Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 011120
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
620 AM CDT FRI MAY 1 2015

UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND SATURDAY
ISSUED AT 255 AM CDT FRI MAY 1 2015

THE MORNING WILL START OUT SUNNY AS A RIDGE OF HIGH PRESSURE
DRIFTS EASTWARD OVER THE AREA. LIGHT VARIABLE WINDS WILL TURN
SOUTHWEST AS THE RIDGE DEPARTS EASTWARD. A SURFACE TROUGH MOVING
INTO MINNESOTA EARLY THIS MORNING WAS PRODUCING A NORTH TO SOUTH
BAND OF SHOWERS. CLOUDS WILL BE ON THE INCREASE FROM THE WEST
LATER TODAY AS THIS TROUGH WORKS INTO THE STATE. DUE TO THE DRY
AIR MASS IN PLACE...PROGS OVERALL IN GOOD AGREEMENT WITH
DIMINISHING THIS BAND OF SHOWERS AS THE TROUGH TRACKS EASTWARD
ACROSS INTO THE TODAY. WILL LEAVE A SMALL CHC POPS OVER NC AND C
WI FOR THE EASTERN EXTENT OF THE PCPN.

LATEST ECMWF DID PRODUCE A LIGHT QPF INTO THE OVERNIGHT HOURS WITH
THE WEAK 850 WAA AND REMNANTS OF THIS TROUGH.  PROGS DO SHOW SOME
MARGINAL MID LEVEL SATURATION...SO WILL INCLUDE ADD A SPRINKLE MENTION
OVER THE NORTH CLOSER TO THE STRONG WAA AND LET THE DAY CREW TAKE
ANOTHER LOOK AT THIS LOW IMPACT ISSUE.

THE HIGH PRESSURE REGION WILL SETTLE INTO THE OHIO VALLEY INTO THE
GREAT LAKES REGION SATURDAY FOR CONTINUED DRY WEATHER. SOUTHWEST
FLOW TODAY THROUGH SATURDAY WILL PRODUCE INCREASINGLY WARMER
TEMPERATURES EACH DAY.

.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY
ISSUED AT 255 AM CDT FRI MAY 1 2015

ZONAL FLOW TO CONT ACROSS THE CONUS THRU THE WEEKEND...HOWEVER THE
DEVELOPMENT OF A BROAD UPR TROF OVER THE WRN CONUS AND A SUBTROPICAL
UPR RDG OVER THE SE CONUS...WL BUCKLE THE FLOW LEADING TO A MORE
ACTIVE WEATHER PATTERN ACROSS THE CNTRL CONUS INCLUDING NE WI.
INITIAL PCPN CHCS ARRIVE LATE SUNDAY INTO MON WITH THE PASSAGE OF
A CDFNT. THIS FNT IS STILL FCST TO STALL JUST TO OUR SOUTH WITH
THE MODELS NOT AGREEING ON HOW FAR SOUTH THE FNT CAN GET BEFORE
GOING STNRY. AS A LARGE PIECE OF THE WRN CONUS UPR TROF LIFTS NE
INTO THE CNTRL PLAINS TOWARD MID-WEEK...THE STALLED BOUNDARY WL
LIFT NORTH AS A WRMFNT AND BRING ADDITIONAL SHWRS/TSTMS TO THE
REGION. TEMPS ARE EXPECTED TO AVERAGE AT OR ABOVE NORMAL THRU THE
PERIOD WITH SUNDAY THE WARMEST DAY.

A WEAK MID-LEVEL SHORTWAVE IS FCST TO MOVE ALONG THE WI/IL BORDER
SAT NGT AS SW WINDS CONT TO PUMP WARMER...MORE MOIST AIR INTO THE
REGION. WHILE AN ISOLATED SHWR MAY GRAZE PARTS OF CNTRL/E-CNTRL WI
DURING THE OVRNGT HOURS...FORCING AND LIFT ARE SO WEAK THAT ANY
PCPN IS JUST TOO ISOLATED TO ADD TO THE FCST ATTM. A MILD NGT IS
EXPECTED WITH MIN TEMPS IN THE UPR 40S TO AROUND 50 DEGS NORTH/
LAKESHORE...50-55 DEG RANGE SOUTH.

