Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 231749
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1249 PM CDT SAT AUG 23 2014

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SYNOPSIS...
ISSUED AT 408 AM CDT SAT AUG 23 2014

WARM AND HUMID WEATHER EXPECTED FOR THE WEEKEND.

AMPLIFICATION PHASE OF UPR PATTERN WL SOON PEAK...WITH DEEP TROF
OVER THE INTERMOUNTAIN WEST...AND A STG RIDGE FM THE LOWER
MISSISSIPPI VALLEY THROUGH NWRN QUEBEC. FCST AREA WL INITIALLY BE
DIRECTLY UNDER THE SHARP RIDGE AXIS. BUT SHRTWV EJECTING OUT OF
THE WRN TROF WL SHOVE THE NRN PORTION OF THE RIDGE EWD STARTING
LATE IN THE WEEKEND. THAT WL RESULT IN FCST AREA COMING UNDER
INFLUENCE OF FAIRLY STG SWLY FLOW BY EARLY NEXT WEEK. THE PATTERN
IS EXPECTED TO BECOME MORE PROGRESSIVE AND DEAMPLIFY LATER IN THE
WEEK...LEAVING A BROAD FAIRLY LOW AMPLITUDE BAND OF WESTERLIES
ACRS SRN CANADA AND THE NRN CONUS BY THE END OF THE FCST PERIOD.

THE PROXIMITY OF THE UPR RIDGE WL KEEP A WARM AND MOIST AIR MASS
ACRS THE AREA THROUGH EARLY NEXT WEEK. THAT WL RESULT IN ABV
NORMAL TEMPS AND HUMID CONDITIONS FOR THE FIRST HALF OF THE FCST
PERIOD. TEMPS SHOULD THEN TREND BACK CLOSER TO NORMAL DURING THE
LATTER PART OF THE PERIOD.

ESTIMATING PCPN IS A BIT TRICKY. AMPLE MOISTURE WL BE ACRS THE
AREA TO FUEL PRECIPITATION. FORCING WL BE SPARSE EARLY AS THE UPR
RIDGE DOMINATES...SO THE COVERAGE OF THE PRECIPITATION WL BE
LIMITED. BUT VERY MOIST AIR COMBINED WITH WK SHEAR WL RESULT IN
EFFICIENT PRECIPITATION PRODUCTION FROM CONVECTION...AND INTENSE
DOWNPOURS. INDICATIONS ARE THAT THE FRONTAL SYSTEM WL BE SLOW TO
CLEAR THE AREA DURING THE LATTER PART OF THE FCST PERIOD...SO MORE
WIDESPREAD SIG PCPN LOOKS POSSIBLE AT THAT TIME. GIVEN THESE
FACTORS...AOA NORMAL AMNTS SEEM LIKELY.
&&

.SHORT TERM...TODAY...TONIGHT...AND SUNDAY
ISSUED AT 408 AM CDT SAT AUG 23 2014

FOG WIDESPREAD ACRS THE AREA AGAIN EARLY THIS MORNING...THOUGH
VSBYS AT MOST LOCATIONS WERE NOT AS LOW AS YDA. THE ONLY AREA
WHERE VSBYS SEEMED LOW ENOUGH TO IMPACT TRAVEL WAS NEAR THE LAKE.
PLAN TO CONT TO HANDLE WITH SPS/S UNLESS CONDITIONS WORSEN
SIGNIFICANTLY.

PCPN CHCS AGAIN TOUGH TO DEAL WITH IN THE FCST. QUITE A FEW SHRA
DEVELOPED OVERNIGHT. A SML CLUSTER OF TSRA BROUGHT TORRENTIAL
RAINS TO THE FLD AREA...POSSIBLY EXTENDING INTO BORDER AREAS OF
WINNEBAGO COUNTY. THE SHOWERS HAVE JUST ABOUT ENDED...BUT WITH WK
ISENT UPGLIDE CONTG AT LOW-LEVELS...CAN/T RULE OUT SOMETHINNG
REFORMING. LIKE YDA...PLAN TO CARRY LOW POPS BUT MENTION ISOLD
SHRA THIS MORNING AND ISOLD TSRA IN THE AFTN. THE SW PORTION OF
THE FCST AREA MAY HAVE A LITTLE BETTER CHC FOR PCPN LATE THIS AFTN
AS WK SHRTWV AND POSSIBLE SOME REMNANTS OF THE CURRENT PLAINS
CONVECTION COULD REACH THAT AREA. OTHER THAN A SLGT CHC OF TSRA
OVER THE NW CORNER OF THE FCST AREA LATE...STUCK WITH DRY FCST FOR
SUN. FCST SOUNDINGS SUGGEST ENOUGH WARMING IN THE 800-700 MB LAYER
TO PROVIDE AN EFFECTIVE CAP.

