Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 041703
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1203 PM CDT TUE AUG 4 2015

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SYNOPSIS...
ISSUED AT 315 AM CDT TUE AUG 4 2015

SEASONABLE TEMPERATURES WITH THE NEXT SUBSTANTIAL OPPORTUNITY FOR
RAIN LATE THIS WEEK.

UPR TROF CENTERED OVER ERN ONTARIO WL GRADUALLY WEAKEN THE NEXT
FEW DAYS. THAT WL LEAVE A RELATIVELY LOW AMPLITUDE BAND OF
WESTERLIES ACRS THE NRN CONUS. THE MEAN RIDGE POSN WL BE OVER THE
ROCKIES/WRN PLAINS...WITH A WK TROF OVER THE E. IT LOOKS LIKE
THERE WL BE SOME TENDENCY FOR UPR ANTICYCLONE CENTER WITHIN THE
SUBTROPICAL RIDGE TO STRENGTHEN OVER THE SRN PLAINS DURING THE
LATTER HALF OF THE PERIOD.

TEMPERATURES WL VARY FM DAY TO DAY WITH THE PASSAGE OF WX
SYSTEMS...BUT PROBABLY NOT DEVIATE TOO FAR FM SEASONAL NORMALS.
ISOLD-SCT SHRA ARE EXPECTED OVER NE WI TDA...BUT THE NEXT
SUBSTANTIAL CHC FOR PCPN WL OCCUR DURING THE LATTER PART OF THE
WORK WEEK. IT SEEMS LIKELY THAT MOST AREAS WL GET SOME RAIN...BUT
PROBABLY NOT ENOUGH TO BRING TOTALS FOR THE 7 DAY PERIOD UP TO
NORMAL. THE CAVEAT IS THAT GAUGING PCPN AMNTS IN CONVECTIVE SITNS
IS ALWAYS TOUGH...AS JUST ONE WELL-PLACED MCS CAN SUPPLY ENOUGH
PCPN FOR THE WHOLE WEEK.
&&

.SHORT TERM...TODAY...TONIGHT...AND WEDNESDAY
ISSUED AT 315 AM CDT TUE AUG 4 2015

SHRTWVS DROPPING SEWD ARND THE WRN FLANK OF LARGE SCALE TROF
GENERATED ISOLD-SCT SHRA OVER NERN WI YDA. WK RETURNS CONTD TO
STREAM SE ACRS LAKE SUPERIOR AND UPPER MICHIGAN EARLY THIS
MORNING...AND WV IMAGERY INDICATED ANOTHER SHRTWV POISED TO CROSS
THE AREA AGAIN MID-DAY. SO INCREASED POPS A BIT IN THE FAR NE FOR
TDA...AND EXPANDED THEM A BIT SWWD. STILL LOOKING AT ISOLD-SCT
COVERAGE THROUGH...WITH NOT EVERYBODY GETTING RAIN.

SOME OF THE GUIDANCE HINTED AT PCPN TOMORROW AFTN...EITHER IN
RETURN FLOW ON THE BACK SIDE OF DEPARTING ANTICYCLONE OR IN LAKE-
BREEZE CONVERGENCE ZONE. BUT DIDN/T SEE ENOUGH SUPPORT IN TERMS
OF INSTABILITY TO ADD THAT TO THE FCST YET.

MADE SOME MINOR ADJUSTMENTS TO TEMPS TDA/TNGT/WED BASED ON HIGHS
YDA AND 850 MB/1000-850 MB THICKNESS TRENDS.

SOME OF THE HI-RES SHRT RANGE GUIDANCE...IN PARTICULAR THE
RAP...INDICATED A FAIRLY DISTINCT WIND SHIFT TO THE NE WOULD WORK
SWD DOWN THE LAKE AND BAY THIS AFTN. THAT/S A FAIRLY COMMON
OCCURRENCE IN SITNS SUCH AS THIS...SO WORKED THAT TREND INTO THE
WIND GRIDS. NOT EXPECTING STG GUSTS BEHIND THE FRONT AT THIS
POINT...BUT THE WIND SHIFT WL PROBABLY BE SHARP ENOUGH TO BE OF
IMPORTANCE TO BOATERS.

