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000
FXUS63 KGRB 111929
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
229 PM CDT SAT MAY 11 2013

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND SUNDAY
ISSUED AT 228 PM CDT SAT MAY 11 2013

THE LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW SURFACE LOW
PRESSURE AND COLD FRONT ACROSS LOWER MICHIGAN THIS AFTERNOON.
BEHIND THE FRONT...A DEEP SHORTWAVE TROUGH COMBINED WITH STEEPENING
LOW LEVEL LAPSE RATES AND AMPLE LOW LEVEL MOISTURE ARE GENERATING
SCATTERED RAIN/SNOW/SLEET SHOWERS OVER EASTERN MINNESOTA TO CENTRAL
WISCONSIN...WHICH SHOULD ADVECT INTO EASTERN WISCONSIN LATER THIS
AFTERNOON. SOLID STRATUS DECK HAS HAD A DIFFICULT TIME ADVECTING
SOUTHWARD...BUT NOW EXTENDS FROM NORTHERN WISCONSIN TO HUDSON BAY.
STILL EXPECT THIS STRATUS DECK TO SAG SOUTH FOR THE REST OF THE
AFTERNOON...DRIVEN BY GUSTY NNW WINDS. FORECAST CONCERNS ARE
PRECIP TRENDS AND TEMPS...INCLUDING FROST/FREEZE HEADLINES.

TONIGHT...THE STRONG SHORTWAVE TROUGH WILL MOVE EAST OVER THE
CENTRAL GREAT LAKES THIS EVENING AND INTO FAR EASTERN ONTARIO
OVERNIGHT.  BEHIND THE SHORTWAVE...A WIDESPREAD STRATUS DECK OVER
NORTHERN WISCONSIN AND ONTARIO SHOULD ADVECT SOUTH WITH THE HELP OF
MODERATELY STRONG NORTHERLY FLOW AND INCREASING INSTABILITY OF LAKE
SUPERIOR.  WITH CYCLONIC FLOW AND COLD ADVECTION...TRENDED
CONSIDERABLY MORE CLOUDY WITH THE SKY COVER TONIGHT.  STILL THINK
WILL SEE CLEARING SKIES AFTER MIDNIGHT OVER CENTRAL AND NORTHEAST
WISCONSIN AS MOISTURE IN THE COLUMN DRIES OUT.  TEMPS THIS MORNING
OVER NORTHERN MINNESOTA WERE IN THE 32-34 DEGREE RANGE...WHICH WILL
BE THE AIRMASS ADVECTING INTO THE AREA TONIGHT.  WITH NO CHANCE OF
DECOUPLING AND CLOUDS POTENTIALLY STICKING AROUND LONGER...HAVE
RAISED LOW TEMPS TOWARDS THE ECMWFBC GUIDANCE...WHICH IS USUALLY ONE
OF THE BETTER PERFORMING TEMP GUIDANCES.  SINCE FROST IS A MINIMAL
CONCERN DUE TO WINDS REMAINING UP...HEADLINES ARE REALLY A FREEZE OR
NO FREEZE SCENARIO.  WITH TEMPS ONLY BRIEFLY REACHING 32 DEGREES
LATE TONIGHT IN CENTRAL WISCONSIN...COORDINATION RESULTED IN A
DECISION TO GO WITH NO HEADLINES TONIGHT...BUT WILL STILL ADVISE
PEOPLE TO TAKE PRECAUTIONS WITH THEIR SENSITIVE PLANTS OVER CENTRAL
WISCONSIN IN THE HWO...IN CASE TEMPS DO FALL MORE THAN EXPECTED.
WILL GO WITH LOWS IN THE UPPER 20S NORTH...TO 32 DEGREES OVER
CENTRAL WISCONSIN...TO THE MID 30S NEAR LAKE MICHIGAN.

SUNDAY...LOW PRESSURE WILL MOVE FURTHER EAST INTO QUEBEC WHILE HIGH
PRESSURE BUILDS INTO THE REGION.  THINK BROKEN CLOUD COVER WILL
CONTINUE TO RESIDE OVER NORTH-CENTRAL WISCONSIN TO START THE MORNING
WHICH SHOULD RETREAT TO THE NORTH.  WITH DIURNAL HEATING
THOUGH...RATHER FLAT DIURNAL CU SHOULD DEVELOP BY LATE MORNING AND
THEN MIX OUT IN THE AFTERNOON.  HIGHS TO TOP OUT IN THE MIDDLE 40S TO
LOWER 50S.

.LONG TERM...SUNDAY NIGHT THROUGH SATURDAY
ISSUED AT 228 PM CDT SAT MAY 11 2013

MAIN FCST CONCERNS INCLUDE FREEZE HEADLINES FOR SUNDAY NIGHT...THE
POTENTIAL FOR SEVERE TSTMS LATE TUESDAY INTO TUESDAY NIGHT...AND
TEMPERATURES THROUGH THE PERIOD.

SFC HIGH PRESSURE WILL RESIDE OVER THE FORECAST AREA ON SUNDAY NIGHT.
CLEAR SKIES AND LIGHT/CALM WINDS WILL ALLOW TEMPS TO DROP BLO FREEZING
ACROSS ALL BUT THE LAKESHORE AREAS. WE HAVE NOT STARTED UP FROST/FREEZE
HEADLINES OVER NORTHERN WI YET...SO NO HEADLINES THERE DESPITE MIN TEMPS
IN THE LOW TO MID 20S. WILL KEEP THE FREEZE WATCH GOING ACROSS THE
SOUTHERN HALF OF THE CWA...AND WOULD ANTICIPATE THAT THIS WILL BE
UPGRADED A FREEZE WARNING WITH THE 4 AM SUNDAY FCST PACKAGE.