A BROAD UPR TROF IS FCST MOVE ACROSS THE U.S.-CANADIAN BORDER
(CENTERED IN THE VCNTY OF MANITOBA/ONTARIO/ND/MN) ON SUNDAY AND
HELP TO PROPEL A CDFNT INTO NW WI BY 00Z MON. THE AIR MASS OVER WI
AHEAD OF THE CDFNT WL BECOME UNSTABLE AND UNCAPPED WITH CAPES
APPROACHING 1500 J/KG AND LI`S DROPPING CLOSE TO -4 OVER CNTRL WI.
SUFFICIENT LIFT TO BE PRESENT BETWEEN THE CDFNT AT THE SFC AND A
DIFFLUENT FLOW ALOFT. 0-6KM SHEAR VALUES OF 20-30 KTS ARE ONLY
MARGINALLY SUPPORTIVE OF ALLOWING TSTMS TO BECOME BETTER
ORGANIZED. ANTICIPATE A CONVECTIVE LINE OF PCPN TO DEVELOP AHEAD
OF THE CDFNT AND PUSH INTO CNTRL WI SUNDAY AFTERNOON. WL HAVE TO
WATCH THESE STORMS CLOSELY DUE TO THE INSTABILITY IN PLACE AS AN
ISOLATED SEVERE STORM IS POSSIBLE. MAX TEMPS REACHING THE 75-80
DEG RANGE...COUPLED WITH DEW POINTS IN THE 50S...COULD ALSO BRING
LOCALLY HEAVY RAINFALL UNDER ANY OF THE TSTMS.

THIS CONVECTIVE LINE OF SHWRS/TSTMS WL MOVE THRU THE REST OF NE WI
SUNDAY EVENING WITH A EFW STRONGER STORMS PERHAPS GENERATING GUSTY
WINDS/SMALL HAIL/HEAVY RAINFALL. THE NORTH WL BEGIN TO DRY OUT
LATER SUNDAY NGT AS HI PRES BUILDS ACROSS THE UPR MS VALLEY. IN
FACT...SKIES COULD ALREADY BE PARTLY CLOUDY BY DAYBREAK IN THE
NORTH...EVEN AS PCPN CONTS OVER E-CNTRL WI. MIN TEMPS TO RANGE
FROM THE LWR TO MID 40S N-CNTRL...LWR TO MID 50S E-CNTRL WI. ANY
LINGERING SHWR ACTIVITY OVER E-CNTRL WI MON MORNING SHOULD QUICKLY
END AS THE CDFNT PUSHES INTO FAR NRN WI AND THE HI PRES BUILDS
INTO THE WRN GREAT LAKES. MORE SUN NORTH/MORE CLOUDS SOUTH WL LEAD
TO UNIFORM TEMPS ACROSS THE FCST AREA AND IT WL BE COOLER DUE TO
NE WINDS EXPECTED. LOOK FOR MAX TEMPS TO GENERALLY RANGE FROM
65-70 DEGS (COOLER LAKESIDE).

THE GENERAL CONSENSUS AMONG THE MODELS IS THAT THE CDFNT WL PULL
UPR STNRY OVER NRN IL MON NGT AS THE FNT ENCOUNTERS THE SUBTROPICAL
RDG OVER THE SE CONUS. AS ADDITIONAL ROUNDS OF SHWRS/TSTMS IMPACT
SRN WI/NRN IL...NE WI TO BE UNDER THE INFLUENCE OF THE HI PRES...
AND WL GO WITH A DRY FCST FOR THE ENTIRE FCST AREA. LITTLE CHANGE
EXPECTED THRU TUE...OTHER THAN THE HI PRES SHIFTS TOWARD THE ERN
GREAT LAKES. HAVE MAINTAINED THE DRY FCST WITH MAX TEMPS ON TUE IN
THE MID TO UPR 60S AWAY FROM LAKE MI AND THE BAY OF GREEN BAY.

AS A SIGNIFICANT PIECE OF THE WRN CONUS UPR TROF BEGINS TO LIFT NE
DURING THE MIDDLE OF NEXT WEEK...INCREASING SOUTHERLY WINDS WL
ALLOW THE STALLED BOUNDARY TO LIFT NWD AS A WRMFNT. EXPECT AT
LEAST A CHC OF SHWRS/TSTMS TO RETURN TO NE WI EITHER LATE TUE NGT
OR WED AS THE FNT APPROACHES. THERE MAY BE LULL IN THE PCPN WED
NGT AS THE WRMFNT CONTS TO LIFT NORTH AND THE UPR TROF/ASSOCIATED
CDFNT TO STILL BE WELL TO OUR WEST (NRN/CNTRL PLAINS). A SURGE OF
WAA INTO WI AND INCREASING INSTABILITY SHOULD KEEP A CHC OF SHWRS/
TSTMS IN THE FCST THRU THU. TEMPS WL REMAIN ABOVE NORMAL FOR BOTH
WED AND THU.
&&

.AVIATION...FOR 12Z TAF ISSUANCE
ISSUED AT 620 AM CDT FRI MAY 1 2015

VFR CONDITIONS TO PREVAIL TODAY THROUGH SATURDAY. A
WEAK TROUGH OF LOW PRESSURE PASSING OVER THIS AFTERNOON AND
EVENING MAY PRODUCE A PERIOD OF MID LEVEL CLOUDS...AND ISOLATED
LIGHT SHOWERS OR SPRINKLES OVER PARTS OF CENTRAL AND NORTH CENTRAL
WISCONSIN.
&&

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

$$

SHORT TERM.....TDH
LONG TERM......AK
AVIATION.......TDH





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