Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 201757
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1257 PM CDT WED AUG 20 2014

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SYNOPSIS...
ISSUED AT 425 AM CDT WED AUG 20 2014

RELATIVELY QUIET TODAY...THEN THE CHANCE OF THUNDERSTORMS RETURNS
FOR TONIGHT AND THURSDAY. REMAINING RATHER HUMID THE NEXT FSEVERAL
DAYS.

THE UPR PATTERN ACRS NOAM WL AMPLIFY THE NEXT SEVERAL DAYS AS A
TROF DEEPENS OVER THE INTERMOUNTAIN WEST AND A DOWNSTREAM RIDGE
BUILDS FM THE LOWER MISSISSIPPI VALLEY...NNEWD...ACRS THE UPR
GREAT LAKES REGION. THIS WL LEAVE THE FCST AREA IN THE RING OF
FIRE REGION FOR CONVECTION FIRING ARND THE PERHPHERY OF THE UPR
RIDGE. THOUGH DIFFERING ON THE EXACT TIMING...MED RANGE MODELS
AGREE THAT ENERGY SHEARING OUT OF THE WRN TROF WL FIRST FLATTEN
THE ERN RIDGE...FOLLOWED BY THE MAIN TROF ITSELF EVENTUALLY
SHIFTG INTO THE PLAINS.

THIS LOOKS LIKE A WET PATTERN...AS AMPLE MOISTURE IS ACTED UPON BY
SHRTWVS RIDING NEWD OUT OF THE WRN TROF AND ARND THE ERN RIDGE.
THOUGH TIMING OF INDIVIDUAL CONVECTIVE EVENTS WL BE DIFFICULT...
THE PATTERN FAVORS ABV NORMAL AND POSSIBLY EVEN EXCESSIVE
RAINFALL. THE AIR MASS ACRS THE AREA WL BE WARM AND HUMID...SO
TEMPS SHOULD BE ABV NORMAL FOR THE MOST PART. OF COURSE TEMPS
COULD BE HELD BACK ON ANY DAYS WITH WIDESPREAD TSTMS.
&&

.SHORT TERM...TODAY...TONIGHT...AND THURSDAY
ISSUED AT 425 AM CDT WED AUG 20 2014

FAIRLY QUIET WX EXPECTED TDA. THE N/NE WL HAVE TO CONTEND WITH
LINGERING PCPN WRAPPING ARND THE WRN FLANK OF THE UPR LOW THAT WL
BE SLOWLY EDGING EWD OUT OF THE RGN. PCPN CHARACTER MAY BE THAT OF
A FINE LIGHT RAIN OR DRIZZLE...BUT COVERAGE WL BE LIMITED...SO
OPTED TO HANDLE IN THE FCST AS ISOLD LGT SHOWERS. ST ADVANCING
ACRS THE REGION THIS MORNING WL PROBABLY TAKE A LITTLE TIME TO
BREAK UP...SO ADJUSTED SKYCON GRIDS ACCORDINGLY.

UPR LOW WL CONTINUE TO EDGE AWAY TNGT. MEANWHILE...CONVECTION
DRIVEN BY ISENT LIFT IN THE FRONTAL ZONE LIFTG NEWD TOWARD THE
REGION COULD AFFECT THE AREA...ESP AFTER MIDNIGHT. FIRST THOUGHT
WAS TO SLOW THE ARRIVAL OF THE PCPN A LITTLE AS DEPARTING UPR LOW
MAY HOLD THINGS UP A BIT. BUT PCPN REALLY ISN/T THAT FAR AWAY
ALREADY...SO STUCK CLOSE TO PREV FCST. NEW ECMWF ALSO FIT WELL
WITH THE GOING FCST.

FRONTAL WAVE SUPPORTED BY SHRTWV EJECTING OUT OF THE WRN TROF
SHOULD REACH THE NRN PLAINS THU AFTN. COMBINED WITH BACKING UPR
FLOW...THAT SHOULD ALLOW WARM FRONT TO LIFT INTO WI BY AFTN.
STUCK WITH THE LIKELY POPS FM THE PREV FCST...THOUGH TIMING OF
BEST PCPN CHCS IS SOMEWHAT UNCERTAIN. IT COULD BE DURING THE
MORNING AS THE NE PORTION OF NOCTURNAL MCS FM THE PLAINS MVS
THROUGH THE AREA...OR IT COULD BE DURING THE AFTN WHEN THE FRONT
NEARS THE AREA. SHEAR WL BE INCREASING AS WLY FLOW ALOFT
STRENGTHENS. THERE WL ALSO BE AMPLE MOISTURE...WITH PWATS
APPROACHING 2 INCHES AND SFC DEWPTS APPROACHING 70F. MAIN UNKNOWN
FOR SVR WL BE THE AMNT OF DESTABILIZATION THAT CAN OCCUR. SPC WENT
WITH 5 PCT CHC FOR SVR IN THE DAY 2 CONVECTIVE OUTLOOK. THATS GOOD
FOR NOW AND WL BEGIN MENTIONING IN THE HWO. RISK WL LIKELY NEED TO
BE BE UPGRADED IF CONFIDENCE INCREASES THAT THERE WL BE ENOUGH
SUNSHINE TO ALLOW THE ATM TO SIGNIFICANTLY DESTALILIZE. PWATS ARND
2 INCHES SUPPORT HEAVY RAIN/FLOODING POTENTIAL...ESP SINCE MANY
AREAS RECEIVED SIG RAINS THE PAST FEW DAYS.

