855
FXUS63 KMKX 210351
AFDMKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
951 PM CST FRI NOV 20 2009
UPDATE
WILL ADD DENSE FOG ADVISORY FOR COUNTIES WEST AND SW OF MADISON
TONIGHT AND SATURDAY MORNING.
PREV DISCUSSION
/ISSUED 224 PM CST FRI NOV 20 2009/
TONIGHT...GOOD LOOKING MID LEVEL SHORT WAVE TRACKS SLOWLY THROUGH
THE CWA OVERNIGHT. THE COLUMN IS DRY OVERALL WITH ASSOCIATED CLOUD
BASES RELATIVELY HIGH THIS AFTERNOON. RADAR IS SHOWING SOME
ELEVATED RETURNS AND SATELLITE SHOWS A RATHER BUMPY MID AND HIGH
LEVEL CLOUD FIELD. COULD HAVE SOME SHALLOW VIRGA OUT THERE BUT
NOTHING IS EXPECTED TO REACH THE GROUND. CLEARING SHOULD BE SLOW.
BUT ONCE IT DOES CLEAR...THE FLOW WILL BE WEAK THROUGH A DEEP
LAYER. LATE TONIGHT WINDS UP THROUGH H6 DON/T GET ABOVE 10KTS AND
THE BNDRY LAYER SHOULD DECOUPLE TO CALM. DWPNTS STILL A BIT
ELEVATED AND WITH GOOD RADITIONAL COOLING AFTER CLOUDS MOVE
OUT...WOULD EXPECT AREAS OF FOG TO DEVELOP. THE EAST AND FAR NORTH
MAY STAY PATCHY IN COVERAGE DUE TO MORE CLOUDS LINGERING LATER.
THIS WEEKEND...ONCE THE S/W EXITS...MID LEVEL RIDGING TAKES OVER
AND KEEPS THE AREA DRY AND MILD. ABOVE NORMAL HIGHS IN THE LOWER TO
MID 50S WITH SUNSHINE EXPECTED FROM TIME TO TIME...ESPECIALLY
EAST.
EARLY NEXT WEEK...BY LATE IN THE WEEKEND INTO EARLY NEXT WEEK...A
LARGE SCALE TROUGH BEGINS TO DIG INTO THE MIDDLE OF THE COUNTRY.
THE NAM AND GFS SHOW AN AREA OF WAA IN THE RETURN FLOW THAT COULD
GENERATE SOME LIGHT QPF JUST WEST OF THE CWA SUNDAY AFTERNOON AND
SUNDAY NIGHT. ON MONDAY...THERE IS DISAGREEMENT BETWEEN THE NAM
AND THE GFS/ECMWF. THE NAM KICKS OUT A LEADING S/W AND KEEPS IT
BACK TO THE WEST...AS AN EXTENSION OF THE LARGER PLAINS TROF. THIS
ALLOWS THE MOISTURE/PCPN TO SPREAD UP INTO THE AREA ON MONDAY. THE
ECMWF AND THE GFS...KICK THIS SHORT WAVE QUICKLY TO THE EAST AND
KEEP IT MORE OF A SEPARATE ENTITY. THEREFORE THE MOISTURE/PCPN
STAY EAST OF OUR AREA. I/LL STICK WITH THE MORE TRUSTWORTHY
GFS/ECMWF ON THIS ONE.
THE BIGGER STRUGGLE TODAY WAS DEALING WITH THE DISPARITY BETWEEN
THE GFS AND ECMWF FOR THE MIDDLE OF THE WEEK. EVENTUALLY A RATHER
STRONG LOW EJECTS OUT OF THE SOUTHERN PLAINS...OUT OF THE BASE OF
THE TROF AND TRACKS INTO THE GREAT LAKES. THE ECMWF HAS BEEN
SLOWER THAN THE GFS OVER THE LAST FEW RUNS AND IS THE MODEL OF
CHOICE BY THE HPC. THE GFS IS...AND HAS BEEN...FAST AND IS MORE
AGGRESSIVE IN PULLING DOWN COLD AIR INTO THE UPPER MIDWEST ON THE
BACK SIDE OF THE LOW. MY MONEY IS ON THE ECMWF...THIS SYSTEM WILL
BRING IN PRECIP TUESDAY THROUGH WEDNESDAY NIGHT. INITIALLY...
CONDITIONS WILL BE WARM ENOUGH TO KEEP IT ALL RAIN. COLD AIR WILL
EVENTUALLY WRAP INTO THIS LOW CHANGING THE PCPN OVER TO RAIN/SNOW
AND EVENTUALLY SNOW. BY THE TIME THIS HAPPENS...AS USUAL...THE
BULK OF THE PCPN WILL BE PULLING OUT. SO FOR NOW...NOT SEEING ANY
TYPE OF SIGNIFICANT WINTER SITUATION SETTING UP.
AVIATION...UPPER WAVE MOVING THROUGH THE STATE WILL BRING CONTINUED
VFR CLOUDS THROUGH TONIGHT...WITH DECREASING CLOUDS WEST TO EAST
EARLY TONIGHT INTO TOMORROW MORNING. LIGHT WINDS FROM WEAK PRESSURE
GRADIENT UNDER HIGH PRESSURE WILL LIKELY LEAD TO SOME FOG
DEVELOPMENT LATER TONIGHT. EXPECT MVFR VISBYS BY MIDNIGHT...WITH IFR
POSSIBLE LATER IN THE NIGHT. MOST OF THE FOG POTENTIAL WILL DEPEND
ON WHEN CLOUDS SCATTER OUT. COULD HOLD ON TO VFR VISBYS LONGER IF
CLOUDS LINGER. WILL HAVE TO KEEP AN EYE ON CLOUD TRENDS THIS
EVENING. OTHERWISE...VISBYS WILL RETURN TO VFR TOMORROW
MORNING...WITH A QUIET DAY ON SATURDAY.
MKX WATCHES/WARNINGS/ADVISORIES
WI...DENSE FOG ADVISORY FROM 1 AM TO 10 AM CST SATURDAY FOR WIZ056-
062-067-068.
LM...NONE.
SHORT/LONG TERM...06
AVIATION/MARINE...06
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page