Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 181637
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1137 AM CDT THU SEP 18 2014

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND FRIDAY
ISSUED AT 322 AM CDT THU SEP 18 2014

LOW LEVEL MOISTURE TRAPPED BELOW A SUBSIDENCE INVERSION HAS RESULTED
IN LOTS OF CLOUDS ACROSS THE AREA. THE CLOUDS HAVE KEPT TEMPERATURES
UP SO DROPPED THE FROST AND FREEZE HEADLINES. THE CLOUDS SHOULD DISSIPATE
AS MOISTURE MIXES OUT AS TEMPERATURES SLOWLY CLIMB. HIGHS TODAY SHOULD
BE A FEW DEGREES LOWER THAN MOS GUIDANCE DUE TO THESE CLOUDS.

CLEARING SKIES EXPECTED THIS EVENING. LOW LEVEL WARM ADVECTION AND
A STEADY BREEZE IN THE BOUNDARY LAYER SHOULD KEEP TEMPERATURES WELL
ABOVE FREEZING AND CLOSE TO MOS GUIDANCE.

SOUTHERLY FLOW WILL BRING INCREASING MOISTURE TO THE REGION FRIDAY.
A LOW LEVEL JET WILL ARRIVE IN THE AFTERNOON AND SHOULD PRODUCE
SCATTERED THUNDERSTORMS MAINLY IN THE NORTH.

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY
ISSUED AT 322 AM CDT THU SEP 18 2014

MODELS REMAINS CONSISTENT AT MID AND UPPER LEVELS SHOWING A BRIEF
PERIOD OF ZONAL FLOW ACROSS THE NORTHERN CONUS THROUGH FRIDAY
NIGHT...THEN A HIGHLY AMPLIFIED PATTEN RETURNS BY EARLY NEXT
WEEK...WITH STRONG RIDGING EXTENDING ACROSS WESTERN CANADA...AND A
DEEP TROUGH OVER THE EASTERN GREAT LAKES. THIS AMPLIFIED PATTERN
WILL LEAD TO A NORTHWEST FLOW OVER THE WESTERN GREAT LAKES. THE
WESTERN RIDGE WILL SLOWLY WEAKEN AND PUSH EAST TOWARD THE GREAT
LAKES REGION THROUGH MID-WEEK. AT THE SURFACE...COLD FRONT WILL
CROSS THE FORECAST AREA SOMETIME BY EARLY SATURDAY AFTERNOON...
WITH HIGH PRESSURE BUILDING INTO THE REGION EARLY NEXT WEEK. TEMPS
ARE EXPECTED TO BE ABOVE NORMAL ON SATURDAY...THEN FALL BACK TO
BELOW NORMAL READINGS NEXT WEEK.

WARM AIR ADVECTION WILL BE WELL UNDERWAY FRIDAY NIGHT...WITH
850MB TEMPS CLIMBING TO 15-18C BY 12Z SATURDAY. MODELS ARE NOW
SHOWING A WEAK SHORTWAVE AHEAD OF THE MORE POTENT SHORTWAVE
FORECAST TO CROSS THE AREA ON SATURDAY. THIS LEAD SHORTWAVE WILL
AID IN THE DEVELOPMENT OF SHOWERS AND STORMS IN THE WARM AIR
ADVECTION REGIME AHEAD OF THE COLD FRONT. A 40-50 KT LOW LEVEL
JET WILL BE POINTED TOWARD WESTERN WI AS WELL...AND SHOULD BE THE
FOCUS FOR STORM DEVELOPMENT...WHICH WILL SPREAD OVER THE AREA.
WILL HAVE HIGHEST POPS OVER THE NORTH IN THE EVENING...THEN
SPREAD LIKELY POPS ACROSS THE ENTIRE AREA FRIDAY NIGHT AS THE BEST
FORCING WORKS ACROSS THE AREA AHEAD OF THE APPROACHING FRONT.
LOCALLY HEAVY WILL BE POSSIBLE AS PRECIPITABLE WATERS CLIMB TO
AROUND 1.5 INCHES. MODELS IN SOME DISAGREEMENT ON HOW MUCH
MOISTURE FROM WHAT WAS TROPICAL STORM ODILE WILL GET PULLED AHEAD
OF THE COLD FRONT...HOWEVER IT BECOMING MORE LIKELY THIS MOISTURE
WILL STAY SOUTH OF THE FORECAST AREA.

