680 FXUS63 KILX 190302 AFDILX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 902 PM CST TUE DEC 18 2012 .DISCUSSION... ISSUED 900 PM CST TUE DEC 18 2012 LOW PRESSURE AT THE SOUTHERN TIP OF LAKE MICHIGAN IS QUICKLY DEPARTING TO THE EAST-NORTHEAST. LOW CLOUDS BEHIND THE LOW ARE COVERING THE NORTHERN HALF OF OUR COUNTIES...WITH SOME VERY GUSTY WINDS IN THE PRESSURE RISES BEHIND THE LOW. PRESSURE GRADIENT IS RATHER COMPACT FOR SEVERAL HUNDRED MILES BEHIND THE LOW. WINDS SHOULD DECREASE BY MIDNIGHT FROM WEST TO EAST...AS THE PRES GRADIENT WEAKENS. CLOUDS WILL REMAIN ALL NIGHT ALONG AND NORTH OF I-74...WITH VARIABLE SOUTHERN EDGE AS FAR SOUTH AS RUSHVILLE-LINCOLN- CHAMPAIGN/DANVILLE FOR A TIME. LOWS TONIGHT WILL BE A LITTLE TOUGHER TO PINPOINT FROM NORTH TO SOUTH DUE TO THE CLOUD COVER AND DIFFERENT WIND REGIMES ACROSS THE AREA. WILL PROBABLY BE SLIGHTLY COLDER IN THE SOUTH THAN WE HAVE GOING...DUE TO LESS CLOUDS AND LIGHTER WINDS FOR A LONGER PERIOD OF THE NIGHT. NO MAJOR CHANGES FOR THE SHORT TERM GRIDS...OTHER THAN UPDATING SKY/WIND. MINOR TEMP ADJUSTMENTS NEEDED AS WELL. A QUICK PEEK AT THE 00Z NAM FOR THE STORM FOR WED NIGHT-THUR NIGHT SHOWS NO BIG CHANGES. RAIN WED NIGHT INTO THURS MORNING...WITH RAIN CHANGING TO SNOW LATE MORNING NW OF IL RIVER AND CHANGING TO SNOW EAST OF THERE IN THE AFTERNOON. 1-3" STILL ON TRACK FOR OUR NW COUNTIES...WITH THE BULK OF THE SNOW FALLING THUR AFTERNOON WHEN THE WINDS REALLY PICK UP...35-50 MPH AT TIMES. IT WILL BE A MESS AS WE HEAD INTO THURS NIGHT AND THE TEMPS FALL DRAMATICALLY. SHIMON && .AVIATION... ISSUED 600 PM CST TUE DEC 18 2012...FOR THE 00Z TAFS LOW PRESSURE CENTERED JUST NORTH OF LACON AT 5 PM WILL MOVE EAST- NORTHEAST THIS EVENING. MVFR CLOUDS AT 2000 FT BEHIND THE LOW WILL MOVE ACROSS PIA BETWEEN 00-01Z AND BMI BY 02Z. THE MVFR CLOUDS WILL BE FOLLOWED BY MVFR VIS AFTER MIDNIGHT...WITH MOST AREAS IN THE 3-4SM BR RANGE AT SOME POINT TONIGHT. CONDITIONS SHOULD RETURN TO VFR BY 13-15Z IN MOST AREAS. PIA MAY REMAIN MVFR DUE TO LIGHT FOG FOR A GOOD PORTION OF THE DAY AS THAT AREA REMAINS IN HIGHER MOISTURE CONTENT NEAR THE SURFACE. RAIN ASSOCIATED WITH THE NEXT MAJOR STORM SYSTEM MAY BEGIN BY 20-22Z WED AFTERNOON FOR PIA AND SPI...AS STRONG MID LEVEL WINDS BRING MOISTURE INTO THE AREA. WE WENT WITH VCSH IN PIA/SPI/BMI FOR NOW. SURFACE WINDS WILL SWING AROUND TO THE EAST-SOUTHEAST BY AFTERNOON...JUST AHEAD OF THE RAIN. HEAVIER RAINS SHOULD HOLD OFF UNTIL WED NIGHT...AFTER THIS TAF PERIOD. SHIMON && .PREV DISCUSSION... ISSUED 325 PM CST TUE DEC 18 2012 MODELS IN FAIRLY GOOD AGREEMENT THIS AFTERNOON BUT DIFFER STILL ON PLACEMENT OF HEAVIEST SNOWFALL WITH UPCOMING WINTER STORM. MODELS HOWEVER DO AGREE ON PATH OF LOW TRACK AND 500MB LOW CUTTING OFF AND TRACKING ACROSS NORTHERN HALF OF IL. MAIN CONCERN IS THE WINTER STORM WED NIGHT THROUGH THUR NIGHT ACROSS THE REGION. SEEMS NAM MAY BE