Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 020350
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1050 PM CDT MON SEP 1 2014

UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE

.SYNOPSIS...
ISSUED AT 233 PM CDT MON SEP 1 2014

WARM AND RATHER HUMID WITH SHOWERS AND THUNDERSTORMS AT TIMES
THROUGH MOST OF THE HOLIDAY-SHORTENED WORK WEEK.

STG SUBTROPICAL RIDGE ACRS THE SRN CONUS WL EXPAND NWD A BIT THE
NEXT FEW DAYS AS SEASONABLY STG AND PROGRESSIVE BAND OF WESTERLIES
TO IT/S N GRADUALLY RECEDES FARTHER NWD. THE PRIMARY FRONTAL ZONE
SEPARATING WARM AND VERY MOIST TROPICAL AIR TO THE S FM COOLER AND
DRIER CANADIAN AIR TO THE N WL REMAIN STETCHED OUT W-E ALONG THE
SRN EDGE OF THE MAIN WESTERLIES...AND CLOSE TO THE FCST AREA.
THIS WL RESULT IN SEVERAL OPPORTUNITIES FOR PCPN...LIKELY RESULTING
IN ABV NORMAL AMNTS. TEMPS AND HUMIDITIES ARE EXPECTED TO REMAIN
AOA NORMAL FOR THE NEXT SEVERAL DAYS...THEN DROP BACK CLOSE TO
NORMAL BY THE WEEKEND.
&&

.SHORT TERM...TONIGHT AND TUESDAY
ISSUED AT 233 PM CDT MON SEP 1 2014

THE LATEST RAP ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A COLD
FRONT SLICING ACROSS NORTH-CENTRAL TO SOUTHWEST WISCONSIN EARLY THIS
AFTERNOON.  PRIMARY AREA OF RAIN AHEAD OF A SHORTWAVE HAS EXITED
NORTHEAST WISCONSIN...BUT ARE SEEING SCATTERED SHOWER AND ISOLATED
THUNDERSTORM DEVELOPMENT ALONG THE COLD FRONT WHERE ML CAPE VALUES
ARE AROUND 400 J/KG.  THIS FRONT WILL CONTINUE TO MARCH EAST THIS
AFTERNOON AND REACH EAST-CENTRAL WISCONSIN BY AROUND 00Z.  WILL HAVE
TO KEEP A SCT SHOWER/ISOLD TSTORM MENTION AHEAD OF THE FRONT UNTIL
THEN.  CLEARING SKIES EXIST BEHIND THE FRONT OVER FAR WESTERN
WISCONSIN AND MINNESOTA.  THEN THE NEXT SHORTWAVE IS QUICKLY MOVING
EAST OVER WESTERN SOUTH DAKOTA WHERE A FEW LIGHTNING STRIKES ARE
OCCURRING.  TIMING THE END OF PRECIP TONIGHT AND POTENTIAL FOR
THUNDERSTORMS TOMORROW ARE THE MAIN FORECAST CONCERNS.

TONIGHT...THE COLD FRONT WILL BE SLIDING SOUTHEAST ACROSS
EAST-CENTRAL AND SOUTHERN WISCONSIN EARLY IN THE EVENING...AND WILL
LEAVE A SLIGHT CHANCE OF SHOWERS OVER CALUMET...KEWAUNEE...AND
MANITOWOC COUNTIES FOR THE 00-01Z PERIOD. THEN SHOULD SEE A CLEARING
PERIOD THROUGH THE REST OF THE EVENING AS DRIER MID-LEVEL AIR WORKS
IN FROM THE WEST.  A MODESTLY TIGHT PRESSURE GRADIENT WILL BE IN
PLACE FOR THE EVENING...BUT SHOULD LOOSEN OVERNIGHT...AND PROBABLY
ENOUGH FOR FOG FORMATION OVER N-C WISCONSIN.  NOT AS CONFIDENT ABOUT
THE REST OF THE AREA AS STATISTICAL GUIDANCE IS RATHER PESSIMISTIC
ABOUT THE THREAT OF FOG.  WILL KEEP A PATCHY MENTION ALONG THE WIS
RIVER VALLEY TOO.  THE NEXT SHORTWAVE WILL BE MOVING INTO THE
NORTHERN MISSISSIPPI VALLEY LATE AND SHOULD HAVE INCREASING CLOUDS
TOWARDS SUNRISE.  LOWS RANGING FROM THE LOW 50S NORTH TO NEAR 60S SOUTH.

