Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 211650
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1150 AM CDT THU AUG 21 2014

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SYNOPSIS...
ISSUED AT 353 AM CDT THU AUG 21 2014

PERIODS OF THUNDERSTORMS TODAY AND TONIGHT. HEAVY RAINFALL
POSSIBLE...MAINLY ACROSS CENTRAL AND EAST-CENTRAL WISCONSIN.

UPR PATTERN ACRS NOAM UNDERGOING AMPLIFICATION...WITH TROF OVER
THE INTERMOUNTAIN WEST AND A RIDGE FM THE LOWER MISSISSIPPI VALLEY
NNEWD TOWARD JAMES BAY. AMPLITUDE SHOULD PEAK EARLY IN THE
WEEKEND...THEN ENERGY EJECTING OUT OF THE WRN TROF WL FLATTEN THE
NRN PORTION OF THE RIDGE/SHOVE IT EWD. THOUGH THE EXACT DETAILS
ARE UNCERTAIN...UPR PATTERN WL LIKELY EVOLVE TOWARD A LOWER
AMPLITUDE REGIME WITH FAIRLY BROAD BAND OF WESTERLIES ACRS SRN
CANADA AND THE NRN CONUS BY THE MIDDLE TO LATTER PART OF NEXT
WEEK.

AMPLE MOISTURE WL BE ACRS THE AREA AND AVAILABLE TO BE ACTED UPON
BY SHRTWVS RIDING NEWD OUT OF THE WRN TROF...SO CONSIDERABLE PCPN
IS LIKELY DURING THE PERIOD. THE MAIN PCPN EVENTS WL BE
TDA/TNGT...AND LATE IN THE WEEKEND/EARLY NEXT WEEK. THE PATTERN
FAVORS ABV NORMAL AND POSSIBLY EVEN EXCESSIVE RAINFALL...ESP ACRS
THE SRN/SWRN PART OF THE FCST AREA. THE AIR MASS ACRS THE AREA WL
BE WARM AND HUMID...BUT DAILY TEMPS WL DEPEND HEAVILY ON THE AMNT
OF CLD COVER AND PRECIP. IT LOOKS LIKLE THE WARMEST TEMPS...
POSSIBLY AOA 90F IN SOME PLACES...WL OCCUR LATE IN THE WEEKEND AND
EARLY NEXT WK...WITH READINGS RETURNING TO NORMAL BY THE END OF
THE PERIOD.
&&

.SHORT TERM...TODAY...TONIGHT...AND FRIDAY
ISSUED AT 353 AM CDT THU AUG 21 2014

INGREDIENTS OF EXCESSIVE RAINFALL EVENT COMING INTO PLACE ACRS
THE RGN...THOUGH THE FOCUS APPEARS TO BE JUST S/SW OF THE FCST
AREA. BAROCLINIC ZONE STRETCHED OUT FM THE NRN PLAINS...ESEWD...TO
THE LOWER GREAT LAKES RGN. 850 MB JET IS DIRECTED INTO THE
BAROCLINIC ZONE ACRS MN ATTM...WHERE AN MCS IS IN THE PROCESS OF
ORGANIZING. A NARROW ZONE OF CONVECTION ALSO STRETCHES FM THE MN
CONVECTION ALL THE WAY TO NRN IN. ONGOING WX NOT HANDLED
ESPECIALLY WELL BY THE MODELS... WHICH COMPLICATES THE REST OF THE
FCST AND MAKES ADDING TEMPORAL RESOLUTION TO THE POPS A REAL
CHALLENGE.

EXPECT MN CONVECTION TO CONT TO CONGEAL...HEADING EWD AND THEN
SEWD FOLLOWING CORFIDI VECTORS. IT IS ALMOST CERTAIN TO AFFECT
THE SW PART OF THE FCST AREA...THOUGH THE NEWD EXTENT IS IN
DOUBT. STRUCTURED POPS WITH A SHARP DECR TO THE NE MID-DAY
TDA...THOUGH THAT MAY NEED ADJUSTMENT. THE COMPLEX WL PROBABLY
ARRIVE BEFORE THE ATM HAS MUCH CHC TO DESTABILIZE...AND THE MORE
STRATIFORM NE QUADARANT OF THE COMPLEX IS WHAT WL AFFECT THE FCST
AREA...SO SVR WX SEEMS UNLIKLEY THIS MORNING.

BACK OUT TO THE W...SHRTWV EJECTING OUT OF THE WRN TROF SHOULD
REACH WRN WI ARND 00Z. ASSUMING SOME AIR MASS RECOVERY OCCURS IN
THE WAKE OF THE LEAD COMPLEX...ADDITIONAL STORMS AND PROBABLY
EVENTUALLY ANOTHER MCS WL LIKELY FORM. DEEP LAYER SHEAR WL BE
INCRG BY THEN AS SHRTWV DRIVES THROUGH THE CREST OF THE UPR
RIDGE...INCRG WLY FLOW AT MID-LEVELS. THINK THE GREATEST SVR
THREAT WL BE WITH THESE STORMS...LATE THIS AFTN INTO THIS EVENING.
PRIMARY RISK WL BE DAMAGING WINDS...THOUGH HAIL WL ALSO BE
POSSIBLE. LOW-LEVEL DIRECTIONAL SHEAR WL BE CONSIDERABLE...BUT ITS
DOUBTFUL INDIVIDUAL CELLS WL REMAIN DISCRETE LONG ENOUGH TO HAVE
ENHANCED TORNADO POTENTIAL.

