Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 292009
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
309 PM CDT WED OCT 29 2014

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND THURSDAY
ISSUED AT 308 PM CDT WED OCT 29 2014

THIS PART OF THE FORECAST IS LESS PROBLEMATIC THAN THE LONG TERM
BUT STILL HAS ENOUGH ISSUES.

LOW CLOUDS ACROSS THE AREA DUE TO LOW LEVEL MOISTURE...AS SEEN ON
THE 12Z GRB SOUNDING...AND CYCLONIC FLOW BOTH ALOFT AND AT THE
SURFACE WERE ERODING THIS AFTERNOON. THERE HAD BEEN SOME SPRINKLES
AND A FEW FLURRIES ACROSS THE NORTH EARLIER IN THE DAY BUT THEY
SEEM TO HAVE ENDED AS WINDS ALOFT BACKED A BIT. CLOUD TRENDS WILL
HAVE A MAJOR IMPACT ON LOWS TONIGHT. A SURFACE RIDGE AND A WEAK
UPPER LEVEL RIDGE MOVING ACROSS WISCONSIN OVERNIGHT SHOULD CLEAR
OUT MOST OF THE LOW CLOUDS...BUT A MID LEVEL SHORT WAVE
APPROACHING FROM THE HIGH PLAINS WILL BRING MIDDLE AND HIGH CLOUDS
TO THE REGION. IF THE MID/HIGH CLOUDS MOVE IN FAST ENOUGH
TEMPERATURES SHOULD BE RATHER MILD TONIGHT...WITH LOWS MAINLY IN
THE 30S. HAVE OPTED TO GO WITH THE CLOUDS AND WARMER TEMPERATURES
FOR TONIGHT...BUT IF THERE IS A PERIOD OF CLEAR/MOSTLY CLEAR
CONDITIONS TEMPERATURES WILL LIKELY DROP LIKE A ROCK WITH LITTLE
WIND TO MIX THE LOWER LEVELS.

MODELS HAD DIFFERENCES IN LOCATION OF PRECIPITATION BUT SEEM TO BE
IN DECENT AGREEMENT IN KEEPING TONIGHT DRY. HAVE SOME SLIGHT
CHANCES GOING FOR THE NORTH EARLY THURSDAY...WITH A MENTION OF
RAIN SHOWERS OR SNOW SHOWERS FOR A COUPLE OF HOUR AS THE MID
LEVEL SHORT WAVE MOVES INTO THE REGION. CHANCES FOR PRECIPITATION
CONTINUE THROUGHOUT THE DAY AS A COLD FRONT AND MID LEVEL TROUGH
MOVE INTO WISCONSIN FROM THE NORTH. TEMPERATURES SHOULD BE WARM
ENOUGH TO KEEP PRECIPITATION IN THE FORM OF RAIN UNTIL THE EVENING
HOURS.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY
ISSUED AT 308 PM CDT WED OCT 29 2014

MEAN FLOW ACROSS THE CONUS TO BECOME HIGHLY AMPLIFIED THIS WEEKEND
WITH DEEP UPR TROFS OVER BOTH COASTS AND AN UPR RDG OVER CNTRL
NOAM. THIS PATTERN IS PROGRESSIVE HOWEVER WITH THE WRN CONUS TROF
SHIFTING EAST INTO THE CNTRL CONUS EARLY NEXT WEEK AND THRU THE
GREAT LAKES AROUND TUE. MEAN FLOW TO THEN TRANSITION TO A WRN
CONUS UPR RDG/ERN CONUS UPR TROF BY THE MIDDLE OF NEXT WEEK. MAIN
FCST FOCUS TO BE INITIALLY ON THE STRONG SHORTWAVE TROF DIVING SE
THRU THE GREAT LAKES THU NGT/FRI BRINGING A FIRST TASTE OF WINTER
WITH SNOW/COLD/WIND. PCPN CHCS THEN RETURN MON/MON NGT WITH THE
WRN CONUS UPR TROF/SFC CDFNT. TEMPS TO BE WELL BELOW NORMAL AT THE
ONSET...BUT STEADILY WARM TO ABOVE NORMAL READINGS FROM MON ONWARD.

