Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 272013
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
313 PM CDT WED AUG 27 2014

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND THURSDAY
ISSUED AT 313 PM CDT WED AUG 27 2014

THE MAIN CONCERN DURING THIS PART OF THE FORECAST IS TIMING OF THE
ONSET OF PRECIPITATION ASSOCIATED WITH A MID LEVEL TROUGH...THE
RIGHT ENTRANCE REGION OF A 250MB JET...ISENTROPIC LIFT IN WARM
ADVECTION WITH AN 850MB JET...AND A WEAK SURFACE SYSTEM.

CLOUDS THAT DEVELOPED DURING THE DAY SHOULD DISSIPATE WITH LOSS OF
DAYTIME HEATING...LEAVING SOME MIDDLE AND HIGH CLOUDS FROM THE
SYSTEM OVER THE PLAINS. UNDER SURFACE HIGH PRESSURE WINDS SHOULD
BE LIGHT. THE COMBINATION OF CLEARING SKIES AND LIGHT WINDS WILL
LIKELY ALLOW FOR SOME FOG...MAINLY IN NORTHERN WISCONSIN.

THE SURFACE HIGH AND UPSTREAM MID LEVEL RIDGE SHOULD KEEP THE
FORECAST AREA DRY THROUGH THURSDAY MORNING. THE 12Z VERSIONS OF THE
NAM/GFS/ECMWF/GEM-NH AND THE 15Z SREF ALL KEPT QPF TO THE
WEST/SOUTHWEST THROUGH 18Z BEFORE SPREADING IT NORTHEAST BETWEEN
18Z THURSDAY AND 00Z FRIDAY. MOST OF THEM DO NOT HAVE QPF COVERING
THE ENTIRE AREA UNTIL AFTER 00Z FRIDAY. FOR THIS REASON HAVE
SLOWED THE ONSET OF PRECIPITATION ACROSS THE AREA...CONFINING
CHANCE POPS TO CENTRAL WISCONSIN DURING THE MORNING BUT MOSTLY
HOLDING OFF RAIN UNTIL LATER IN THE AFTERNOON ACROSS MUCH OF
NORTHEAST WISCONSIN. BUFKIT SHOWED NO MORE THAN DOUBLE DIGIT CAPE
VALUES ON FRIDAY SO HAVE USED MOSTLY SHOWERS WORDING WITH A
MENTION OF CHANCE OR SLIGHT CHANCE FOR THUNDER...ONCE THE RAIN
GETS STARTED.

EXPECT NEAR NORMAL LOWS TONIGHT WITH FEW CLOUDS...LIGHT
WINDS...AND 40S AND 50S DEW POINTS. TEMPERATURES WILL LIKELY BE
BELOW NORMAL ON THURSDAY WITH INCREASING CLOUDS AND PRECIPITATION
SPREADING ACROSS THE STATE.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY
ISSUED AT 313 PM CDT WED AUG 27 2014

PCPN TRENDS AND HEAVY RAINFALL POTENTIAL THROUGH MONDAY WILL
BE THE MAIN FCST CONCERNS.

HAVE DETAILED THE HEAVY RAINFALL THREAT FOR THU NGT THROUGH SAT
IN THE HYDROLOGY SECTION BELOW. THE MAIN CHANGES FROM THE PREV
FCST WERE TO SHIFT THE HIGHER POPS AND QPF AMOUNTS FARTHER NORTH
THURSDAY NIGHT. WITH THIS IN MIND...WILL EXPAND THE ESF FARTHER
NORTH TO INCLUDE THE ENTIRE CWA.

LINGERING PCPN SHOULD TAPER OFF OVER THE CWA SATURDAY EVG...WITH
MAINLY DRY CONDITIONS EXPECTED UNDER WEAK HIGH PRESSURE LATE SAT
NGT INTO SUNDAY.