SOME UNCERTAINTY REMAINS FOR SATURDAY...WITH MODELS SHOWING
VARYING SOLUTIONS ON TIMING OF THE FRONT/SHORTWAVE AND DEGREE OF
INSTABILITY. WILL NOT MAKE MAJOR CHANGES TO THE SATURDAY FORECAST
AT THIS POINT...OTHER THAN TO KEEP ALL POPS IN THE CHANCE CATEGORY
DUE TO THIS UNCERTAINTY. THE TREND HAS BEEN TO LOWER POPS...AS THE
SURFACE FRONT WILL BE EXITING IN THE MORNING...THE LOW LEVEL JET
WILL BE VEERING AND WEAKENING...AND THE POTENT SHORTWAVE LOOKS TO
LAG WELL BACK ACROSS NORTHERN MN AROUND MIDDAY. THE MORE LIKELY
SCENARIO WILL BE ANOTHER ROUND OF STORMS WILL FIRE SOUTH AND EAST
OF THE FORECAST AREA...WHERE BETTER INSTABILITY...STEEPER LAPSE
RATES RESIDE AHEAD OF THE COLD FRONT. IT COULD ACTUALLY TURN OUT
TO BE A DECENT AFTERNOON WITH LITTLE TO NO RAIN AND ABOVE NORMAL
TEMPS. SPEAKING OF TEMPS...THEY ALSO BE TRICKY...AS TEMPS ALOFT
WILL STILL SUPPORT HIGHS IN THE UPPER 70S TO EVEN SOME LOWER 80S
BEHIND THE FRONT...IF SUFFICIENT CLEARING CAN OCCUR BEFORE THE
COOLER AIR MOVES IN.

MAIN SHORTWAVE AND UPPER TROUGH SWING ACROSS THE AREA SATURDAY
NIGHT...WITH ENOUGH MOISTURE REMAINING IN THE CYCLONIC FLOW TO
KEEP CHANCES FOR SHOWERS IN THE FORECAST...WITH THE HIGHER CHANCES
OVER THE NORTH. LOW/MID LEVEL MOISTURE LINGERING INTO
SUNDAY...WITH THE CYCLONIC FLOW PERSISTING OVER THE REGION. 850MB
TEMPS DROP INTO THE LOW/MID SINGLE DIGITS...SO ADDITIONAL
INSTABILITY SHOWERS WILL BE POSSIBLE...ALONG WITH PLENTY OF
CLOUDS...ESPECIALLY OVER NORTHERN AND EASTERN WI. THE CYCLONIC
FLOW LOOSENS ITS GRIP SUNDAY NIGHT AND MONDAY...AS THE UPPER
RIDGE AND SURFACE HIGH PRESSURE BUILD IN FROM THE WEST. DRY
WEATHER IS EXPECTED MONDAY THROUGH WEDNESDAY AS THE HIGH SLOWLY
MOVES EAST OVER THE GREAT LAKES.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1137 AM CDT THU SEP 18 2014

PLENTY OF MVFR AND IFR BKN/OVC CIGS NORTH OF A STALLED
COLD FRONT ACROSS THE REGION.  THOUGH CIGS SHOULD RISE TO MVFR
EVERYWHERE THIS AFTERNOON...THE CLOUDS WILL BE SLOW TO DISSIPATE
TONIGHT UNTIL WARMER LOW LEVEL AIR ARRIVES.  THIS WARMER AIR WILL
GRADUALLY MOVE FROM NORTH TO SOUTH ACROSS THE REGION LATE THIS
EVENING AND OVERNIGHT.  IF SKIES DO CLEAR FOR A PERIOD...THERE WILL
BE POTENTIAL FOR LOW STRATUS TO REDEVELOP BUT CONFIDENCE IS LOW.
ANY LINGERING LOW CIGS TO IMPROVE QUICKLY TO VFR FRIDAY MORNING
THOUGH MID AND HIGH CLOUDS WILL BE ON THE INCREASE.
&&

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

$$

SHORT TERM.....RDM
LONG TERM......BERSCH
AVIATION.......MPC





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