Area Forecast Discussion
Issued by NWS Green Bay, WI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KGRB 282311
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
611 PM CDT SAT MAR 28 2015

UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE

.SYNOPSIS...
ISSUED AT 305 PM CDT SAT MAR 28 2015

PRETTY TYPICAL LATE MARCH WEATHER...WITH TEMPERATURES UNDERGOING
CONSIDERABLE DAILY VARIATION. SEVERAL ROUNDS OF PRECIPITATION...
WITH PRECIPITATION TYPE A FORECAST ISSUE MUCH OF THE TIME.

THE LARGE SCALE WL HAVE MODEST AMPLITUDE MOST OF THE PERIOD AS
PROGRESSIVE AND QUITE ENERGETIC BAND OF WESTERLIES WL CONT ACRS
MUCH OF THE CONUS AND SRN CANADA. THERE MAY BE SOME SPLITTING
INTO SEPARATE STREAMS AT TIMES. THE LACK OF AMPLITUDE ON THE LARGE
SCALE WILL RESULT IN TEMPERATURES ROLLERCOASTERING ARND NORMAL
WITH THE PASSAGE OF EACH WX SYSTEM. THERE WL BE SEVERAL
OPPORTUNITIES FOR PCPN...WITH AMNTS LIKELY ENDING UP NR NORMAL FOR
THE PERIOD.
&&

.SHORT TERM...TONIGHT AND SUNDAY
ISSUED AT 305 PM CDT SAT MAR 28 2015

MAIN FORECAST CONCERN THROUGH SUNDAY IS PRECIPITATION CHANCES AND
TYPE SUNDAY MORNING AND AFTERNOON.

THROUGH TONIGHT...QUIET WEATHER IS EXPECTED AS HIGH PRESSURE
DRIFTS TO THE EAST. AN APPROACHING COLD FRONT WILL LEAD TO
INCREASING SOUTH WINDS AND CLOUD AFTER MIDNIGHT...HOWEVER DRY
CONDITIONS WILL HOLD THROUGH OUT NORTHEAST WISCONSIN THROUGH 12Z
SUNDAY. TEMPERATURES WILL BE STEADY AS WAA RAMPS UP THROUGH THE
NIGHT.

A COMPLEX YET QUICK HITTING STORM SYSTEM WILL SWING
THROUGH THE STATE SUNDAY. SLOWED DOWN THE ARRIVAL OF PRECIPITATION
PER MODEL GUIDANCE AND DUE TO THE AMOUNT OF DRY AIR THAT THIS
SYSTEM WILL NEED TO OVERCOME. DONT EXPECT ANYTHING TO GET GOING
BEFORE 12Z SUNDAY. AFTER THAT...MODELS IN GOOD AGREEMENT OF
PRECIPITATION OVERSPREADING THE AREA AS AN UPPER LEVEL TROUGH AND
ASSOCIATED FRONTAL SYSTEM PUSH INTO THE REGION. IMPRESSIVE AMOUNT
OF FORCING WITH FEATURE AS A SHARP SHORTWAVE PUNCHES IN AHEAD OF
THE FRONT. MODELS ARE IN DECENT AGREEMENT ON THE TIMING OF THESE
FEATURES AND PRECIPITATION OVERSPREADING THE AREA BY 15Z...THEN
DIMINISHING IN THE AFTERNOON.

MODELS DO NOT AGREE ON HOW QUICKLY WARM AIR WILL SURGE INTO THE
AREA. 12Z GFS CONTINUED TO BE VERY WARM...WHILE THE NAM12 WAS ON
THE OPPOSITE END OF THE SPECTRUM AND WAS SIGNIFICANTLY COOLER.
TRIED TO LEAN TOWARDS SREF/ECMWF SOLUTIONS AS THEY WERE A GOOD
COMPROMISE AND WERE FAIRLY CONSISTENT RUN TO RUN.

