Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 052306
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
506 PM CST THU MAR 5 2015

UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND FRIDAY
ISSUED AT 321 PM CST THU MAR 5 2015

TEMPERATURES MAIN CONCERN TONIGHT AND FRIDAY WITH WARM ADVECTION
REGIME IN PLACE. FOR TONIGHT...BETTER PRESSURE GRADIENT AND
INCREASING LOW LEVEL WINDS WILL BE AFTER MIDNIGHT. TO COMPLICATE
MATTERS...CLEAR SKIES...LIGHTER WINDS AND LOW DEW POINTS WILL
ALLOW FOR TEMPERATURES TO FALL THIS EVENING. TEMPERATURES LATE
TONIGHT SHOULD SLOWLY RISE DUE TO INCREASING WINDS AND CLOUDS.

TEMPERATURES ON FRIDAY EVEN MORE PROBLEMATIC DUE TO CLOUD COVER
AND INVERSION ALOFT. NEW MET/MAV GUIDANCE HAS COME IN ABOUT 8
DEGREES COLDER THAN GOING FORECAST. SEEN CASES IN THE FIRST DAY OF
THE WARM ADVECTION REGIME WHERE MAX TEMPERATURES FAIL TO REACH
PREVIOUS DAYS FORECAST. HAVE LOWERED MAX TEMPERATURES 3 TO 5
DEGREES...BUT WOULD NOT BE SURPRISED IF MIDNIGHT SHIFT HAD TO
LOWER EVEN MORE. FLURRIES ARE POSSIBLE ON FRIDAY.

.LONG TERM...FRIDAY NIGHT THROUGH THURSDAY
ISSUED AT 321 PM CST THU MAR 5 2015

THE UPPER PATTERN CONTINUES TO BE SPLIT WITH THE NORTHERN STREAM
FEATURING A WEST COAST RIDGE AND A BROAD EASTERN TROUGH. SEVERAL
SHORTWAVES WILL RUN THROUGH THIS WEEKEND INTO EARLY NEXT
WEEK...RESULTING IN UNSETTLED WEATHER FOR THE AREA THIS WEEKEND.
THOUGH UNSETTLED...LIMITATIONS IN LIFT AND MOISTURE WILL KEEP
IMPACTS LIGHT. AFTER THIS...THE LONGWAVE TROUGH LOSES INFLUENCE
OVER THE AREA AS A WEAK UPPER RIDGE BUILDS ACROSS THE CENTRAL US.
HOW LONG THIS WARMER AIR WILL HANG AROUND IS OPEN TO DEBATE AND
FORTUNATELY CURRENTLY OUT OF THE FORECAST PERIOD. MODELS CURRENTLY
DIFFER GREATLY WITH THE HANDLING OF A PACIFIC SYSTEM AS IT MOVES
FROM NW CANADA INTO THE MIDWESTERN US. MORE ON THIS IN THE COMING
DAYS. FOR NOW...LET`S ENJOY THE MARCH THAW.

FRIDAY NIGHT THROUGH SUNDAY...
THE FIRST OF THESE WEAK SYSTEMS WILL DIVE SOUTHEAST INTO THE
REGION LATE FRIDAY NIGHT INTO SATURDAY MORNING...WITH A SURFACE
LOW SCRAPING ACROSS THE NORTHERN EDGE OF LAKE SUPERIOR. THERE DOES
APPEAR TO BE ENOUGH MOISTURE ALONG WITH SOME MODEST LIFT PROVIDED
BY THE ASSOCIATED UPPER SHORTWAVE TO MANAGE SOME FLURRIES OR LIGHT
SNOW IN THE NORTH AND FAR NORTHEAST. SNOW FARTHER SOUTH INTO
CENTRAL AND EAST CENTRAL WISCONSIN IS MORE OF A QUESTION. BOTH THE
EURO AND GFS DEVELOP AREAS OF LIFT BOTH NORTH AND WELL TO OUR
SOUTH...LEAVING SOUTHERN PARTS OF THE FORECAST AREA IN A REGION OF
COMPENSATING DOWNWARD MOTION. UNSURE IF THIS IS REAL...BUT IT HAS
BEEN SOMEWHAT PERSISTENT. CONTINUED SOUTHWESTERLY WINDS AND CLOUDS
SHOULD KEEP TEMPERATURES IN THE MIDDLE TEENS TO LOWER 20S. AS THE
CLIPPER MOVES OFF...SNOW WILL COME TO AN END FOR MOST ON SATURDAY
MORNING...WITH THE FAR NORTH SEEING A CHANCE FOR LIGHT SNOW
SHOWERS TO LINGER INTO THE AFTERNOON. TEMPERATURES WILL RISE INTO
THE 30S FOR MOST DESPITE THE PASSAGE OF A WEAK COLD FRONT.

