Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 241116
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
616 AM CDT FRI OCT 24 2014

UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND SATURDAY
ISSUED AT 321 AM CDT FRI OCT 24 2014

THE LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A LOW LEVEL
TROUGH MOVING EAST ACROSS LAKE MICHIGAN EARLY THIS MORNING.  BEHIND
THE TROUGH...RUC SOUNDINGS ARE SHOWING A LOWERING INVERSION WITH PLENTY
OF BOUNDARY LAYER MOISTURE TRAPPED BENEATH THIS INVERSION.
WIDESPREAD STRATUS AND FOG ARE SHOWING NO SIGNS OF BREAKING UP...AND
ARE EXPANDING WESTWARD INTO MINNESOTA.  CURRENT VSBYS ARE LOCALLY
DENSE OVER CENTRAL AND NORTH-CENTRAL WISCONSIN...BUT MOST OF THE
VSBYS IN THIS AREA ARE BETWEEN 1/2 AND 1 1/2 SM.  VSBYS FARTHER EAST
ARE BEHAVING BUT SOME POTENTIAL FOR LOWERING AS TEMPS CONTINUE TO
COOL TONIGHT.  IN GENERAL THOUGH...VSBYS SEEM TO BE SLOWLY FALLING
SO WILL CONTINUE THE DENSE FOG ADVISORY EVEN THOUGH CRITERIA IS
TECHNICALLY NOT BEING MET.  LOOKING UPSTREAM...A LARGE AREA OF
CIRRUS IS PUSHING EAST ACROSS THE NORTHERN MISSISSIPPI VALLEY.  A
WEAK TROUGH IS POSITIONED OVER THE CENTRAL PLAINS BUT IS INACTIVE AT
THE MOMENT.  FORECAST CONCERNS INCLUDE FOG TRENDS FOLLOWED BY
CLOUDS/TEMPS.

TODAY...THE LOW LEVEL TROUGH WILL CONTINUE TO MOVE EAST INTO
MICHIGAN THIS MORNING.  MEANWHILE...WIDESPREAD LOW STRATUS AND FOG
WILL HANG AROUND THROUGH THE MORNING COMMUTE.  CIRRUS...BROUGHT IN
BY A BEEFY 120KT JET STREAK WILL SPREAD ACROSS THE FORECAST AREA
THIS MORNING...AND LIKELY SLOW THE DISSIPATION OF THE STRATUS/FOG
DESPITE ITS SHALLOW NATURE.  THINKING IT MAY TAKE UNTIL EARLY
AFTERNOON FOR THE STRATUS/FOG TO MIX OUT OVER CENTRAL AND
NORTH-CENTRAL WISCONSIN WHERE CIRRUS WILL BE THICKER THAN FARTHER
EAST.  ONCE IT BURNS OFF THOUGH...SHOULD SEE PLENTY OF FILTERED
SUNSHINE THROUGH THE CIRRUS. THERE WILL BE A WEAK LOW LEVEL TROUGH
THAT WILL MOVE INTO CENTRAL WISCONSIN LATE IN THE AFTERNOON WHICH
WILL BRING SCATTERED CLOUDS AROUND 5KFT.  SATURATION DEPTH IS VERY
SHALLOW...SO THINK THERE IS LITTLE CHANCE OF PRECIP.  MIXING HEIGHTS
LOOK SHALLOW ONCE AGAIN SO USED A COMBO OF THE ECMWF AND CONS BLENDS
WHICH DROPPED HIGHS A DEGREE.

TONIGHT...THE LOW LEVEL TROUGH WILL CONTINUE EAST ACROSS CENTRAL AND
NORTHEAST WISCONSIN THIS EVENING.  WILL CONTINUE TO SEE SCT CLOUDS
WITH THIS TROUGH BUT THEN SHOULD SEE CLEARING ONCE THE TROUGH EXITS
OVERNIGHT.  PROGGED SOUNDINGS INDICATE THAT MOISTURE WILL AGAIN GET
TRAPPED BENEATH THE SUBSIDENCE INVERSION.  BUT UNLIKE THIS
MORNING...WILL HAVE A TIGHTER PRESSURE GRADIENT IN PLACE. THIS WILL
MAKE IT DIFFICULT FOR DENSE FOG TO DEVELOP BUT COULD LEAD TO THE
GENERATION OF A LOW STRATUS DECK.  CONFIDENCE IS RATHER LOW IF THIS
WILL OCCUR AND WILL PASS CONCERNS ON TO THE NEXT SHIFT. LOWS MAINLY
IN THE 40S.

SATURDAY...A SHORTWAVE TROUGH MOVING ACROSS THE LAKE SUPERIOR WILL
SEND A COOL FRONT ACROSS THE AREA EARLY IN THE PERIOD.  WEAK COLD
ADVECTION WILL TAKE PLACE THE ENTIRE DAY BUT SURFACE WINDS WILL BE
FROM THE WEST WHERE THE AIR IS STILL RELATIVELY MILD.  THOUGH IT
WILL BE WINDY...TEMPS SHOULD STILL RISE INTO THE MID 50S NORTH TO
LOW 60S SOUTH WITH SUNNY SKIES.

.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY
ISSUED AT 321 AM CDT FRI OCT 24 2014

MAIN FCST CONCERN IN THE LONG TERM WILL BE THE SYSTEM MOVING
THROUGH THE GREAT LAKES REGION SUNDAY NIGHT THROUGH TUESDAY NIGHT.

