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000
FXUS63 KGRB 201136
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
636 AM CDT MON MAY 20 2013

UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE

.SHORT TERM...TODAY AND TONIGHT
ISSUED AT 446 AM CDT MON MAY 20 2013

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
AND TONIGHT. FIRST COMPLEX OF SHOWERS AND STORMS EXITING NORTHEAST
WISCONSIN EARLY THIS MORNING. COULD NOT RULE OUT SOME REDEVELOPMENT
OF SHOWERS AND STORMS LATER THIS MORNING INTO EARLY THIS AFTERNOON...
BUT MAIN ACTION SHOULD BE LATE THIS AFTERNOON AND TONIGHT. DAYTIME
HEATING WITH HIGHS IN THE UPPER 70S AND 80S WILL ALLOW THE ATMOSPHERE
TO BECOME VERY UNSTABLE THIS AFTERNOON. MODIFIED SOUNDINGS AT GREEN
BAY AND WAUSAU INDICATED CAPES AT LEAST 1-2 THOUSAND J/KG...LOW WET
BULB HEIGHTS NEAR TEN THOUSAND FEET AND HIGH WINDEX VALUES OF 45
TO 60 KNOTS BASED ON TEMPERATURES IN THE UPPER 70S AND LOWER 80S
WITH DEW POINTS IN THE UPPER 50S TO MIDDLE 60S. DAMAGING WINDS AND
LARGE HAIL WILL BE THE PRIMARY THREATS WITH THE STRONGEST STORMS.
SHOWERS AND STORMS WILL GRADUALLY DIMINISH OVERNIGHT.

DID BUMP HIGHS UP A FEW DEGREES TODAY BASED ON EARLIER EXIT OF
STORMS AND AMPLE PARTIAL SUNSHINE ALONG WITH THE WARM START TO THE
DAY.

.LONG TERM...TUESDAY THROUGH SUNDAY
ISSUED AT 446 AM CDT MON MAY 20 2013

THE LARGE CLOSED UPPER CYCLONE CURRENTLY OVER THE CENTRAL CONUS
WILL WEAKEN AND SHIFT TO THE EAST MID TO LATE THIS WEEK. A RIDGE IS
THEN FORECAST TO BUILD OVER THE PLAINS AS ANOTHER CLOSED UPPER
CYCLONE MOVES TO THE PACIFIC NORTHWEST BY THE END OF THE WORK
WEEK.

THERE WILL BE PLENTY OF CHANCES FOR SHOWERS AND THUNDERSTORMS THROUGH
THE MIDDLE OF THE WEEK AS SHORT WAVE ENERGY ROTATES AROUND THE
UPPER LEVEL CYCLONE WHILE IT SLOWLY WEAKENS AND MOVES EAST OF
WISCONSIN. THE MAIN ISSUE IN THE LONG TERM IS THE TIMING OF THESE
SHORT WAVES...WHICH IS DIFFICULT TO NAIL DOWN VERY FAR AHEAD OF
TIME. HAVE MAINLY JUST KEPT SHOWERS AND THUNDERSTORMS LIKELY
WORDING THROUGH WEDNESDAY. THE RIDGE AND SURFACE HIGH PRESSURE
SHOULD KEEP THE REST OF THE WORK WEEK DRY.

DAYTIME HIGH TEMPERATURES WILL START OUT ABOVE NORMAL BEFORE
FALLING TO 5 TO 10 DEGREES BELOW NORMAL FROM MIDWEEK THROUGH THE
COMING WEEKEND.
&&

.AVIATION...FOR 12Z TAF ISSUANCE
ISSUED AT 631 AM CDT MON MAY 20 2013

FIRST ROUND OF THUNDERSTORMS EXITED NORTHEAST WISCONSIN SHORTLY
BEFORE SUNRISE THIS MORNING. NEXT SHORTWAVE ACROSS NORTHERN
ILLINOIS WILL BRING A CHANCE OF SHOWERS TO KATW/KGRB THIS MORNING.
ATTENTION THEN TURNS TO THIS AFTERNOON WITH EXPECTED CONVECTION
REDEVELOPING AS UPPER LEVEL DISTURBANCES SWINGS ACROSS THE AREA.
SOME OF THE STRONGER STORMS WILL BE CAPABLE OF PRODUCING STRONG
WINDS OVER 50 KNOTS AND LARGE HAIL. THE SHOWERS AND STORMS WILL
TAPER OR END AFTER MIDNIGHT. LATE TONIGHT...MVFR CONDITIONS
ARE POSSIBLE DUE TO FOG.

&&

.MARINE...
ISSUED AT 446 AM CDT MON MAY 20 2013

SEVERAL ROUNDS OF THUNDERSTORMS ARE EXPECTED THROUGH
TUESDAY. FIRST ROUND IS ALREADY MOVING ACROSS THE COASTAL WATERS
OF DOOR COUNTY EARLY THIS MORNING. THIS ACTIVITY SHOULD EXIT THE
AREA SHORTLY AFTER SUNRISE. COULD NOT RULE OUT REDEVELOPMENT THIS
MORNING...BUT NEXT ROUND OF SHOWERS AND STORMS SHOULD OCCUR LATER
THIS AFTERNOON AND TONIGHT. THE STORMS LATER THIS AFTERNOON AND
EVENING COULD PRODUCE STRONG WINDS OR LARGE HAIL. MOIST AIR FLOWING
OVER THE COLDER WATERS OF THE BAY AND LAKE WILL RESULT IN FOG AT
TIMES THROUGH TUESDAY NIGHT. THE FOG MAY BE LOCALLY DENSE WITH
VISIBILITIES BELOW ONE MILE AT TIMES.
&&

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

$$

SHORT TERM.....ECKBERG
LONG TERM......MG
AVIATION.......ECKBERG
MARINE.........ECKBERG