SOME UNCERTAINTY WITH THE TEMP FCST AS WELL. GENERALLY WENT AOA
GUIDANCE VALUES TDA WITH THE EXPECTATION THAT THE FOG/ST WL
DISSIPATE AND AT LEAST SOME SUN WL OCCUR THIS AFTN. ALSO THINK
GUIDANCE MAY BE TOO COOL BECAUSE MANY OF THE MODELS ARE PRODUCING
TOO MUCH PCPN/CLOUD COVER. IF CLDS DON/T DECR AS EXPECTED...THE
FCST MAX TEMPS WL END UP TOO HIGH. WARMING TEMPS ALOFT AND
PROBABLY EVEN FEWER CLDS SUPPORTED GOING AOA GUIDANCE AGAIN ON
SUNDAY. GUIDANCE MINS FOR TNGT ALSO SEEMED A BIT COOL CONSIDERING
LAST NIGHTS LOWS AND CURRENT TEMPS.

PATCHY FOG MAY FORM AGAIN TNGT...BUT WITH A LITTLE MORE WIND IN
THE BOUNDARY LAYER WE ARE MORE LIKELY TO END UP WITH A ST LAYER
THAN DENSE FOG.

.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY
ISSUED AT 408 AM CDT SAT AUG 23 2014

LITTLE CHANGE IN THE MEAN FLOW ADVERTISED BY THE MDLS WITH AN
INITIAL HIGHLY-AMPLIFIED FLOW THRU TUE AND THEN A LESS AMPLIFIED
FLOW THRU LATE NEXT WEEK. THE MAIN PLAYERS AT THE ONSET OF THE
FCST TO BE A LARGE UPR RDG FROM THE DEEP SOUTH TO NEW ENGLAND AND
A BROAD UPR TROF FROM S-CNTRL CANADA TO CA. WARM/MUGGY/UNSETTLED
WEATHER TO CONT THRU MON BEFORE THE PASSAGE OF A CDFNT ON MON
GRADUALLY BRINGS COOLER/LESS HUMID CONDITIONS TO THE REGION WITH
THE HELP OF A MID-WEEK SHORTWAVE TROF WHICH WL BRING MORE PCPN TO
THE AREA.

PCPN CHCS TO INCREASE FROM WEST TO EAST AHEAD OF A CDFNT SUNDAY
NGT. DESPITE THE BETTER FORCING PASSING TO OUR NORTH ASSOCIATED
WITH AN UPR LOW HEADED TOWARD LAKE WINNIPEG...THE ABUNDANT LOW-
LEVEL MOISTURE ACROSS WI WL LEAD TO THE POTENTIAL OF HEAVY RAIN
TOWARD CNTRL WI AFTER MIDNGT. SEVERE RISK LOOKS MINIMAL MAINLY DUE
TO THE HIGH FREEZING LEVELS. THERE COULD STILL BE SOME SMALL
HAIL...BUT THE HEAVY RAIN THREAT REMAINS THE MAIN CONCERN WITH PW
VALUES RUNNING BETWEEN 1.5 AND 2.O INCHES.

THE MOVEMENT OF THIS CDFNT CONTS TO BE A PROBLEM HEADED INTO MON
AS THE LARGE UPR RDG ANCHORED FROM TX TO NEW ENGLAND...ESSENTIALLY
ACTS AS ROADBLOCK. THE MDLS HAVE VARIOUS SOLUTIONS AS TO HOW FAR
SOUTH TO TAKE THE FNT BEFORE PULLING UP STNRY. IF THE CDFNT BEGINS
TO STALL ACROSS CNTRL WI...THIS COULD SET-UP A FAVORABLE
CONVERGENCE CORRIDOR WITH WIDESPREAD SHWRS AND TSTMS. IF THE CDFNT
CAN CONT TO SAG SOUTH THRU THE DAY...NRN WI COULD ACTUALLY SEE
PCPN END MON AFTERNOON. MAJORITY OF THE MDLS FAVOR THE LATTER
SOLUTION...THUS HAVE PLACED HIGHER POP VALUES OVER E-CNTRL WI AND
TAPERED POPS OFF TO ONLY SLGT CHC NORTH. MON SHOULD ALSO BE THE
LAST OF THE VERY WARM/HUMID DAYS WITH MOST LOCATIONS IN THE 80-85
DEG RANGE.

