AREA FORECAST DISCUSSION
NWS CHICAGO IL
AFDCHI 600 PM CST SAT FEB 15 2003
AVIATION DISCUSSION FOR 00 UTC TAFS
WILL FORECAST CEILINGS 2000 FT BROKEN THROUGH 14 UTC.
EXCEPT IN ROCKFORD. THE ACARS SOUNDING AT 2314 UTC OVER
ORD SHOW A NORTHEAST WIND UP TO 700 MB WITH SUBSTANTIAL
SPEEDS. THE SURFACE CYCLONE IS OVER ARKANSAS. THE
OVERRUNING WITH THIS LOW STILL REACHES CENTRAL ILLINOIS.
BUT NOT NORTH ENOUGH TO AFFECT THE TAFS EXECPT THE WIND.
WILL FORECAST WINDS 25 TO 30 KNOTS. THERE IS A CIRCULATION
OVER EASTERN IOWA SEEN USING THE PROFILER DATA. THERE IS
STRONG POSITIVE DIFFERENTIAL VORTICITY ADVECTION FROM
850 MB TO 300 MB WITH THE CIRCULATION. THAT WILL BE A
PART OF THE NEGATIVE OMEGA FIELDS THAT WILL HELP KEEP
CLOUDS IN THE TAFS AT LEAST THROUGH THE EARLY MORNING.
WHW
PUBLIC DISCUSSION FOR AFTERNOON ZONES:
MAIN QUESTION THIS AFTN IS WHAT TO DO WITH ONGOING WSW'S. PRIND IS
TO KEEP WARNING FOR SRN TIER OF COUNTIES GOING AND EXTEND TO 12Z SUN
BASED ON RGNL RADAR LOOPS/SATLT/MODEL GUIDENCE AND COORD WITH ILX.
WILL ALSO EXTEND SNOW/BLOWING SNOW ADVSRY TO 06Z.
IR SATLT TRENDS SHOWS SRN EDGE OF ENHANCED CLOUDS ASSD WITH MID
TROPOSPHERIC SYS ACRS IA MOVG EWD INTO NRN/CNTRL IL. RADAR MOSAICS
SHOW EXTENSIVE LGT-MDT SNOW WITH THIS AREA WHICH IS FCST TO MOV EWD
ACRS SRN 1/3 OF FA TNGT. POTL FOR 2-4 ADDL INCHES IN WARNING AREA
WITH 1-2 IN ADVSRY. MAIN CONCERN IS WITH WIND EFFECTS ON ALREADY
FALLEN SNOW CREATING BLOWING AND DRIFTING WITH OCNL WHITE-OUT
CONDS. WINDS AOA 20 MPH WITH POWDERY SNOW LOOK LIKE THEY'LL
CONTINUE MOST OF NGT SO WILL HAVE TO EXTEND WRNG THROUGH OVRNGT
HRS.
CLRG FROM NW-SE ACRS FA DURG SUN THEN WX NIL INTO MID WEEK.
QUICK LOOK BEYOND TONIGHT...NO MAJOR CHANGES PLANNED...WITH GO WITH
AVN THROUGH EXTENDED PD.
.CHI...WINTER STORM WARNING THROUGH TONIGHT FOR
LIVINGSTON...FORD IROQUOIS AND BENTON COUNTIES. SNOW AND
BLOWING SNOW ADVISORY THROUGH THIS EVENING FOR
LASALLE...GRUNDY...KANKAKEE...JASPER AND NEWTON COUNTIES.
MERZLOCK
AREA FORECAST DISCUSSION
NWS BURLINGTON VT
AFDBTV 245 PM EST SAT FEB 15 2003
HI PRESS RIDGE TO CONT TO BUILD ACRS THE FA TONITE THRU MON. STORM
SYS TO MOVE ACRS THE SE USA TONITE THRU SUN NITE...THEN TO THE SOUTH
AND EAST OF SRN NEW ENG ON MON AND MON NITE. NEXT STORM SYS TO MOVE
ACRS SRN CANADA AND THE GREAT LKS REGION ON TUE/TUE NITE AND THEN
ACRS THE FA ON WED. HI PRESS TO BUILD IN ACRS THE FA FRO THU. UPR
TROF TO MOVE ACRS THE FA ON MON NITE THRU EARLY ON TUE.
STRONG H85 CAA TO TAKE PLACE ACRS THE FA TONITE WITH WEAKER CAA FOR
SUN AND EARLY ON SUN NITE...THEN WK WAA FOR LATE ON SUN NITE THRU MON
NITE. SOME LOW-LVL MSTR ADVECTION TO AFFECT THE FA LATE ON MON AND
INTO MON NITE. LOW-LVL MSTR TO RETURN ACRS THE FA ON MON NITE THRU
MUCH OF WED NITE. MID-LVL MSTR TO AFFECT THE FA ON MON NITE AND TUE.
PW VALUES LOOK TO BE BLO 0.2" ACRS THE FA THRU EARLY ON MON...THEN
AROUND 0.3" AFTER THAT THRU TUE.
WINDS SHOULD SLACKEN INTO THIS EVENING ACRS THE FA AND NOT A FACTOR
FOR THE REST OF THE FIRST THREE PERIODS. THE NEXT FEW DAYS SHOULD SEE
A SLOW INCREASE IN THE CLD COVER ACRS THE FA (FROM SOUTH TO NORTH)...
WITH CHC POPS ACRS SE VT ON MON NITE LOOKING LIKE A GOOD COMPROMISE
BETWEEN THE 12Z ETA/AVN SOLNS FOR THEN. CHC POPS ON TUE AND WED STILL
LOOK A GOOD IDEA AS WELL WITH THOSE NEXT TWO SYSTEMS MOVING THRU THE
FA THEN. AFTER TONITE...THE FA APPEARS TO BE ON THE UPSLIDE IN TERM
OF TEMPS.
INTO THE REST OF THE EXTENDED PERIOD...THERE LOOKS TO BE A LULL IN
THE ACTION ON FRI BEFORE A STORM AFFECTS THE FA ON SAT. WILL MOVE CHC
OF SN FROM FRI TO SAT FOR NOW.
FYI...AIRCRAFT AND SPOTTER REPORTS INDICATE THAT LK CHAMP APPEARS TO
HAVE FINALLY FROZEN OVER.
WRK ZONES OUT UNDER ALBWRKCWF. FINAL ZFP BY 4 PM.
.BTV...NONE.
MURRAY