Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 271200
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
700 AM CDT MON OCT 27 2014

UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND TUESDAY
ISSUED AT 343 AM CDT MON OCT 27 2014

MORE ACTIVE NEXT 24 HOURS AS NOTABLE UPSTREAM TROUGH IMPACTS THE
FORECAST AREA.

AS ADVERTISED...SUBSTANTIAL WAA AND CONVERGENCE ASSOCIATED WITH 40
KT LOW-LEVEL JET...IN CONCERT WITH ELEVATED INSTABILITY HAS ALLOWED
FOR THE DEVELOPMENT OF A SOLID BAND OF SHOWERS AND THUNDERSTORMS
THIS MORNING. EMBEDDED THUNDER HAS STEADILY INCREASED IN AREAL
COVERAGE LAST HOUR OR SO. UPSTREAM SHORTWAVE IMPULSE CURRENTLY
OVER NORTHWEST IOWA ALSO CONTRIBUTING MORE ORGANIZED SYNOPTIC-
SCALE LIFT AND DESTABILIZATION. OTHER THAN THE 00Z NAM...AND
PERHAPS THE ECMWF...NONE OF THE OTHER GUIDANCE REALLY SEEMED TO HAVE
A DECENT HANDLE ON CURRENT CONVECTIVE ACTIVITY MOVING ACROSS THE
FORECAST AREA. THUS WILL LEAN MORE TOWARD THE NAM/ECMWF FOR THE
FIRST 12 HOURS OF THE FORECAST.

EXPECT CURRENT NW-SE ORIENTATED BAND OF SHOWERS AND THUNDERSTORMS
TO CONTINUE TO ADVANCE NORTHEAST ACROSS THE FORECAST AREA THIS
MORNING. BULK OF THE ACTIVITY SHOULD BE EAST AND NORTH OF THE FOX
VALLEY BY 5 AM OR SO. HAVE SEEN SOME UPSTREAM REPORTS OF PEA SIZE
HAIL NEAR LACROSSE...THUS WOULD NOT BE AT ALL SURPRISED TO SEE SOME
SMALL HAIL WITH THE ACTIVITY OVER NORTHCENTRAL WISCONSIN THIS
MORNING. WITH SHORTWAVE IMPULSE STILL UPSTREAM OVER NORTHERN
IOWA...SHOWER AND SCATTERED THUNDERSTORM ACTIVITY MAY PERSIST A BIT
LONGER OVER CENTRAL AND NORTHERN WISCONSIN WELL INTO THE MID-MORNING
HOURS. MOST LIKELY AREA TO SEE A BREAK IN THE ACTIVITY LATER THIS
MORNING WOULD BE THE FOX VALLEY AS PRIMARY ZONE OF WAA SHIFTS OFF TO
THE EAST. ADJUSTED POPS ACCORDING BY GRADUALLY TRIMMING BACK ON THE
POPS OVER THE SOUTHERN THIRD OF THE FORECAST AREA DURING THE MORNING
AND KEEPING HIGHER POPS ACROSS THE NORTH DURING THE DAY.
TEMPERATURES TODAY WILL BE TRICKY ESPECIALLY OVER THE FOX VALLEY.
SOME MODEL GUIDANCE SUGGESTS WARM FRONT MAY IMPINGE ON THE SOUTHERN
FOX VALLEY THIS AFTERNOON. ALSO WITH CLOUD COVER UPSTREAM NOT AS
WIDESPREAD AS EARLIER EXPECTED...COULD BE A FEW MORE BREAKS IN THE
CLOUD COVER. OPTED TO UP MAX TEMPERATURES UP A FEW DEGREES OVER THE
FOX VALLEY THIS AFTERNOON.