ODD MODEL OUT WITH TIMING OF HEAVIEST SNOWFALL...QUICKER THAN OTHERS. SO WILL LEAN TOWARD A BLEND OF THE GFS/ECMWF/SREF FOR THIS PACKAGE. OTHER CONCERNS ARE IN THE EXTENDED WITH ANOTHER SYSTEM ON OR JUST AFTER CHRISTMAS. WILL JUST FOLLOW ALLBLEND FOR NOW UNTIL MODELS GET BETTER AGREEMENT. SHORT TERM...TONIGHT THROUGH FRIDAY CONFIDENCE IN NEAR TERM FORECAST HIGH WITH MODELS AGREEING ON LOCATION OF STORM TRACK AND RESULTING PLACEMENT OF HEAVIEST SNOWFALL. NAM SEEMS TOO QUICK WITH SNOWFALL/PCPN THROUGH THE PERIOD SO LIKE A BLEND OF GFS/ECMWF FOR TIMING. LOW PRESS AREA WILL COME OUT OF PLAINS TOMORROW EVENING AND MOVE NORTHEAST THROUGH THURSDAY...REACHING TO NEAR PONTIAC BY 18Z THURSDAY. AS THIS SYSTEM DEVELOPS/DEEPENS IN THE SOUTHERN PLAINS IT WILL BRING IN QUITE A BIT OF WARM MOIST AIR INTO THE MISS VALLEY THROUGH TOMORROW NIGHT. THIS COMBINED WITH A STRONG DYNAMIC SYSTEM...EXPECTING PLENTY OF RAIN/RAIN SHOWERS ACROSS THE AREA BEGINNING TOMORROW AND CONTINUING INTO TOMORROW NIGHT. SHOULD BE ENOUGH INSTABILITY ON THE SFC IN THE WARM SECTOR AND ELEVATED CLOSE TO THE WARM FRONT...TO HAVE SOME ISOLATED/CHANCE OF THUNDERSTORMS EMBEDDED IN THE RAIN. BY THURSDAY MORNING AS THE SYSTEM CONTINUES TO MOVE NORTHEAST AND DEEPEN SOME...THE THUNDER CHANCES WILL GET PUSHED QUICKLY TO THE EAST AND MUCH COLDER AIR WILL ADVECT IN FROM THE WEST. PCPN WILL CONTINUE ACROSS THE AREA WITH RAIN BECOMING MIXED WITH SNOW DURING THE MORNING HOURS AND THEN CHANGING TO ALL SNOW BY LATE MORNING INTO THE AFTERNOON HOURS IN THE EAST. ALONG WITH THIS...THE PRESSURE GRADIENT WILL TIGHTEN WITH THIS SYSTEM AND BRING VERY STRONG GUSTY WINDS TO THE NORTHERN THIRD OF THE CWA. IN AREAS THAT HAVE SNOWFALL...THERE WILL BE BLOWING SNOW AS WELL...MAINLY THURSDAY INTO THURSDAY NIGHT. WIND GUSTS WILL BE ADVISORY CRITERIA...AND COMBINE WITH SNOWFALL OF 1-3 INCHES NORTHWEST OF A JACKSONVILLE TO BLOOMINGTON LINE...WITH HIGHEST AMOUNTS AROUND GALESBURG...A WINTER WEATHER ADVISORY MAY BE NEEDED FOR THE 4TH THROUGH 5TH PERIODS. BEING THIS EVENT IS FAR ENOUGH AWAY...WILL LET TONIGHTS SHIFT DECIDE ON ADVISORY AND CONTINUE TO HIGHLIGHT CONCERNS FOR THUR AND THUR NIGHT IN THE HWO AND SPS. ONCE THE SNOW AND BLOWING STOPS LATE THURSDAY NIGHT...DRY AND COLDER WEATHER IS EXPECTED FOR FRIDAY. TEMPS WILL BE VERY WARM AHEAD OF THE NEXT SYSTEM AND THEN TEMPS WILL BE FALLING ON THURSDAY WITH WARMEST TEMPS EARLY THURSDAY MORNING AND THEN FALLING 20+ DEGREES IN THE AFTERNOON. LONG TERM...FRIDAY NIGHT THROUGH TUESDAY DRY WEATHER EXPECTED THROUGH THE WEEKEND AND THEN ANOTHER SYSTEM IS POSSIBLE NEXT WEEK. ECMWF BRING SYSTEM IN FOR CHRISTMAS DAY WHILE GFS IS MUCH LATER. FOR NOW WILL JUST STICK WITH THE ALL- BLEND WHICH HAS POPS FOR WED NIGHT AND TUESDAY. THIS EVENT FAR ENOUGH AWAY THAT MODELS SHOULD HOPEFULLY COME INTO BETTER AGREEMENT. AUTEN && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$