Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 302335
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
635 PM CDT WED JUL 30 2014

UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND THURSDAY
ISSUED AT 336 PM CDT WED JUL 30 2014

CHANCES FOR AND TIMING OF SHOWERS AND THUNDERSTORMS ARE THE MAIN
CONCERNS THROUGH THURSDAY.

GENERAL SURFACE FLOW ACROSS WISCONSIN WAS RATHER WEAK THIS
AFTERNOON...BUT THERE WAS A WIND SHIFT ACROSS THE NORTHWEST PART
OF THE STATE. BEHIND THE WIND SHIFT NORTHWEST WINDS PREVAILED WITH
SOME GUSTS AROUND 20 KNOTS PRODUCING MORE SIGNIFICANT SURFACE
CONVERGENCE. AN UPPER LEVEL SHORT WAVE WAS MOVING INTO THE REGION
FROM WESTERN ONTARIO AND THERE WERE SOME SHOWERS AND THUNDERSTORMS
AHEAD OF IT THIS AFTERNOON...FROM NORTHERN MINNESOTA AND UPPER
MICHIGAN...INTO NORTHWEST WISCONSIN. LOCAL MESOANALYSIS INDICATED
AROUND 250J/KG MUCAPE AND LITTLE/NO CIN ACROSS NORTH CENTRAL
WISCONSIN BUT NO CAPE FOR THE REST OF THE AREA AS OF 19Z.
HOWEVER...SURFACE TO 1.5KM LAPSE RATES WERE AT LEAST 10K/KM AND 0
TO 3KM LAPSE RATES WERE IN EXCESS OF 7K/KM. MID LEVEL INSTABILITY
WAS UNIMPRESSIVE.

12Z NAM AND GFS AND 00Z ECMWF KEPT SOME QPF IN THE STATE INTO AT
LEAST THE MORNING HOURS ON THURSDAY...BUT THE 12Z EC SEEMED TO BE
MORE IN LINE WITH WHAT IS ACTUALLY OCCURRING. AS A RESULT OF
THIS...HAVE GONE WITH CHANCES FOR SHOWERS AND THUNDERSTORMS LATE
THIS AFTERNOON INTO EARLY EVENING...TAPERING OFF OVERNIGHT. LIGHT
WINDS AND LITTLE CLOUD COVER WILL LIKELY RESULT IN PATCHY FOG
TOWARD MORNING. HAVE THEN BROUGHT POPS BACK INTO THE FORECAST FOR
THURSDAY AFTERNOON.

MADE ONLY MINOR CHANGES TO TEMPERATURES...MAINLY BLENDED THE PREVIOUS
FORECAST WITH SOME OF THE BEST PERFORMING MODEL GUIDANCE.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY
ISSUED AT 336 PM CDT WED JUL 30 2014

PRECIPITATION THURSDAY NIGHT INTO SATURDAY WILL PRIMARILY BE
DIURNALLY DRIVEN IN THE WEAKENING CYCLONIC FLOW ALOFT. WHILE SHORT
WAVE TIMING WILL BE DIFFICULT...WILL FOCUS BEST POP TRENDS WITH
THE H500 TEMP PROGS. TEMPS SLIGHTLY MODIFY THURSDAY EVENING
HOWEVER ALL PROGS IN AGREEMENT WITH COOLER H5 TEMPS FOR LATE
THURSDAY NIGHT INTO FRIDAY BEFORE MODIFYING AGAIN FOR LATE FRIDAY
NIGHT INTO SATURDAY. PROGS ALSO INDICATE A SHORT WAVE TROUGH
SLIDING THROUGH ON FRIDAY WITH THE COLDER AIR. WILL KEEP THE
HIGHER END CHC POPS FOCUSED FOR FRIDAY...AND LIGHTER DIURNAL LOWER
END CHC POPS OR DRY ELSEWHERE.

UPPER PATTERN BEGINS TO CHANGE THIS WEEKEND AS THE UPPER LOW
WEAKENS AND LIFTS NORTHEASTWARD AND THE WESTERN STATES RIDGE
BREAKS DOWN TO SOME DEGREE. MODELS ATTEMPTS TO TRACK A SHORT WAVE
OVER THE RIDGE THIS WEEKEND...THEN SLOWLY DROP THIS WAVE AND A
FRONTAL SYSTEM INTO THE WESTERN GREAT LAKES REGION LATER SUNDAY
INTO MONDAY. THE FRONT SLOWS DOWN OR STALLS NEXT WEEK IN THE LESS
AMPLITUDE FLOW AND WILL BE A FOCUS OF CONVECTION. AT THIS TIME THE
FRONT IS PROGGED TO DROP INTO IOWA AND NORTHERN ILLINOIS BY NEXT
TUESDAY BUT COULD BE CLOSE ENOUGH FOR A CONTINUED PCPN CHANCE FOR
PARTS OF CENTRAL WISCONSIN AND EAST CENTRAL WISCONSIN.
&&

.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 624 PM CDT WED JUL 30 2014

SHOWERS AND THUNDERSTORMS MOVING SOUTH OUT OF THE U P YET AGAIN
THIS EVENING. QUESTION IS HOW LONG THEY WILL HOLD TOGETHER. MESO
MODEL SUGGESTS FEW SHOWERS MOVING INTO CENTRAL AND EAST CENTRAL
AFT 01Z...THOUGH THE STORMS WILL BE MOVING INTO A MUCH MORE STABLE
REGION. THUS WILL ONLY CARRY SHOWERS SOUTH OF RHI. LIGHT WINDS AND
DECREASING CLOUDS AFTER MIDNIGHT WILL ALLOW AREAS OF FOG TO
DEVELOP ONCE AGAIN SIMILAR TO LAST NIGHT. &&

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

$$

SHORT TERM.....MG
LONG TERM......TDH
AVIATION.......TE





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