000
FXUS63 KGRB 121730
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1230 PM CDT WED JUN 12 2013

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND THURSDAY
ISSUED AT 340 AM CDT WED JUN 12 2013

SOME VERY ELEVATED SHOWERS AND THUNDERSTORMS WERE
MOVING ACROSS EAST CENTRAL AND CENTRAL WISCONSIN AT 0830 UTC. THE
BASES WERE AROUND 12000 FT SO MUCH OF THE RAIN WAS EVAPORATING
BEFORE REACHING THE GROUND WITH MOST PLACES RECEIVING ONLY A FEW
HUNDREDTHS OF AN INCH. THIS ACTIVITY SHOULD WEAKEN AFTER SUNRISE
AS CLOUD TOPS WARM AND UPPER JETS ASSOCIATED WITH THE ACTIVITY
MOVE EAST.

THE BIG QUESTION FOR THE AFTERNOON AND EVENING IS THE NORTHERN
EXTENT OF THE CONVECTIVE COMPLEX EXPECTED OVER NORTHERN ILLINOIS
AND SOUTHERN WISCONSIN. THINK THE 03Z SREF HAS ABOUT AS GOOD A
HANDLE ON THE PRESENT ACTIVITY AS ANY OF THE MODELS SO MOSTLY USED
IT AS GUIDANCE FOR THIS AFTERNOONS ACTIVITY. HIGHS TODAY WILL BE
HIGHEST OVER THE FAR NORTH WHERE THERE SHOULD BE SUNSHINE AND
LOWEST NEAR THE LAKE AND BAY WITH EASTERLY FLOW FROM THE COLD
WATER.

ANY LEFTOVER SHOWERS IN EAST CENTRAL WISCONSIN SHOULD END THIS
EVENING WITH CLEARING EXPECTED TONIGHT AS LARGE SURFACE HIGH NORTH
OF LAKE SUPERIOR DROPS SOUTH. THE SOURCE REGION FOR THE AIR IS
FROM LARGELY ICE COVERED HUDSON BAY SO HIGHS THURSDAY SHOULD BE A
FEW DEGREES BELOW NORMAL WITH LOW RELATIVE HUMIDITY.

.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY
ISSUED AT 340 AM CDT WED JUN 12 2013

THE LATEST GFS ENSEMBLE MEAN INDICATES THAT THE PREDOMINATE UPPER
AIR PATTERN WILL CONSIST OF TROUGHING OVER THE WESTERN AND
NORTHEASTERN CONUS AND RIDGING OVER THE ROCKIES AND GREAT PLAINS
THROUGH THE PERIOD.  MEDIUM RANGE MODELS ARE IN GOOD AGREEMENT THROUGH
00Z SUNDAY...AND THEN BREAK DOWN AS A SHORTWAVE DIGS ACROSS THE
NORTHERN GREAT PLAINS OR WESTERN GREATS LAKES REGION.  THE ECMWF IS
THE MOST AGGRESSIVE WITH THIS SHORTWAVE DURING THE SUNDAY TO MONDAY
PERIOD WHILE THE GFS/GEM KEEP IT WEAKER AND FARTHER NORTH.  THE
OVERALL PATTERN IS AMPLIFYING OVER WESTERN NORTH AMERICA DURING THIS
TIME...BUT TROUGHING OVER EASTERN CANADA SUPPORTS MORE ZONAL FLOW.
THE 00Z MODELS ARE TRENDING TOWARDS THE ECMWF...AND WILL TREND THAT
WAY AS WELL.

THURSDAY NIGHT THROUGH FRIDAY NIGHT...CANADIAN HIGH PRESSURE WILL
MOVE ACROSS THE REGION THURSDAY NIGHT AND FRIDAY.  NORTH WINDS
ORIGINATING OUT OF THE HIGH WILL PUSH IN A SEASONABLE AND DRY
AIRMASS THURSDAY EVENING...DROPPING PWATS BELOW 0.5 INCHES.  SKIES
WILL BE MOSTLY CLEAR DURING THIS STRETCH WITH LOWS IN THE 40S AND
50S...AND HIGHS IN THE LOWER TO MID 70S.  CLOUDS WILL THEN BE ON THE
INCREASE FRIDAY NIGHT AS WARM ADVECTION CRANKS UP OVER THE NORTHERN
PLAINS.  SHOULD SEE A THUNDERSTORM COMPLEX MOVE SOUTHEAST OVER
SOUTHERN MINNESOTA OR IOWA AND POSSIBLY WEAKER CONVECTION FURTHER
NORTH THAT WILL MAKE A RUN AT CENTRAL WISCONSIN LATE.  LOWS WILL BE
WARMER BUT MAINLY IN THE 50S.

REST OF THE FORECAST...THE WARM ADVECTION WILL ROLL ACROSS THE
REGION SATURDAY AND SATURDAY NIGHT...FOLLOWED BY A COLD FRONT SUNDAY
OR SUNDAY NIGHT.  TRACK/STRENGTH OF THAT SHORTWAVE WILL DETERMINE
THE AMOUNT OF FORCING ALONG THE COLD FRONT AND WHETHER SEVERE
WEATHER WILL BE POSSIBLE.  DO NOT THINK THE WEEKEND WILL BE A
WASHOUT...BUT TOUGH TO REMOVE POPS ANY PERIOD.  SUNDAY LOOKS TO HAVE
A BETTER CHANCE OF BEING DRY.  ONCE THE SHORTWAVE MOVES THROUGH
THOUGH...ANOTHER COOL CANADIAN HIGH WILL ARRIVE.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1230 PM CDT WED JUN 12 2013

BAND OF FRONTOGENTICAL FORCED SHWRS/ISOLATED TSTMS
CONTS TO LIFT E-NE INTO CNTRL/N-CNTRL WI...BUT ACTIVITY IS
EXPECTED TO DISSIPATE WITH TIME AS MAIN FOCUS SHIFTS TO THE SOUTH
WHERE A CONVECTIVE AREA OF STRONG TO SEVERE TSTMS ARE EXPECTED TO
DEVELOP. CNTRL/E-CNTRL WI TO REMAIN ON THE NRN FRINGE OF THIS
ANTICIPATED TSTM ACTIVITY...THUS CANNOT RULE OUT A TSTM THIS
AFTERNOON FOR THE AUW...CWA...ATW AND GRB TAF SITES. AWAY FROM ANY
TSTM ACTIVITY...VFR CONDITIONS WL PREVAIL ESPECIALLY FROM THIS
EVENING ONWARD AS CANADIAN HI PRES DROPS SOUTH INTO THE GREAT
LAKES.
&&

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

$$

SHORT TERM.....RDM
LONG TERM......MPC
AVIATION.......AK