Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 060905
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
405 AM CDT WED MAY 6 2015

FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND THURSDAY
ISSUED AT 405 AM CDT WED MAY 6 2015

PCPN TRENDS...TEMPERATURES AND FOG/STRATUS POTENTIAL ARE THE MAIN
FCST CONCERNS.

A H8 WARM FRONT WAS LIFTING NORTH ACROSS THE REGION EARLY THIS
MORNING...AND GENERATING SCT/NMRS SHOWERS OVER THE FORECAST AREA.
HAVE NOT SEEN ANY LIGHTNING ANYWHERE IN THE STATE...THOUGH A FEW
STRIKES WERE NOTED IN IOWA. HIGH PRESSURE WAS SHIFTING EAST
THROUGH THE GREAT LAKES...WITH STRONG RETURN FLOW BRINGING
MOISTURE INTO THE UPPER MISSISSIPPI VALLEY. DEW POINTS IN THE
50S AND LOWER 60S WERE REPORTED IN IN SOUTHERN MN...IOWA AND
ILLINOIS...ALONG WITH WIDESPREAD LOW STRATUS AND FOG.

THE ELEVATED WARM FRONT WILL SHIFT NORTH OF GRB CWA LATER THIS
MORNING...SO SHOWERS SHOULD GRADUALLY LIFT NORTH AND WEAKEN.
MODELS CONTINUE TO SHOW INSTABILITY INCREASING OVER OUR SW
COUNTIES THIS AFTERNOON...WHICH MAY LEAD TO SCT TSTM DEVELOPMENT
LATER IN THE DAY. THIS WILL BE DEPENDENT ON WHETHER OR NOT THERE
ARE ENOUGH BREAKS IN THE STRATUS CLOUDS TO ALLOW SUFFICIENT
HEATING. USED A BLEND OF THE TOP PERFORMING GUIDANCE SETS FOR MAX
TEMPS...BUT LOWERED READINGS A FEW DEGREES IN THE SOUTH DUE TO
STRATUS CONCERNS.

ANY LINGERING CONVECTION IN OUR SW COUNTIES SHOULD TEND TO WEAKEN
AFTER SUNSET...BUT AN INCREASING LOW-LEVEL JET AND A WEAK S/W TROF
WILL KEEP A SMALL CHC OF SHRA/TSRA GOING ACROSS OUR WESTERN
COUNTIES OVERNIGHT. LOW TEMPERATURES WILL BE MAINLY IN THE
50S...WITH MID TO UPPER 40S IN FAR NE WI AND ALONG THE LKSHR.

A 35-45 KT LOW-LEVEL JET WILL RESIDE OVER THE REGION ON THURSDAY...
WITH DAYTIME MIXING LEADING TO WINDY CONDITIONS BY LATE MORNING.
MOISTURE AND INSTABILITY WILL INCREASE ACROSS OUR NW COUNTIES
DURING THE AFTERNOON...AS A COLD FRONT APPROACHES FROM MN. HAVE
TRENDED POPS FROM LIKELY NW TO SLIGHT CHC OR DRY IN FAR EASTERN
WI. THE STRONG SOUTH WINDS WILL PULL WARMER AIR INTO THE REGION...
ALLOWING TEMPS TO RISE INTO THE UPPER 70S AND LOWER 80S BEFORE THE
SHOWERS ARRIVE.

HAVE ADDED SOME FOG TO LAKE MICHIGAN AND SOME OF THE SHORELINE
AREAS LATER TODAY THROUGH THURSDAY...AS LOW-LEVEL MOISTURE
ADVECTS OVER THE COLD WATERS. CONFIDENCE IS NOT HIGH ENOUGH TO
ISSUE MARINE FOG ADVISORIES YET. HAVE HELD OFF ON MENTIONING
FOG FOR THE REST OF THE INLAND AREAS...AS MOS GUIDANCE SHOWS
SUBSTANTIAL TEMP/DEW POINT SPREADS CONTINUING OVERNIGHT...AND
BOUNDARY LAYER WINDS INCREASING TO 25 TO 30 KTS. THIS SHOULD
SUPPORT CONTINUED STRATUS DEVELOPMENT INSTEAD OF WIDESPREAD FOG.

.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY
ISSUED AT 405 AM CDT WED MAY 6 2015

FOCUS WAS GIVEN IN THE LONG TERM FORECAST TO THE THURSDAY NIGHT
AND FRIDAY PERIOD TO TRY AND RESOLVE PCPN CHANCES WITH A FRONTAL
PASSAGE. AFTER FRIDAY...THE LONG TERM BECOMES MUDDLED AND COULD
NOT ADD MUCH DETAIL WITH CERTAINTY.