UNDER THE ASSUMPTION THAT THIS CDFNT CAN SAG INTO SRN WI (OR EVEN
EXTREME NRN IL) BEFORE STALLING...THIS WOULD LEAVE NE WI WITH NO
DISCERNABLE SURFACE OF UPR LEVEL WEATHER FEATURES TO GENERATE
ADDITIONAL PCPN. IF ANYTHING...THE ATMOSPHERE WL RELOAD OVER THE
PLAINS AHEAD OF THE PRIMARY UPR TROF MOVING INTO THE ROCKIES. JUST
NOT CONFIDENT ENUF YET TO PULL THE SLGT CHC POPS JUST YET...BUT
EXPECT MOST OF THE FCST AREA TO BE DRY. THIS STALLED BOUNDARY
LOOKS TO BECOME MORE ACTIVE (AND PERHAPS LIFT A TAD NORTH) ON TUE
AS THE UPR TROF MOVES THRU THE ROCKIES AND SEVERAL SHORTWAVES
EJECT NEWD TOWARD THE GREAT LAKES. WL NOT GET OVERLY CUTE WITH THE
TIMING YET...BUT INDICATIONS ARE THAT THE SHWRS/TSTMS WOULD BE AN
AFTERNOON EVENT FOR NE WI ON TUE. MAX TEMPS COULD HAVE QUITE A
RANGE DEPENDING ON WHERE THE BOUNDARY TO RESIDE AND HOW FAST THE
PCPN ARRIVES. READINGS COULD RANGE FROM AROUND 70 DEGS FAR N-CNTRL
WI TO THE LWR 80S CNTRL/E-CNTRL WI.

THE TUE NGT THRU WED NGT TIME FRAME APPEARS TO BE THE MAIN SHOW AS
FAR AS PCPN GOES AS THE UPR TROF SHIFTS EAST...EVENTUALLY REACHING
THE WRN GREAT LAKES. EXACTLY WHERE THE QUASI-STNRY FNT TO RESIDE
WL DETERMINE THE EXTENT/LOCATION OF THE RAIN AND POSSIBLY FLOODING
POTENTIAL AS SEVERAL ROUNDS OF LOCALLY HEAVY RAINFALL ARE EXPECTED.
SUFFICIENT FORCING/LIFT/MOISTURE WL BE PRESENT...SO THIS SITUATION
WL NEED TO BE MONITORED IN THE COMING DAYS.

AS MODEST UPR RIDGING DEVELOPS OVER THE WRN CONUS LATE NEXT WEEK...
THE FLOW OVER WI TO TURN W-NW WITH WEAK HI PRES AT THE SURFACE
MOVING INTO THE GREAT LAKES. THIS CHANGE IN THE UPR FLOW TO USHER
COOLER/LESS HUMID AIR INTO THE FCST AREA WITH MAX TEMPS BOTH THU
AND FRI AT OR SLIGHTLY BELOW NORMAL FOR LATE AUGUST. ONLY FLY IN
THE OINTMENT FOR LATE NEXT WEEK WOULD BE IF THE OLD BOUNDARY
DECIDES TO MAKE A RETURN VISIT...OR AT LEAST GET CLOSE ENUF TO
BRING THE PCPN THREAT BACK INTO THE FCST.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1247 PM CDT SAT AUG 23 2014

VERY MOIST AIR AND WEAK LOW LEVEL FORCING WILL ALLOW
FOR SCATTERED SHOWERS AND PERHAPS A FEW ISOLATED THUNDERSTORMS
THIS AFTERNOON AND OVERNIGHT. SHOWERS ALTHOUGH WIDELY SCATTERED WILL
BE SLOW MOVING AND WILL PRODUCE BRIEF HEAVY DOWNPOURS...ESPECIALLY
ACROSS THE FOX VALLEY INCLUDING GRB AND ATW TAF SITES.

LOW STRATUS AND AREAS OF FOG WILL ALSO BE RATHER PERSISTENT
THROUGH DAYBREAK SUNDAY WITH GENERALLY IFR CIGS AND VISIBILITIES.
COULD BE A BRIEF IMPROVEMENT TO MVFR CONDITIONS BETWEEN ABOUT 21Z
AND 03Z ESPECIALLY OVER CENTRAL WISCONSIN TAF SITES...BUT
ANTICIPATE STATUS AND FOG TO REDEVELOP THEREAFTER.

&&

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

$$

SYNOPSIS.......SKOWRONSKI
SHORT TERM.....SKOWRONSKI
LONG TERM......KALLAS
AVIATION.......ESB






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