MAIN TROUGH THEN DEEPENS AND APPROACHES THE FORECAST AREA LATE
THIS AFTERNOON AND EARLY EVENING. ALTHOUGH MODELS DIFFER ON THE
DETAILS...GENERAL SCENARIO WOULD BE FOR THE COLD FRONT TO ENTER
CENTRAL WISCONSIN AROUND 00Z WITH SURFACE WAVE TO MOVE ALONG THE
FRONT AND DEEPEN AS IT MOVES NORTHEAST ROUGHLY FROM ARX TO GRB
BETWEEN 00Z AND 06Z TUESDAY.

ECMWF MORE ROBUST IN DEVELOPING QPF OVER MAINLY THE SOUTHEAST HALF
OF THE FORECAST AREA THIS EVENING AS SURFACE WAVE AND FRONT CROSS
THE AREA...WHILE GFS/NAM SUGGEST LESS DEVELOPMENT ALONG THE FRONT
AND FOCUS BULK OF QPF TO THE NORTHWEST OF THE FORECAST
AREA...WITH DRY SLOT IMPINGING ON CENTRAL WISCONSIN TOWARD
MIDNIGHT. OPTED TO TAKE THE MIDDLE OF THE ROAD AND KEEP BROAD
BRUSH HIGH CHANCE POPS ACROSS THE ENTIRE FORECAST AREA OVERNIGHT.

AS SURFACE LOW PUSHES NORTHEAST OF THE AREA TUESDAY...DRY
INTRUSION SHOULD MAKE ITS WAY ACROSS THE SOUTHERN HALF OF THE
FORECAST ARE WITH SOME RESIDUAL WRAP AROUND SHOWER ACTIVITY
PERSISTING ACROSS NORTHERN WISCONSIN INTO TUESDAY AFTERNOON. WILL
TURN SHARPLY COOLER ON TUESDAY WITH 850 TEMPS CRASHING TO -2 TO -4 C
OVER CENTRAL WISCONSIN BY 00Z WEDNESDAY. WILL FEEL QUITE A BIT MORE
BLUSTERY THAN LAST FEW DAYS.

.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY
ISSUED AT 343 AM CDT MON OCT 27 2014

FOR THE END OF THE WEEK...THE LATEST GFS ENSEMBLE MEAN HAS SHIFTED
THE LONGWAVE TROUGH AXIS OVER THE EASTERN NOAM SLIGHTLY TO THE EAST
COMPARED TO YESTERDAYS RUN.  THIS TREND ALSO OCCURRED IN THE LATEST
ECMWF AND GFS SOLUTIONS...WHICH ARE IN MUCH BETTER AGREEMENT ALSO
COMPARED TO LAST NIGHT.  WILL EMPLOY A GENERAL MODEL BLEND AS A
RESULT.

TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...A CLOSED SHORTWAVE TROUGH
WILL BE EXITING TO THE NORTHEAST AWAY FROM THE NORTH-CENTRAL GREAT
LAKES TUESDAY NIGHT.  BEHIND THE WAVE...COMMA HEAD MOISTURE WILL BE
PASSING OVERHEAD DURING THE NIGHT BEFORE EXITING EARLY WEDNESDAY
MORNING.  WITH AMPLE LOW LEVEL MOISTURE AND NORTHWEST WINDS
GENERATING MOISTURE FLUXES OFF LAKE SUPERIOR...SEEMS LIKE A VERY
GOOD RECIPE FOR BROKEN TO OVERCAST CONDITIONS WITH OCCASIONAL RAIN
TO SNOW SHOWERS ACROSS NORTHERN WISCONSIN.  WOULD NOT BE SURPRISING
TO SEE LIGHT PRECIP REACH AS FAR SOUTH AS THE ROUTE 29 CORRIDOR.
PRECIP WILL BE ENDING WEDNESDAY MORNING AS MID-LEVEL MOISTURE PULLS
OUT AND LOW LEVEL FLOW BACKS TO THE WESTERLY DIRECTION.  BUT WITH
LOW LEVEL THERMAL TROUGHING IN PLACE...CLEARING WILL BE DIFFICULT
BEFORE MID-LEVEL MOISTURE RETURNS WEDNESDAY AFTERNOON OR WEDNESDAY
NIGHT.  THIS SECOND ROUND OF MID-LEVEL MOISTURE WILL BE ACCOMPANIED
BY WEAK WARM ADVECTION AND AN EQUALLY WEAK SHORTWAVE.  PROGGED
SOUNDINGS INDICATE A DRY WEDGE IN THE MID-LEVELS...AND THIS KEEPS A
CHANCE OF PRECIP TOO SMALL TO INCLUDE IN THE FORECAST.  LITTLE
CHANGES TO TEMPS OVER THE PERIOD.

