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000
FXUS63 KGRB 151803
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
103 PM CDT SAT JUN 15 2013

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND SUNDAY
ISSUED AT 327 AM CDT SAT JUN 15 2013

WEAKENING FRONTAL SYSTEM WILL MOVE ACROSS THE AREA
TODAY AND EXIT EASTERN WISCONSIN THIS EVENING. UPPER LEVEL
DIFFLUENT FLOW COMBINED WITH LOW LEVEL WARM ADVECTION ARE
COMBINING TO PRODUCE SHOWERS AND ELEVATED THUNDERSTORMS ACROSS
THE SOUTHWEST HALF OF THE FORECAST AREA EARLY THIS MORNING. THE
BEST WARM ADVECTION MOVES ACROSS THE REGION THIS MORNING SO EXPECT
THE AREA OF PRECIPITATION TO MOVE EAST BUT WEAKEN AFTER SUNRISE AS
CLOUD TOPS WARM AND LOW LEVEL JET WEAKENS. WHAT HAPPENS IN THE
AFTERNOON IS A GOOD QUESTION. THERE ISN/T MUCH OF A TRIGGER OTHER
THAN CONVERGENCE ALONG THE WEAKENING FRONT BUT FORECAST SOUNDINGS
HAVE 1500 J/KG OR MORE OF CAPE OVER CENTRAL WISCONSIN BY LATE
AFTERNOON WITH A BIT LESS OVER THE EAST. THE WIND FIELD IS NOT
IMPRESSIVE AND NEITHER ARE WET BULB ZERO HEIGHTS SO SEVERE
POTENTIAL SEEMS LOW. COULD GET SOME STORMS WITH GUSTY WINDS AND
HEAVY RAIN THIS AFTERNOON.

WHATEVER ACTIVITY GETS GOING THIS AFTERNOON SHOULD EXIT EASTERN
WISCONSIN THIS EVENING AS DRIER AIR ARRIVES. THINK LOWS WILL BE
CLOSER TO GFS MOS VALUES IF SKIES CLEAR.

FATHERS DAY SHOULD BE PRETTY NICE WITH SUNSHINE...WARM
TEMPERATURES AND COMFORTABLE DEW POINTS. IT WILL BE A BIT BREEZY IN
THE AFTERNOON. THINK HIGHS WILL BE A DEGREE OR TWO ABOVE MOS AS
THE WEST WIND IS A DOWN SLOPE OVER EASTERN PART OF THE FORECAST
AREA AND LOW DEW POINTS IN THE NORTH WILL ALLOW FOR A LARGE DIURNAL
RANGE.

.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY
ISSUED AT 327 AM CDT SAT JUN 15 2013

MEDIUM RANGE MODELS SHOW THAT AN AMPLIFICATION OF THE UPPER AIR
PATTERN WILL TAKE PLACE THIS WEEK...AS A RESULT OF A DEEP UPPER LOW
DRIFTING OFF THE PAC NW...WHICH WILL LEAD TO A STRONG RIDGE BUILDING
DOWNSTREAM OVER THE PLAINS.  WISCONSIN WILL RESIDE DOWNSTREAM OF
THIS RIDGE FOR MUCH OF THE WEEK UNDER NW FLOW ALOFT.  THE ECMWF/GEM ARE
IN VERY GOOD AGREEMENT WITH THIS LARGE-SCALE PICTURE...AND WILL USE
THESE MODELS FOR THIS FORECAST.

SUNDAY NIGHT THROUGH MONDAY NIGHT...A SHORTWAVE TROUGH WILL BE
DROPPING SOUTHEAST OVER WESTERN LAKE SUPERIOR AND THE FAR NORTHERN
MISSISSIPPI VALLEY SUNDAY NIGHT.  THE SHORTWAVE HAS TRENDED WEAKER
OVER THE PAST DAY OF MODEL RUNS...BUT FORCING AND MOISTURE SEEM
SUFFICIENT FOR SHOWERS ACROSS NORTHERN WISCONSIN LATE SUNDAY NIGHT.
INHERITED PRECIP CHANCES LOOK TO BE IN GOOD SHAPE.  THE SHORTWAVE
WILL PUSH ACROSS THE REGION ON MONDAY AND WILL HAVE A CHANCE TO
INTERACT WITH MODEST DIURNAL INSTABILITY.  SO WILL EXPAND POPS OVER
CENTRAL AND NORTHEAST WISCONSIN.  THE SHORTWAVE WILL PUSH A COLD
FRONT ACROSS THE AREA BY THE START OF MONDAY EVENING...AND A VERY
DRY AIRMASS WILL ARRIVE FOR MONDAY NIGHT.  SKIES WILL CLEAR OUT AND
WINDS WILL TURN LIGHT.  WILL THEREFORE LOWER MIN TEMPS OVER N-C
WISCONSIN.

REST OF THE FORECAST...HIGH PRESSURE WILL HANG ACROSS THE REGION
TUESDAY AND WEDNESDAY...WHICH LOOK DRY AND SEASONABLE.  MODELS THEN
INDICATE A SHORTWAVE DROPPING INTO THE REGION WEDNESDAY NIGHT OR
THURSDAY WHICH WILL PUSH A WEAK COLD FRONT INTO THE STATE.  FORCING
DOES NOT LOOK PARTICULARLY STRONG AND TIMING WILL PROBABLY CHANGE A
BIT...SO WILL KEEP POPS IN THE SLIGHT CHANCE RANGE.  THE MID-LEVEL
RIDGE WILL CREEP CLOSER TO THE REGION BY LATE IN THE NEXT WORK
WEEK...WHEN THE NEXT SOLID CHANCE OF PRECIP WILL ARRIVE.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 100 PM CDT SAT JUN 15 2013

BATCH OF ISOLATED-SCATTERED SHOWERS MOVING ACROSS CENTRAL AND
EAST-CENTRAL WISC ALONG WEAK CONVERGENCE ZONE. LARGER AREA OF
ORGANIZED CONVECTION MOVING INTO SOUTHEAST MN AND IA THIS
AFTERNOON WILL AFFECT SOUTHERN AIRPORTS WITH MVFR CIG/VSBY IN
SHOWERS AND STORMS. ADDITIONAL SHOWERS ACROSS THE NORTH EXPECTED
LATER THIS AFTERNOON AHEAD OF WEAK UPPER TROF.

&&

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

$$

SHORT TERM.....RDM
LONG TERM......MPC
AVIATION.......JKL