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000
FXUS63 KGRB 131727
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1227 PM CDT MON MAY 13 2013

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND TUESDAY
ISSUED AT 415 AM CDT MON MAY 13 2013

COLD UPPER TROUGH WILL EXIT THE REGION TODAY WITH
WARM ADVECTION PRODUCING SOME MIDDLE AND HIGH CLOUDS IN THE
AFTERNOON. THE LEFT EXIT REGION OF A 500MB JET WILL APPROACH THE
AREA THIS AFTERNOON AND EVENING AND PRODUCE SOME LIFT IN AN
ATTEMPT TO PRODUCE PRECIPITATION. THE AIR IS QUITE DRY SO IT MIGHT
BE MORE LIKE VIRGA OR SPRINKLES THAN SHOWERS. WILL KEEP A CHANCE
OF SHOWERS LATE IN THE DAY IN THE WESTERN COUNTIES. TEMPERATURES
WILL GET OFF TO A COOL START SO EXPECT HIGHS A DEGREE OR TWO BELOW
GUIDANCE.

THE BEST UPPER SUPPORT ASSOCIATED WITH THE JET MOVES ACROSS NORTHERN
WISCONSIN TONIGHT THOUGH THERE IS STRONG WARM AIR ADVECTION ACROSS
ENTIRE AREA SO WILL KEEP IN A CHANCE OF SHOWERS. LOWS TONIGHT
SHOULD BE AROUND 15 DEGREES HIGHER THAN THIS MORNING WITH CLOUD
COVER AND A STEADY BREEZE.

A WARM FRONT WILL APPROACH FROM THE SOUTHWEST TUESDAY. IT NOW LOOKS
LIKE THE FRONT WILL NOT MAKE IT THROUGH THE AREA UNTIL LATE
AFTERNOON OR EVENING. SOUTHEAST WINDS NORTH OF THE FRONT WILL HOLD
TEMPERATURES DOWN NEAR THE LAKE AND BAY. THERE MAY BE SOME
ELEVATED SHOWERS OR THUNDERSTORMS NORTH OF THE WARM FRONT BUT
THINK THE BEST CHANCE OF RAIN WILL COME LATER WITH THE PASSAGE OF
THE COLD FRONT.

.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY
ISSUED AT 415 AM CDT MON MAY 13 2013

INITIAL FAST-MOVING NEAR ZONAL FLOW ACROSS THE CONUS TO BRING ONE
PACIFIC SYSTEM THRU THE GREAT LAKES TUE NGT BEFORE THE PATTERN
BEGINS TO AMPLIFY AND BECOME SPLIT OFF THE WEST COAST TOWARD NEXT
WEEKEND. THIS PATTERN SHIFT WL BRING AN UPR TROF TO THE WRN CONUS
THU/FRI AND INTO THE CNTRL CONUS SAT/SUNDAY. AS GULF MOISTURE
STARTS TO GET PULLED NORTH INTO THE GREAT LAKES BY THIS UPR TROF...
PCPN CHCS WL BE ON THE INCREASE OVER NE WI. TEMPS ARE EXPECTED TO
BE ABOVE NORMAL THRU THE END OF THE WORK WEEK AND THEN GO BELOW
NORMAL AS PCPN CHCS GO UP.

THE EXTENT OF SHWR/TSTM ACTIVITY REMAINS THE MAIN QUESTION ACROSS
THE REGION FOR TUE NGT AS A CDFNT DRIVES THRU WI. MDLS CONT TO
SHOW ADEQUATE INSTABILITY WITH LI`S SUB-ZERO...STRONG SHEAR AND
STEEP MID-LEVEL LAPSE RATES. HOWEVER...THE ATMOSPHERE TO BE CAPPED
IN ADVANCE OF THE FNT AND GULF MOISTURE IS PRACTICALLY NON-EXISTENT.
BELIEVE THE MDLS ARE OVERHYPING THE DEW PTS (MID TO UPR 50S) WHEN
UPR 40S TO LWR 50S MORE LIKELY. STRONGEST FORCING TO BE OVER NRN
WI...CLOSER TO THE BETTER MID-LEVEL SUPPORT MOVING ACROSS SRN
ONTARIO. HAVE KEPT THE HIGHER POP WORDING FOR NRN WI (NOT AS HI AS
THE GFS WOULD SUGGEST) WITH ONLY A LOW END POP FOR CNTRL/E-CNTRL WI.
AS FOR THE SVR POTENTIAL...IT LOOKS TO BE ISOLATED AT BESET (IF IT
OCCURS AT ALL) DUE TO THE STRONG CAP. CAA AND INCREASED SUBSIDENCE
BEHIND THE CDFNT WL LEAD TO A MOSTLY SUNNY AND BLUSTERY WED ACROSS
THE FCST AREA. DEEP MIXING THRU AROUND 800 MB SHOULD ALLOW MAX TEMPS
TO CLIMB INTO THE LWR TO MID 70S.

