Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 030311
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
911 PM CST MON MAR 2 2015

UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE
AND NEW INFORMATION ADDED TO UPDATE SECTION

.UPDATE...
ISSUED AT 854 PM CST MON MAR 2 2015

NO HEADLINE CHANGES THIS EVENING.

THE AIR MASS ACROSS THE AREA RIGHT NOW IS QUITE DRY AT LOW-LEVELS.
00Z GRB RAOB WAS VERY DRY BLO 600 MB...BUT SOUNDINGS TO THE SOUTH AND
WEST HAD MORE MOISTURE AND WERE MORE FAVORABLE FOR PCPN. THE
INCOMING MOISTURE FOR THE SNOW EVENT IS PRIMARILY AT MID-LVLS
ANYWAY...WITH PWATS ON THE 00Z TOP RAOB NOW UP TO 0.60 INCHES. SO
THE DRY AIR ARND 850 MB WL PROBABLY NOT BE A MAJOR LIMITING FACTOR
IN SNOWFALL TOTALS...THOUGH IT WL NEED TO BE OVERCOME BEFORE SNOW
CAN START FALLING.

LOOKS LIKE LEAD BAND OF LIFT WL SWEEP THROUGH THE FCST AREA AFTER
ABOUT 08Z. MODELS OFFERED VARYING IDEAS ON WHETHER/WHERE
SATURATION WOULD OCCUR...AND IF THERE WL BE ANY SNOW WITH THE LEAD
BAND OF PCPN. BEST GUESS IS THAT THE LEAD BAND WL RESULT IN
ENOUGH MOISTENING OF LOW-LEVELS FOR SOME SNOW...ESP ACRS THE
N/NE. THEN THERE WL BE A LULL AS DRY AIR ARND 850 MB CIRCULATES
BACK THROUGH THE FCST AREA...WITH THE MAIN SNOW EVENT PROBABLY
GETTING GOING IN THE 12-15Z TIME FRAME. THE STARTING TIMES OF OUR
ADVISORY DO NOT LINE UP VERY WELL WITH THIS THINKING. BUT
CONSIDERING THE UNCERTAINTY REGARDING THE BEHAVIOR OF THE LEAD
BAND OF PCPN...WAS NOT COMFORTABLE TOTALLY RE-DOING THE STARTING
TIMES OF THE ADVISORY. WL ALLOW IT TO RIDE AS IS AND ADD SOME
EXPLANATION OF THE LULL/BREAK IN SNOW EXPECTED AS THE LOW- LEVEL
DRY AIR CIRCULATES BACK THROUGH THE FCST AREA.

UPDATED PRODUCT SUITE OUT ASAP.
&&

.SHORT TERM...TONIGHT AND TUESDAY
ISSUED AT 310 PM CST MON MAR 2 2015

MAIN FORECAST CONCERNS WILL BE SNOW AMOUNTS AND SNOW START TIMES
LATE TONIGHT INTO TUESDAY.

QUIET WEATHER PREVAILED ACROSS THE STATE AS HIGH PRESSURE SPREAD
ACROSS THE GREAT LAKES REGION. THE QUIET WEATHER WILL COME TO AN
ABRUPT END LATE TONIGHT AND TUESDAY MORNING AS ACCUMULATING
SNOWFALL IS EXPECTED ACROSS THE ENTIRE AREA.

THE HIGH PRESSURE WILL PUSH INTO THE EASTERN GREAT LAKES
TONIGHT...AS A LOW PRESSURE SYSTEM DEVELOPS IN THE CENTRAL
PLAINS. THIS WILL ALLOW WARM AIR ADVECTION TO BEGIN...AND
TRANSPORT MOISTURE BACK INTO THE STATE...LEADING TO MID AND UPPER
LEVEL CLOUDS TO INCREASE ACROSS THE AREA THIS AFTERNOON AND
EVENING. THE CLOUDS WILL LOWER AND THICKEN THROUGH THE EVENING AND
EARLY OVERNIGHT HOURS. SOME LIGHT SNOW AND FLURRY ACTIVITY IS
POSSIBLE AFTER 10-11PM AS A RIBBON OF HIGHER RH MOVES THROUGH AND
THE AREA WILL BE IN A FAVORABLE WAA REGIME WITH INCREASING
ISENTROPIC LIFT AND IN THE RRQ OF A DEPARTING JET AND THE LFQ OF
AN APPROACHING JET. ACCUMULATIONS UP TO AN INCH ARE POSSIBLE WITH
THIS ACTIVITY...BUT THE MAJORITY OF THE ACCUMULATING SNOW WILL HOLD
OFF UNTIL TUESDAY AM.

