Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 240928
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
428 AM CDT SUN AUG 24 2014

FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST ISSUANCE

.SYNOPSIS...
ISSUED AT 417 AM CDT SUN AUG 24 2014

WARM AND HUMID WITH SOME THUNDERSTORMS AT TIMES THE NEXT COUPLE
DAYS...THEN COOLER AND DRIER MID-WEEK.

UPR PATTERN NEAR THE PEAK OF AMPLIFICATION PHASE...WITH DEEP TROF
OVER THE INTERMOUNTAIN WEST...AND A STG RIDGE FM THE LOWER
MISSISSIPPI VALLEY THROUGH QUEBEC. STG SHRTWV EJECTING OUT OF THE
WRN TROF WL FLATTEN/SHOVE THE NRN EXTENSION OF THE RIDGE EWD DURING
THE NEXT COUPLE DAYS. A MORE PROGRESSIVE AND SOMEWHAT LOWER
AMPLITUIDE FLOW REGIME IS EXPECTED TO DEVELOP DURING THE WEEK AS
THE MAIN WESTERLIES CONSOLIDATE OVER THE FAR NRN CONUS AND SRN
CANADA...PROBABLY LEAVING THE SRN PORTION OF THE WRN TROF BEHIND
OVER THE COUNS IN A WK/DIFFUSE SRN STREAM.

VERY WARM/HUMID AIR MASS WL DOMINATE THE AREA EARLY...RESULTING IN
ABV NORMAL TEMPS AT THE START OF THE FCST PERIOD. TEMPS WL HEAD
BACK TOWARD SEASONAL NORMALS AND HUMIDITIY LEVELS WL DECREASE BY
THE LATTER HALF OF THE FCST PERIOD. ASSESSING PCPN IS A BIT MORE
COMPLEX. THE VERY MOIST AIR ACRS THE AREA EARLY IN THE FCST PERIOD
WOULD CERTAINLY SUPPORT HEAVY PCPN AMNTS...THOUGH LARGE SCALE
DYNAMICS AREN/T REALLY IN SYNC WITH THE COLD FRONT CROSSING THE
REGION...SO GETTING WIDESPREAD SIG PCPN ISN/T A SLAM DUNK. THERE
ARE ALSO UNCERTAINTY OVER WHETHER OR NOT FRONTAL SYSTEM WL STALL
CLOSE ENOUGH TO THE AREA TO GENERATE PCPN IN LATER PERIODS.
SO ALTHOUGH THE MOST LIKELY SCENARIO IS THAT WE END UP WITH ABV
NORMAL PCPN...THAT CERTAINLY ISN/T A GIVEN.
&&

.SHORT TERM...TODAY...TONIGHT...AND MONDAY
ISSUED AT 417 AM CDT SUN AUG 24 2014

SLIGHTLY DRIER AIR WORKED INTO THE AREA FM THE E LATE YDA. THAT
COMBINED WITH A LITTLE MORE BOUNDARY LAYER WIND AND EXTENSIVE HIGH
/MID CLDS WAS KEEPING FG FM BECOMG A PROBLEM THIS MORNING. BAND OF
SHRA WITH MINOR SHRTWV WORKG THROUGH THE UPR RIDGE ACRS THE AREA
WL AFFECT THE W EARLY...BUT SHOULD WEAKEN. SHRA AND MAYBE EVEN A
FEW TSRA N OF CONVECTIVELY INDUCED VORT TRACKING ACRS SRN LAKE
MICHIGAN COULD WRAP BACK INTO E-C WI THIS MORNING. ALIGNED POPS
WITH WITH RADAR TRENDS FOR THE START OF THE FCST...THEN KEPT ISOLD
SHRA THROUGH THE MORNING BEFORE ENDING PCPN FOR THE AFTN. FEWER
LOW CLDS AND LESS FG THAN THE PAST FEW DAYS SHOULD MAKE IT EASIER
TO GET SOME SUN LATER TDA...ONCE THE HIGH/MID STUFF SHIFTS
NE. TRIMMED MAX TEMPS A BIT EVERYWHERE...BUT THE MOST IN THE NE
WHICH SHOULD BE THE LAST TO BREAK OUT.