THE CDFNT IS FCST TO SETTLE TOWARD THE OHIO RIVER VALLEY AND
EVENTUALLY COME TO A HALT WED NGT AS A WEAK AREA OF HI PRES PUSHES
TOWARD THE WRN GREAT LAKES. THE MDLS DO SHOW A SECONDARY WEAK
BOUNDARY SLIDING SE INTO WI AHEAD OF THE HI PRES...BUT WITH NOT
MOISTURE TO UTILIZE...EXPECT A QUIET NGT UNDER MOSTLY CLEAR TO
PARTLY CLOUDY SKIES. THIS WEAK AREA OF HI PRES DRIFTS ACROSS THE
AREA ON THU KEEPING THE TRANQUIL WEATHER IN PLACE WITH ABOVE
NORMAL TEMPS. LOOK FOR MAX TEMPS TO TOP OUT AGAIN IN THE LWR TO
MID 70S...EXCEPT PERHAPS A BIT COOLER NEAR LAKE MI AS WINDS TURN
ONSHORE.

FCST ISSUES BECOME A FACTOR STARTING AS EARLY AS THU NGT WITH THE
SFC HI MOVING AWAY AND THE NEW UPR TROF HITTING THE WEST COAST.
DOWNSTREAM UPR RIDGING ACROSS THE CNTRL CONUS AND THE BEGINNING OF
SW WINDS INCREASING...SHOULD START TO LIFT THE OLD CDFNT NWD AS A
WRMFNT. EXACTLY HOW FAR NORTH THIS WRMFNT CAN GET WL DETERMINE
WHETHER ANY PCPN CAN REACH ANY PART OF NE WI. ANTICIPATE THE BETTER
CHCS TO OCCUR TO OUR WEST THU NGT WHERE THE LOW-LEVEL JET IS AIMED
AND STRONGER MOISTURE CONVERGENCE IS FOCUSED. THIS UNCERTAINTY
CARRIES OVER INTO FRI AS THE WRMFNT EDGES CLOSER TO WI AND MOISTURE
TRANSPORT STEADILY INCREASES THRU THE DAY. PREFER TO KEEP ONLY LOW
CHC POPS IN THE FCST FOR NOW UNTIL THE MDLS GET A BETTER HANDLE ON
THIS DEVELOPING SITUATION.

PCPN CHCS WOULD GRADUALLY INCREASE OVER NE WI NEXT WEEKEND AS THE
UPR TROF PUSHES EAST INTO THE CNTRL CONUS...THE UPR RDG SLIDES JUST
TO OUR EAST...GULF MOISTURE REACHES WI AND THE WRMFNT SETS UP JUST
TO OUR SOUTH. TOO EARLY TO TRY AND DETERMINE WHICH PERIOD WOULD
HAVE THE BEST CHC OF SEEING PCPN...BUT WOULD EXPECT TO SEE SOME
TSTMS OF THE ELEVATED NATURE. MORE CLOUDS/PCPN CHCS/E-SE COMPONENT
OF THE WIND WL LEAD TO COOLER TEMPS FOR SAT AND SUNDAY WITH
READINGS DIPPING SLIGHTLY BELOW NORMAL FOR THE THIRD WEEK OF MAY.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1227 PM CDT MON MAY 13 2013

A WARM FRONT OVER THE NORTHERN MISSISSIPPI VALLEY WILL
SHIFT EAST ACROSS WISCONSIN LATE THIS AFTERNOON THROUGH THE
EVENING.  IT WILL BRING A COUPLE HOUR PERIOD OF LIGHT RAIN
SHOWERS...BUT CIGS TO REMAIN VFR DUE TO VERY DRY AIR IN THE LOW
LEVELS.  CIGS WILL LOWER A BIT AFTER THE RAIN DEPARTS LATE THIS
EVENING BUT LOW LEVEL WIND SHEAR WILL THEN DEVELOP FOR A PERIOD.
CLOUDS TO CLEAR LATE TONIGHT AND INTO THE MORNING WHICH WILL SET UP
VFR CONDITIONS FOR MUCH OF THE DAY TOMORROW.
&&

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

$$

SHORT TERM.....RDM
LONG TERM......KALLAS
AVIATION.......MPC