AN AREA OF MODERATE (BRIEFLY HEAVY?) SNOW WILL SPREAD ACROSS THE
AREA ON TUESDAY...AS STRONG WAA...ISENTROPIC LIFT AND QC FORCING
PUSH THROUGH THE STATE. NOSE OF A 40-45 KT LOW LEVEL JET MOVES
INTO EAST-CENTRAL WI AS WELL...WHICH WILL ENHANCE LIFT THERE.
FORCING/LIFT IS GREATEST DURING THE 12-18Z PERIOD...WHEN THE
MAJORITY OF THE SNOW WILL FALL. OPERATIONAL MODELS ARE ON THE
LOWER END OF SNOW TOTALS...GENERALLY BETWEEN 1.5" AND 3.5". NAM
HAS CONTINUED TO BE ON THE LOW SIDE...WITH THE GFS/GEM/ECMWF IN
THE MIDDLE OR TOWARD THE HIGHER VALUES. SREF SNOW PLUMES RANGE
FROM 2 TO 7 INCHES. SO THERE STILL REMAINS SOME CONCERN THIS EVENT
WILL BE TOWARD THE LOWER END OF THINGS... ESPECIALLY WITH THE FAST
MOVEMENT AND NOT IDEAL LIFT IN THE SNOW GROWTH REGION (TEMPS TOO
WARM). WILL CONTINUE TO PLACE THE HIGHEST QPF AMOUNTS (AROUND
0.30") OVER THE FOX VALLEY AND LAKESHORE...WITH LOWER AMOUNTS OVER
THE NORTH. HOWEVER HIGHER SNOW TO LIQUID RATIOS (BETWEEN 15-20 TO 1)
WILL BE OVER NORTHERN WI. SO IN THE END...MOST SPOTS ARE STILL
FORECAST TO RECEIVE 3-4 INCHES...WITH MOST OF THAT FALLING IN A
2-4 HOUR WINDOW. THEREFORE...NO MAJOR CHANGES PLANNED WITH THE
WINTER WEATHER ADVISORY. CONSIDERED DELAYING THE START TIME
SLIGHTLY AS BULK OF SNOW NOT EXPECTED TO PUSH INTO MOST OF NORTH-
CENTRAL UNTIL AFTER 12Z. HOWEVER...THINK ACCUMULATIONS ASSOCIATED
WITH THE LIGHT SNOW OVERNIGHT IS ENOUGH TO KEEP THE 09Z START
TIME. ALSO CONSIDERED STARTING THE ENTIRE FOX VALLEY WITH THE REST
OF THE CURRENT ADVISORY (09Z)...BUT WILL LEAN TOWARD A SLIGHTLY
SLOWER ONSET OF MAIN BATCH OF SNOW SO THE 12Z START TIME SHOULD
WORK OUT.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY
ISSUED AT 310 PM CST MON MAR 2 2015

ARCTIC AIR WILL RETURN TO WISCONSIN TUESDAY NIGHT
THROUGH THURSDAY AS A SIGNIFICANT UPPER TROUGH DROPS INTO THE
WESTERN GREAT LAKES. SUBZERO TEMPERATURES EXPECTED ACROSS THE
WESTERN HALF OF OUR FORECAST AREA TUESDAY NIGHT AND EARLY
WEDNESDAY WHICH WILL PRODUCE WIND CHILLS OF 20 TO 25 BELOW ZERO.
HIGHS WEDNESDAY SHOULD BE AROUND 25 DEGREES BELOW NORMAL WITH
SUBZERO WIND CHILLS ALL DAY. WEDNESDAY NIGHT SHOULD BE THE COLDEST
NIGHT OF THE WEEK WITH BELOW ZERO TEMPERATURES AND WIND CHILLS OF
20 TO 30 BELOW ZERO. LAKE EFFECT SNOW SHOWERS POSSIBLE IN NORTH
CENTRAL WISCONSIN BUT ICE COVER ON LAKE SUPERIOR AND LESS THAN
FAVORABLE WINDS WILL WORK TO KEEP ACCUMULATIONS DOWN TO LESS THAN
AN INCH.

MILDER TEMPERATURES EXPECTED FRIDAY THROUGH EARLY NEXT WEEK AS THE
LARGE UPPER RIDGE OVER THE WESTERN UNITED STATES MOVE EAST AND
MODIFIED PACIFIC AIR BEGINS TO ARRIVE FROM THE PLAINS STATES. A
FEW CLIPPER LIKE SYSTEMS COULD APPROACH FROM THE NORTHWEST ALONG
THE WESTERN EDGE OF THE COLD AIR AND PRODUCE SOME LIGHT SNOW BUT
THE MODELS ARE NOT CONSISTENT WITH TRACK OR TIME OF ARRIVAL.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 854 PM CST MON MAR 2 2015

NOT MUCH CHG TO OVERALL FCST THINKING FM PREV TAF PKG. MAIN CHGS
WL BE TO ADJUST TIMING OF THE SNOW TO REFLECT THE LATEST TRENDS IN
THE OBS. THE MOST SIG SNOW WL PROBABLY MV THROUGH DURING THE
MID-LATE MORNING...WITH SNOW TAPERING OFF IN THE AFTN. CAN/T
TOTALLY RULE OUT PCPN CHGG TO FZDZ AS INTENSITY WANES IN THE
AFTN...BUT AT THIS POINT THE PROBABLILITY OF THAT OCCURRING DOES
NOT SEEM GREAT ENOUGH TO WARRANT CARRYING FZDZ IN THE TAFS.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 3 AM TO 6 PM CST TUESDAY FOR WIZ005-
010>012-018-019-030-035>037-045-048>050.

WINTER WEATHER ADVISORY FROM 6 AM TO 6 PM CST TUESDAY FOR WIZ013-
020>022-031-038>040-073-074.
&&

$$

UPDATE.........SKOWRONSKI
SHORT TERM.....BERSCH
LONG TERM......RDM
AVIATION.......SKOWRONSKI








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