WHILE THE CDFNT TO ALREADY BE EXITING THE AREA EARLY THU EVENING...
IT IS THE PASSAGE OF A VIGOROUS SHORTWAVE TROF LATER THU NGT THAT
WL BRING A MAJOR CHANGE TO OUR WEATHER PATTERN...USHERING IN AN
EARLY TASTE OF WINTER TO ALL OF THE GREAT LAKES. THIS UPR TROF HAS
A LOT OF DYNAMICS ASSOCIATED WITH IT RANGING FROM VERY STEEP LOW-
LEVEL LAPSE RATES TO STRONG Q-G FORCING. THE INITIAL FCST PROBLEMS
TO BE THE EXTENT OF THE PCPN...PCPN TYPE (CHANGEOVER) AND SNOW
ACCUMULATION NUMBERS (MAINLY FOR THE NORTH). AT THE ONSET...MOISTURE
IS LACKING WITH THIS SYSTEM. HOWEVER...AS WINDS TURN TO THE NORTH...
MOISTURE FROM LAKE SUPERIOR WL BECOME AVAILABLE AND AT LEAST CHC
POPS WL BECOME NECESSARY OVER ALL OF NE WI. AS STRONG CAA TAKES OVER
THRU THE NGT...RAIN WL BECOME MIXED WITH AND EVENTUALLY CHANGE TO
ALL SNOW EXCEPT NEAR LAKE MI. THE CRASH IN 8H TEMPS TO AROUND -10C
BY 12Z FRI WL ALSO LEAD TO LAKE EFFECT SNOWS FOR N-CNTRL WI AS
DELTA-T VALUES RISE INTO THE UPR TEENS. ONLY NEGATIVE FOR HIGHER
ACCUMULATIONS WOULD BE THE STRONG WINDS WHICH COULD TEAR SNOW
BANDS APART. NEVERTHELESS...PARTS OF VILAS CNTY COULD RECEIVE UP
TO 3" OF FRESH SNOW BY DAYBREAK. LASTLY...WL NEED TO MONITOR WIND
SPEEDS LATER THU NGT AND A POTENTIAL WIND ADVY FOR AT LEAST DOOR
CNTY AS GUSTS COULD SURPASS 45 MPH.

THE LAKE EFFECT POTENTIAL FOR N-CNTRL WI WL CONT THRU FRI MORNING
BEFORE TAPERING OFF IN THE AFTERNOON AS A LARGE ARA OF HI PRES
BUILDS INTO THE REGION BRINGING DRIER AIR AND LOWERING INVERSION
HEIGHTS. ADDITIONAL ACCUMULATIONS OF UP TO ONE-HALF INCH ARE
POSSIBLE OVER VILAS CNTY. THE REST OF NE WI WL SEE ONLY AN
ISOLATED MORNING SNOW SHWR OR FLURRIES WITH SKIES BECOMING AT
LEAST PARTLY SUNNY IN THE AFTERNOON. THE BIGGER STORY MAY BE THE
WINDY CONDITIONS (ESPECIALLY IN THE MORNING) WITH GUSTS AGAIN
SURPASSING 40 MPH IN THE EAST. POTENTIAL WIND ADVY CRITERIA MAY
STILL BE MET OVER DOOR CNTY. FRI WL BE A RAW DAY WITH MAX TEMPS
ONLY IN THE LWR TO MID 30S NORTH...AROUND 40 DEGS SOUTH.

THE HI PRES IS EXPECTED TO MOVE INTO THE WRN GREAT LAKES FRI NGT
AND BRING THE COLDEST AIR OF THE SEASON TO NE WI. UNDER MAINLY
CLEAR SKIES AND DIMINISHING WINDS...MIN TEMPS WL RANGE FROM THE
MID TO UPR TEENS N-CNTRL WI...TO THE UPR 20S OVER DOOR CNTY.
SUNNY AND DRY CONDITIONS ARE FCST FOR SAT AS THE HI PRES PASSES
OVERHEAD. EVEN WITH THE SUNSHINE...THE COOL AIR MASS ALOFT COUPLED
WITH THE COLD START TO THE DAY WL ONLY YIELD MAX TEMPS IN THE UPR
30S TO LWR 40S.

AS THE SFC HI SLIDES TO OUR EAST SAT NGT...A RETURN FLOW DEVELOPS
ACROSS WI WITH WAA GRADUALLY TAKING OVER. THE APPROACH OF THE UPR
RDG LATE SAT NGT INTO SUNDAY WL KEEP OUR WEATHER QUIET...ALBEIT
WITH SOME INCREASE IN CLOUDS AS SOUTHERLY WINDS BEGIN TO TAP INTO
GULF MOISTURE. MAX TEMPS ON SUNDAY SHOULD BE AROUND 5 DEGS WARMER
THAN SAT...GENERALLY IN THE LWR TO MID 40S. THE EWD MOVEMENT OF A
POSITIVE-TILTED LONGWAVE TROF...PRECEDED BY A CDFNT...WL BRING
THAT NEXT CHC OF PCPN TO THE REGION BY MON AFTERNOON. A STRONGER
SURGE OF WAA ON MON COULD SEND MAX TEMPS OVER SRN SECTIONS OF THE
FCST AREA TO THE 50 DEG MARK.