FORCING THEN WANES LATER TNGT AS THE SHRTWV SHIFTS E AND 850 MB
FLOW VEERS WLY. UPR HEIGHTS ACRS THE AREA BUILD FRI AND THE UPR
FLOW BECOMES INCREASINGLY ANTICYCLONIC. HARD TO ABSOLUTELY RULE
OUT PCPN GIVEN THE AVAILABLE MOISTURE AND POSSIBLE BOUNDARIES ACRS
THE RGN...THOUGH LARGE SCALE FORCING IS DEFINITELY UNFAVORABLE. WL
COVER WITH SLGT CHC POPS.

TEMPS TRICKY DUE TO AMNT OF CLDS AND PCPN. TRIMMED MAXES SOME
TDA...BUT STAYED CLOSER TO THE WARMER GUIDANCE PRODUCTS FRI AS NOT
MUCH CONVECTION IS EXPECTED THEN.

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY
ISSUED AT 353 AM CDT THU AUG 21 2014

500MB RIDGE EXPECTED TO DOMINATE ACROSS THE EASTERN UNITED STATES
THIS WEEKEND. MAIN QUESTION IF QUICK RIDGE WILL FLATTEN NEXT WEEK
AS THE CANADIAN/GFS/ECMWF HAS VARIOUS SOLUTIONS ON HOW QUICK RIDGE
WILL FLATTEN BY THE MIDDLE OF NEXT WEEK.

FOR FRIDAY NIGHT...IT SHOULD BE FAIRLY QUIET ALTHOUGH KEPT A
SMALL POP DUE TO LINGERING PRECIPITATION FROM FRIDAY AFTERNOON OR
SHORTWAVE ENERGY THAT COULD KICK OFF AN ISOLATED STORM. WARM FRONT
SHOULD LIFT NORTHWARD ON SATURDAY AND SATURDAY NIGHT...BRINGING
WARM AND HUMID CONDITIONS AND THE CHANCES FOR THUNDERSTORMS. SOME
CONCERN ON NORTHWARD PUSH OF WARM FRONT AS LOW WILL MOVING ACROSS
THE NORTHERN PLAINS/NORTHERN MINNESOTA. DEPENDING ON WHERE FRONT
SETS UP...WILL DETERMINE HOW WARM WE GET SUNDAY AFTERNOON. BEYOND
SUNDAY... A LOT OF UNCERTAINTY IN FRONTAL POSITIONS DUE TO THE
DIFFERENCES IN BREAKING DOWN THE 500MB RIDGE...AND WHERE OUTFLOW
BOUNDARIES MAY ENHANCE THE SOUTHWARD PUSH OF THE FRONT.

DID RAISE MAX TEMPERATURES SEVERAL DEGREES SUNDAY AND A FEW
DEGREES ON MONDAY. DID ADD THE LOCAL INFLUENCES TO MAX/MIN
TEMPERATURE GRIDS DURING THE PERIOD...ADDING A FEW DEGREES TO THE
TYPICAL WARM SPOTS FOR HIGHS EACH DAY AND NUDGED DOWN LOWS A
DEGREE OR TWO IN THE TYPICAL COLDER SPOTS.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1047 AM CDT THU AUG 21 2014

WIDESPREAD MVFR/IFR CLOUDS AND MVFR VSBYS INTO EARLY AFTERNOON
WITH A FEW BREAKS BEHIND DECAYING CONVECTIVE SYSTEM MOVING ACROSS
CENTRAL AND EAST-CENTRAL WI. ADDITIONAL CONVECTION LATE THIS
AFTERNOON/EVE ASSOCIATED WITH MAIN SYSTEM.

&&

.HYDROLOGY...
ISSUED AT 353 AM CDT THU AUG 21 2014

LUCKILY...WE ARE NOW A COUPLE DAYS REMOVED FM THE LAST HEAVY RAIN
EVENT. THAT COMBINED WITH THE FOCUS OF HEAVIEST RAINS MOSTLY
LIKELY BEING S/SW OF THE AREA KEEP THE THREAT FROM RISING TO THE
LEVEL OF REQUIRING A FLASH FLOOD WATCH. WL HANDLE BY ISSUING AN
ESF AND MENTIONING HEAVY RAIN/FLOODING POTENTIAL IN THE HWO.
&&

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

$$

SYNOPSIS.......SKOWRONSKI
SHORT TERM.....SKOWRONSKI
LONG TERM......ECKBERG
AVIATION.......JKL
HYDROLOGY......SKOWRONSKI






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