PRECIPITATION SHOULD START AS SNOW AND CONTINUE THROUGH EARLY
MORNING. AFTER 15Z...PRECIP SHOULD TRANSITION TO RAIN FROM SW TO
NE AS WARMER AIR INVADES THE STATE...WITH SOME SLEET POSSIBLE
DURING THIS TRANSITION. AT 18Z...MAINLY NORTHERN AND THE NORTHEAST
CORNER WILL STILL HAVE A CHANCE OF SEEING FREEZING PRECIPITATION.
WORRIED THAT STRONG FORCING MOVING THROUGH AROUND 18Z WILL KEEP
THINGS COOLER ALOFT...AND FREEZING PRECIP WILL LINGER IN THESE
AREAS. LOW LEVEL CRITICAL THICKNESSES ON THE SREF AND ECMWF
SUPPORT THIS IDEA...SO KEPT THE SNOW A LITTLE LONGER FOR THE
NORTH/NORTHEAST. IT WONT BE TOO LONG THOUGH AFTER THE BETTER
FORCING MOVES OUT AND THE WARM AIR WINS...WITH ALMOST ALL OF THE
CWA CHANGING OVER THE ALL RAIN BY 21Z SUNDAY. ACCUMULATIONS AROUND
AN INCH ARE POSSIBLE TO THE NORTH WHERE PRECIP WILL REMAIN SNOW
THE LONGEST...HOWEVER THE CHANGE OVER TO RAIN AND WARMER TEMPS
MEANS ANYTHING THAT STICKS WONT LAST LONG.

PRECIPITATION WILL TAPER OFF FROM WEST TO EAST SUNDAY AFTERNOON AS
THE MAIN SYSTEM PULLS AWAY AND THE FRONT CLEARS THE AREA AFTER
21Z. MODELS SHOW ANOTHER WEAK SHORTWAVE NUDGING INTO THE AREA
BEHIND THE FRONT...SO LINGERING PRECIP SHOULD CONTINUE LATE SUNDAY
AFTERNOON...HOWEVER IT SHOULD REMAIN SCATTERED AND LIGHT.

GUSTY SOUTH WINDS SUNDAY MORNING WILL VEER WEST IN THE AFTERNOON
AS THE FRONT PUSHES THROUGH THE AREA...WITH THE STRONGEST WINDS
IN EASTERN WISCONSIN WHERE GUSTS COULD REACH 35MPH EARLY IN THE
AFTERNOON.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY
ISSUED AT 305 PM CDT SAT MAR 28 2015

PCPN FM THE SYSTEM THAT AFFECTS THE AREA SUNDAY MAY LINGER INTO
SUNDAY NIGHT. CARRIED TRACE PRECIPITATION /SPRINKLES OR FLURRIES/
ACRS MUCH OF THE AREA THROUGH THE EVENING. THE FLOW COULD BE NWLY
ENOUGH FOR SOME LAKE-EFFECT IN N-C WI. CONTD TO CARRY THAT IN THE
FCST...BUT TRAJECTORIES WERE NOT FAVORABLE ENOUGH TO TAKE POPS
BEYOND CHC CATEGORY. SUBSIDENCE IN THE CAA SHOULD RESULT IN DECRG
CLDS IN ALL BUT THE LAKE-EFFECT AREAS AFTER MIDNIGHT.

THE NEXT FCST ISSUE WL BE SYSTEM DIVING SE ACRS THE AREA MON
NGT/TUE MORNING. IT/S A FAIRLY SML SYSTEM...SO THERE ARE
TIMING/PLACEMENT DIFFERENCES OF THE MAIN PCPN BAND BTWN THE
MODELS. IT ALSO HAS SOME SIMILARITIES TO A SYSTEM THAT DROPPED A
NARROW BAND OF WARNING CRITERIA SNOWS ON SE MN/NE IA/FAR SW WI
LAST WEEK. TOOK POPS UP TO HIGH CHC ACRS THE N...WHICH APPEARS TO
BE THE MOST FAVORED LCN FOR PCPN. DID NOT WANT TO GO ANY HIGHER
YET GIVEN THE MODEL DIFFERENCES. FOR NOW WL MENTION AN INCH OR TWO
OF SNOW IN ACRS THE FAR N/NE IN THE HWO...BUT SYSTEM WL NEED TO BE
MONITORED CLOSELY.

