Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 291944
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
244 PM CDT FRI AUG 29 2014

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND SATURDAY
ISSUED AT 243 PM CDT FRI AUG 29 2014

THE MAIN FCST FOCUS CONTS TO BE THE HEAVY RAIN POTENTIAL OVER THE
NEXT 24 HOURS AS A MOISURE-LADEN ATMOSPHERE AWAITS A TRIGGER.

THE 19Z MSAS SFC ANALYSIS INDICATED A BROAD AREA OF WEAK LOW PRES
OVER THE UPR MS VALLEY. A WRMFNT EXTENDED EWD THRU CNTRL WI...
WHILE A CDFNT STRETCHED SW FROM CNTRL MN TO CNTRL NEBRASKA. MUCH
OF NE WI RESIDED IN A QUIET ZONE BETWEEN PCPN TO THE NORTH
ASSOCIATED WITH THE 8H WRMFNT...PCPN TO THE WEST ASSOCIATED WITH
THE SFC LOW/CDFNT AND PCPN TO THE SOUTH AND EAST ASSOCIATED WITH A
SHORTWAVE. THE LACK OF PCPN HAS ALLOWED FOR SOME CLEARING TO TAKE
PLACE WITH SOME LOCATIONS SOARING INTO THE 80S.

SHWRS AND TSTMS ARE STILL EXPECTED TO OVERSPREAD THE REGION THIS
EVENING AS THE WEAK SFC LOW/ASSOCIATED CDFNT MOVE INTO THE WRN
GREAT LAKES...WITH A TRAILING SHORTWAVE TROF PUSHING INTO THE UPR
MS VALLEY/MIDWEST. PLENTY OF LOW-LEVEL MOISTURE IN PLACE OVER NE
WI WITH DEW POINTS IN THE 60S TO AROUND 70 DEGS AND PW VALUES AT
1.5"+. AIR MASS TO ALSO BE UNSTABLE THIS EVENING WITH CAPES
BETWEEN 1K AND 2K J/KG AND LI`S AROUND -5...ALTHO INSTABILITY WL
WEAKEN A BIT UPON SUNSET. NEVERTHELESS...EXPECT TO SEE PCPN EXPAND
IN COVERAGE THIS EVENING...ESPECIALLY AS A JET STREAK LIFTS NE
FROM THE MIDWEST AND CREATES A COUPLED JET STRUCTURE WITH ANOTHER
JET MAX OVER CNTRL ONTARIO. IN GENERAL...ANTICIPATE PCPN AMOUNTS
TO AVERAGE IN THE 0.50 TO 1" RANGE...BUT WITH SO MUCH MOISTURE IN
THE AIR...WOULD NOT BE SURPRISED TO SEE SOME TOTALS SURPASS 1.5"
BY DAYBREAK. AN ESF HAS ALREADY BEEN ISSUED HIGHLIGHTING THE
THREAT FOR HEAVY RAIN AND POSSIBLE FLOODING OF URBAN AREAS/NEAR
RIVERS AND STREAMS. MILD NGT ON TAP WITH MIN TEMPS ONLY IN THE LWR
TO MID 60S NORTH...MID TO UPR 60S SOUTH.

SHWRS/TSTMS TO BE ONGOING INTO SAT AS THE CDFNT DRIVES THRU THE
REST OF WI ACCOMPANIED BY THE SHORTWAVE TROF. EVEN THO WE LOSE THE
UPR JET SUPPORT...THERE IS STILL PLENTY OF LIFT (CDFNT)...FORCING
(TROF) AND MOISTURE AVAILABLE FOR PCPN TO CONT THRU SAT MORNING
BEFORE GRADUALLY DIMINISHING FROM WEST TO EAST DURING THE
AFTERNOON. ANOTHER ONE-QUARTER TO ONE-HALF INCH OF RAINFALL IS
POSSIBLE WHICH COULD AGGRAVATE ANY FLOODING (IF THERE IS ANY). MAX
TEMPS ARE EXPECTED TO RANGE FROM AROUND 70 DEGS NORTH TO THE UPR
70S SOUTH.

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY
ISSUED AT 243 PM CDT FRI AUG 29 2014

PCPN TRENDS FOR THE END OF THE LABOR DAY WEEKEND WILL BE THE
MAIN FCST CONCERN FOR THE EXTENDED PERIOD.

WILL MAINTAIN SMALL POPS OVER FAR NE WI SATURDAY EVENING...AS A
S/W TROF MOVES THROUGH...BUT WEAK RIDGING ALOFT SHOULD BRING DRY
CONDITIONS OVERNIGHT INTO SUNDAY. PATCHY FOG IS ANTICIPATED SAT
NGT...AS WINDS DECREASE AND PARTIAL CLEARING OCCURS. PCPN SHOULD
MOVE INTO NW WI LATE SUNDAY AFTERNOON...AS A LOW-LEVEL JET BECOMES
FOCUSED THERE...BUT WILL CONTINUE TO HOLD OFF POPS FOR OUR WSTRN
COUNTIES UNTIL EVG. WAA AND PARTLY CLOUDY SKIES SHOULD ALLOW TEMPS
TO WARM INTO THE UPPER 70S AND LOWER 80S AT MOST LOCATIONS.

