AREA FORECAST DISCUSSION
NWS GREEN BAY WI
AFDGRB 200 PM CDT FRI APR 6 2001
STRONG UPPER SYSTEM COMING OUT OF EASTERN COLORADO WILL BRING SHOWERS
AND THUNDERSTORMS TO THE AREA TONIGHT AND EARLY SATURDAY...AND PERHAPS
SOME STRONG GRADIENT WINDS SATURDAY AFTERNOON AND EVENING. THERE IS
QUITE A BIT OF DIFFERENCE AT THE SFC BETWEEN THE AVN AND ETA/NGM AFTER
24 HOURS...BUT NOT MUCH DIFFERENCE AT 500 MB. NCEP DOESN/T HAVE A BIG
PREFERENCE BETWEEN THEM...BUT SLIGHTLY FAVORS THE ETA.
LOOKED AT 18Z WINDS FROM COMMERCIAL AIRCRAFT (ACARS). THE STRONGEST
JETSTREAM WINDS FAVOR THE 6HR ETA FORECAST A BIT BETTER THAN THE AVN. IN
ADDITION AIRCRAFT SOUNDING FROM OKC AT 18Z SHOWS 850 MB WINDS OF 50 TO
55 KNOTS WHICH VERFIES THE ETA 6HR FCST (55KTS) BETTER THAN THE AVN
(40KTS). THIS SUGGESTS THAT THE SYSTEM IS STRONGER (AND PROBABLY A BIT
SLOWER) THAN THE AVN PREDICTS. SO WILL GO IN THE DIRECTION OF THE ETA AS
FAR AS THE DETAILS GO...BUT ALL THREE MODELS AGREE WITH THE GENERAL
PATTERN.
EXPECT SHOWERS AND THUNDERSTORMS TO ARRIVE THIS EVENING AND CONTINUE
OVERNIGHT AS STRONG 850 MB WINDS BRING WARM...MOIST AIR OVER COOL AIR
NEAR THE SURFACE. THINK THUNDERSTORM WINDS GUSTS WILL HAVE A HARD TIME
MAKING IT TO THE SURFACE THROUGH THE INVERSION...WHICH BUFKIT DEPICTS TO
BE 3000 TO 4000 FEET DEEP AT 06Z. THERE COULD BE ISOLATED GUSTS OF
STRONG WINDS BY DAYBREAK AS INVERSION WEAKENS. WET BULD ZERO HEIGHTS ARE
FAIRLY LOW...BUT 500MB TEMPS AREN/T VERY COLD. THINK LARGE HAIL
UNLIKELY.
WARM FRONT FCST TO MOVE NORTH OF AREA TO NEAR MICHIGAN BORDER BY LATE
SATURDAY AFTERNOON. MUCH OF AREA SHOULD BE IN DRY SLOT FOR AWHILE
SATURDAY...THOUGH AMOUNT OF SUNSHINE DOUBTFUL. WITH NEARLY DRY ADIABATIC
LAPSE RATES IN LOW LEVELS WE SHOULD GET A LOT OF MIXING...AND BRING
WINDS OF 20 TO 40 MPH TO SURFACE IN THE SOUTHERN HALF OF THE AREA. ANY
PRECIPITATION IN THE WARM SECTOR SHOULD BE SHOWERY. OCCLUDED FRONT
SWEEPS BY LATE IN THE DAY...WHICH COULD TOUCH OF SCATTERED
THUNDERSTORMS. SEVERE WEATHER POSSIBLE IF SURFACE HEATING AND STEEP
LAPSE RATES ARE REALIZED. WILL ISSUE A WIND ADVISORY FOR THE SOUTHERN
HALF OF THE FCST AREA.
COORDINATED WITH MKE...THANKS
.GRB...WIND ADVISORY FOR SATURDAY FOR SOUTHERN HALF.
RDM
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