Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 190903
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
403 AM CDT FRI SEP 19 2014

FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND SATURDAY
ISSUED AT 402 AM CDT FRI SEP 19 2014

LOW LEVEL MOISTURE TRAPPED UNDER AN INVERSION IS
ONCE AGAIN PRODUCING LOW CLOUDS ACROSS MUCH OF THE AREA EARLY
TODAY. IT WILL PROBABLY MIX OUT BY MIDDAY IN MOST PLACES. STRONG
WARM ADVECTION AT 850MB TODAY BUT THERE IS LITTLE MOISTURE BELOW
500MB SO WE DO NOT EXPECT ANY PRECIPITATION EXCEPT MAYBE IN THE
FAR NORTH DURING THE AFTERNOON. HIGHS TODAY WILL DEPEND ON HOW
QUICKLY THE CLOUDS DEPART. TEMPERATURES WILL BE COOLER ALONG THE
LAKESHORE.

THERE IS A BETTER CHANCE OF SHOWERS AND THUNDERSTORMS TONIGHT AS A
WEAK COUPLED JET MOVES ACROSS THE REGION WHILE STRONG LOW LEVEL
WARM ADVECTION CONTINUES. THIS SHOULD PRODUCE A BROKEN AREA OF
PRECIPITATION THAT MOVES SLOWLY SOUTH ACROSS THE AREA. TEMPERATURES
WILL NOT FALL MUCH DUE TO CLOUD COVER AND A STEADY BREEZE.

A COLD FRONT WILL MOVE ACROSS THE AREA SATURDAY. THERE SHOULD BE
ABUNDANT LOW LEVEL MOISTURE AVAILABLE AHEAD OF THE FRONT BUT THE
QUESTION IS WHETHER THERE WILL BE ENOUGH INSTABILITY TO ELIMINATE
AN INVERSION AND GET THUNDERSTORMS BEFORE THE FRONT GOES BY.
FORECAST SOUNDINGS SUGGEST THAT THERE MAY BE 1000 J/KG OF CAPE BY
AFTERNOON WITH MID LEVEL WINDS OF 40 TO 50 KNOTS. SO AN ISOLATED
SEVERE THUNDERSTORM WITH STRONG WINDS IS NOT OUT OF THE QUESTION.

.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY
ISSUED AT 402 AM CDT FRI SEP 19 2014

MID/UPPER TROUGH WILL SLIDES OVER THE AREA ON SATURDAY NIGHT AND
SUNDAY...WITH A NORTHWEST FLOW DOMINATING THE WESTERN GREAT LAKES.
THIS WILL BE THE BEST PERIOD FOR RAIN IN THE EXTENDED. THE
AMPLIFIED PATTERNS RETURNS BY EARLY NEXT WEEK...WITH STRONG
RIDGING OVER WESTERN CANADA AND A TROUGH OVER EASTERN CANADA AND
THE EASTERN GREAT LAKES. THE RIDGE WILL SLIDE EAST EARLY NEXT
WEEK...AND BRING A FAIRLY QUIET UPPER LEVEL PATTERN TO THE
EASTERN 2/3 OF CANADA AND U.S. HOWEVER...MODELS NOW SHOW A WEAK
DISTURBANCE IN THE MID-LEVELS CROSSING INTO THE PLAINS BY MID-
WEEK. THIS COULD THROW SOME ISSUES INTO THE DRY FORECAST AS WE
HEAD TOWARD LATE WEDNESDAY AND THURSDAY. AT THE SURFACE...A
SPRAWLING HIGH PRESSURE WILL SLOWLY BUILD INTO THE WESTERN GREAT
LAKES EARLY NEXT WEEK...WITH RETURN FLOW SETTING UP AS THE HIGH
SPREADS TOWARD THE EASTERN SEABOARD.

PRECIP CHANCES WILL BE THE MAIN FORECAST CHALLENGE TO START OFF
THE EXTENDED FORECAST...AS UPPER TROUGH SLIDES ACROSS THE REGION.
INGREDIENTS SEEM TO BE COMING TOGETHER FOR MORE OF A WIDESPREAD
PRECIP EVENT...ESPECIALLY OVER NORTHER WISCONSIN...ON SATURDAY
NIGHT AS SYNOPTIC LIFT WILL BE ENHANCED WITH THE AREA IN THE LEFT
FRONT QUAD OF THE UPPER JET AND TWO POTENT SHORTWAVES WILL BE
CROSSING THE REGION. THE ECMWF AND GEM ARE ON BOARD WITH THIS
THINKING...BUT THE GFS AND NAM ARE A LITTLE LESS BULLISH. MOISTURE
SEEMS MORE THAN SUFFICIENT UNDER THE CYCLONIC FLOW. WILL KEEP THE
POPS MAINLY IN THE HIGH CHANCE CATEGORY...BUT CAN SEE THEM NEEDING
TO BE BUMPED UP...ESPECIALLY OVER THE NORTH.

THE BEST FORCING AND MOISTURE EXIT THE EARLY SUNDAY MORNING...AS
DRIER AIR AND RIDGING BEGIN TO WORK INTO THE WESTERN GREAT LAKES.
CYCLONIC FLOW...LINGERING MOISTURE...AND COOL AIR ALOFT WILL KEEP
AT LEAST A CHANCE OF SHOWERS THROUGH THE DAY. DRY WEATHER IS THEN
EXPECTED SUNDAY NIGHT INTO EARLY NEXT WEEK...AS UPPER AND SURFACE
RIDGING DOMINATE THE REGION. SOME QUESTIONS ENTER THE FORECAST
LATE WEDNESDAY AND THURSDAY...AS MODELS NOW SHOW A WEAK MID-LEVEL
SHORTWAVE TROUGH AND INCREASING MOISTURE PUSHING FROM THE NORTHERN
PLAINS INTO THE WESTERN GREAT LAKES. WILL HOLD ON TO THE DRY
FORECAST...HOWEVER IF MODELS CONTINUE TO HANG ON TO THIS
TREND...POPS WILL BE NEEDED BY THURSDAY.

TEMPS LOOK TO START OFF A LITTLE BELOW NORMAL...WITH SOME CHILLY
NIGHTS EXPECTED...THEN SLOWLY MODERATING TEMPS ARE EXPECTED EARLY
TO MID NEXT WEEK.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1029 PM CDT THU SEP 18 2014

OVERALL VFR CONDITIONS EXPECTED OVERNIGHT INTO FRIDAY
OVER MOST PLACES. HOWEVER PATCHES OF IFR/MVFR CIGS AND VSBYS WITH
FOG MAY DEVELOP OVERNIGHT. LLWS CONDITIONS MAY DEVELOP OVER THE
WEST HALF OF THE STATE LATE TONIGHT FOLLOWED WITH GUSTY SOUTH
WINDS OVER MOST LOCATIONS STARTING LATE FRIDAY MORNING AND
CONTINUE INTO THE AFTERNOON.
&&

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

$$

SHORT TERM.....RDM
LONG TERM......BERSCH
AVIATION.......TDH





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