000
FXUS63 KGRB 181950
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
250 PM CDT SAT MAY 18 2013

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND SUNDAY
ISSUED AT 250 PM CDT SAT MAY 18 2013

PCPN TRENDS TO BE THE PRIMARY FOCUS OVER THE NEXT 24 HOURS AS
ACTIVE WEATHER TO OCCUR OVER THE PLAINS AND THEN ATTEMPT TO MOVE
NEWD TOWARD THE WRN GREAT LAKES.

THE 19Z MSAS SFC ANALYSIS SHOWED AN AREA OF HI PRES OVER WRN
QUEBEC WITH A PAIR OF WEAK LOW PRES AREAS OVER THE PLAINS. A BROAD
SOUTH WIND BETWEEN THESE WEATHER FEATURES WAS BRINGING GULF
MOISTURE NWD WITH DEW PTS IN THE UPR 50S TO LWR 60S OVER THE SRN
HALF OF WI. RADAR MOSAIC SHOWED MOST OF THE SHWR ACTIVITY FROM
THIS MORNING HAD FIZZLED OUT LEAVING SKY CONDITIONS RANGING FROM
MOSTLY CLEAR TO MOSTLY CLOUDY.

WELL-PRONOUNCED UPR TROF WL CONT TO DIG ACROSS THE ROCKIES TNGT AS
THE PAIR OF LOW PRES SYSTEMS TO RESIDE OVER THE PLAINS. GULF
MOISTURE WL BE ABUNDANT AND CONT FEEDING NORTH THRU THE CNTRL
CONUS. AS THE LOW-LEVEL JET INCREASES THRU THE NGT AND SEVERAL
SHORTWAVES EJECT NEWD FROM THE UPR TROF...EXPECT TO SEE ANOTHER
ROUND OF SHWRS/TSTMS DEVELOP OVER THE PLAINS AND MOVE NE INTO THE
UPR MS VALLEY/MIDWEST OVRNGT. FOR NE WI...ALL THIS ACTIVITY SHOULD
REMAIN TO OUR WEST LEAVING THE REGION UNDER PARTLY CLOUDY SKIES
WITH RELATIVELY LIGHT WINDS. THIS SCENARIO COULD LEAD TO FOG
FORMATION AS LOW-LEVEL MOISTURE GRADUALLY INCREASES SO HAVE ADDED
THIS POTENTIAL TO THE FCST. AWAY FROM COOL LAKE MI...INLAND MIN
TEMPS TO BE MILD WITH MOST LOCATIONS ONLY DROPPING INTO THE 50S.

THE UPR TROF IS FCST TO ENTER THE PLAINS AND HAVE A NEGATIVE TILT
TO IT ON SUNDAY WHICH WHEN COMBINED WITH SUFFICIENT INSTABILITY/
SHEAR/MOISTURE...SHOULD LEAD TO AN ACTIVE WEATHER DAY ACROSS THE
PLAINS AND MID-MO VALLEY. THE OVERNIGHT CONVECTION TO OUR WEST WL
TRY TO PUSH EAST INTO WI SUNDAY MORNING...BUT IS ALSO EXPECTED TO
WEAKEN AS THE LOW-LEVEL JET WEAKENS. THE MAIN QUESTION FOR OUR
FCST IS WHETHER THE ATMOSPHERE TO OUR WEST WL BE ABLE TO DESTABILIZE
SUFFICIENTLY TO ALLOW THE NEXT ROUND OF STORMS TO FIRE AND PUSH EWD
SUNDAY AFTERNOON. MOISTURE TO BE PLENTIFUL WITH PW VALUES AROUND
1.5 INCHES (ALMOST 200 PERCENT OF NORMAL) AND DEW PTS CLIMBING
INTO THE LWR 60S. CAPES SHOULD SURPASS 1K J/KG WITH SUB-ZERO LI`S.
IF CONVECTION CAN FIRE TO OUR WEST...THESE STORMS WOULD MOVE INTO
A FAVORABLE ENVIRONMENT AND PRODUCE AT LEAST LOCALLY HEAVY RAIN
WITH A SMALL CHC OF HAIL. HAVE FOCUSED HIGHER POPS OVER CNTRL WI
FOR SUNDAY AFTERNOON...BUT KEPT THE EAST MAINLY DRY AS ANY ACTIVITY
WOULD HOLD OFF TIL SUNSET. A SUMMER FEEL TO THE AIR ON SUNDAY WITH
MAX TEMPS AWAY FROM THE LAKE REACHING THE UPR 70S TO LWR 80S ALONG
WITH SOME HUMIDITY.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY
ISSUED AT 250 PM CDT SAT MAY 18 2013

