000 FXUS63 KILX 080255 AFDILX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 855 PM CST SAT NOV 7 2009 .DISCUSSION... ISSUED 852 PM CST SAT NOV 7 2009 WEAK FRONTAL BOUNDARY ACRS NW IL NOT EXPECTED TO MAKE MUCH MORE PROGRESS SOUTHEAST OVERNIGHT. LIGHT WINDS AND CLEAR SKIES HAVE LED TO A QUICK TEMP DECLINCE OVER THE FORECAST AREA THIS EVENING AS A RESULT...WL HAVE TO ADJUST THE OVERNIGHT LOWS DOWN A CATEGORY. MAY SEE SOME PATCHY GROUND FOG FORM TOWARDS DAWN AS WELL WITH THE LIGHT WIND REGIME BUT NOT EXPECTING ANYTHING WIDESPREAD OR LONG LASTING IN THE MRNG. FRONTAL BOUNDARY SHOULD BEGIN SHIFTING BACK NORTH AS A WARM FRONT TOMORROW AS UPPER LEVEL HEIGHTS BUILD IN RESPONSE TO SHORTWAVE ENERGY PUSHING INTO THE PLAINS. NICE WEATHER TO CONTINUE INTO MONDAY WITH UNSEASONABLY WARM TEMPS. UPDATED ZONE FORECAST WILL BE OUT BY 915 PM. SMITH && .AVIATION... ISSUED 515 PM CST SAT NOV 7 2009 MAIN FORECAST CONCERN WILL BE WITH THE POTENTIAL FOR SOME GROUND FOG DEVELOPMENT AFTR 09Z TNT. OTHERWISE...VFR CONDITIONS ARE EXPECTED FOR THE REMAINDER OF THIS FORECAST PERIOD. WEAK FRONTAL BOUNDARY JUST TO OUR WEST IS EXPECTED TO HOLD NEARLY STATIONARY OVERNIGHT BEFORE RETURNING NWD AS A WARM FRONT TOMORROW. SFC WNDS HAVE DECREASED CONSIDERABLY OVER THE PAST 12 TO 18 HOURS AND EXPCT LIGHT SE WINDS AND MOSTLY CLEAR SKIES TNT INTO SUN MRNG. AS THE FRONT SHIFTS WELL NORTH OF OUR AREA ON SUNDAY...SURFACE WINDS WL INCREASE OUT OF THE SOUTH BY LATE MRNG WITH A FEW GUSTS ARND 20 KTS. SMITH && .PREV DISCUSSION... ISSUED 140 PM CST SAT NOV 7 2009 18Z SURFACE MAP SHOWING WEAK COLD FRONTAL BOUNDARY BEGINNING TO ENTER FAR NORTHWEST ILLINOIS...EXTENDING SOUTHWEST TO NEAR KANSAS CITY. TEMPERATURES HAVE SURGED INTO THE MID 70S ACROSS THE WESTERN CWA EARLY THIS AFTERNOON...AND WERE AROUND 70 IN THE EAST. THE ENTIRE REGION WAS DEVOID OF CLOUDS...ASIDE FROM A FEW CIRRUS CLOUDS MOVING NORTHEAST ACROSS MISSOURI. MAIN FORECAST ISSUES FOR THE DAY INVOLVE FRONTAL PASSAGES IN THE MONDAY/TUESDAY TIME FRAME...AS WELL AS LATE NEXT WEEK. SHORT TERM...TONIGHT THROUGH TUESDAY... CURRENT COLD FRONT EXPECTED TO BECOME STATIONARY OVERNIGHT...NORTH OF THE CWA...THEN LIFT BACK NORTH ON SUNDAY. ANOTHER UNSEASONABLY MILD DAY IS ANTICIPATED ACROSS THE AREA ON SUNDAY...WITH HIGHS AGAIN REACHING THE 70S. SKIES EXPECTED TO BECOME PARTLY CLOUDY LATE TONIGHT AS THE FRONT APPROACHES...THEN CLEAR UP AGAIN ON SUNDAY. LOW PRESSURE EXPECTED TO FORM IN KANSAS ON SUNDAY AND MOVE NORTHEAST INTO THE MIDWEST. A COLD FRONT WILL SHARPEN UP AS A RESULT AS IT MOVES EAST TOWARD THE CWA. MODELS IN REASONABLE AGREEMENT THROUGH 48 HOURS...THEN THE NAM BECOMES SHARPLY DIVERGENT WITH THE SPEED OF THIS FRONT...AND RATHER GLARING WITH ITS DIFFERENCES BY TUESDAY. WILL SIDE WITH THE SLOWER SUITE OF GUIDANCE AS A RESULT...BRINGING THE FRONT THROUGH THE AREA MONDAY NIGHT AND EXITING TUESDAY MORNING. EXTRATROPICAL LOW IN THE NORTHERN GULF OF MEXICO TO PRECLUDE MUCH MOISTURE RETURN AHEAD OF THE FRONT. WILL CONTINUE WITH SLIGHT CHANCES ACROSS THE NORTHWEST CWA ON MONDAY...WITH RAIN CHANCES SPREADING OVER THE CWA MONDAY NIGHT. SOUTHEAST CWA MAY STAY DRY UNTIL TUESDAY MORNING. DID BUMP UP POPS A BIT MONDAY NIGHT INTO THE 40 PERCENT RANGE...PRIMARILY WEST OF I-55. A CLEARING TREND IS EXPECTED ON TUESDAY AND TUESDAY NIGHT...AS HIGH PRESSURE BUILDS INTO THE MID-MISSISSIPPI VALLEY BEHIND THE FRONT. LONG TERM...WEDNESDAY THROUGH SATURDAY... UPPER LEVEL RIDGING TO ADVANCE EAST ACROSS THE CONUS MIDWEEK...AS A TROUGH BEGINS TO DIG ACROSS THE WESTERN STATES IN RESPONSE TO LEFTOVER ENERGY FROM A POWERFUL LOW MOVING SOUTHEAST FROM THE GULF OF ALASKA. LONGER RANGE MODELS BEGIN TO DIVERGE SIGNIFICANTLY BY FRIDAY. THE GFS IS RATHER AGRESSIVE IN DEVELOPING A STRONG UPPER LOW ACROSS THE NORTHERN PLAINS...WITH SHARPLY COLDER CONDITIONS SPREADING IN BEHIND A FRONT ON SATURDAY. MEANWHILE...THE NEWLY ARRIVED ECMWF HAS A BOUNDARY OSCILLATING ACROSS THE AREA THROUGH THE WEEKEND...BEFORE FINALLY PUSHING THROUGH SUNDAY EVENING. AT THIS POINT...WILL SIDE MORE WITH THE ECMWF...KEEPING THE CWA DRY THROUGH FRIDAY NIGHT AND INCLUDING ONLY SILENT 20 POPS FOR SATURDAY AS THE MODELS TRY TO RESOLVE THEIR DIFFERENCES. GEELHART && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$