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000
FXUS63 KGRB 230923
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
423 AM CDT WED APR 23 2014

FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND THURSDAY
ISSUED AT 420 AM CDT WED APR 23 2014

SHORT RANGE MODELS ARE NOW IN PRETTY GOOD AGREEMENT
ABOUT SLOWING THE ARRIVAL OF PRECIPITATION INTO THE FORECAST AREA
THIS AFTERNOON. MIDDLE AND HIGH CLOUDS WILL INCREASE TODAY AHEAD
OF THE COMPLEX SYSTEM OVER THE PLAINS BUT RAIN WILL PROBABLY HOLD
OFF UNTIL AFTER DARK IN MOST AREAS. TWO AREAS OF JET ENERGY
APPROACHING FROM THE SOUTHWEST SHOULD BRING US PERIODS OF SHOWERS
TONIGHT AND THURSDAY. EASTERLY COMPONENT OF THE WIND FROM LAKE
MICHIGAN WILL KEEP THE LOW LEVELS VERY STABLE...SO WHATEVER
THUNDERSTORMS THAT MAY OCCUR WILL BE ELEVATED ABOVE THE STABLE
LAYER. EVAPORATIVE COOLING MAY CREATE SOME PRECIPITATION TYPE
ISSUES IN THE FAR NORTH LATE TONIGHT AND EARLY TUESDAY. IT/S NOT
OUT OF THE QUESTION FOR THERE TO BE A COUPLE INCHES OF WET SNOW IN
THE FAR NORTH AS 850MB TEMPERATURES ARE FORECAST TO BE SUB
FREEZING. THE BIG QUESTION IS THE BOUNDARY LAYER. HIGHS TODAY
SHOULD BE AROUND 5 DEGREES BELOW NORMAL IN MOST AREAS WHILE HIGHS
THURSDAY WILL BE 10 DEGREES OR MORE BELOW NORMAL DUE TO CLOUDS AND
PRECIPITATION.

.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY
ISSUED AT 420 AM CDT WED APR 23 2014

MEAN FLOW TO BRIEFLY DEAMPLIFY THRU THE END OF THE WORK WEEK AND
ALLOW A PACIFIC SYSTEM TO AFFECT NE WI THRU AT LEAST FRI. FLOW
BECOMES STRONGLY AMPLIFIED THIS WEEKEND AS A STRONG UPR TROF DIGS
TOWARD THE CNTRL ROCKIES AND DOWNSTREAM UPR RIDGING OCCURS OVER
CNTRL NORTH AMERICA. THIS UPR TROF TO EVENTUALLY CLOSE OFF INTO AN
UPR LOW OVER THE CNTRL PLAINS AND SLOWLY DRIFT EAST TOWARD THE
MID-MS VALLEY EARLY NEXT WEEK. MAIN FCST ISSUES CONT TO CENTER
AROUND THE CLOSED UPR LOW AND ITS EVENTUAL TRACK FOR EXTENT OF
PCPN...AS WELL AS TEMPS WHICH MAY BE COOL ENUF FOR SNOW TO
DEVELOP.

THE NEGATIVELY-TILTED SHORTWAVE TROF TO PIVOT NE ACROSS WI THU NGT
AS THE SFC LOW ALSO MOVE NE AND DRAGS A CDFNT THRU THE FCST AREA
THU EVENING. PLENTY OF LIFT AVAILABLE BETWEEN THE CDFNT AND COUPLED
JET STRUCTURE ALOFT TO GENERATE RAIN SHWRS. AS TEMPS BEGIN TO COOL
OVRNGT...THERE IS A GOOD POTENTIAL TO SEE THE PCPN BECOME MIXED OR
EVEN CHANGE TO ALL SNOW ACROSS FAR NRN WI. WHILE THE BULK OF THE
HEAVIER PCPN WL HAVE EXITED WI BY THE TIME THE AIR MASS COOLS...
THERE COULD BE A LITTLE ACCUMULATION ON GRASSY SFCS IN THE FAR
NORTH BY DAYBREAK. MIN TEMPS TO RANGE FROM THE LWR 30S N-CNTRL...
TO THE LWR 40S OVER E-CNTRL WI.

THE UPR LOW IS FCST TO SLOWLY DRIFT ACROSS NRN SECTIONS OF THE
GREAT LAKES ON FRI AND KEEP A CYCLONIC FLOW ACROSS WI. IN
ADDITION...THE MDLS SHOW A SECONDARY CDFNT DROPPING SWD THRU WI.
LASTLY...THE COOL AIR ALOFT COULD ADD A BIT OF INSTABILITY TO THE
ATMOSPHERE. WL NEED TO CARRY AT LEAST CHC POPS FOR MOST OF NE WI
WITH HIGHEST VALUES PLACED IN THE NORTH. MAX TEMPS TO RANGE FROM
THE LWR TO MID 40S NORTH TO THE LWR TO MID 50 SOUTH.