STG SHRTWV EJECTING OUT OF THE WRN TROF WAS SUPPORTING CYCLONE
OVER THE NRN PLAINS THIS MORNING...WHICH WL MV TO NW ONTARIO BY
MON EVENING. CONVECTION FIRING ALONG THE TRAILING COLD FRONT AND
AIDED BY TAIL OF UPR SHRTWV SHOULD DEVELOP TO OUR W THIS AFTN/EVE.
IT PROBABLY WON/T REACH WRN PORTIONS OF THE FCST AREA UNTIL ARND
OR AFTER MIDNIGHT. BUT ADDITIONAL DEVELOPMENT COULD OCCUR OVER THE
N AHEAD OF THE MAIN CLUSTER OF STORMS AS THE 850 MB FLOW
STRENGTHENS DURING THE EVENING AND GETS DIRECTED INTO THE AREA AND
OVER LINGERING LOW-LEVEL FRONTAL ZONE. MAIN SVR RISK WL BE TO OUR
W...THOUGH SOME RISK OF WINDS/HAIL WL EXIST OVER N-C WI LATE
TNGT. SPC HAD THAT AREA ON 5 PCT CHC SVR IN SWODY1 OUTLOOK...AND
THAT LOOKED RIGHT ON TARGET.

SOME UNCERTAINTY EXISTS OVER THE EWD/SEWD PROGRESS OF THE STORMS
OVERNIGHT. THE COLD FRONT WL STILL BE BACK TO THE W...BUT THE
STORMS MAY SHIFT EWD AHEAD OF IT BEING FED BY SWLY 850 MB FLOW.
REMANTS OF CONVECTIVE COMPLEX OR AT LEAST OUTFLOW WL PROBABLY WORK
ACRS MOST IF NOT ALL OF THE FCST AREA BY MON MORNING. BUT ATM
SHOULD HAVE TIME TO RECOVER/DESTABILIZE FOR ANOTHER ROUND OF
STORMS MON AFTN...THIS TIME FOCUSED ON THE SE PART OF THE FCST
AREA. LARGER SCALE FORCING WL BE MUCH LESS FAVORABLE THAN OUT TO
OUR W THIS AFTN...AS SHRTWV HEADS OFF TO THE NE AND 850 MB FLOW
VEERS MORE WLY. CONVERGENCE ON THE COLD FRONT WL BE LIMITED...SO
COVERAGE OF TSRA WL PROBABLY BE LIMITED. ANY STORMS THAT FORM WL
PROBABLY POSE A RISK OF SVR WX...BUT GIVEN LESS FAVORABLE LARGE
SCALE SET-UP...SPC LIMITED SVR RISK TO 5 PCT CHC OF SVR IN THE
SWODY2 PRODUCT. THAT SEEMS QUITE REASONABLE. MAIN ADJUSTMENT TO
MAX TEMPS MON WAS TO INCR THE NW-SE GRADIENT BY EDGING MAXES DOWN
IN THE NW AND RAISING THEM A BIT IN THE SE.

.LONG TERM...MONDAY NIGHT THROUGH SATURDAY
ISSUED AT 417 AM CDT SUN AUG 24 2014

LONG RANGE MDLS INDICATE A RATHER AMPLIFIED MEAN FLOW ACROSS THE
CONUS WITH THE MOVEMENT OF AN UPR TROF FROM THE PACIFIC NW TO THE
GREAT LAKES BEING THE PRIMARY WEATHER FEATURE TO IMPACT NE WI
WEATHER. THE INITIAL WARM/HUMID AIR MASS WL COME TO AN END BY MID-
WEEK UPON THE PASSAGE OF A CDFNT. THE MAIN CHANGE IN THE FCST
COMES DURING THE MID-WEEK PERIOD AS THE 00Z MDL OUTPUTS (SANS THE
GFS) NOW SLOW THE EWD MOVEMENT OF THIS UPR TROF AND ALLOWS THE
CDFNT TO SAG FARTHER SOUTH INTO IL BEFORE PULLING UP STNRY. WHAT
SEEMED LIKE A WET TUE NGT THRU WED NGT PERIOD NOW LOOKS TO BE
MAINLY DRY WITH THE PCPN DELAYED UNTIL THE END OF THE WEEK. MDLS
HAVE BEEN INCONSISTENT WITH ALL OF THESE TIMING CHANGES...THUS
CONFIDENCE IS RATHER LOW IN THE LATER PERIODS OF THE FCST.

THE LATEST TIMING AMONG THE MDLS HAS THE CDFNT MOVE THRU ALL BUT
E-CNTRL WI MON NGT. THE FNT WL BE SLOWING ITS FORWARD PROGRESS AS
IT BEGINS TO ENCOUNTER THE BROAD UPR RDG STRETCHED FROM TX TO NEW
ENGLAND. CONVECTION COULD ALREADY BE ONGOING MON EVENING AS THE
ATMOSPHERE IS EXPECTED TO BE VERY UNSTABLE WITH CAPES AROUND 3K
J/KG AND LI`S DOWN TO AROUND -8. CANNOT RULE OUT A FEW STRONGER
STORMS CAPABLE OF PRODUCING LOCALIZED DAMAGING WINDS OR BORDERLINE
SEVERE HAIL. NRN WI SHOULD BEGIN TO DRY OUT AFTER MIDNGT AS THE
FNT SETTLES INTO CNTRL WI. COOLER/LESS HUMID AIR IS EXPECTED TO
SLOWLY FILTER INTO WI BEHIND THE FNT AND THIS SHOULD ALLOW MIN
TEMPS TO RANGE FROM THE MID 50S TO AROUND 60 DEGS NORTH...TO THE
MID TO UPR 60S OVER E-CNTRL WI.

