Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 281112
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
612 AM CDT THU AUG 28 2014

NEW INFORMATION ADDED TO UPDATE SECTION

.UPDATE...
ISSUED AT 612 AM CDT THU AUG 28 2014

ALTHOUGH AUTOMATIC OBSERVATIONS NOT OBSERVING DENSE FOG...SOME SPOTTERS
REPORTING POCKETS OF DENSE FOG OVER NORTHERN WISCONSIN. LIKELY
LOCATIONS WHERE THE LOW LEVEL INVERSION WAS STRONGER...GETTING A
WIDESPREAD RANGE OF SURFACE TEMPS FROM THE UPPER 30S TO UPPER 40S
ACROSS THE NORTH.
&&

.SHORT TERM...TODAY...TONIGHT...AND FRIDAY
ISSUED AT 334 AM CDT THU AUG 28 2014

EARLY THIS MORNING...REGIONAL RADARS SHOW A LARGE CLUSTER OF
SHOWERS AND STORMS OVER EASTERN NEBRASKA AND WESTERN IOWA
GRADUALLY WORKING NORTH. THIS AREA OF SHOWERS AND STORMS WITHIN A
REGION OF DEEP MOISTURE WHERE PWATS CLIMB TO 2.00 INCHES AND 850
WARM FRONT. THIS MOIST AIR MASS WILL WORK INTO SOUTHWEST
WISCONSIN LATER TODAY AND THEN STATEWIDE OVERNIGHT TO DEVELOP
SHOWERS AND STORMS FROM NORTH TO SOUTH. TREND OF MODELS HAS BEEN
TO DELAY THE ARRIVAL OF THE PCPN TODAY AND OVER THE NORTHEAST HALF
THIS EVENING DUE TO INITIALLY DRY FEED OF AIR FROM DEPARTING
SURFACE HIGH PRESSURE AND UPPER RIDGE. BRUNT OF THE PCPN WILL BE
DRIVEN WITH THE APPROACHING H850 WARM FRONT WHICH EXITS TO THE
NORTHEAST FRIDAY MORNING TO DIMINISH THE CONVECTION BRIEFLY FROM
SOUTHWEST TO NORTHEAST. HOWEVER ANTICIPATE COVERAGE TO BE ON THE
INCREASE AGAIN FROM WEST TO EAST IN THE AFTERNOON AS THE MID LEVEL
TROUGH SLIDES OVER AND WILL BE THE FOCUS OF MORE CONVECTION. AS
FAR AS UPPER JET SUPPORT...BETTER LIFT APPEARS TO BE OVER
NORTHWEST WISCONSIN AND MINNESOTA OVERNIGHT...BUT WITH LIGHTER
WINDS OVER THE FORECAST AREA...POTENTIAL SLOWER STORM MOVEMENT
WITH THE INCREASING DEEPER MOISTURE COULD PRODUCE LOCALLY HEAVY
RAIN. A BIT BETTER UPPER JET SUPPORT ARRIVES LATER FRIDAY AS THE
MID TROUGH APPROACHES TO PRODUCE MORE LIFT. FOR MORE INFORMATION
ON THE HEAVY RAIN POTENTIAL AND GOING HEADLINES SEE THE HYDROLOGY
SECTION BELOW.

WILL DOWNPLAY THE TSRA INITIALLY DUE TO LACK OF INSTABILITY...BUT
WILL FOCUS CONVECTION IN THE CONVERGENT REGION OF THE 850 FRONT.
EXPANDED THUNDER LATE TONIGHT AND ESPECIALLY INTO FRIDAY WITH AN
BIT MORE UNSTABLE AIR SPREADING NORTH IN THE WAKE OF THE 850 WARM
FRONT.

FOR THE START OF THE TODAY...MOST AREAS SHOULD SEE SOME SUNSHINE
BEFORE CLOUDS INCREASE FROM THE SOUTHWEST WITH THE APPROACHING
FRONTAL SYSTEM. BUT WILL HAVE TO DEAL WITH SOME MOISTURE TRAPPED
BELOW AN INVERSION AT 6000-7000 FEET AS PER 00Z GRB SOUNDING WITH
FOLLOW UP BUFKIT FORECAST SOUNDING DATA SUGGESTING THESE CLOUDS
MAY LINGER AT LEAST THE MORNING HOURS.

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY
ISSUED AT 334 AM CDT THU AUG 28 2014

NO CHANGE TO THE EXPECTED UPPER AIR PATTERN OVER THE NEXT WEEK.
STILL LOOKING FOR A SOUTHERN STREAM SHORTWAVE TO MOVE ACROSS THE
REGION THIS WEEKEND FOLLOWED BY A LARGE TROUGH TO SET UP OVER
WESTERN NORTH AMERICA NEXT WEEK.  FIRST FOR THE SOUTHERN STREAM
SHORTWAVE EARLY THIS WEEKEND...THE GFS AND GEM ARE IN VERY GOOD
AGREEMENT WITH THE TRACK AND STRENGTH OF A SURFACE LOW ACROSS
SOUTHERN WISCONSIN ON SATURDAY...WHILE THE ECMWF IS WEAKER AND A
LITTLE FASTER.  CONSIDERING THE MODELS HAVE BEEN TRENDING
QUICKER...CANNOT RULE OUT THE ECMWF.  WILL STICK WITH A BLEND OF THE
GFS AND ECMWF.  THE MEDIUM RANGE MODELS ALSO AGREE PRETTY WELL WITH
THE TIMING OF A COLD FRONT AND LEADING EDGE OF THE WESTERN NOAM
TROUGH ON MONDAY.  WILL STICK WITH THE ECMWF FOR LATER PERIODS.

