FXUS63 KILX 100158 CCA
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL  
855 PM CDT FRI APR 9 2004

.DISCUSSION...
MAIN FCST CONCERN THIS EVENING IS WHEN WILL THE PCPN MAKE IT DOWN TO 
THE SFC. RADAR HAS BEEN SHOWING RETURNS OVER THE AREA ALL 
EVENING...BUT THIS HAS BEEN ALL VIRGA SO FAR DUE TO THE DRY LOW 
LEVELS. KILX SOUNDING THIS EVENING ALSO VERIFIES THIS. THE PCPN 
TRIES TO MOVE INTO THE AREA FROM THE WEST BUT MOVES INTO DRIER AIR 
AND DRIES UP. SFC OBS SHOWING COPIOUS MID AND UPPER LVL CLOUDS WITH 
N-NE FLOW AND DEWPOINTS IN THE LOW-MID 30S. 

FEEL THAT THE PRECIP WILL EVENTUALLY SATURATE THE COLUMN AND MAKE IT 
TO THE SFC...PROBABLY MORE SO AROUND MIDNIGHT AND AFTERWARDS. BEST 
CHANCES APPEAR TO BE CENTRAL AND SOUTH...LESS TO THE NORTH AS THE 
DRIER AIR IS BETTER ENTRENCHED AND FURTHER AWAY FROM THE BETTER 
LIFT. 

WILL ISSUE UPDATE SOON TO REMOVE EVENING WORDING. TUFF CALL ON HOW 
TO HANDLE THE POPS TONIGHT. MAY LOWER POPS A TAD ACROSS THE NORTHERN 
MOST ZONES BUT WILL PROBABLY LEAVE THE REST THE SAME.

&&

.PREV DISCUSSION...
FORECAST CHALLENGES AHEAD INCLUDE NORTHERN EXTENT OF PRECIP TONIGHT 
INTO SATURDAY ALONG WITH TEMPS...WITH LONGER TERM CONCERNS REVOLVING 
AROUND EVENTUAL EXIT OF LONGWAVE TROF TO OUR EAST AND WARMER TEMPS 
LATE NEXT WEEK. 


SHORT TERM...TONIGHT THROUGH MONDAY
BOTH MODELS INDICATING SOME DECENT 300K ISENT ASCENT STARTING THIS 
EVENING AND HOLDING INTO SATURDAY MORNING BEFORE THE LIFT WEAKENS 
WITH TIME. ETA QPF SEEMS TO BE VERIFYING THE BEST...AT LEAST IN THE
PAST 6 TO 9 HOURS SO WL TEND TO SIDE WITH IT DURING THE SHORT TERM. 
SFC ANALYSIS INDICATING BROAD NORTHERLY FLOW AROUND LARGE COLD 
CANADIAN HIGH WITH SFC DEW POINTS IN THE TEENS ACRS THE NRN MIDWEST. 
MODEL SOUNDINGS REALLY HAVING A TOUGH TIME SATURATING THE LOW LEVELS 
WITH BEST LAYERED RH AND LIFT ACRS THE SOUTH. THAT IS WHERE THE 
HIGHER POPS WL BE LOCATED THROUGH SATURDAY...WITH PROGRESSIVELY 
LOWER POPS NORTH. SFC WAVE AND DEEPER MOISTURE/CONVECTION WL BE 
LOCATED WELL SOUTH OF OUR FCST AREA WITH WEAK VORT MAXES ROTATING 
EWD ACRS CNTRL IL SAT AFTERNOON INTO THE EVENING KEEPING LIGHT RAIN 
CHANCES GOING. BEST LIFT AND MOISTURE SHIFTS TO OUR EAST LATE SAT 
NIGHT INTO SUNDAY WITH PRECIP CHANCES DIMINISHING FROM WEST TO EAST. 
MODELS INDICATING CNTRL IL IN BETWEEN WEATHER SYSTEMS SUNDAY AND 
EARLY MONDAY WITH STRONGER SYSTEM ACRS THE GULF COAST AND SOUTHEAST 
STATES...AND FAIRLY VIGOROUS UPPER LOW DRIFTING SOUTHEAST INTO THE 
MIDWEST ON MONDAY...SO WL GO WITH A DRY FCST ON SUNDAY. AS THE 500 
MB LOW APPROACHES DURING THE DAY ON MONDAY...OUR PRECIP CHANCES WILL 
INCREASE AGAIN DURING THE DAY...AND CONTINUE INTO MONDAY EVENING 
BEFORE PRECIP CHANCES END FROM NW TO SE TUE MORNING. FAIRLY COLD 
TEMPS ALOFT WITH SHALLOW WARM LAYER AT LOW LEVELS ON FCST SOUNDINGS. 
IF SYSTEM HOLDS OFF UNTIL MONDAY EVENING AFTR DARK...MAY SEE ANOTHER 
COLDER AIR WORK IN AT THE LOWER LEVELS TO PRODUCE A MIX OF RAIN AND 
SNOW. FOR NOW...WL GO WITH RAIN CHANCES.


LONG TERM...TUESDAY THROUGH FRIDAY
MEDIUM AND LONG RANGE MODELS REALLY SHOWING THEIR DIFFERENCES WITH 
THE MOVMNT OF THE LONGWAVE TROF ACRS THE EASTERN LAKES. EACH MODEL 
RUN HAS SLOWED THE PROGRESSION OF THE TROF DOWN WITH THIS MORNINGS 
RUNS INDICATING AN EVEN STRONGER SHORTWAVE DROPPING SE INTO THE 
LNGWV TROF POSITION MIDWEEK. FEEL THIS MORNINGS UKMET DEPICTION OF 
THE TROF OVR THE LAKES REGION AND THE WRN US TROF ABOUT 12 HOURS 
SLOWER THAN WHAT THE ECMWF WAS SHOWING IS THE WAY TO GO. AS A 
RESULT...WITH THE STRONGER...MORE AMPLIFIED PATTERN...WL INTRODUCE 
LOW PRECIP CHANCES (20 POPS) WED EVENING ALONG THE COLD FRONT ACRS 
OUR NW...AND SLIDE PRECIP CHANCES SOUTHEAST OVERNIGHT. GFS 850 TEMPS 
ON THURSDAY ON THE DOWNWARD TREND (-3 TO -8C) SO HAVE ADJUSTED AFTN 
TEMPS DOWN AS WELL...BUT MAY HAVE NOT GONE COOL ENOUGH BASED ON LOW 
LVL COLD ADVECTION PATTERN BEHIND TROF. SAME MAY HOLD TRUE FOR 
FRIDAY AS BEST LOW LVL WARM ADVECTION WILL BE WELL WEST OF US...SO 
AFTERNOON TEMPS MAY NEED TO BE ADJUSTED DOWNWARD A CATEGORY OR TWO 
MODEL RUNS SHOW SIMILAR TRENDS. FLOW ACRS THE PACIFIC FCST TO BECOME 
ZONAL WITH TROF SHIFTING INTO THE WRN US...ALLOWING RIDGE TO BUILD 
OVR THE CNTRL U.S. WITH MORE SPRING-LIKE TEMPS ACRS CNTRL IL 
SATURDAY AND SUNDAY.   

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
IL...NONE. 

&&

$$
HALL