Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 010003
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
703 PM CDT SUN AUG 31 2014

UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE

.SYNOPSIS...
ISSUED AT 218 PM CDT SUN AUG 31 2014

WARM AND RATHER HUMID WITH SHOWERS AND THUNDERSTORMS AT TIMES FOR
THE REST OF THE HOLIDAY WEEKEND AND THROUGH THE UPCOMING WORK
WEEK.

STG SUBTROPICAL RIDGE ACRS THE SRN CONUS WL EXPAND NWD A BIT AS
SOMEWHAT PROGRESSIVE BAND OF WESTERLIES GRADUALLY RECEDES NWD
DURING THE PERIOD. NOTHING SPECIAL ABOUT THIS PATTERN FOR THIS
TIME OF YEAR...AS THE WESTERLIES ARE TYPICALLY STRONGER THAN
DURING THE MIDDLE SUMMER...BUT ARE STILL USUALLY CENTERED N OF THE
AREA.

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 MUCH OF THE TIME. THIS WL RESULT IN
SEVERAL OPPORTUNITIES FOR PCPN...LIKELY RESULTING IN ABV NORMAL
AMNTS. TEMPS ARE EXPECTED TO REMAIN AOA NORMAL FOR MUCH OF THE
FCST PERIOD BEFORE DROPPING BACK CLOSE TO NORMAL LATE. IT WILL
ALSO BE HUMID AT TIMES.
&&

.SHORT TERM...TONIGHT AND MONDAY
ISSUED AT 218 PM CDT SUN AUG 31 2014

THE LATEST RAP ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW LOW
PRESSURE MOVING NORTHEAST OVER FAR NORTHWEST MINNESOTA AND A COLD
FRONT MOVING EASTWARD FROM THE LOW TO THE CENTRAL GREAT PLAINS.
STORMS HAVE BEGUN TO FIRE ALONG THE FRONT OVER SOUTH CENTRAL
MINNESOTA...BUT THE ATMOSPHERE IS STRUGGLING TO DESTABILIZE DUE IN
PART TO A PRONOUNCED CAP AND DRY AIR ON THE 18Z MINNEAPOLIS
SOUNDING.  HOWEVER...AS A SHORTWAVE OVER NEBRASKA MOVES INTO THE
NORTHERN MISSISSIPPI VALLEY...THE CAP IS EXPECTED TO WEAKEN LATE
THIS AFTERNOON THAT WILL RESULT IN A FAVORABLE ENVIRONMENT FOR
SEVERE STORMS.  THESE STORMS COULD MOVE INTO NORTH-CENTRAL WISCONSIN
LATER THIS EVENING.  THE MAIN SHORTWAVE IS MOVING EAST OVER EASTERN
WYOMING AND ANTICIPATED TO ARRIVE INTO WISCONSIN LATE TONIGHT INTO
MONDAY MORNING...ALONG WITH THE COLD FRONT.  THUNDERSTORM TIMING AND
IMPACTS ARE THE MAIN FORECAST CONCERNS.

TONIGHT...A COLD FRONT WILL SLOWLY MOVE ACROSS THE NORTHERN
MISSISSIPPI VALLEY AS IT WAITS FOR A SHORTWAVE OVER WYOMING TO GIVE
IT A FORWARD PUSH.  ASSUMING STRONG TO SEVERE CONVECTION AHEAD OF
THE FRONT DEVELOPS AS PLANNED LATER THIS AFTERNOON INTO THIS
EVENING...GUIDANCE SUGGESTS THIS CONVECTION WILL MAKE A RUN AT
NORTH-CENTRAL WISCONSIN LATE THIS EVENING...THOUGH WILL BE WEAKENING
AS DIURNAL INSTABILITY IS LOST.  MODELS SUGGEST AROUND 1000 J/KG OF
ELEVATED CAPE WILL BE PRESENT AS THIS CONVECTION APPROACHES THE
NORTHWEST FORECAST AREA SO NOT OUT OF THE QUESTION THAT A FEW STRONG
STORMS COULD REACH NORTH-CENTRAL WISCONSIN.  AN ISOLATED SEVERE
STORM CANNOT BE RULED OUT...MAINLY FOR DAMAGING WINDS AND LARGE
HAIL.  WOULDNT BE SURPRISE TO SEE A FEW HOUR BREAK OVERNIGHT BETWEEN
THIS CONVECTION AS IT WEAKENS/LIFTS TO THE NORTHEAST...AND A MORE
WIDESPREAD AREA OF SHOWERS AND THUNDERSTORMS AHEAD OF THE MAIN
SHORTWAVE WHICH WILL MOVE INTO THE NORTHERN MISSISSIPPI VALLEY BY
12Z.  THIS AREA OF PRECIP SHOULD MOVE ACROSS CENTRAL AND
NORTH-CENTRAL WI LATE TONIGHT.  ELEVATED CAPES LOOK TO BE APPROX 500
J/KG SO NOT ANTICIPATING SEVERE CONVECTION.  LOWS MAINLY IN THE
MIDDLE 60S.

