000
FXUS63 KGRB 181142
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
642 AM CDT SAT MAY 18 2013

UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND SUNDAY
ISSUED AT 426 AM CDT SAT MAY 18 2013

MORE AMPLIFIED PATTERN THIS PERIOD AS WESTERN TROF DIGS SOUTHEAST
AND CUTS OFF OVER THE CENTRAL PLAINS. BUILDING HEIGHTS OVER STATE
TODAY AS RIDGE MOVES EAST ACROSS STATE THIS PERIOD WILL LEAD TO
LESSENING CHANCE OF PCPN TODAY. LOCAL RADARS CURRENTLY SHOWING
ISOLD TO SCATTERED SHOWERS OVER NORTHERN WI. TO THE WEST...AREA OF
THUNDERSTORMS MOVING THROUGH MN AND FAR WESTERN WI NORTH OF
STATIONARY/WARM FRONT AND AHEAD OF VORT EJECTING OUT OF UPPER
TROF. MOST TEMPERATURES REMAIN IN THE LOWER 50S AT THIS TIME GIVEN
CLOUDS AND EAST FLOW.

AGAIN...FOCUS OF FORECAST ON PCPN CHANCES AND TEMPS. SHOWERS OVER
NORTHERN WI NORTH OF 850H BAROCLINC ZONE...AREA OF SIG WAA. HAVE
TRENDED TOWARDS A BLEND OF NAM AND EC...AND MESO HRRR MODELS. ALL
SUGGEST PCPN TO SHIFT NORTH THIS MORNING...LEAVING MUCH OF CWA DRY
THIS AFTERNOON. HAVE KEPT A BUFFER OF CHANCE POPS OVER WEST.

RIDGE AXIS PASSES OVERHEAD TONIGHT. HAVE STAYED WITH DRY FORECAST.
ON SUNDAY...PCPN CHANCES INCREASE THROUGH THE DAY AS RIDGE TO BE
EAST OF STATE AND DYNAMICS WITH UPPER TROF COME IN TO PLAY.
STRENGTHENING LLVL FLOW (30 TO 35 KTS AT 850) STRAIGHT OUT OF GULF
TO BRING PW VALUES TO 1.5 INCHES OR GREATER. INSTABILITY INCREASES
WITH MID LEVEL LAPSE RATES AT 7. EC SUGGESTS CAPE VALUES AROUND
1K...NAM SHOWING NORMAL HIGH BIAS. THOUGH MODEL SOUNDINGS SHOW
STRONG CIN OVER EAST THROUGH DAY. HAVE STAYED DRY EAST THROUGH THE AFTN.

TEMPS TO BE A HEADACHE AGAIN TODAY WITH CLOUDS...ONGOING PCPN AND
EAST FLOW OFF LAKE. DID NOT STRAY TOO FAR FROM PREVIOUS FORECAST.
WENT A BIT HIGHER ON CLOUDS GIVEN PLENTY OF CIRRUS FLOWING THIS
WAY FROM UPSTREAM CONVECTION. STAYED WITH TEMPS HITTING 80 ON SUN
AS BEST PERFORMING GUIDANCE SUGGESTS...THOUGH UNCERTAINTY SIG
GIVEN POSSIBLE CONVECTION.

.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY
ISSUED AT 426 AM CDT SAT MAY 18 2013

PRECIPITATION CHANCES FOR MUCH OF THE UPCOMING WEEK ARE THE MAIN
CONCERNS DURING THIS PART OF THE FORECAST.

THUNDERSTORMS LOOK LIKE A PRETTY GOOD BET ACROSS THE AREA ON
SUNDAY NIGHT WITH SHORT WAVE ENERGY PASSING THROUGH...AN
APPROACHING SURFACE LOW AND A FRONTAL BOUNDARY MOVING NORTHEAST
ACROSS THE AREA. THOUGH EASTERLY COMPONENT OF SURFACE FLOW OFF
LAKE MICHIGAN MAY LESSEN THE CHANCES FOR STORMS IN THE EAST.

HAVE LIKELY POPS FOR MONDAY AND MONDAY NIGHT. SPC DAY 3 OUTLOOK
HAD CENTRAL AND EAST CENTRAL WISCONSIN IN SLIGHT RISK AS A SURFACE
LOW APPROACHES AND A CLOSED 500MB CYCLONE MAKES ITS WAY TOWARD THE
STATE. STILL QUITE A BIT OF UNCERTAINTY REGARDING THIS SEVERE
THREAT.

THE SURFACE LOW SHOULD MAKE ITS WAY INTO WESTERN WISCONSIN ON
TUESDAY AS BOTH THE SURFACE AND UPPER LEVEL SYSTEMS MAKE THEIR WAY
ACROSS THE WESTERN GREAT LAKES REGION. THUNDER CHANCES SHOULD
DIMINISH AS THE SYSTEMS PASS EAST OF THE FORECAST AREA AND THE
CHANCE OF SHOWERS SHOULD FINALLY COME TO AN END BY THE END OF THE
WORK WEEK.

TEMPERATURES AT THE START OF THE PERIOD ARE EXPECTED TO BE ABOVE
NORMAL BUT COOLER TEMPERATURES ARE FORECAST FOR THE REST OF THE
WEEK...WITH HIGHS MAINLY IN THE 60S EACH DAY.
&&

.AVIATION...FOR 12Z TAF ISSUANCE
ISSUED AT 632 AM CDT SAT MAY 18 2013

SOME UNCERTAINTY WESTERN SITES WITH PATH/LONGEVITY OF STORMS
ONGOING OVER MN. STORMS TRENDING TO TURN RIGHT THIS
MORNING...THOUGH WEAKEN AS THEY MOVE EAST. BASIC TREND OF THE FORECAST
IS DRY AS RIDGE BUILDS IN. LIGHT WINDS AND AVAILABLE MOISTURE...TO
LEAD TO MVFR FOG OVERNIGHT. INCREASING CHANCE OF STORMS LATE SUN
INTO MON.

&&

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

$$

SHORT TERM.....TE
LONG TERM......MG
AVIATION.......TE