BEGINNING OF THIS FCST PERIOD LOOKS FAIRLY STRAIGHT FORWARD.
MODELS CONSISTENT IN SHOWING AN AREA OF HIGH PRESSURE MOVING OVER
THE STATE...WITH CLEAR SKIES AND COOL TEMPERATURES. DECREASED MIN
TEMPS A DEGREE OR TWO AS MODELS HAVE BEEN TRENDING TOWARDS LOWER
TEMPS...AND CLEAR SKIES WITH LIGHTER WINDS SHOULD ALLOW FOR
TEMPERATURES TO QUICKLY DROP.

CONTINUED QUIET WEATHER ON SUNDAY QUIET AS HIGH PRESSURE SHIFTS
TO OUR EAST. THIS WILL PUT THE AREA IN SOUTHERLY FLOW...WHICH
MEANS WARMING TEMPERATURES BUT INCREASING CLOUDS. ABOVE NORMAL
TEMPERATURES HIGH TEMPERATURES CAN BE EXPECTED ON SUNDAY...WITH
SKIES BECOMING PARTLY CLOUDY THROUGH THE AFTERNOON AS WAA RAMPS UP
AND MOISTURE INCREASES. STILL SHOULD BE A NICE DAY.

THINGS START BECOMING MORE ACTIVE BEGINNING SUNDAY EVENING. A WARM
FRONT LIFTS NORTH THROUGH THE AREA AFTER 00Z MONDAY...WHICH WILL
BRING PCPN TO THE AREA FROM SOUTHWEST TO NORTHEAST OVERNIGHT. KEPT
THE GENERAL CHANCE POPS FOR MUCH OF THE AREA AS MODELS DISAGREE
WITH THE TIMING OF THE FRONT AND MODELS HAVE GENERAL LIGHT PCPN
OVERSPREADING THE AREA...WITH THE HEAVIEST QPF ARRIVING AFTER
MIDNIGHT.

MODELS BEGIN TO DISAGREE AFTER THAT AS A LOW PRESSURE SYSTEM MOVES
OUT OF THE NORTHERN PLAINS AND THEN INTENSIFIES OVER THE NORTHERN
GREAT LAKES REGION. GENERAL MODEL TRENDS WOULD HAVE SPOTTY LIGHT
PCPN CONTINUING ON MONDAY BEFORE THE SYSTEM STRENGTHENS IN
RESPONSE TO A SHARP UPPER LEVEL TROUGH SWEEPING THROUGH THE
NORTHERN CONUS. AFTER THE DAY ON MONDAY...MODELS HAVING
DIFFICULTIES WITH THE EXACT TIMING AND INTENSITY OF THE SYSTEM.
LEANED TOWARDS THE ECMWF FOR THIS FCST AS IT SEEMED TO BE A GOOD
COMPROMISE BETWEEN ALL THE MODELS. IN ADDITION... THE 00Z ECMWF
PICKED UP ON THE FASTER MODEL TRENDS THAT HAVE BEEN NOTED ON MANY
OF THE OTHER MODELS. EITHER WAY...PCPN SHOULD INTENSIFY STARTING
MONDAY NIGHT AS FORCING INCREASES. IN ADDITION...KEPT THE
ISOLATED THUNDER IN THE FCST AS SOME ELEVATED CAPE IS NOTED ON THE
GFS BUFKIT SOUNDINGS ON SUNDAY NIGHT AND MONDAY...AND THEN RAPID
INTENSIFICATION SHOULD RESULT IN SOME THUNDER MONDAY NIGHT.

RAIN SHOULD CONTINUE ON TUESDAY BEFORE THE LOW FINALLY IS SWEPT
AWAY WITH THE EXITING UPPER LEVEL TROUGH TUESDAY NIGHT. THE REST
OF THE FORECAST LOOKS LIKE IT WILL BE MAINLY DRY AS A SURFACE
RIDGE AND WEAK UPPER LEVEL RIDGE MAKE THEIR WAY INTO THE REGION.

EXPECT HIGH TEMPERATURES ABOUT 5 TO 10F WARMER THAN NORMAL
SATURDAY THROUGH TUESDAY...THEN BACK TO NEAR NORMAL HIGHS FOR
WEDNESDAY AND THURSDAY.
&&

.AVIATION...FOR 12Z TAF ISSUANCE
ISSUED AT 616 AM CDT FRI OCT 24 2014

WIDESPREAD LOW CIGS AND FOG WILL BE SLOW TO BURN OFF THIS MORNING AS
A RESULT OF CIRRUS SLOWING DOWN THE DIURNAL WARMING CURVE.  BUT
ANTICIPATE SLOWLY IMPROVING CONDITIONS AFTER AROUND 15Z TO POSSIBLY
VFR BY MIDDAY.  SOME CONCERN THAT BKN MVFR CIGS COULD LINGER UNTIL
MID-AFTERNOON THOUGH.  A WEAK LOW LEVEL TROUGH WILL BRING AN AREA OF
3-5KFT CLOUDS TO THE AREA LATE THIS AFTERNOON INTO THIS EVENING.
THEN ONCE THIS TROUGH DEPARTS...MODELS ARE SUGGESTING LOW STRATUS
AND/OR FOG COULD REFORM LATE TONIGHT.  THE BOUNDARY LAYER WILL BE
MORE MIXY SO THINK THAT THE PROBABILITY OF DENSE FOG IS LOW...BUT
THE FORMATION OF LOW STRATUS IS A BETTER BET.  WILL LET THE NEXT
SHIFT ANALYZE FURTHER BEFORE ADDING IFR CIGS.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 10 AM CDT THIS MORNING FOR WIZ005-010-
018-030-035-036-045.
&&

$$

SHORT TERM.....MPC
LONG TERM......ALLEN
AVIATION.......MPC






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