MONDAY...THE SHORTWAVE TROUGH WILL LIFT NORTHEAST ACROSS WISCONSIN
MONDAY MORNING...DRIVING THE AREA OF SHOWERS AND THUNDERSTORMS
ACROSS NORTH-CENTRAL AND NORTHEAST WISCONSIN.  THE HEAVIEST RAINFALL
LOOKS TO OCCUR OVER CENTRAL AND NORTH-CENTRAL WISCONSIN WITH THIS
EVENT AND COULD SEE AN INCH TO 1.50 INCHES IF CONVECTION REACHES
INTO THIS AREA THIS EVENING.  WITH PRECIPITATION OCCURRING DURING
THE MORNING AND THE SHORTWAVE LIFTING NORTHEAST OF THE AREA IN THE
AFTERNOON...SEEMS LIKE AN AWFULLY SMALL TIME PERIOD FOR
REDEVELOPMENT OF STORMS ALONG THE COLD FRONT OVER NORTHEAST
WISCONSIN.  THE BEST BET MAY BE TO HAVE STORMS CONTINUOUSLY REFIRE
ALONG THE TAIL OF THE SHORTWAVE...BUT THIS ADMITTEDLY SEEMS LIKE
A SMALL CHANCE SINCE THE ATMOSPHERE WILL HAVE BEEN WORKED OVER
BY THIS TIME...AND PRECIPITATION WILL HAVE SQUASHED SURFACE BASED
INSTABILITY.  AS A RESULT...SPC HAS SHIFTED THE SLIGHT RISK OF
SEVERE WEATHER TO THE SOUTH AND EAST OF THE FORECAST AREA AND THIS
SEEMS REASONABLE.  WILL MENTION THE CHANCE OF GUSTY WINDS AND SMALL
HAIL BUT LEAVE THE THREAT OF SEVERE WEATHER OUT OF THE HWO.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY
ISSUED AT 218 PM CDT SUN AUG 31 2014

SOME LINGERING PCPN WL BE POSSIBLE MON EVENING...MAINLY OVER E-C
WI. CARRIED CHC POPS INTO THE EARLY EVENING. WHILE ISOLD SHRA
COULD LINGER WELL INTO THE NGT...THE MAIN POOL OF INSTABILITY WL
BE WELL S BY THEN...SO OPTED TO GO WITH A DRY FCST AFTER MIDNIGHT.
LATER SHIFTS MAY NEED TO TAKE ANOTHER LOOK AT THAT.

THERE ARE PROS AND CONS FOR PCPN CHCS TUE. ON ONE HAND...UPR TROF
WL STILL BE ACRS THE AREA DURING THE MORNING...AND WNWLY UPR FLOW
WL KEEP MODEST MID-LVL LAPSE RATES ACRS THE RGN. ON THE OTHER...
UPR HEIGHTS WL BE RISING AS THE TROF SHIFTS E...AND QG FORCING
WL BE FAVORING SUBSIDENCE. OPTED TO KEEP FAIRLY LOW POPS...BUT
WENT WITH ISOLD SHRA ACRS ALL BUT THE FAR SRN PART OF THE AREA.
PCPN UNLIKELY TO BE A BIG DEAL...BUT CONFIDENCE IN TOTALLY DRY DAY
ISN/T THAT GREAT EITHER.

UPR HEIGHTS SHOULD CONT TO RISE TUE NGT/WED. STAYED DRY TUE NGT...
BUT N-C WI WL BE CLOSE ENOUGH TO THE RETURN FLOW TO JUSTIFY
HAVING A CHC OF TSRA WED.

WENT WITH A BLEND OF TOP PERFORING GUIDANCE PRODUCTS FOR TEMPS...
WHICH WERE DOMINATED BY THE ECMWF AND IT/S MOS AND BIAS-CORRECTED
DERIVATIVES.

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

.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 647 PM CDT SUN AUG 31 2014

IFR STRATUS HAS MOVED OFF LAKE INTO LAKESHORE COUNTIES AND PARTS
FOX VALLEY. INCREASING WINDS AT LOW LEVELS MID TO LATE EVENING
SHOULD DIMINSH THIS STRATUS. A COLD FRONT WILL MOVE ACROSS THE
REGION LATE TONIGHT INTO MONDAY...SCATTERED MVFR CIGS AND
VSBYS...LOCALLY IFR...WILL DEVELOP DUE TO HEAVY RAIN AND POSSIBLE
THUNDERSTORMS. SOME STORMS MAY CONTAIN STRONG GUSTY WINDS AS THEY
MOVE INTO CENTRAL AND NORTH-CENTRAL WISCONSIN LATE IN THE EVENING
AND OVERNIGHT. HAVE ADDED TS TO TAFS WITH THIS ISSUANCE...THOUGH
CURRENT ACTIVITY OVER WESTERN EXPECTED TO STAY WEST OF TAF SITES
THROUGH MIDNIGHT GIVEN MORE STABLE AIR MASS OVER EASTERN WI. &&

.GRB WATCHES/WARNINGS/ADVISORIES...
BEACH HAZARDS STATEMENT FROM MONDAY MORNING THROUGH MONDAY
EVENING FOR WIZ022-040-050.
&&

$$

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





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