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY
ISSUED AT 315 AM CDT TUE AUG 4 2015

PLENTY OF POTENTIAL FORECAST PITFALLS IN THE MEDIUM RANGE MODELS
TONIGHT.  THE GFS IS MOST AGGRESSIVE IN GENERATING PRECIP IN THE
WARM ADVECTION ZONE WEDNESDAY NIGHT...WHILE THE CANADIAN AND ECMWF
ONLY BRING PRECIP ACROSS NORTHERN WI.  THE CANADIAN AND ECMWF ARE
ALSO WELL ALIGNED WITH A SHORTWAVE MOVING ACROSS THE REGION THURSDAY
NIGHT INTO EARLY FRIDAY.  EVEN THOUGH THERE ARE NO SIGNS OF THIS
SHORTWAVE IN THE ENSEMBLE MEANS...PREFER THE ECMWF/GEM BLEND THROUGH
FRIDAY.  THEREAFTER...SPREAD BECOMES TOO LARGE TO SELECT A CLEAR
MODEL CONSENSUS.

WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...HIGH PRESSURE WILL BE
CENTERED ACROSS THE CENTRAL GREAT LAKES AT THE START OF WEDNESDAY
EVENING...BEFORE SHIFTING EAST AS WARM ADVECTION MOVES INTO THE
REGION LATE.  THE WARM ADVECTION IN CONCERT WITH MID-LEVEL FGEN WILL
LEAD TO A CHANCE OF SHOWERS ACROSS N-C WISCONSIN LATE IN THE NIGHT.
AS LOW PRESSURE MOVES INTO THE NORTHWEST GREAT LAKES ON
THURSDAY...CHANCES OF SHOWERS AND STORMS WILL ALSO SPREAD INTO
CENTRAL WI.  THEN LOW PRESSURE WILL MOVE INTO WESTERN WISCONSIN
THURSDAY NIGHT SPREADING WIDESPREAD SHOWERS AND THUNDERSTORMS OVER
ALL OF N-C AND NE WI.

REST OF THE FORECAST...SHOWERS AND STORMS COULD LINGER INTO FRIDAY
THEN EXIT FRIDAY NIGHT AS A SHORTWAVE MOVES EAST OF THE REGION.
MODELS ARE ALL OVER THE PLACE THIS WEEKEND...BUT POTENTIAL IS THERE
FOR DRY CONDITIONS ON SATURDAY BEFORE PRECIP CHANCES INCREASE AGAIN
LATE IN THE WEEKEND INTO EARLY NEXT WEEK.  TEMPERATURES ARE TOUGH
PENDING RAIN CHANCES...BUT POTENTIAL FOR WARMER TEMPS THAN
ADVERTISED ON THURSDAY AND ALSO LATE IN THE WEEKEND.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1137 AM CDT TUE AUG 4 2015

PRIMARILY VFR CONDITIONS WITH LIGHT WINDS ARE STILL EXPECTED. WITH
SOME GUIDANCE EVEN SUGGESTING FOG AS FAR SOUTH AS INTO THE FOX
VALLEY AND BRIEF PERIODS OF FOG IN EXTREME NORTH CENTRAL WISCONSIN
THIS MORNING...DECIDED TO INTRODUCE SOME HINT AT TRANSIENT FOG
NEAR SUNRISE AT THE NORTH CENTRAL AND CENTRAL WISCONSIN SITES.
STILL...A WIDE RANGE OF OPINIONS FROM DENSE FOG TO NO FOG EXIST IN
THE GUIDANCE AND FUTURE ISSUANCES MAY MORE CONFIDENTLY PUT FORTH
SPECIFICS. THOUGH SOME GUIDANCE SUGGESTED IT...DO NOT CURRENTLY
EXPECT VIS REDUCTIONS AT GRB OR ATW SO LEFT THEM OUT.
&&

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

$$

SYNOPSIS.......SKOWRONSKI
SHORT TERM.....SKOWRONSKI
LONG TERM......MPC
AVIATION.......LUCHS



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