TUESDAY...THE SHORTWAVE TROUGH WILL MOVE ACROSS WISCONSIN DURING THE
MORNING BEFORE EXITING BY MID TO LATE AFTERNOON.  THERE MAY BE A
SPOTTY SHOWER WITH THE WAVE EARLY IN THE MORNING...BUT WITH DAYTIME
HEATING...MODELS PROJECT STEEP LOW LEVEL LAPSE RATES DEVELOPING ALL
THE WAY UP TO 750MB.  CONVECTIVE TEMPERATURES ARE ONLY PROJECTED TO
REACH THE LOWER TO THE MIDDLE 70S...WHICH ARE SLIGHTLY BELOW THE
FORECASTED MAX TEMPS FOR THE DAY.  IN ADDITION...ML CAPES ARE
PROJECTED TO RANGE FROM 500-1000 J/KG BY MIDDAY TO EARLY AFTERNOON
WITH NO CAP IN PLACE.  AS A RESULT...SHOULD SEE ISOLATED SHOWERS
EARLY BECOME MORE SCATTERED BY MIDDAY AS CONVECTIVE TEMPS ARE
APPROACHED.  WITH THOSE CAPES...CANNOT RULE OUT THUNDERSTORMS...AND
WILL KEEP A MENTION IN THE FORECAST.  LOW FREEZING LEVELS AROUND
10KFT AND 0-6KM BULK SHEARS OF 30-35 KTS SUGGEST GUSTY WINDS AND
SMALL HAIL WILL BE POSSIBLE WITHIN ANY THUNDERSTORMS.  HIGHS RANGING
FROM THE LOWER 70S NORTH TO UPPER 70S SOUTH.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY
ISSUED AT 233 PM CDT MON SEP 1 2014

ISOLD-SCT SHRA WL PROBABLY BE GONE BY TOMORROW NGT...SO WL START
THE LONG-TERM FCST OUT DRY. WK SFC PRESSURE GRADIENT AND 10-15 KT
WLY FLOW AT 850 MB WL NOT BE IDEAL FOR FOG TOMORROW NGT. BUT
GIVEN RECENT RAINS...WL MENTION PATCHY FOG ACRS THE AREA AFTER
MIDNIGHT.

QUIET WX SHOULD AT LEAST LINGER INTO WED...AND QUITE LIKELY LAST
THE WHOLE DAY. WL JUST BRUSH SOME LOW CHC POPS ACRS THE NW PART
OF THE AREA IN THE AFTN IN CASE SOME CONVECTION FM THE W CAN MAKE
IT THAT FAR E IN THE RELATIVELY FAST/FLAT WLY FLOW ALOFT.

A 24-36 HR PERIOD OF VERY ACTIVE WX WL PROBABLY FOLLOW FOR THE
LATTER HALF OF THE ABBREVIATED WORK WEEK. STG SHRTWV IN THE MAIN
BAND OF WESTERLIES WL BE PROGRESSING EWD ALONG THE U.S./CANADIAN
BORDER WED NGT...LIKELY RESULTING IN CYCLONGENESIS ACRS THE NRN
PLAINS. STRENGTHENING LLJ WL LIKELY VEER INTO THE FCST AREA
DURING THE NGT...PROBABLY BRINGING AN MCS FROM THE NRN PLAINS EWD
INTO THE FCST AREA. THE MAIN RESERVOIR OF VERY MOIST AND UNSTABLE
AIR WL BE TO THE SW...SO THE SVR THREAT WL MOST LIKELY REMAIN TO
OUR W. BUT WL NEED TO CLOSELY MONITOR THE SITN OVER THE NEXT FEW
DAYS AS THE FCST AREA WL BE ON THE ERN EDGE OF ELEVATED MIXED
LAYER...WITH FAIRLY STEEP MIDDLE LEVEL LAPSE RATES EDGING IN FM
THE W.

AS WAS THE CASE THIS MORNING AND BACK LAST MONDAY /AUG 25/...
CONVECTIVE POTENTIAL THU WL DEPEND ON THE BEHAVIOR OF THE
DEPARTING NOCTURNAL CONVECTION. WHAT MAY BE DIFFERENT THIS TIME
IS HIGHER UPR HEIGHTS AND STRONG WLY FLOW ALOFT DRIVING ELEVATED
MIXED LAYER ACRS THE AREA...RESULTING IN VERY WARM TEMPS ALOFT AND
POSSIBLY RESULTING IN STG CAPPING. ASSUMING CONVECTION SHUTS
DOWN...TEMPS WL LIKELY SOAR WELL INTO THE 80S WITH DWPTS RISING
INTO THE LOWER TO MIDDLE 70S. IF THAT OCCURS...A VERY VOLATILE ATM
COULD BE IN PLACE AS THE COLD FRONT STARTS IT/S PUSH ACRS THE AREA
THU AFTN/EVENING.

TOO MANY IF/S TO GET TOO SPECIFIC WITH THE FCST THIS FAR OUT...
BUT GIVEN THE OVERALL LOOK OF THE LARGE SCALE SET-UP...WL BEGIN TO
OPEN THE DOOR TO SOME SVR POTENTIAL IN THE HWO.

COOLER AND DRIER AIR WL PUSH INTO THE AREA IN THE WAKE OF THE
FRONT...AND LIKELY LINGER INTO EARLY NEXT WEEK.

NO SIG CHGS NEED TO BROAD-BASED EXTENDED FCST INITIALIZATION
GRIDS.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1047 PM CDT MON SEP 1 2014

CLEARING SKIES THIS EVENING AND DIMINISHING SURFACE WINDS WILL LIKELY
LEAD TO GROUND FOG FORMATION LATE TONIGHT...THOUGH STRONGER FLOW
JUST OFF THE SURFACE SHOULD LIMIT EXTENT. WEAK DISTURBANCES MOVING
THROUGH THE FLOW WILL BRING A CHANCE OF SHOWERS AND THUNDERSTORMS
BY TUESDAY MORNING. &&

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

$$

SYNOPSIS.......SKOWRONSKI
SHORT TERM.....MPC
LONG TERM......SKOWRONSKI
AVIATION.......TE






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