FRIDAY NIGHT THROUGH SATURDAY NIGHT...A SHORTWAVE TROUGH WILL LIFT
NORTHEAST FROM THE CENTRAL GREAT PLAINS TO THE WESTERN GREAT LAKES
FRIDAY NIGHT...AND WILL SEND A SURFACE LOW INTO SOUTHWEST WISCONSIN
BY 12Z SATURDAY.  AHEAD OF THIS SYSTEM...QG FORCING AND MID LEVEL
FGEN WILL INCREASE WHILE PWATS WILL CLIMB JUST SHY OF 2 INCHES.  AS
A RESULT...THINK ANOTHER ROUND OF HEAVY RAIN IS LIKELY LATE FRIDAY
NIGHT INTO SATURDAY MORNING...THIS TIME OVER CENTRAL AND NORTHEAST
WISCONSIN.  THE RAIN WILL PUSH OUT SATURDAY AFTERNOON AS THE SYSTEM
EXITS TO THE EAST...BUT CLEARING WILL LIKELY BE SLOW TO OCCUR BEHIND
THE SYSTEM.  IF CLEARING DOES OCCUR SATURDAY NIGHT...FOG WILL LIKELY
BE AN ISSUE AFTER ALL OF THE RAINFALL.

REST OF THE FORECAST...MODELS ARE PICKING UP ON A WEAK SHORTWAVE
THAT ARRIVES SUNDAY MORNING THAT COULD PRODUCE A FEW SHOWERS.  SINCE
HIGH PRESSURE WILL BE CENTERED ACROSS THE REGION...THINK THE
POTENTIAL IS TOO LOW TO INCLUDE IN THE FORECAST.  WILL CONTINUE THE
DRY FORECAST WITH HIGHS IN THE 70S.  THE NEXT FRONT WILL THEN MOVE
ACROSS THE REGION SUNDAY NIGHT INTO MONDAY.  FORCING AND MOISTURE
ALONG THE FRONT LOOK VERY GOOD ONCE AGAIN.  SOME INDICATIONS THAT A
LLJ WILL TRY TO ADVECT ELEVATED INSTABILITY INTO CENTRAL AND
EAST-CENTRAL WISCONSIN DURING THIS TIME WHICH WOULD CREATE A CHANCE
OF STRONG TO SEVERE STORMS GIVEN THE DECENT WIND FIELDS ALOFT.  A
LITTLE TOO EARLY YET FOR THESE SORTS OF DETAILS BUT DEFINITELY
SOMETHING TO WATCH.  PRECIP WILL END WITH THE EXIT OF THE FRONT
MONDAY AFTERNOON AS THE UPPER TROUGH SETTLES ACROSS THE REGION FOR
TUESDAY.  HEIGHTS WILL REBOUND ON WEDNESDAY AND SHOULD SEE A WARMING
TREND BEGIN.
&&

.AVIATION...FOR 12Z TAF ISSUANCE
ISSUED AT 553 AM CDT THU AUG 28 2014

INVERSION OVERNIGHT WAS GENERATING A MIX OF MVFR/VFR CIGS BETWEEN
1000 FEET AND 3500 FEET. EVEN SOME POCKETS OF IFR CIGS WERE ALSO
SHOWING UP OVER PARTS OF CENTRAL WISCONSIN AND CIGS OVERALL WERE
LOWERING THE LAST FEW HOURS. PROGS SUGGEST THIS INVERSION HANGS
AROUND THIS AM AND AS A RESULT MVFR/IFR CIGS MAY LINGER THIS AM.
FOG SO FAR HAS BEEN LIMITED BUT STILL ANTICIPATE LOCALIZED
MVFR/IFR VSBYS THROUGH 14Z.

STILL ANTICIPATE CIGS TO TURN TO MAINLY VFR CONDITIONS LATER TODAY
INTO TONIGHT...PRIOR TO WIDESPREAD MVFR CIGS AND VSBYS DUE TO
SHOWERS AND STORMS SPREADING FROM NORTH TO SOUTH TONIGHT.
&&

.HYDROLOGY...
ISSUED AT 334 AM CDT THU AUG 28 2014

LATEST FORECAST INFORMATION CONTINUES TO SUGGEST TWO
PERIODS OF RAIN LATER TODAY INTO SATURDAY. ROUND ONE WITH THE DEEP
MOISTURE RETURN AND WARM FRONT WORKING NORTHWARD. INSTABILITY NOT
IMPRESSIVE AT THE ONSET BUT LIGHT WINDS ALOFT SUPPORT A SLOWER
STORM MOVEMENT. SOME QUESTION AS TO THE RATE OF THIS NORTHERN
FRONTAL MOVEMENT AS TO IF THEIR WILL BE A BREAK FOR MOST AREAS.
BLEND OF THE MODELS INDICATE THE HIGHER RAIN AMOUNTS MAY FALL OVER
CENTRAL WISCONSIN. BUT ANTICIPATE RAIN TO BE ON THE INCREASE
AGAIN LATER FRIDAY AND ESPECIALLY FRIDAY NIGHT INTO SATURDAY FROM
WEST TO EAST AS THE MID LEVEL TROUGH SLIDES OVER.

WILL CONTINUE WITH THE ESF THIS MORNING BUT CONSIDERATION OF A
FLOOD WATCH MAY BE NEEDED WITH LATER SHIFTS IF FOLLOWING MODEL
RUNS SUGGESTS THE FRIDAY NIGHT TO SATURDAY RAIN WILL FALL OVER THE
SAME AREA AS THE FIRST ROUND.
&&

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

$$

UPDATE.........TDH
SHORT TERM.....TDH
LONG TERM......MPC
AVIATION.......TDH
HYDROLOGY......TDH






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