HAMweather.com Area Forecast Discussion for County Warning Area ILX

Thu, 16 Feb 2012 05:33:03 GMT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1122 PM CST WED FEB 15 2012

.DISCUSSION...
ISSUED 832 PM CST WED FEB 15 2012

THE MIDDLE SECTIONS OF CENTRAL IL ARE CURRENTLY IN A PRECIPITATION 
LULL...WITH RAIN CONTINUING OVER THE NORTHWEST AND SOUTHEAST. THE 
MAIN SHORTWAVE IS NOW ENTERING SOUTHWESTERN MO AND WILL TRACK ACROSS 
IL LATER TONIGHT. ANOTHER BATCH OF RAIN IS ACCOMPANYING THE WAVE... 
WITH THE LEADING EDGE APPROACHING THE MS RIVER. THEREFORE AREAS THAT 
ARE RAIN-FREE FOR NOW WILL SEE AN UPSWING IN PRECIPITATION LATE 
TONIGHT AND DURING THE OVERNIGHT. LIGHTNING/IR SATELLITE DATA SHOWS 
LOW-TOPPED CONVECTION NEAR THE CENTER OF THE SHORTWAVE/VORT MAX 
EXTENDING TOWARD COLUMBIA MO. WATER VAPOR SATELLITE LOOPS SHOW 
DRYING/SUBSIDENCE OVER OK IN THE WAKE OF THE VORT MAX...WHICH  
ATTESTS TO THE DYNAMICS/LARGE SCALE ASCENT AIDING THE CONVECTION. 
THUS WILL KEEP THE THUNDER MENTION GOING IN THE FORECASTS. WITH ALL 
OF THE CLOUDS AND WARM DEWPOINTS AROUND...TEMPERATURES ARE HOLDING 
UP IN THE UPPER 30S TO MID 40S. AFTER THE SURFACE LOW PASSES THROUGH 
BEFORE DAWN...READINGS SHOULD COME DOWN INTO THE FORECASTED RANGE SO 
NO CHANGES ARE INDICATED FOR NOW. 

04

.AVIATION...
ISSUED 1122 PM CST WED FEB 15 2012

PATCHES OF RAIN AND WIDESPREAD VISIBILITIES BELOW 1SM ARE THE RULE 
OVER THE CENTRAL IL TAF SITES. THE BACK EDGE OF THE PRECIPITATION IS 
ALONG A WEAK COLD FRONT THAT LIES ALONG A LINE JUST WEST OF RFD TO 
BRL TO COU. SOME CONVECTION WILL REMAIN POSSIBLE AHEAD OF THE FRONT 
WITH RADAR/SATELLITE SHOWING HIGHER REFLECTIVITIES AND COOLER CLOUD 
TOP TEMPS JUST NORTHWEST OF THE AREA. AFTER THE FRONT PASSES THROUGH 
DURING THE 08Z-11Z TIMEFRAME...SLOW IMPROVEMENT IN VISIBILITIES AND 
CEILINGS WILL TAKE PLACE. WILL CONTINUE THE TREND IN THE PREVIOUS 
TAFS AND KEEP CEILINGS BLOW 1K FT UNTIL 14Z-16Z...THEN MVFR CEILINGS 
AFTER THAT UNTIL MID AFTERNOON. 

04

.PREV DISCUSSION...
ISSUED 220 PM CST WED FEB 15 2012

RAIN CONTINUES TO EXPAND NORTH AND EAST INTO CENTRAL AND EAST 
CENTRAL ILLINOIS EARLY THIS AFTERNOON. THE INITIAL BAND OF RAIN HAS 
AFFECTED PARTS OF SOUTH CENTRAL THRU SOUTHEAST IL STARTING THIS 
MORNING AND CONTINUES INTO EARLY THIS AFTERNOON. HOWEVER...AS A 
RATHER POTENT UPPER LEVEL WAVE...CURRENTLY OVER NORTHERN OKLAHOMA 
EARLY THIS AFTERNOON MOVES NORTHEAST...THE RAIN SHIELD HAS BEGUN TO 
EXPAND FURTHER NORTH AND EAST AND EXPECT THIS TO CONTINUE THRU LATE 
THIS AFTERNOON.

SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT
FORECAST CONCERNS THIS PERIOD WILL BE TIMING OF THE RAIN MOVING OUT 
OF THE FORECAST AREA THURSDAY MORNING FOLLOWED BY TEMPERATURES AS WE 
WORK OUR WAY INTO THE WEEKEND.

