT MOVE TO THE N-NE.
FOR NOW...HAVE SPLIT THE MODEL DIFFERENCE WHICH BRINGS A GLANCING
BLOW TO FAR ERN WI WED AFTERNOON...BUT HAVE KEPT ANY SNOW
ACCUMULATIONS TO LESS THAN AN INCH. ANYONE WITH TRAVEL PLANS
TOWARD SE WI OR NRN IL WL WANT TO CHECK THE LATEST FCSTS AS TRAVEL
MAY BECOME QUITE MESSY DOWN THAT WAY. MAX TEMPS FOR WED WL RANGE
FROM THE LWR 30S OVER N-CNTRL WI TO THE MID 30S ACROSS ERN WI.

.LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY
ISSUED AT 237 PM CST TUE DEC 23 2014

PROGS CONTINUE TO HINT OF SOME PRECIPITATION BRUSHING OVER FAR
EASTERN WISCONSIN WEDNESDAY EVENING UNTIL THE UPPER LOW SYSTEM
SHIFTS EASTWARD. AFTER A PERIOD OF BLUSTERY NORTHWEST WINDS
WEDNESDAY EVENING...DIMINISHING WINDS EXPECTED OVERNIGHT AS A WEAK
RIDGE OF HIGH PRESSURE WORKS INTO THE AREA.

XMAS DAY EXPECTED TO BE QUIET...THEN LIGHT SNOW WILL BE ON THE
INCREASE LATE IN THE WEEK AS A TROUGH OF LOW PRESSURE AND MID
LEVEL SHORT WAVE SLIDE OVER THE MID SECTION OF THE COUNTRY. PROGS
SUGGEST THE LIGHT SNOW APPEARS TO BE FOCUSED IN THE TRAILING
BAROCLINIC PORTION FROM NORTHWEST WISCONSIN LATE THURSDAY NIGHT
INTO FRIDAY BEFORE TROUGH PASSAGE FRIDAY AFTERNOON INTO EVENING.
FORECAST TEMPS SUGGEST A VERY LIGHT MIX POSSIBLE OVER EAST CENTRAL
WISCONSIN FRIDAY AFTERNOON.

THE QUIET ZONAL FLOW WITH SLIGHTLY COOLER THAN NORMAL TEMPERATURES
WILL CONTINUE INTO THE WEEKEND. MEDIUM RANGE MODELS ARE NOT
INDICATING MUCH SNOW WITH A SHORT WAVE DROPPING INTO THE GREAT
LAKES REGION WHICH DEEPENS THE TROUGH OVER THE REGION EARLY NEXT
WEEK. THERE IS SOME AGREEMENT WITH AN ARCTIC SURGE OF AIR BY THE
MIDDLE OF NEXT WEEK AND USUALLY A CLIPPER TYPE SYSTEM PRECEDES
THIS BUT SO FAR NO INDICATION. AVAILABLE PROGS SUGGESTS SOME
SLIGHT MODERATION IN TEMPS LATE NEXT WEEK.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1006 PM CST TUE DEC 23 2014

PLENTY OF LINGERING LOW-LEVEL MOISTURE WL REMAIN ACRS THE AREA
OVERNIGHT AND INTO WEDNESDAY MORNING. CORRIDOR ACRS CENTRAL INTO
NE WI NR SFC LOW WL HAVE LGT WINDS AND MOISTURE OVER THE RECENT
SNOW...AND MAY HAVE SOME PATCHY DENSE FOG OVERNIGHT. THAT
CORRIDOR SHOULD FALL MAINLY BTWN THE C AND E-C WI TAF SITES...BUT
COULD CREEP BACK INTO CWA/AUW SO WL CARRY SOME LOW VSBYS AT THOSE
SITES. OTHERWISE...MORE SIG IMPROVEMENT IN CONDITIONS WL HAVE TO
WAIT UNTIL TOMORROW WHEN NLY FLOW STRENGTHENS ON THE WRN FLANK OF
CYCLONE LFTG ACRS LOWER MICHIGAN.
&&

.HYDROLOGY...
ISSUED AT 237 PM CST TUE DEC 23 2014

MILD CONDITIONS OVER NORTHEAST WISCONSIN THROUGH WEDNESDAY ALONG
WITH RAINFALL AMOUNTS OF 0.25 TO 0.75 INCHES THROUGH TUESDAY
AFTERNOON MAY AFFECT ICE CONDITIONS ON AREA RIVERS AND LAKES.
&&

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

$$

UPDATE.........SKOWRONSKI
SHORT TERM.....KALLAS
LONG TERM......TDH
AVIATION.......SKOWRONSKI
HYDROLOGY......TDH







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