673 
FXUS63 KILX 030155
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
855 PM CDT WED MAY 2 2012

.DISCUSSION...
ISSUED 845 PM CDT WED MAY 2 2012

00Z ILX SOUNDING DEPICTING A FAIRLY SIGNIFICANT CAP JUST ABOVE
850 MB WITH PLENTY OF CAPE/ELEVATED INSTABILITY ABOVE WITH MOST
UNSTABLE CAPES OF +2000 J/KG. UPSTREAM SOUNDING FROM SPRINGFIELD
MISSOURI INDICATING AN EVEN STRONGER CAP IN PLACE AND THAT IS OUR
SOURCE REGION FOR THE OVERNIGHT HOURS AND INTO THU MORNING. 
CONVECTION TRYING TO ORGANIZE TO OUR NORTHWEST EARLY THIS EVENING
IN EASTERN IOWA BUT THOSE STORMS WERE MOVING NE AND WILL STAY TO
OUR NORTH. COLD FRONT APPROACHING THE MISSOURI RIVER WILL BRING
ABOUT A LARGER COMPLEX OF STORMS OVERNIGHT...AND THOSE ARE
EXPECTED TO PUSH ACRS PARTS OF IOWA LATE TONIGHT...AND SIMILAR TO
WHAT OCCURED EARLIER THIS MORNING...APPROACH OUR WEST AND NORTHWEST
COUNTIES BY DAWN THURSDAY.

AS A RESULT...EXCEPT FOR AREAS ALONG AND NORTH OF A RUSHVILLE TO
BLOOMINGTON LINE...WHERE 20-30 PERCENT POPS WILL CONTINUE FOR THE
OVERNIGHT HOURS...THE REST OF THE AREA SHOULD REMAIN DRY.
SOUTHERLY WINDS HAVE KEPT THE EARLY EVE TEMP FALL TO A MINIMUM
ACRS THE AREA SO HAVE MADE SOME ADJUSTMENTS...OTHERWISE THE
CURRENT FORECAST IS IN GOOD SHAPE SO NO UPDATE WILL BE NEEDED.

SMITH
&&

.AVIATION...
ISSUED 625 PM CDT WED MAY 2 2012

MAIN FOCUS FOR SHOWERS AND THUNDERSTORMS TONIGHT WILL BE TO OUR
WEST AND NORTH...WITH THE OUTSIDE CHANCE SOME OF THE CONVECTION
MAY AFFECT OUR NORTHERN TAF SITES IN THE 09Z TO 12Z TIME FRAME.
AT THIS POINT WILL LEAVE OUT OF 00Z TAFS AND WATCH THE TRENDS
THIS EVENING TO OUR NORTHWEST. OTHERWISE...VFR CONDITIONS ARE
EXPECTED THRU TOMORROW WITH A LOW PROBABILITY FOR SOME LIGHT
FOG IN THE NORTH BUT WITH ALL AREAS MIXING OUT WELL THIS AFTN
AND WINDS HOLDING UP TONIGHT...WILL NOT INCLUDE IN TAFS THIS
EVENING. MODELS SUGGEST SOME MVFR CIGS POSSIBLE ACRS FAR WESTERN
IL BTWN 10Z-13Z WITH PROBABILITIES DECREASING MARKEDLY AS YOU
HEAD EAST. AT THIS TIME...WILL INCLUDE ONLY A SCATTERED GROUP AT
2000 FEET TO COVER THE POTENTIAL FOR PIA AND SPI. 

SURFACE WINDS WILL CONTINUE FROM A SOUTHERLY DIRECTION WITH A FEW
GUSTS AROUND 20 KTS FOR THE NEXT HOUR OR SO WITH WINDS HOLDING UP
OVERNIGHT FROM THE SOUTH AT 10 TO 15 KTS. WINDS WILL CONTINUE FROM
A SOUTHERLY DIRECTION TOMORROW AT 12 TO 17 KTS WITH GUSTS AROUND
25 KTS AT TIMES...ESPECIALLY DURING THE AFTERNOON HOURS.

SMITH
&&

.PREV DISCUSSION...
ISSUED 234 PM CDT WED MAY 2 2012

MCS REMNANTS HAVE FINALLY DISSIPATED FOR THE MOST PART ACROSS 
CENTRAL ILLINOIS...AND WILL ALLOW FOR A GOOD AMOUNT OF LATE 
AFTERNOON SUN ACROSS THE ENTIRE FORECAST AREA. THIS SHOULD TIGHTEN 
UP A SIZABLE N-S TEMPERATURE SPREAD ACROSS THE REGION.