THE CDFNT IS PROGGED TO REACH SRN WI ON TUE...BUT NOT YET COME TO
A COMPLETE HALT. SRN SECTIONS OF THE FCST AREA MAY BE CLOSE ENUF
TO THIS BOUNDARY TO KEEP AT LEAST A SMALL CHC OF SHWRS/TSTMS IN
THE FCST. MEANWHILE...WEAK HI PRES WL ATTEMPT TO PUSH SOUTH INTO
THE UPR MS VALLEY/NRN SECTIONS OF THE GREAT LAKES. NRN WI MAY BE
ABLE TO SEE AT LEAST SOME SUNSHINE ON TUE WITH THE RAIN CHCS
STAYING TO THE SOUTH. MAX TEMPS TO RANGE FROM THE LWR TO MID 70S
N-CNTRL...TO THE LWR 80S OVER PARTS OF CNTRL AND E-CNTRL WI.

THE GFS REMAINS THE ODD MDL OUT WITH ITS DEPICTION OF STALLING THE
FNT OVER CNTRL WI COMPARED TO THE OTHER MDLS WHICH ALLOW THE FNT
TO CROSS OVER THE IL BORDER BEFORE PULLING UP STNRY. THIS LATTER
SOLUTION WOULD KEEP A VAST MAJORITY OF PCPN SOUTH OF THE FCST AREA
AND PLAN TO SLASH POPS DOWN NEXT TO NIL OVER NRN WI AND ONLY SMALL
CHCS FOR CNTRL/E-CNTRL WI JUST IN CASE THE FNT STALLS EARLIER THAN
ANTICIPATED. MAY NEED TO TWEAK TEMPS DOWN A LITTLE OVER THE NORTH
WITH LESS OF A RAIN THREAT. EXCEPT FOR THE JACKRABBIT GFS...OTHER
MDLS HAVE SLOWED THE PROGRESS OF THE PRIMARY UPR TROF MOVING THRU
THE ROCKIES ON WED. THIS DELAY WOULD KEEP THE STNRY FNT OVER NRN
IL AND THE WEAK HI PRES OVER THE NRN GREAT LAKES. WHAT APPEARED AS
A WET DAY 24 HOURS AGO...NOW HAS THE LOOK OF A MAINLY DRY DAY WITH
COOLER/LESS HUMID CONDITIONS. THEREFORE...HAVE RADICALLY CHANGED
WED/S FCST AS FAR AS POPS ARE CONCERNED...BUT KEPT TEMPS CLOSE TO
THE PREVIOUS FCST.

THE FCST CONTS ITS INCONSISTENT WAYS HEADED INTO THU AS THE UPR
TROF TO STILL BE TRUDGING THRU THE ROCKIES WITH THE BOUNDARY WELL
TO OUR SOUTH. HAVE AGAIN KEPT POPS EITHER NIL OR VERY LOW DUE TO A
LACK OF ANY FOCUSING MECHANISM. THE UPR TROF IS NOW EXPECTED TO
FINALLY REACH THE WRN GREAT LAKES FRI NGT INTO SAT WITH THE
POTENTIAL OF A SURFACE WAVE MOVING ALONG THE FNTL BOUNDARY. THERE
SHOULD BE ENUF MID-LEVEL FORCING TO COMBINE WITH THE FNT ITSELF TO
PRODUCE A CHC OF SHWRS AND TSTMS OVER NE WI. MAY EVENTUALLY NEED
TO RAISE POPS FOR FRI/FRI NGT...BUT KEPT THE FCST ALONG THE LINES
OF THE CONSENSUS SOLUTION FOR NOW DUE TO UNCERTAINTY INVOLVED.
&&

.AVIATION...FOR 12Z TAF ISSUANCE
ISSUED AT 417 AM CDT SUN AUG 24 2014

PATCHES OF LOW CLDS WERE ARND THE AREA THIS MORNING...ESPECIALLY
JUST TO OUR W. WL PROBABLY HAVE SOME MVFR CIGS FOR A TIME TDA...
BUT EXPECT A DECR IN CLDS FM SW-NE THIS AFTN. POOR FLIGHT
CONDITIONS WL DEVELOP ACRS N-C WI TNGT DUE TO TSRA. FG WL ALSO
PROBABLY BE MORE OF AN ISSUE THAN THIS MORNING.
&&

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

$$

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







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