ANY LINGERING PCPN SHOULD COME TO AN END FRI EVENING AS THE
CYCLONIC FLOW WEAKENS AND INSTABILITY DECREASES. THE REST OF FRI
NGT WL SEE THE SRN EXTENSION OF HI PRES TO BEGIN TO BUILD INTO THE
WRN GREAT LAKES. SKY COVER IS EXPECTED TO GRADUALLY BECOME PARTLY
CLDY OVRNGT WITH ENUF BOUNDARY LAYER WINDS TO PREVENT TEMPS FROM
DROPPING TOO FAR. LOOK FOR READINGS TO DIP INTO THE 25-30 DEG
RANGE NORTH...30-35 DEG RANGE SOUTH. THE EVOLUTION INTO A HIGHLY
AMPLIFIED FLOW REALLY TAKES SHAPE BY SAT AS THE DEEP UPR TROF
PUSHES ACROSS THE WRN CONUS WITH UPR HEIGHTS BUILDING ACROSS THE
CNTRL CONUS. NE WI TO REMAIN ON THE COOL SIDE OF THE DEVELOPING
UPR RDG WITH HI PRES AT THE SFC BUILDING SWD INTO THE GREAT LAKES.
HAVE KEPT SAT DRY...BUT COOL WITH MAX TEMPS A GOOD 10 TO 20 DEGS
BELOW NORMAL.

FCST ISSUES BEGIN SAT NGT WITH THE HANDLING OF THE UPR TROF AS THE
MDLS SHOW THE TROF CLOSING OFF INTO AN UPR LOW. THE ECMWF REMAINS
A LITTLE QUICKER IN LIFTING THIS NEW UPR LOW NEWD COMPARED TO THE
GFS/GEM. A GOOD TREND IS THAT THE ECMWF HAS SLOWED DOWN FROM ITS
PREVIOUS RUN AND EXPECT THE MDLS TO WAFFLE A BIT WITH THIS SYSTEM
FOR SEVERAL MORE DAYS. A PERSISTENT DRY FETCH OF AIR ON EAST WINDS
WL ALSO RETARD THE ADVANCE OF ANY PCPN AHEAD OF THIS SYSTEM.
THEREFORE...HAVE KEPT MOST OF NE WI DRY SAT NGT WITH ONLY A TOKEN
POP FOR CNTRL WI TO MATCH UP WITH SURROUNDING OFFICES TO THE SOUTH
AND WEST. EVEN GOING INTO SUNDAY...PCPN WL STRUGGLE TO ADVANCE
NEWD AND WITH THE UPR LOW ONLY REACHING THE CNTRL PLAINS LATE ON
SUNDAY...PREFER TO KEEP POPS LOW CNTRL WI/NIL FAR NRN WI FOR SUNDAY.

EVENTUALLY...THE DRY AIR FEED FROM THE SFC HI WL BE OVERCOME BY
SURGES OF MOISTURE LIFTING NORTH OVER A WRMFNT THAT IS PROGGED TO
REACH CNTRL SECTIONS OF IL/INDIANA EARLY NEXT WEEK. THE CLOSED UPR
LOW IS FCST TO GRADUALLY SHIFT EAST ACROSS THE MID-MS VALLEY...BUT
THIS TRACK IS FAR FROM CERTAIN AS THE MDLS CONT TO STRUGGLE WITH
THIS FEATURE. ANOTHER POTENTIAL PROBLEM COULD BE PCPN TYPE...
ESPECIALLY IF THE ECMWF TURNS OUT TO BE CORRECT. THIS MDLS WOULD
SUGGEST SNOW POTENTIAL BOTH SUNDAY NGT AND MON NGT WITH MEASURABLE
ACCUMULATIONS. LOW CONFIDENCE ON ANY ONE PARTICULAR MDL SOLUTION
WL PRECLUDE HITTING SNOW MUCH AT THIS TIME. ONE THING HERE IS THAT
MON AND TUE WL NEED AT LEAST CHC POPS WHICH IS A WETTER TREND
COMPARED TO 24 HOURS AGO AND HAVE RAISED POPS ACCORDINGLY.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1038 PM CDT TUE APR 22 2014

QUIET WX EXPECTED THROUGH TOMORROW AS SFC RIDGE CROSSES THE RGN.
HIGH AND THEN MIDDLE CLDS WL SPREAD BACK ACRS THE AREA
TOMORROW...BUT VFR CONDITIONS ARE EXPECTED. PCPN AND SOME LOWER
CIGS SHOULD BEGIN OVERSPREADING THE AREA AFTER 00Z.
&&

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

$$

SHORT TERM.....RDM
LONG TERM......KALLAS
AVIATION.......SKOWRONSKI