THE BEST CHC OF SEEING PCPN APPEARS TO BE MON NGT AS THE CDFNT
MOVES ACROSS WI...FOLLOWED BY THE UPR TROF AFTER MIDNGT. HAVE
RAISED POPS TOWARD THE HI CHC CATEGORY AND WITH THE INFLUX OF
MOISTURE IN PLACE AHEAD OF THE CDFNT...POPS MAY NEED TO BE RAISED
FURTHER IF MDL TRENDS PERSIST. THE RAIN MAY BEGIN TO MIX WITH SNOW
OVER THE FAR NORTH LATE MON NGT INTO TUE MORNING BEFORE THE PCPN
TAPERS OFF LATE ON TUE. THE MEAN FLOW BY TUE TO BE IN THE PROCESS
OF BECOMING TEMPORARILY MORE ZONAL...THUS LITTLE PROSPECT OF ANY
LAKE EFFECT FOR NRN WI.

TOWARD THE MIDDLE OF NEXT WEEK...THEM MDLS ARE HAVING ISSUED WITH
HOW MUCH TO DIG THE NEXT PACIFIC SYSTEM INTO THE GREAT LAKES.
PREVIOUS MDL RUNS KEPT THIS SYSTEM TO OUR NORTH. HOWEVER...THE 12Z
RUNS NOW DIG THIS SYSTEM SE INTO THE GREAT LAKES ON WED. HAVE KEPT
THIS PERIOD DRY FOR NOW BASED ON THE MDL UNCERTAINTY...BUT MAY
NEED TO ADD A POP EVENTUALLY IF THE MDLS PROVIDE SOME CONTINUITY.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1254 PM CDT WED OCT 29 2014

THERE WERE FEW BREAKS IN THE CLOUDS ACROSS THE AREA TODAY WITH LOW
LEVEL MOISTURE AND CYCLONIC FLOW BOTH AT THE SURFACE AND ALOFT.
CIGS WERE MAINLY MVFR...EXCEPT IN THE EAST WHERE CONDITIONS WERE
VFR AND CLOUD BASES WERE IN THE 3000FT TO 3500FT RANGE AT 17Z.

EXPECT SOME IMPROVEMENT LATE THIS AFTERNOON OR THIS EVENING WITH
THE APPROACH OF A SURFACE RIDGE AND WEAK UPPER LEVEL RIDGE. MOST
LOCATIONS...EXCEPT IN THE FAR NORTH...SHOULD BECOME VFR DURING
THE EVENING OR OVERNIGHT. A SYSTEM QUICKLY APPROACHING THE AREA
FROM MONTANA WILL BRING MIDDLE AND HIGH CLOUDS OVERNIGHT AND
THURSDAY MORNING...WITH SOME MVFR CIGS DEVELOPING BEFORE THE END
OF THE TAF VALID PERIOD.
&&

.MARINE...
ISSUED AT 308 PM CDT WED OCT 29 2014

GALE WATCH REMAINS IN EFFECT FOR LATE THURSDAY NIGHT INTO FRIDAY
EVENING. A VIGOROUS SHORTWAVE TROF WILL SWEEP ACROSS THE REGION
THURSDAY NIGHT AND THEN MOVE SE OF THE AREA ON FRIDAY. STRONG
NORTH TO NW WINDS ARE EXPECTED BEHIND THIS SYSTEM WITH GALE FORCE
GUSTS OF 40 TO 45 KNOTS POSSIBLE. CANNOT RULE OUT SOME GUSTS ACROSS
NORTHERN DOOR COUNTY APPROACHING STORM FORCE IF THE MODELS WITH THE
STRONGER 925MB WINDS ARE CORRECT. WINDS WILL GRADUALLY SUBSIDE
LATE FRIDAY AFTERNOON AND FRIDAY NIGHT.
&&

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

$$

SHORT TERM.....MG
LONG TERM......KALLAS
AVIATION.......MG
MARINE.........KALLAS






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