THE QUICK SUCCESSION OF CLIPPERS CONTINUES...WITH THE NEXT MOVING
THROUGH SATURDAY NIGHT AND SUNDAY. THIS NEXT CLIPPER DOES NOT DIVE
AS FAR SE AS ITS PREDECESSOR BUT IT DOES APPEAR TO GENERATE BETTER
FORCING WITH A SLIGHTLY MORE FAVORABLE JET SETUP (THOUGH NOT QUITE
AS MUCH AS IT APPEARED IN PREVIOUS DAYS) AND BOTH THE EURO AND GFS
GENERATING AN AREA OF FRONTOGENESIS THAT COULD HELP CONTRIBUTE
LIFT. THERE ARE TWO MAJOR ISSUES. ONE IS TIMING - THE EURO AND
CANADIAN ARE QUICKER AND MORE AGGRESSIVE WITH SNOW SATURDAY NIGHT
INTO SUNDAY MORNING WHILE THE GFS COMES IN A BIT MORE SLOWLY ON
SUNDAY. THE OTHER QUESTION INVOLVES MOISTURE. WITH LITTLE TO NO
TIME TO RECOVER FOLLOWING THE FIRST CLIPPER...MODEST AMOUNTS OF
MOISTURE COULD BE A LIMITING FACTOR DESPITE MORE ATTRACTIVE
DYNAMICS. HIGH TEMPS ARE EXPECTED TO REACH INTO THE 30S...AND THE
LOCAL WARM BAND FROM WAUTOMA THROUGH SHAWANO HAVE AN OUTSIDE SHOT
AT THREATENING 40 DEGREES WITH PRE-FRONTAL WARMING. BECAUSE OF
THIS...THE WARMEST AREAS COULD SEE A PARTIAL OR EVEN TOTAL
CHANGEOVER TO RAIN IF PRECIPITATION DOES FALL.

BECAUSE OF THE LARGE IMPACT ON SENSIBLE WEATHER THE SMALL
DIFFERENCES IN THE GUIDANCE HAVE PRESENTED...CONFIDENCE IN THE
PRECISE DETAILS IS RELATIVELY LOW AT THIS TIME.

MONDAY THROUGH WEDNESDAY...
ONE MORE CLIPPER SWINGS THROUGH THE NORTHERN STREAM TROUGH EARLY
NEXT WEEK...BUT UPPER FLOW ACROSS THE EASTERN US BECOMES
ESSENTIALLY ZONAL. THIS WILL KEEP THE SHORTWAVE AND THE LOW
BENEATH IT FARTHER UP INTO ONTARIO...ELIMINATING SIGNIFICANT
IMPACT IN WISCONSIN. THE AREA WILL BE DOMINATED LESS BY THE
NORTHERN STREAM TROUGH...WHICH WEAKENS AND MOVES EAST.
INSTEAD...WE SEE MORE INFLUENCE FROM A SURFACE HIGH OVER THE
TENNESSEE VALLEY WHILE A WEAK UPPER RIDGE BUILDS OVER THE CENTRAL
US. THIS WILL HELP THE WARMUP FROM THE COLD OF FEBRUARY CONTINUE
IN EARNEST. BY MIDWEEK...PARTS OF CENTRAL WISCONSIN MAY WELL
REACH THE LOWER 50S.

THE FORECAST FOR THE SECOND HALF OF THE WEEK BECOMES MUCH MORE
MUDDLED AS THE MODELS STRUGGLE WITH THE MORE ZONAL FLOW. THE GFS
IS MUCH MORE AGGRESSIVE WITH A LOW ON WEDNESDAY...TAKING A STRONG
LOW ACROSS ONTARIO WITH A COLD FRONT SWEEPING THROUGH WISCONSIN
WEDNESDAY NIGHT...THE END OF THE FORECAST PERIOD. MEANWHILE...THE
ECMWF IS SLOWER AND BRINGS A MUCH WEAKER SURFACE LOW FARTHER
SOUTH THROUGH MINNESOTA AND NORTHERN WISCONSIN...BUT BEYOND THE
END OF THE FORECAST PERIOD. FOR NOW...WILL INTRODUCE A VERY LOW
CHANCE FOR RAIN AT THE END OF THE FORECAST PERIOD ALONG WITH A
HALT TO THE WARMING TREND.
&&

.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 451 PM CST THU MAR 5 2015

VFR CONDITIONS WILL PERSIST TONIGHT INTO FRIDAY AS HIGH PRESSURE
PASSES S OF THE AREA. MAIN AVIATION FCST ISSUE IS THE POTENTIAL
FOR LOW CLD DECK WITH MVFR CAT CIGS FRIDAY. THE NAM IS THE MOST
AGGRESSIVE WITH THE LOW CLD FORMATION...AND EVEN SUGGESTS SOME
FLURRIES ARE POSSIBLE. THE ECMWF IS MUCH DRIER...WITH PROBABLY
ONLY SCT-BKN CLDS WITH VFR BASES. HARD TO PICK THE CORRECT
SOLUTION AT THIS POINT...AND CONFIDENCE IN THIS ASPECT OF THE
FCST IS LOW. BUT THERE AREN/T ANY LOW CLDS IN NE KS RIGHT
NOW...AND GIVEN SFC DEW PT DEPRESSIONS ARE AOA 25F DEG IN THAT
AREA...MOISTURE IS LIMITED AS WELL. SO OPTED TO BACK AWAY FM
WIDESPREAD MVFR CIGS TOMORROW AFTN. JUST KEPT THEM IN FAR N-C WI
DURING THE LATE AFTN...WHERE ECMWF SHOWING LOW-LEVELS CLOSEST TO
SATURATION.
&&

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

$$

SHORT TERM.....ECKBERG
LONG TERM......LUCHS
AVIATION.......SKOWRONSKI








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