LATEST SURFACE ANALYSIS HAD WEAK LOW PRESSURE CENTERED OVER THE 
CENTRAL PLAINS...WITH A NEARLY STATIONARY FRONTAL BOUNDARY CURVING 
NORTHEAST ACROSS THE GREAT LAKES REGION. IN ADDITION...SOUTH OF THE 
MAIN BOUNDARY...NUMEROUS OUTFLOW BOUNDARIES WERE EVIDENT...INCLUDING 
SOME ACROSS THE FORECAST AREA. A RATHER ACTIVE AND PREDOMINANTLY 
MESOSCALE DRIVEN PRECIPITATION PATTERN IS ANTICIPATED OVER THE NEXT 
SEVERAL DAYS ACROSS THE MIDWEST. THE PRIMARY FORECAST CONCERN TODAY 
REVOLVES TRYING TO TIME/PLACE PRECIPITATION CHANCES WITH FRONTAL 
AND/OR OUTFLOW BOUNDARIES IN THE VICINITY...COUPLED WITH MAINLY WEAK 
IMPULSES IN PERSISTENT A WEST SOUTHWEST UPPER LEVEL FLOW. THE 
POSITION OF THE SURFACE BOUNDARIES WILL ALSO PRODUCE A TRICKY 
TEMPERATURE FORECAST FOR THE NEXT SEVERAL DAYS.

12Z MODELS IN FAIR AGREEMENT THROUGH THE PERIOD. WHILE THE LARGE 
SCALE AGREEMENT IS NOT TOO BAD...THERE IS MUCH MORE SPREAD IN THE 
SMALLER SCALE DETAILS WHICH ARE VERY IMPORTANT TO OUR LOCAL FORECAST 
CONCERNS. HAVE GENERALLY FOLLOWED A MODEL BLEND FOR MUCH OF THE 
PERIOD DUE TO THE UNCERTAINTY...BUT HAVE ALSO CONSIDERED 
EXTRAPOLATION AND CONCEPTUAL MODELS FOR THE VERY SHORT RANGE 
FORECAST. 

SHORT TERM...TONIGHT THROUGH SATURDAY...STILL SOME CONVECTION MAKING 
ITS WAY ACROSS FORECAST AREA ALONG/AHEAD OF ONE OF THE MAIN OUTFLOW 
BOUNDARIES...BUT THIS SHOULD BE MOSTLY OUT OF THE AREA IN THE NEXT 
FEW HOURS. THEN...ATTENTION FOR MOST OF THE NIGHT SHOULD TURN TO OUR 
NORTHWEST ALONG THE MAIN FRONTAL BOUNDARY WHERE MCS DEVELOPMENT 
SHOULD OCCUR OVER IOWA AND/OR NEBRASKA. SOME OF THIS DEVELOPMENT MAY 
IMPACT NORTHWEST PORTION OF THE FORECAST AREA BY LATE TONIGHT. MCS 
REMNANTS OR ADDITIONAL DEVELOPMENT ALONG AN OUTFLOW BOUNDARY ARE
POSSIBLE IN WESTERN SECTIONS OF THE FORECAST AREA ON THURSDAY.

SOMEWHAT MORE WIDESPREAD PRECIPITATION CHANCES ARE ANTICIPATED 
THURSDAY NIGHT INTO FRIDAY NIGHT...AND POSSIBLY INTO SATURDAY. THESE 
HIGHER CHANCES WILL OCCUR AS AN UPPER LEVEL WAVE TURNS THE MEAN FLOW 
A LITTLE MORE WESTERLY ACROSS THE MIDWEST...ALLOWING THE MAIN 
FRONTAL BOUNDARY TO SLOWLY SINK SOUTH THROUGH THE FORECAST AREA.

DAYTIME HIGHS IN THE 80S AND NIGHTTIME LOWS IN THE 60S SHOULD 
PREVAIL THROUGH THE PERIOD TO THE SOUTH OF THE MAIN FRONTAL 
BOUNDARY. HOWEVER...THE HIGHS HAVE THE POTENTIAL TO BE QUITE A BIT 
COOLER DEPENDING ON THE EXTENT OF PRECIPITATION COVERAGE AND 
ASSOCIATED CLOUD COVER.

LONG TERM...SUNDAY THROUGH WEDNESDAY...A FEW COOLER DAYS ARE 
ANTICIPATED THROUGH THE PERIOD WITH THE MAIN FRONTAL BOUNDARY 
EXPECTED TO LIE SOUTH OF THE FORECAST AREA. HOWEVER...THE FRONT WILL 
STILL BE CLOSE ENOUGH TO SUPPORT ALMOST A DAILY THREAT OF 
SHOWERS/STORMS AS UPPER LEVEL DISTURBANCES RIDE ALONG THE BOUNDARY.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$