A STRONGER/BIGGER PACIFIC SYSTEM WL TRACK TOWARD LAKE SUPERIOR
DURING THE MIDDLE PART OF THE WEEK. ENOUGH WARM AIR SHOULD BE
DRAWN NWD AHEAD OF THAT SYSTEM FOR PCPN TO BE MAINLY RAIN. TEMPS
WL BE TRICKY...AND WL LIKELY BE AFFECTED BY CLDS/PCPN.

FINALLY...THERE ARE INDICATIONS...ESP ON THE ECMWF...OF SECONDARY
DEVELOPMENT AS THE COLD FRONT FROM THE MID-WK SYSTEM STALLS S OF
THE AREA. THE PAST 2 RUNS OF THE ECMWF DEVELOPED A VERY DEEP
CYCLONE WITH THIS. THE 00Z RUN PUT HEAVY PCPN AMNTS INTO E-C
WI...WHILE THE 12Z RUN IS NOW A LITTLE FARTHER S. SYSTEMS SUCH AS
THIS CAN BE A REAL PROBLEM...SINCE THE DYNAMICS GENERATING THE
VERY RAPID DEEPENING OF THE CYCLONE CAN EASILY COOL THE AIR COLUMN
ON THE NW FLANK OF THE SYSTEM ENOUGH TO RESULT IN HEAVY SNOW.
THAT/S AN OUTLIER POSSIBILITY FOR NOW...BUT BEARS WATCHING.
&&

.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 604 PM CDT SAT MAR 28 2015

LOW LEVEL WIND SHEAR AND PRECIPITATION TYPES MAIN CONCERN LATE
TONIGHT AND SUNDAY MORNING. POTENT SYSTEM MOVING ACROSS THE
NORTHERN PLAINS THIS AFTERNOON WILL SWEEP ACROSS THE REGION
LATE TONIGHT INTO SUNDAY MORNING...BRINGING RAIN...SLEET AND SNOW.
IT APPEARS PRECIPITATION WILL NOT ARRIVE UNTIL AFTER 12Z FOR THE
CENTRAL WISCONSIN TAF SITES AND ACROSS EASTERN WISCONSIN BY MID
TO LATE MORNING. MAIN BRUNT OF PRECIPITATION WILL BE FROM 13Z TO
19Z. STILL SOME QUESTIONS ON HOW MUCH WARM AIR WILL WORK INTO THE
REGION...THUS EXPECTING A MIX OF SNOW AND SLEET CHANGING OVER TO
RAIN AROUND MIDDAY AT MOST LOCATIONS EXCEPT OVER THE FAR NORTH
WHERE IT COULD LINGER INTO EARLY AFTERNOON. BUFKIT SOUNDINGS
SUPPORT WIND SHEAR FROM ABOUT 09Z TO AROUND 15Z SUNDAY AT MOST
LOCATIONS AT 220/230 DEGREES AT 40 TO 50 KNOTS. WITH THE 00Z
TAFS...DID BUMP UP SURFACE WIND GUSTS ON SUNDAY DUE TO STRONG
WINDS JUST OFF THE SURFACE. MAY NOT BE HIGH ENOUGH AT SOME SITES
TOMORROW AFTERNOON IF WE SHOULD GET SOME DEEPER MIXING.

&&

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

$$

SYNOPSIS.......SKOWRONSKI
SHORT TERM.....ALLEN
LONG TERM......SKOWRONSKI
AVIATION.......ECKBERG






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.