A S/W TROF AND UPPER LEVEL JET ENERGY WILL APPROACH THE REGION
SUNDAY NIGHT...WITH A 40-50 KT LLJ RAMPING UP AHEAD OF THE
ADVANCING COLD FRONT. MOST OF THE DYNAMICS WILL MOVE THROUGH LATE
SUNDAY NIGHT AND MONDAY MORNING...SO THE HIGHEST POPS (LIKELY) AND
QPF WILL BE FOCUSED DURING THAT TIME FRAME. SUSPECT THAT ABUNDANT
CLOUD COVER AND WIDESPREAD SHOWER ACTIVITY WILL LIMIT INSTABILITY
ON MONDAY...SO NOT EXPECTING ANY ORGANIZED SEVERE THUNDERSTORMS...
DESPITE THE PASSAGE OF THE COLD FRONT. TORRENTIAL RAINFALL AND
GUSTY WINDS MAY ACCOMPANY THE STRONGER STORMS. HAVE LOWERED POPS
ON MONDAY AFTERNOON...AS THE BEST S/W ENERGY TRACKS THROUGH THE
LAKE SUPERIOR REGION...AND A DRY SLOT PUNCHES INTO THE FORECAST
AREA.

FAST ZONAL FLOW WILL SET UP OVER THE WESTERN GREAT LAKES FOR THE
REST OF THE WEEK. A WEAK S/W TROF MAY BRING ISOLD/SCT SHOWERS ON
TUESDAY...BUT TUESDAY NIGHT AND WEDNESDAY LOOK DRY. MODELS ALL
SUGGEST THAT A WEST-EAST ORIENTED FRONTAL BOUNDARY WILL SET UP
ACROSS THE REGION FOR THE END OF THE WEEK...BUT THE POSITION AND
MOVMT OF THE BOUNDARY VARIES FROM MODEL TO MODEL. THE PRESENCE OF
THE BOUNDARY...PLUS THE RETURN OF A MOIST AND UNSTABLE AIR
MASS...SUPPORTS THE MENTION OF CHC POPS THURSDAY INTO FRIDAY.
CONFIDENCE IN THE OVERALL DETAILS IS LOW.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1235 PM CDT FRI AUG 29 2014

WRMFNT CUTTING ACROSS CNTRL SECTIONS OF WI THIS AFTERNOON IS
EXPECTED TO CONT MOVING NORTH AND BE THE PRIMARY FOCUS FOR
ADDITIONAL SHWRS/ISOLATED TSTMS. VSBYS HAVE BEEN REDUCED TO IFR
CONDITIONS NORTH OF THIS FNT...BUT EXPECT AN IMPROVEMENT TO AT
LEAST MVFR CONDITIONS LATER THIS AFTERNOON ONCE THE FNT CLEARS THE
AREA. BRIEF CLEARING BEHIND THE WRMFNT OVER THE SRN HALF OF WI
SHOULD CONT WITH ONLY AN ISOLATED TSTM EXPECTED AS THE ATM HAS
BECOME UNSTABLE. THE MAIN ACTION SHOULD COME TNGT AS A WEAK SFC
LOW AND UPPER LEVEL TROUGH OF LOW PRESSURE MOVE TOWARD WI. PLENTY
OF MOISTURE AVAILABLE...THUS ANTICIPATE A ROUND OF SHWRS/TSTMS TO
MOVE THRU NE WI TNGT AND WHEN ITS NOT RAINING...FOG WL BE AN
ISSUE. LOOK FOR BOTH CIGS/VSBYS TO SETTLE INTO THE IFR CATEGORY
WITH LOCALIZED LIFR CONDITIONS IN THICKER FOG. PCPN CHCS WOULD
THEN CARRY OVER INTO SAT AS THE UPPER TROUGH MOVES THRU THE
REGION. THERE MAY BE SOME MODEST IMPROVEMENT IN BOTH THE CIGS AND
VSBYS BY AFTERNOON WITH MVFR CONDITIONS ANTICIPATED.
&&

.HYDROLOGY...
ISSUED AT 243 PM CDT FRI AUG 29 2014

HAVE ALREADY ISSUED THE HYDROLOGIC OUTLOOK WITH THE CONCERN OF
FLOODING OF URBAN AREAS/RIVERS AND STREAMS FOR TNGT INTO SAT.
THERE IS PLENTY OF MOISTURE IN THE ATM FOR SHWRS/TSTMS TO FEED OFF
OF AND WITH POSSIBLE TRAINING OF PCPN...RAINFALL AMOUNTS COULD BE
QUITE IMPRESSIVE BY THE TIME THE PCPN DIMINISHES LATE SAT/SAT NGT.
MOST OF NE WI WL END UP WITH BETWEEN 1 TO 2 INCHES OF RAIN WITH
LOCALLY HIGHER AMOUNTS POSSIBLE.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
BEACH HAZARDS STATEMENT UNTIL 10 PM CDT THIS EVENING FOR WIZ022-
040-050.
&&

$$

SHORT TERM.....AK
LONG TERM......TSK
AVIATION.......AK
HYDROLOGY......AK





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