MODELS ARE IN GOOD AGREEMENT THAT A CUTOFF LOW WILL
SLOWLY DRIFT FROM THE CENTRAL PLAINS TO THE WESTERN GREAT LAKES
BEFORE LIFTING OUT AND WEAKENING BY THE END OF NEXT WEEK. THERE
SHOULD BE PLENTY OF CHANCES FOR SHOWERS AND THUNDERSTORMS. MUCH OF
THE ACTIVITY WILL BE ELEVATED AND NORTH OF A NEARLY STATIONARY
WARM FRONT. SEVERE THREAT IS MOSTLY TO OUR SOUTH NEAR AND SOUTH OF
THE SURFACE WARM FRONT. SLOW MOVING SHOWERS AND THUNDERSTORMS
COULD PRODUCE LOCALLY HEAVY RAIN BUT SOIL HAS BEGUN TO DRY AND
RIVER LEVELS HAVE FALLEN RECENTLY. FLOOD THREAT WOULD PROBABLY BE
LIMITED TO SMALL STREAMS AND URBAN AREAS.

UPPER LOW LIFTS OUT THURSDAY WITH NORTHWEST UPPER FLOW FOLLOWING
WITH COOLER AND DRIER AIR FOR THE END OF THE WEEK. THERE IS SOME
FROST POTENTIAL FRIDAY NIGHT AND SATURDAY NIGHT WITH LIGHT WINDS
AND DRY AIR.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1148 AM CDT SAT MAY 18 2013

WEAKENING BAND OF LIGHT SHOWERS CONTS TO LINGER FROM
NORTH-CENTRAL TO WEST-CENTRAL WI THRU THE AFTERNOON. WHILE MOST
CIGS/VSBYS WL REMAIN VFR...THERE ARE SCATTERED POCKETS OF MVFR CIGS
AS LOW-LEVEL MOISTURE STEADILY INCREASES OVER THE REGION. A NEW
ROUND OF SHWRS/TSTMS ARE EXPECTED TO FIRE OVER THE CNTRL CONUS
THIS EVENING...BUT REMAIN TO OUR WEST DURING THE OVRNGT HOURS.
HOWEVER...SOUTH WINDS ALOFT WL CONT TO PUMP WARM/MOIST AIR INTO WI
WITH DEW PTS CLIMBING INTO THE MID 50S. AS WINDS GO LIGHT TNGT...
ANTICIPATE FOG TO DEVELOP WHICH WOULD SEND VSBYS DOWN INTO THE MVFR
CATEGORY. CANNOT RULE OUT A BRIEF IFR CIG AS WELL OVER THE RHI TAF
SITE WHERE MORE RAIN HAS FALLEN OVER THE PAST 12 HOURS. VFR
CONDITIONS SHOULD RETURN AROUND 15Z SUNDAY AS THE MORNING FOG
BURNS OFF. PCPN CHCS TO INCREASE OVER CNTRL WI BY SUNDAY AFTERNOON
AS A WRMFNT STARTS TO LIFT NWD INTO SW WI.
&&

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

$$

SHORT TERM.....KALLAS
LONG TERM......RDM
AVIATION.......AK