A STRONG COLD FRONT AND S/W TROF WILL SWEEP THROUGH THE AREA LATE
SUNDAY NIGHT INTO MONDAY...AND PRODUCE ANOTHER SWATH OF SIGNIFICANT
PCPN. DEPENDING ON THE TIMING OF THE FRONT...AND AMOUNT OF CLOUD
COVER AND HEATING THAT OCCURS AHEAD OF IT...SEVERE TSTMS MAY BE
A CONCERN. INCREASING DEEP LAYER SHEAR (40-50 KTS) AND MID-LEVEL
WINDS WILL BE FAVORABLE...BUT INSTABILITY IS IN QUESTION.

AFTER THE FRONT CLEARS THE REGION...QUIETER AND MAINLY DRY
CONDITIONS ARE ANTICIPATED INTO MIDWEEK.

TEMPERATURES ARE EXPECTED TO REMAIN AT OR A LITTLE ABOVE NORMAL
THROUGH THE PERIOD...WITH HIGHS IN THE 70S AND LOWS IN THE 50S
AND LOWER 60S.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1255 PM CDT WED AUG 27 2014

CIGS WERE GENERALLY IN THE 3000-4000FT RANGE...MAINLY NORTH OF
HIGHWAY 29. EXPECT VFR CONDITIONS TO CONTINUE THROUGHOUT THE DAY
WITH CU GENERALLY BREAKING UP AND HIGHER CLOUDS PUSHING IN FROM
THE SOUTHWEST. WINDS SHOULD REMAIN LIGHT UNDER SURFACE HIGH
PRESSURE. EXPECT AREAS OF MVFR...AND SCATTERED IFR...VSBYS IN FOG
WITH HIGH PRESSURE OVER THE REGION AND AN UPSTREAM MID LEVEL
RIDGE. FOG IS EXPECTED TO DISSIPATE DURING THE EARLY PART OF THE
MORNING. VFR CONDITIONS SHOULD PREVAIL FOR THE REST OF THE MORNING
AS IT APPEARS THAT CONVECTION WILL HOLD OFF UNTIL AFTERNOON.
&&

.HYDROLOGY...
ISSUED AT 313 PM CDT WED AUG 27 2014

A VERY MOIST AIR MASS WILL RETURN TO THE REGION
THURSDAY AFTERNOON AND EVENING...WITH PWATS INCREASING TO 1.5 TO
2.0 INCHES AND H8 DEW POINTS INCREASING TO 14 TO 16 C OVER CENTRAL
AND NORTHEAST WISCONSIN. A WARM FRONT WILL LIFT NORTH ACROSS THE
REGION...WITH A 30 TO 40 KT LOW- LEVEL JET ASCENDING THE BOUNDARY.
THIS WILL BRING THE POTENTIAL FOR HEAVY RAIN TO CENTRAL WI LATE
THU AFT/EVG...AND THE REST OF THE CWA OVERNIGHT INTO EARLY FRIDAY.
A SLOW MOVG SFC LOW AND BOUNDARY WILL RESIDE OVER THE REGION INTO
SATURDAY...WITH AN UPPER LEVEL TROF AND RRQ OF UPPER JET AIDING IN
PCPN DEVELOPMENT NEAR THE BOUNDARY. MORE HEAVY RAIN WILL LIKELY
OCCUR...BUT CONFIDENCE IN THE PLACEMENT IS LOW. OVERALL...MODEL
TRENDS SUPPORT THE SFC LOW...FRONTAL BOUNDARY AND DEEPEST MOISTURE
SHIFTING INTO OUR SE COUNTIES ON SATURDAY...SO SUSPECT THE HEAVY
RAINFALL POTENTIAL WILL SHIFT TO OUR SE COUNTIES. RIVER LEVELS
ARE NEAR NORMAL AND CAN HANDLE A FEW INCHES OF RAIN...SO FLOODING
CONCERNS WOULD MAINLY BE FOR SMALL STREAMS AND URBAN AREAS AT THIS
TIME. WILL UPDATE THE ESF PRODUCT...EXPANDING IT TO COVER THE ENTIRE
CWA.
&&

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

$$

SHORT TERM.....MG
LONG TERM......KIECKBUSCH
AVIATION.......MG
HYDROLOGY......KIECKBUSCH





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