Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 231738
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1238 PM CDT SAT APR 23 2016

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND SUNDAY
ISSUED AT 335 AM CDT SAT APR 23 2016

PCPN TRENDS...A CHANCE OF TSTMS...AND HEAVY RAIN POTENTIAL
TONIGHT INTO SUNDAY...ARE THE MAIN FCST CONCERNS.

CANADIAN HIGH PRESSURE OVER LAKE SUPERIOR AND NE WI WILL SHIFT
EAST TODAY...ALLOWING SOUTH WINDS TO DEVELOP. THIS WILL CAUSE
MILDER AIR TO RETURN TO THE REGION...WITH HIGHS WARMING INTO
THE UPPER 50S TO MIDDLE 60S AWAY FROM LAKE MICHIGAN. WAA WILL
ALSO RESULT IN AN INCREASE IN CLOUDS ACROSS FAR NORTHERN WI
THIS MORNING...AND ACROSS THE NW HALF OF THE FORECAST AREA
THIS AFTERNOON...BUT DRY CONDITIONS WILL PREVAIL.

HAVE SLOWED DOWN THE ARRIVAL OF PCPN TONIGHT...WITH MOST OF
THE SHOWER ACTIVITY EXPECTED AFTER MIDNIGHT...AS A 30+ KT LLJ
DEVELOPS...AND WAA AND MID-LEVEL FRONTOGENETIC FORCING
STRENGTHENS. THE STRONGEST FORCING WILL OCCUR OVER NORTHERN
WI...SO WILL CONTINUE CATEGORICAL POPS NEAR THE UPPER MICHIGAN
BORDER...TAPERING TO CHANCE POPS IN C/EC WI. WEAK ELEVATED
INSTABILITY WORKS INTO SOME OF WESTERN COUNTIES OVERNIGHT...
SO HAVE ADDED A SLGT CHC OF TSTMS THERE.

A FRONTAL BOUNDARY WILL STRENGTHEN OVER THE REGION ON SUNDAY...
WITH HIGH TEMPERATURES EXPECTED TO RANGE FROM THE UPPER 40S
IN THE FAR NORTH TO THE LOWER 70S IN PARTS OF CENTRAL WI.
MOISTURE WILL CONTINUE TO STREAM INTO THE REGION...WITH
PRECIPITABLE WATER VALUES RISING TO 1.0 TO 1.3 INCHES...AND H8
DEW POINTS INCREASING TO AROUND 10 C IN C/EC WI. STRONG ISENT
LIFT AND FRONTOGENETIC FORCING...AS WELL AS SOME SHORT-WAVE
ENERGY...WILL RESIDE OVER THE NORTHERN TWO-THIRDS OF THE CWA...
LEADING TO THE POTENTIAL FOR HEAVY RAINFALL. THE BEST INSTABILITY
WILL DEVELOP OVER C/EC WI...SO THE GREATEST THREAT OF TSTMS
WILL BE OVER OUR SOUTHERN COUNTIES.

.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY
ISSUED AT 335 AM CDT SAT APR 23 2016

MODELS CONTINUE TO SHOW A COOL AND WET PATTERN FOR THE UPCOMING
WEEK.

A COLD FRONT PUSHING SOUTH ACROSS THE AREA...COMBINED WITH
APPROACHING SURFACE AND 500MB LOWS...WILL BRING RAIN TO THE AREA
SUNDAY NIGHT AND MONDAY. MODELS SHOWED THE AXIS OF HIGHEST QPF
NEAR THE WISCONSIN/UPPER MICHIGAN BORDER SUNDAY NIGHT THROUGH
MONDAY MORNING...BEFORE SHIFTING SOUTH OF THE FORECAST AREA MONDAY
AFTERNOON. LOCATIONS IN THE VICINITY OF THE WI/UP BORDER ARE
EXPECTED TO PICK UP AN INCH OR MORE OF RAIN 00Z-18Z MONDAY. THERE
WILL ALSO BE SOME CAPE/INSTABILITY...MAINLY ACROSS THE SOUTHERN
HALF OF THE AREA...SO A CHANCE FOR THUNDER HAS BEEN INCLUDED
SUNDAY NIGHT AND MONDAY. RAIN CHANCES TAPER OFF MONDAY NIGHT AS
THE SURFACE AND UPPER LOWS MOVE AWAY...AND TUESDAY THROUGH TUESDAY
NIGHT SHOULD BE DRY AS A MID LEVEL RIDGE AND SURFACE HIGH PRESSURE
MOVE ACROSS/NORTH OF THE REGION. RAIN CHANCES RETURN AND INCREASE
WEDNESDAY THROUGH THURSDAY WITH THE APPROACH OF THE NEXT SURFACE
SYSTEM AND 500MB LOW/TROUGH. THESE FEATURES SHOULD MOVE THROUGH
RELATIVELY QUICKLY SO DRY WEATHER IS EXPECTED TO RETURN BY FRIDAY.

CLOUDS AND RAIN WILL KEEP TEMPERATURES DOWN AND NORTHEAST/EASTERLY
SURFACE FLOW SHOULD KEEP IT COOL ON THE DRY DAYS. AS A
RESULT...DAYTIME HIGHS ARE FORECAST TO BE AROUND 10 DEGREES BELOW
NORMAL FOR MUCH OF THE LONG TERM.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1238 PM CDT SAT APR 23 2016

SCATTERED TO BROKEN CLOUDS BETWEEN 2500 AND 3500 FEET
SHOULD DISSIPATE BY SUNSET. LOWER CLOUDS AND SHOWERS ARE EXPECTED
LATE TONIGHT AND SUNDAY AS A LOW PRESSURE SYSTEM APPROACHES FROM
THE WEST. IFR CONDITIONS EXPECTED NORTH OF A WISCONSIN RAPIDS TO
MARINETTE LINE AFTER 10Z SUNDAY WITH MVFR FURTHER SOUTH.
&&

.HYDROLOGY...
ISSUED AT 335 AM CDT SAT APR 23 2016

WILL NEED TO KEEP AN EYE ON THE HYDRO SITUATION OVER
THE EARLY PART OF NEXT WEEK...AS MOST MODELS SHOW POTENTIAL FOR
2-3 INCHES OF RAIN OCCURRING OVER NORTHERN WI SUNDAY INTO MONDAY.
THIS WILL CAUSE RISES ON DOWNSTREAM RIVERS...THOUGH THE FULL
IMPACT IS UNCERTAIN AT THIS TIME. WILL CONTINUE TO MENTION HEAVY
RAINFALL AND MINOR FLOODING POTENTIAL IN THE HAZARDOUS WEATHER
OUTLOOK...AND LET THE DAY SHIFT DECIDE IF A HYDROLOGIC OUTLOOK
NEEDS TO BE ISSUED.
&&

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

$$

SHORT TERM.....KIECKBUSCH
LONG TERM......MG
AVIATION.......RDM
HYDROLOGY......KIECKBUSCH



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