MODELS IN GENERAL AGREEMENT THRU THURSDAY MORNING WITH THE MOVEMENT 
OF THE SOUTHERN PLAINS UPPER WAVE AS IT GETS KICKED RAPIDLY NE FROM 
ANOTHER IMPRESSIVE CLOSED UPPER SYSTEM NOW MOVING INTO SOUTH CENTRAL 
CALIFORNIA. FORECAST SOUNDINGS STILL SHOWING SOME FAIRLY DECENT 
700-500 MB LAPSE RATES PUSHING ACRS THE AREA IN ADVANCE OF THE 
SHEARING OUT VORT MAX WITH K INDICES PUSHING AT OR JUST ABOVE 30 
TONIGHT ACRS THE CENTRAL AND SOUTHERN PORTIONS OF THE FORECAST AREA 
CONTINUING TO SUPPORT THE MENTION OF THUNDER. NAM-WRF FORECAST 
SOUNDINGS ACRS OUR FAR NORTHWEST CWA CONTINUES TO SUGGEST THE LOW 
LEVELS WILL BE TOO WARM TO SUPPORT ANY SNOW OR MIXED PRECIP ON THE 
BACKSIDE OF THE SYSTEM LATE TONIGHT INTO THURSDAY MORNING. IN 
FACT...MODELS CONTINUE TO INDICATE THAT THE DEEPER MOISTURE SHOULD 
BE SHUNTED OFF TO OUR EAST BY THURSDAY MORNING. OUR FAR EAST AND 
SOUTHEAST MAY SEE SOME LINGERING LIGHT RAIN OR DRIZZLE IN THE 12Z TO 
15Z TIME FRAME...BUT MOST OF THE MEASUREABLE PRECIP SHOULD MOVE OUT 
OF OUR AREA THU MORNING.

HIGH PRESSURE EXPECTED TO BUILD EAST INTO THE MIDWEST THURSDAY NIGHT 
INTO FRIDAY BRINGING QUIET WEATHER TO THE REGION. A NORTHERN STREAM 
SHORTWAVE IS THEN FORECAST TO SHIFT SOUTHEAST INTO THE LOWER LAKES 
FRIDAY NIGHT INTO SATURDAY. WITH MOST OF THE DEEPER MOISTURE SHUNTED 
OFF TO OUR EAST AND SOUTHEAST...FEEL THE DRIER LOOK DEPICTED ON THE 
ECMWF IS THE WAY TO GO RIGHT NOW...SO WILL KEEP PRECIP OUT OF THE 
FORECAST AS THE BETTER FORCING/LIFT REMAINS ACRS THE SOUTHERN GREAT 
LAKES. HIGH PRESSURE WILL THEN BUILD IN FROM THE NORTHWEST SATURDAY 
NIGHT INTO SUNDAY BRINGING QUIET WEATHER WITH VERY LITTLE IN THE WAY 
OF TEMPERATURE CHANGE. OUR WARMEST DAY SHOULD BE FRIDAY IN ADVANCE 
OF THE NORTHERN STREAM WAVE WITH A SOUTHWEST WINDS HELPING TO PUSH 
THE MERCURY WELL INTO THE 40S...WITH SOME READINGS PUSHING INTO THE 
LOWER 50S ACRS THE WEST AND SOUTHWEST FRIDAY AFTN. TEMPERATURES IN 
THE WAKE OF THE SYSTEM ON SATURDAY SHOULD "COOL" BACK DOWN INTO THE 
UPPER 30S NORTH TO THE UPPER 40S SOUTH.

LONG TERM...SUNDAY THROUGH WEDNESDAY

ABOVE NORMAL TEMPERATURES TO CONTINUE THROUGH THIS FORECAST PERIOD 
AS MEDIUM RANGE MODELS INDICATE UPPER LEVEL HEIGHTS TO BUILD NORTH 
ACRS THE REGION IN ADVANCE OF ANOTHER SIGNIFICANT SHORTWAVE THAT IS 
FORECAST TO PUSH ACRS THE NORTHERN GREAT LAKES TUESDAY INTO WED.

SOUTHWEST FLOW AHEAD OF THIS FEATURE SHOULD HELP PUSH TEMPERATURES 
INTO THE 40S ACRS THE ENTIRE AREA MONDAY...AND WELL INTO THE 40S 
TUESDAY...WITH LOWER 50S POSSIBLE ACRS THE SOUTHEAST. A SECONDARY 
WAVE IS THEN FORECAST TO DROP SOUTHEAST INTO THE LOWER LAKES AND 
PHASE WITH A SOUTHERN STREAM SHORTWAVE WHICH SHOULD DEEPEN A SURFACE 
WAVE TO OUR SOUTH AND SPREAD RAIN NORTHWARD INTO THE FORECAST AREA 
TUESDAY NIGHT AND WEDNESDAY. THE GFS IS MUCH MORE AGGRESSIVE WITH 
THE UPPER WAVE AND AS A RESULT MORE BULLISH WITH THE PRECIP SPREADING
MUCH FURTHER NORTH INTO OUR AREA TUESDAY NIGHT INTO WEDNESDAY WITH 
850 TEMPS SUPPORTING ALL RAIN. THE LATEST ECMWF...BRINGS THE 
SECONDARY NORTHERN STREAM WAVE SOUTHEAST BUT AT A SLOWER CLIP...AND 
AS A RESULT...ANY PHASING/DEEPENING OF THE SURFACE SYSTEM HOLDS OFF 
UNTIL THE SYSTEM IS TO OUR EAST ON WEDNESDAY. 

UNFORTUNATELY...DUE TO THE MODELS HAVING A DIFFICULT TIME RESOLVING 
THE PHASING ISSUES LATER TUESDAY INTO WEDNESDAY...POPS WILL CONTINUE 
IN THE GRIDS STARTING MONDAY NIGHT AND HOLDING THRU WEDNESDAY WITH 
THE BETTER CHANCES FOR RAIN APPEARING TO BE DURING THE 
TUESDAY-WEDNESDAY TIME FRAME.

SMITH

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