A SFC COLD FRONT WILL BE PASSING THROUGH THE GREAT LAKES REGION
THURSDAY NIGHT AND FRIDAY. MODELS CONTINUE TO HAVE ISSUES WITH PCPN
AHEAD OF THE FRONT THURSDAY NIGHT. WITHOUT ANY SIGNIFICANT FORCING
AND A BROAD WAA REGIME IN PLACE OVER THE STATE...CANNOT PROVIDE
MUCH DETAIL FROM PREVIOUS FORECAST. THE BETTER CHANCES FOR SHOWERS
AND THUNDERSTORMS LOOKS TO BE IN NORTH CENTRAL WI BEFORE MIDNIGHT
AS A WEAKEN SHORTWAVE PASSES THROUGH AND WASHES OUT.

MODELS HAVE AT LEAST SOME AGREEMENT ON THE TIMING OF A COLD FRONT
ON FRIDAY...WITH THE LATEST GFS40/GEFS BEING A GOOD COMPROMISE.
THE 00Z ECMWF IS STILL A BIT FAST...AND THE NAM80 IS TOO STRONG
BASED ON THE LACK OF UPPER LEVEL SUPPORT. BEST CHANCES FOR PRECIP
FRIDAY MORNING THROUGH EARLY AFTERNOON WITH THE ACTUAL FRONTAL
PASSAGE. DRY AIR NEAR THE SFC SHOULD RESULT IN JUST LIGHT PCPN.
BUFKIT SOUNDINGS THROUGH THURSDAY NIGHT AND FRIDAY MORNING DO SHOW
A MODERATE MIDLEVEL INSTABILITY...THOUGH THE AMOUNT OF INSTABILITY
AND THE STRENGTH OF A CAPPING INVERSION VARIES FROM MODEL TO MODEL.
SOME OF THE STORMS THURSDAY NIGHT AND FRIDAY MORNING COULD BE
STRONG...WITH HIGHER WIND GUSTS POSSIBLE...BUT WITHOUT ANY STRONG
FORCING MECHANISM THE SEVERE THREAT REMAINS MINIMAL.

AFTER THE FRONT SWEEPS THROUGH THE STATE...WEAKENING AS IT MOVES
EAST...IT SHOULD THEN STALL OUT AND SETTLE SOMEWHERE IN NORTHERN
IL THROUGH LOWER MICHIGAN. THE REST OF THE FORECAST WILL DEPEND ON
THE PLACEMENT OF THIS WEAK BOUNDARY AND WAVES OF LOW PRESSURE
RIDING NORTHEAST ALONG IT OUT OF THE SOUTHERN PLAINS. EXPECT
ACTIVE WEATHER WITH OCCASIONAL PRECIP STARTING THIS
WEEKEND...HOWEVER IT DOESNT LOOKS LIKE A WASH OUT THROUGH THE
BEGINNING OF NEXT WEEK THOUGHT NOT ENOUGH CONFIDENCE IN WHEN THIS
WOULD OCCUR TO HIGHLIGHT A DRIER PERIODS. THE UPPER LEVELS ALSO
BECOME MORE UNSETTLED AND WOULD SUPPORT MORE WIDESPREAD AND
HEAVIER RAINS WITH ANY ROUNDS OF PRECIP THAT DO MOVE THROUGH.
GIVEN THE PLACEMENT.

AFTER ONE LAST DAY WITH WELL ABOVE NORMAL CONDITIONS
FRIDAY...TEMPS SHOULD FALL BACK TO NEAR NORMAL AFTER THE COLD
FRONT SWEEPS THROUGH FRIDAY NIGHT AND WILL STAY NEAR NORMAL INTO
NEXT WEEK.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1047 PM CDT TUE MAY 5 2015

A STATIONARY FRONT OVER NORTHERN ILLINOIS WILL GRADUALLY
LIFT NORTH OVER THE NEXT 24 HOURS.  VFR CIGS WITHIN A DRY AIRMASS
WILL GRADUALLY LOWER TONIGHT AS THE FRONT DRAWS CLOSER.  TIMING IS
SUSPECT DUE TO THE DRY AIRMASS...BUT THINK MVFR CIGS WILL LIFT NORTH
INTO THE TAFS SITES AFTER 06Z TONIGHT.  ONCE IN PLACE...CIGS WILL
LIKELY REMAIN VFR UNTIL WEDNESDAY AFTERNOON ACCORDING TO THE LATEST
GUIDANCE. SCATTERED LIGHT SHOWERS NOW LOOK LIKE A DECENT BET AT ALL
TAF SITES OVERNIGHT.
&&

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

$$

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






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