AN UPPER LEVEL RIDGE WILL BUILD OVER THE REGION MONDAY INTO TUESDAY...
WITH LOW-LEVEL WAA KICKING IN MONDAY INTO MONDAY NIGHT. THE WAA SURGE
WILL BRING INCREASING CLOUDS...WITH A CHANCE OF SHOWERS OVER OUR WSTRN
COUNTIES ON MONDAY...AND OVER THE ENTIRE CWA MONDAY NIGHT.

ON TUESDAY...A WARM FRONT IS EXPECTED TO LIFT NORTHWARD INTO CENTRAL
WI DURING THE AFTERNOON. TEMPERATURES WILL BE A TOUGH CALL...AS CLOUDS
AND EAST WINDS NORTH OF THE FRONT COULD HOLD READINGS IN THE 50S/60S
OVER THE LAKESHORE AND FAR NE WI...WHILE MIXING THROUGH 850 MB OVER
CENTRAL WI WOULD BE SUPPORTIVE OF HIGHS IN THE UPPER 80S/LOWER 90S
IN THE FAR SW PART OF THE CWA. NOT CONFIDENT ENOUGH TO GO WITH THAT
LARGE OF A GRADIENT OVER THE FORECAST AREA...BUT WILL HAVE UPPER 50S/
LOWER 60S NEAR THE LAKE...WITH INLAND LOCATIONS RANGING FROM THE UPPER
60S OVER FAR NE WI TO THE LOWER 80S IN CENTRAL WI.

WILL CARRY A SLGT CHC/CHANCE OF TSTMS NORTH OF THE WARM FRONT ON
TUESDAY...AS THE MODELS SHOW A SURGE OF INSTABILITY ARRIVING DURING
THE AFTERNOON...BUT ALSO SOME POTENTIAL CAPPING. AM CONCERNED ABOUT
THE POTENTIAL FOR SVR TSTMS TUESDAY NIGHT...AS THE WARM FRONT LIFTS
NORTH...FOLLOWED BY THE COLD FRONTAL PASSAGE OVERNIGHT. MODELS ARE
IN DECENT AGREEMENT ON MUCAPE INCREASING TO 1500-2000 J/KG...
ALONG WITH DEEP LAYER SHEAR OF 45-55 KNOTS...0-3 KM HELICITIES OF
300-500...AND MID-LEVEL LAPSE RATES INCREASING TO 7-7.5 C/KM. THE
GFS MODEL SEEMS TO DEPICT THIS BEST...WITH A BULLSEYE OF QPF OVER
THE NE HALF OF THE FORECAST AREA. WILL ADD A MENTION OF POSSIBLE
SVR TSTMS LATE TUESDAY INTO TUESDAY NIGHT TO THE HAZARDOUS WEATHER
OUTLOOK.

THE COLD FRONT IS EXPECTED TO SHIFT SOUTH OF THE AREA WEDNESDAY INTO
THURSDAY NIGHT...RESULTING IN A GENERAL LULL IN THE PCPN. THE FRONT
WILL LIFT BACK TO THE NORTH LATE IN THE WEEK...BRINGING THE CHANCE
OF TSTMS BACK INTO THE REGION ON FRI/SAT.

ALTHOUGH TEMPERATURES WILL START OFF ON THE COOL SIDE...THEY SHOULD
AVERAGE ABOVE NORMAL FROM TUESDAY THROUGH SATURDAY.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1237 PM CDT SAT MAY 11 2013

A STRONG UPPER LEVEL DISTURBANCE WILL PASS ACROSS THE
AREA THROUGH THIS EVENING.  WIDESPREAD LOW END VFR CIGS UPSTREAM
COMBINED WITH AFTERNOON INSTABILITY WILL LEAD TO ISOLATED TO
SCATTERED RAIN SHOWERS FROM EARLY THIS AFTERNOON THROUGH ABOUT
MID-EVENING.  SNOW WILL LIKELY MIX IN WITH THE RAIN OVER N-C
WISCONSIN...WHICH COULD DROP VSBYS TO MVFR LEVELS.
OTHERWISE...GUSTY NW WINDS WILL PREVAIL UNTIL SUNSET.  CLOUDS TO
STICK AROUND OVER N-C WISCONSIN FOR MUCH OF THE NIGHT AS FLOW WILL
REMAIN OFF LAKE SUPERIOR.  NOT AS CLEAR CUT OVER CENTRAL AND
NORTHEAST WISCONSIN.  SHARP CYCLONIC FLOW AND COLD LOW LEVEL
TEMPERATURES ARGUES FOR CLOUDS TO STICK AROUND LONGER THAN WHAT THE
MODELS SUGGEST.  WILL TREND THAT DIRECTION...THOUGH CIGS SHOULD
REMAIN VFR.  A STEADY WIND OF AROUND 10 KTS SHOULD PREVENT FROST
FROM FORMING THOUGH TEMPS WILL BE AROUND FREEZING.  SCT-BKN CLOUD
COVER TOMORROW BUT NW WINDS WILL REMAIN GUSTY.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
FREEZE WATCH FROM LATE SUNDAY NIGHT THROUGH MONDAY MORNING FOR
WIZ020-030-031-035>040-045-048>050-073-074.
&&

$$

SHORT TERM.....MPC
LONG TERM......KIECKBUSCH
AVIATION.......MPC