Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 301807
AFDGRB

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

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND THURSDAY
ISSUED AT 352 AM CDT WED JUL 30 2014

PCPN TRENDS AND TEMPERATURES WILL BE THE MAIN FCST CONCERNS.

A S/W TROF WAS MOVG THROUGH NE WI EARLY THIS MORNING...BUT SHOWER
ACTIVITY HAD DIMINISHED DUE TO THE ARRIVAL OF A DRIER AIR MASS AND
NIGHTTIME STABILITY. ANOTHER S/W TROF...CURRENTLY OVER NORTHERN
ONTARIO...WILL BRUSH THROUGH FAR NE WI THIS AFTERNOON...ALONG WITH
THE LFQ OF A 70 KT JET. GIVEN THE PRESENCE OF A DRIER AIR MASS
AND MARGINAL INSTABILITY (CAPE ONLY 300-500 J/KG)...EXPECT DAYTIME
CONVECTION TO BE WEAKER...WITH LESS COVERAGE. WILL ONLY CARRY
CHANCE POPS ACROSS THE AREA...WITH THE HIGHEST POPS IN FAR NE WI.
CONVECTION SHOULD LINGER INTO THE EVG...THEN GRADUALLY WEAKEN.
USED A BLEND OF THE BETTER PERFORMING GUIDANCE SETS FOR TODAY AND
TONIGHT...WHICH YIELDED HIGHS IN THE 70S...AND LOWS IN THE UPPER
40S AND 50S.

NORTHWEST FLOW ALOFT WILL CONTINUE ON THURSDAY...BUT NO
SIGNIFICANT DYNAMIC FORCING IS EXPECTED DURING THE DAY. MODELS
SUGGEST THAT THE GREATEST INSTABILITY WILL OCCUR ACROSS THE
SW HALF OF THE CWA DURING THE AFTERNOON...BUT THE BEST LLVL
CONVERGENCE IS EXPECTED OVER FAR NE WI. WILL ONLY HAVE LOW-END
CHANCE POPS OVER THE FORECAST AREA...DUE TO THE LACK OF A
SIGNIFICANT TRIGGER. H8 TEMPS WILL BE 2-3 DEGREES C WARMER
THAN TODAY...SO HIGH TEMPS SHOULD WARM INTO THE MIDDLE 70S
TO LOWER 80S.

.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY
ISSUED AT 352 AM CDT WED JUL 30 2014

THE LATEST GFS ENSEMBLE MEAN INDICATES THAT BELOW NORMAL HEIGHTS
AT 500MB WILL PERSIST ACROSS THE WESTERN GREAT LAKES REGION
THROUGH EARLY NEXT WEEK THOUGH WILL GRADUALLY MODERATE OVER THIS
PERIOD. THE MEDIUM RANGE MODELS ARE ALSO ON BOARD WITH THIS
SCENARIO AND AGREE WELL WITH THE LARGE SCALE FEATURES...SO WILL
USE A BLEND OF THE ECMWF AND GFS.

THURSDAY NIGHT THROUGH FRIDAY NIGHT...MODELS SHOW A SHORTWAVE
BYPASSING THE REGION TO THE WEST AND SOUTH THURSDAY NIGHT...AS IT
MOVES AROUND THE PERIPHERY OF THE EASTERN CONUS TROUGH.  AS A
RESULT...SCATTERED SHOWERS AND A FEW THUNDERSTORMS WILL LIKELY
CONTINUE INTO THURSDAY EVENING BEFORE DIMINISHING OVERNIGHT.  VERY
LITTLE CHANGES INTO FRIDAY AND FRIDAY NIGHT...WITH THE UPPER
TROUGHING OVERHEAD.  SHOWERS AND STORMS SHOULD REDEVELOP FRIDAY
AFTERNOON BEFORE DIMINISHING GRADUALLY THROUGH THE EVENING. MAX AND
MIN TEMPS SHOULD REMAIN STEADY OVER THE PERIOD.

REST OF THE FORECAST...MID-LEVEL HEIGHTS REBOUND A LITTLE ON
SATURDAY BEFORE ANOTHER SHORTWAVE ARRIVES TOWARDS SUNDAY AFTERNOON.
OF THE DAYS THIS WEEKEND...SATURDAY LOOKS TO HAVE A BETTER CHANCE OF
BEING DRY.  THIS SHORTWAVE WILL DROP A WEAK FRONT ACROSS THE REGION
SUNDAY NIGHT INTO MONDAY...PROLONGING THE CHANCE OF PRECIP.
POSSIBLY TURNING DRY WITH HIGH PRESSURE BUILDING INTO THE REGION BY
NEXT TUESDAY.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 107 PM CDT WED JUL 30 2014

NOT A GREAT DEAL OF CONFIDENCE IN THIS FORECAST. FOG DISSIPATED
AND CU DEVELOPED ACROSS MOST OF THE AREA BY MIDDAY...BUT CIGS AND
VSBYS WERE IN THE VFR CATEGORY AT 17Z. CHANCES FOR SHOWERS AND
THUNDERSTORMS PRESENT THE BIGGEST CHALLENGE. VISIBLE SATELLITE
IMAGERY SHOWED AN AREA OF CLOUDS...THAT APPEARED TO HAVE SOME
VERTICAL DEVELOPMENT...MOVING FROM JUST SOUTHEAST OF INL TO NEAR
DLH SINCE MID MORNING. THE 12Z INL SOUNDING WAS QUITE UNSTABLE
ABOVE A SURFACE INVERSION BUT...RADAR MOSAIC SHOWED LITTLE. HAVE
OPTED TO KEEP THE GENERAL IDEA OF AFTERNOON SHOWER AND
THUNDERSTORM DEVELOPMENT IN CONTINUED UPPER LEVEL CYCLONIC
FLOW...WITH CONVECTION DYING OFF IN THE EVENING. 12Z NAM/12Z
GFS/00Z ECMWF ALL SHOWED AREAS OF QPF IN THE STATE TODAY BUT
CONTINUED IT DURING THE NIGHT AND EVEN INTO THURSDAY. TOTALS WERE
GENERALLY LOW AND LOCATIONS DID NOT ALWAYS MATCH UP...SO HAVE
OPTED FOR THE SIMPLE PLAN FOR NOW. LIGHT WINDS AND DECREASING
CLOUDS TONIGHT WILL ALLOW AREAS OF FOG TO DEVELOP ONCE AGAIN.
&&

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

$$

SHORT TERM.....KIECKBUSCH
LONG TERM......MPC
AVIATION.......MG






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