.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY
ISSUED AT 425 AM CDT WED AUG 20 2014

AN UNUSUAL 500MB PATTERN FOR THIS SUMMER IS SETTING UP ACROSS THE
UNITED STATES LATE IN THE WORK WEEK INTO THE UPCOMING WEEKEND.
500MB RIDGE EXPECTED TO BUILD ACROSS THE SOUTH CENTRAL UNITED
STATES WHILE 500MB TROUGH ENTERS THE WEST COAST BY FRIDAY. 500MB
RIDGE WILL BE FIRMLY ENTRENCHED ACROSS THE MISSOURI VALLEY THIS
WEEKEND. THIS PATTERN SHOULD BRING ABOVE NORMAL TEMPERATURES TO
THE AREA. THE RIDGE WILL NOT LAST LONG ACROSS THE WESTERN GREAT
LAKES AS RIDGE WILL BREAK DOWN BY THE MIDDLE OF NEXT WEEK.

FOR THURSDAY NIGHT...THERE IS SOME POTENTIAL FOR STRONG OR SEVERE
THUNDERSTORMS THURSDAY EVENING AS WARM FRONT MOVES ACROSS THE
REGION. 850MB JET MODEST AROUND 30 KNOTS WHICH SHOULD VEER TO THE
WEST OVERNIGHT. THINK MOST OF THE CONVECTION WOULD BE DURING THE
EVENING WITH ONLY SMALL CHANCES AFTER MIDNIGHT (HIGHEST ACROSS
NORTHEAST WISCONSIN). FRIDAY COULD END UP MAINLY DRY AS SOME DRIER
BEHIND DEPARTING SYSTEM ARRIVES. ALSO...MODIFIED SOUNDINGS
INDICATED CONVECTIVE TEMPERATURES IN THE LOWER TO MIDDLE
90S...WHICH WE WOULD NOT REACH. HAVE LOWERED CHANCES OF STORMS
SUBSTANTIALLY FOR FRIDAY AND FRIDAY NIGHT AS SOME OF THE MODELS
PUSH BOUNDARY FAR ENOUGH SOUTH TO KEEP THE REGION DRY. LATER
SHIFTS MAY BE ABLE TO PULL THE SLIGHT CHANCES FOR RAIN IF THIS
SCENARIO HOLDS TRUE. NEW ECMWF NOW SLOWER WITH THE RETURN OF
PRECIPITATION. 12Z RUN INDICATED SATURDAY WHILE 00Z RUN TONIGHT
NOW TAKING AIM FOR SATURDAY NIGHT. WILL CONTINUE WITH MID RANGE
CHANCES FOR RAIN. A LOT OF UNCERTAINTY IN HOW QUICK THE 500MB
RIDGE WILL BREAK DOWN EARLY NEXT WEEK. LATEST GFS WOULD SUGGEST A
TON OF RAIN...BUT THINK OUTFLOW BOUNDARIES WILL EVENTUALLY PUSH
SOUTHWARD AT SOME POINT LATE THIS WEEKEND INTO EARLY NEXT WEEK.
DID NOT STRAY FAR FROM PREVIOUS FORECAST AS DUE TO THE UNCERTAINTY
IN THE TIMING OF SHOWERS AND STORMS AND WILL BOUNDARY WILL SET UP.
COULD BE A VERY ACTIVE PATTERN WITH SUMMER TIME HEAT AND HUMIDITY
AT TIMES.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1257 PM CDT WED AUG 20 2014

MOSTLY MVFR CIGS ACROSS THE AREA SHOULD GRADUALLY IMPROVE TO VFR
FROM SOUTH TO NORTH DURING THE DAY BEFORE CLOUDS START TO CLEAR.
SURFACE HIGH PRESSURE...LIGHT WINDS AND LOW LEVEL MOISTURE WILL
ALLOW FOG TO DEVELOP OVERNIGHT WITH WIDESPREAD MVFR AND IFR VSBYS.
A WARM FRONT WILL PUSH NORTHEAST INTO WISCONSIN ON THURSDAY AS LOW
PRESSURE OVER THE PLAINS APPROACHES THE STATE. WEAK SHORT WAVE
ENERGY...INCREASING INSTABILITY AND THE SURFACE BOUNDARY WILL LEAD
TO THE DEVELOPMENT OF SHOWERS AND STORMS...BEGINNING TO IMPACT
CENTRAL WISCONSIN TOWARD MORNING AND CONTINUING NORTHEAST
THROUGHOUT THE DAY. PREVAILING CIGS SHOULD BE MOSTLY VFR BUT
SHOWERS AND STORMS WILL BRING MVFR...AND SOME IFR...CIGS AND
VSBYS.
&&

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

$$

SYNOPSIS.......SKOWRONSKI
SHORT TERM.....SKOWRONSKI
LONG TERM......ECKBERG
AVIATION.......MG





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