REST OF THE FORECAST...A WEAK SURFACE RIDGE AXIS WILL MOVE ACROSS
THE REGION ON THURSDAY THOUGH PROGGED SOUNDINGS SHOW PLENTY OF
MID-LEVEL MOISTURE OVERHEAD.  THIS SHOULD YIELD A PARTLY SUNNY TO
MOSTLY CLOUDY DAY.  THEN A STRONG COLD FRONT WILL BE DIVING
SOUTHEAST ACROSS THE REGION THURSDAY EVENING.  THIS FRONT SHOULD BE
ACCOMPANIED BY RAIN AND SNOW SHOWERS OVER NORTHERN WISCONSIN AND
MAINLY RAIN SHOWERS OVER THE CENTRAL PART OF THE STATE.  WINDS WILL
SHIFT TO THE NORTHWEST BEHIND THE FRONT AND WILL USHER 850MB TEMPS
OF -10C.  SHOULD HAVE WIDESPREAD LAKE CLOUDS ACROSS MUCH OF
NORTH-CENTRAL AND NORTHEAST WISCONSIN.  CLOUDS WILL LIKELY LINGER
INTO FRIDAY BUT MIXING SHOULD YIELD AT LEAST PARTIAL CLEARING OVER
EAST-CENTRAL AND CENTRAL WISCONSIN.  CANADIAN HIGH PRESSURE THEN
QUICKLY MOVES ACROSS THE AREA FRIDAY NIGHT AND SATURDAY.  THEN TEMPS
QUICKLY REBOUND IN RETURN FLOW BY SUNDAY.
&&

.AVIATION...FOR 12Z TAF ISSUANCE
ISSUED AT 659 AM CDT MON OCT 27 2014

MAINLY VFR CIGS INTO EARLY AFTERNOON IN THE WAKE OF MORNING
SHOWER AND THUNDERSTORM ACTIVITY ASSOCIATED WITH STROMG LOW-LEVEL
JET.

RATHER POTENT TROUGH OVER THE DAKOTAS WILL SWING EAST TOWARD
WISCONSIN LATE THIS AFTERNOON AND THIS EVENING. A SURFACE WAVE
WILL STRENGTHEN ON THE COLD FRONT AND MOVE NORTHEAST ACROSS THE
STATE THIS EVENING. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
WILL BECOME MORE NUMEROUS THIS AFTERNOON AS THE COLD FRONT
APPROACHES. MVFR CIGS WILL RETURN AS THIS SHOWER ACTIVITY
REDEVELOPS AND MOVES ACROSS THE STATE OVERNIGHT. SOME IFR CIGS ARE
POSSIBLE OVER NORTHERN WISCONSIN STARTING EARLY THIS EVENING AND
INTO THE OVERNIGHT WHERE PRECIPITATION WILL BE MORE PERSISTENT
NORTH OF THE SURFACE LOW. GUSTY WEST WINDS WILL DEVELOP ACROSS THE
STATE MONDAY MORNING IN THE WAKE OF THE COLD FRONT WITH SCATTERED
SHOWERS PERSISTING MAINLY ACROSS NORTHERN WISCONSIN INTO MONDAY
AFTERNOON.
&&

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

$$

SHORT TERM.....ESB
LONG TERM......MPC
AVIATION.......ESB






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