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000 FXUS63 KILX 241922 AFDILX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 222 PM CDT FRI OCT 24 2008 .DISCUSSION... ISSUED 200 PM CDT FRI OCT 24 2008 UPPER LOW CURRENTLY OVR EAST CENTRAL IOWA WILL CONTINUE TO SLOWLY SHIFT EAST AND NORTH OVER THE NEXT 24 HOURS. SEVERAL VORT LOBES WERE ROTATING AROUND THE UPPER LOW AND HAVE COMBINED WITH DAYTIME HEATING TO HELP TO EXPAND THE AREA OF SHOWERS ACRS ERN IOWA AND THE WESTERN HALF OF ILLINOIS. EVEN HAD A LIGHTNING STRIKE SHOW UP OVR THE PAST HOUR NEAR PEORIA. UPPER WAVE OVR CNTRL CANADA EARLY THIS AFTN WL HELP TO PUSH THE UPPER LEVEL WAVE OFF TO OUR NORTHEAST ON SATURDAY. PATTERN ACRS NORTH AMERICA WL BECOME AMPLIFIED AS THE NEXT SHORTWAVE DEEPENS IN OVER THE GREAT LAKES ON SUNDAY BRINGING THE COLDEST AIR MASS TO THE MIDWEST SO FAR THIS FALL SEASON. SHORT TERM...TONIGHT THROUGH MONDAY MODELS VERY SIMILAR DURING THE PERIOD...ALTHOUGH THE NAM-WRF CONTINUES TO ADVERTISE A QUICKER FROPA ON SUNDAY COMPARED WITH THE GFS/GFS ENSEMBLE MEAN. AM TENDED TO SIDE MORE WITH THE NAM- WRF MODEL AS IT SEEMS TO HAVE A BETTER TRACK RECORD IN HANDLING THE COLD AIR INTRUSIONS IN THE MIDWEST. UPPER WAVE IS FORECAST TO WEAKEN AS IT GETS ABSORBED BY A NRN STREAM WAVE ON SATURDAY. THE LAST OF THE SHORTWAVES ROTATING AROUND THE UPPER SYSTEM WL PRODUCE SCATTERED SHOWERS MAINLY ACRS THE NORTH HALF OF THE FCST AREA TNT WITH THE PRECIP SHIFTING NORTH AND EAST OF THE AREA SATURDAY MRNG. NEXT UPPER WAVE COMING SOUTHEAST OUT OF CNTRL CANADA WILL ACT TO AMPLIFY THE PATTERN OVR THE LOWER 48 EARLY NEXT WEEK. THE COLD FRONT ASSOCIATED WITH THIS SYSTEM IS SLATED TO MOVE THRU ON SUNDAY ACCOMPANIED BY GUSTY WINDS AND COLDER TEMPERATURES...ESPECIALLY LATE IN THE DAY. BEST UPPER LEVEL FORCING AND JET SUPPORT CONTINUES TO SUGGEST ANY PRECIP WITH THE FRONT WL BE TO OUR NORTH AND EAST. MODELS SHOWING A RATHER DEEP TROF OVER THE GREAT LAKES EARLY NEXT WEEK WHICH WILL HELP BRING IN FREEZING TEMPERATURES TO MOST OF THE FORECAST AREA...STARTING IN AREAS NORTH OF I-72 MONDAY MRNG. LONG TERM...TUESDAY THROUGH FRIDAY THE SFC RIDGE AXIS WILL BE CLOSE TO THE AREA TUESDAY MRNG AND THAT APPEARS TO BE THE PRIMARY TIME FOR A HARD FREEZE OVR MOST OF THE FORECAST AREA WITH EARLY MORNING LOWS IN THE UPPER 20S TO LOWER 30S. MEDIUM RANGE MODELS REALLY START TO DIVERGE AFTR WEDNESDAY WITH RESPECT TO THE DEEP UPPER TROF TO OUR EAST AND HOW QUICKLY THAT WL BE MOVING AWY FROM THE MIDWEST. MODELS SUGGEST THE UPPER TROF WL SHIFT INTO THE EASTERN PORTION OF THE COUNTRY BY WEDNESDAY OF NEXT WEEK ALLOWING UPPER LEVEL HEIGHTS TO RISE OVR THE MIDWEST. THIS SHOULD BRING A MODERATING TREND TO THE AREA WED MORNING. HOWEVER...THE LATEST ECMWF BRINGS SHORTWAVE ENERGY SE OUT OF CANADA HELPING TO CARVE OUT ANOTHER TROF OVR THE LAKES REGION...WHICH WOULD BRING ANOTHER SHOT OF COOL AIR TO THE REGION FOR THE SECOND HALF OF NEXT WEEK. THIS SOLUTION IS ABOUT 180 DEGREES OUT OF PHASE WITH THE GFS/GFS ENSEMBLES SO AT THIS POINT AM INCLINED TO SIDE MORE WITH THE GFS SOLUTIONS WITH THE RIDGE BUILDING ACRS THE CNTRL US...WHILE ANY SHORTWAVE TRACKING SE OUT OF CANADA WL REMAIN WELL TO OUR NORTH. NO SIGNIFICANT CHANGES WL BE MADE TO THE EFP WITH TEMPERATURES STARTING OUT BELOW NORMAL AND RETURNING TO NEAR NORMAL AS WE HEAD TOWARDS THE END OF THE PERIOD...WITH LITTLE IF ANY SIGNIFICANT PRECIP EXPECTED NEXT WEEK. SMITH && .AVIATION... ISSUED 1232 PM CDT FRI OCT 24 2008 BAND OF LIGHT SHOWERS CURRENTLY EXTENDING FROM NEAR KGBG TO JUST SOUTH OF KSPI WILL CONTINUE TO ROTATE N/NE ACROSS THE AREA THIS AFTERNOON. HAVE COVERED THIS FEATURE WITH TEMPO GROUPS FOR -SHRA AT THE TAF SITES. CEILINGS HAVE BEEN VARIABLE THIS MORNING...AS A FEW PATCHES OF CLEARING DEVELOPED. IN GENERAL...SHOULD SEE CEILINGS AROUND 1500FT FOR THE BALANCE OF THE AFTERNOON. ONCE BAND OF LIGHT PRECIP SHIFTS OUT OF THE AREA BY EARLY EVENING...CEILINGS WILL SLOWLY BEGIN TO RISE...ALTHOUGH 12Z MODEL RH PROFILES CONTINUE TO INDICATE LOW OVERCAST PERSISTING THROUGHOUT THE NIGHT. WILL IMPROVE CEILINGS TO 3500FT THIS EVENING...THEN EVEN FURTHER TO AROUND 5000FT AFTER 14Z. WINDS WILL INITIALLY BE FROM THE SOUTH THIS AFTERNOON...BUT WILL VEER TO THE WEST BY EVENING AS THE LOW SKIRTS BY TO THE NORTH. BARNES && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$
