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000 FXUS63 KILX 280455 AFDILX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 1155 PM CDT MON OCT 27 2008 .DISCUSSION... ISSUED 858 PM CDT MON OCT 27 2008 FLOW ACROSS CENTRAL AND SOUTHEAST ILLINOIS IS BECOMING INCREASINGLY NEUTRAL AT THE SURFACE AND ALOFT AS RIDGING APPROACHES FROM THE PLAINS. SKIES ARE CLEARING A BIT MORE SLOWLY THAN ANTICIPATED THIS EVENING...BUT SHOULD STILL CLEAR BY MORNING. THE CLEARING SKIES...DIMINISHING WINDS AND DRY AIRMASS WILL ALLOW WIDESPREAD FREEZING CONDITIONS TO DEVELOP BY MORNING. GOING FORECAST IS IN GOOD SHAPE. ONLY PLAN ON MAKING MINOR TWEAKS FOR THE LATEST AND EXPECTED TRENDS. BAK && .AVIATION... ISSUED 1155 PM CDT MON OCT 27 2008 SKIES HAVE PRETTY MUCH CLEARED ACROSS THE CENTRAL ILLINOIS TERMINALS LATE THIS EVENING. EXPECT THESE QUIET/VFR CONDITIONS TO PERSIST THROUGH THE 06Z TAF PERIOD AS UPPER/SURFACE RIDGING STARTS TO BUILD INTO THE REGION. STILL EXPECT WINDS TO PICK UP INTO THE 10-15 KT RANGE WITH DIURNAL HEATING TUESDAY...BUT THEY WILL NOT BE NEARLY AS GUSTY AS IN RECENT DAYS. BAK && .PREV DISCUSSION... ISSUED 145 PM CDT MON OCT 27 2008 UPPER TROF FIRMLY ENTRENCHED OVER THE GREAT LAKES THIS AFTERNOON BRINGING CHILLY TEMPERATURES TO THE REGION. SEVERAL WEAK DISTURBANCES ROTATING SOUTHEAST OUT OF THE NRN PLAINS COMBINED WITH SOME DAYTIME HEATING HAS PRODUCED SOME ISOLATED SPRINKLES ACRS PARTS OF EAST CENTRAL AND SOUTHEAST ILLINOIS OVR THE PAST SVL HOURS. SURFACE HIGH PRESSURE TO OUR WEST WILL GRDLY WORK ITS WAY EAST OVR THE NEXT SVL DAYS BRINGING UNSEASONABLY COLD TEMPERATURES TO THE AREA THRU WED. UPPER TROF TO SHIFT OFF TO THE EAST AFTR WED ALLOWING THE CENTER OF THE COLD AIR MASS TO SHIFT AWAY FROM CNTRL IL BRINGING MODERATING TEMPERATURES TO THE AREA FOR THE END OF THE WEEK. SHORT TERM...TONIGHT THROUGH THURSDAY MAIN FORECAST CONCERN WL BE WITH THE POTENTIAL FOR A WIDESPREAD FREEZING TONIGHT AS ALL MODELS INDICATE THE CU/STRATOCU CLOUD FIELD WL DISSIPATE WITH THE LOSS OF DAYTIME HEATING LATE THIS AFTN WITH CLEARING SKIES FROM WEST TO EAST OVERNIGHT. WESTERN EDGE OF CLOUD SHIELD LOOKING MORE CELLULAR AS WE HEAD THRU THE EARLY AFTERNOON HOURS AS CONVECTIVE TEMPS HAVE BEEN REACHED...SUGGESTING ONCE WE LOSE THE DAYTIME HEATING...WE SHOULD SEE A DIMINISHING OF THE CLOUD COVER LATER THIS EVENING. 12Z MAV GUID ONCE AGAIN HAS WARMED TEMPS UP A FEW DEGREES (2 TO 4 DEGREES) FROM THE 00Z RUN FOR THE OVERNIGHT LOWS INDICATING THAT CLOUDS MAY BE SLOWER TO CLEAR THAN EXPECTED. STILL NOT MAKING ANY SIGNIFICANT CHANGES TO GOING TEMPS BASED ON THE ABOVE REASONING. IN ADDITION...UPSTREAM OBS SHOWING DEW POINTS HAVE MIXED DOWN INTO THE UPPER TEENS TO LOWER 20S...SO ANY SIGNIFICANT BREAKS IN THE CLOUD COVER LATER TONIGHT WL LEAD TO OVERNIGHT LOWS AS COLD AS THE MET/FWC GUIDANCE VALUES (MID TO UPPER 20S). CURRENT HEADLINES FOR FREEZING TEMPERATURES STILL LOOKING ON TARGET FOR TUESDAY MORNING. THE LARGE COLD FAIR WEATHER SYSTEM WILL EDGE SLOWLY EASTWARD ON TUESDAY AND WEDNESDAY CONTINUING TO BRING RATHER CHILLY TEMPERATURES TO CENTRAL ILLINOIS. 850 TEMP FORECASTS INDICATE HIGH TEMPS IN THE UPPER 40S ON TUESDAY WITH MID OR UPPER 50S LOOKING REASONABLE FOR WED AFTN. ANOTHER COLD NIGHT LOOKS LIKELY TUESDAY NIGHT INTO WED MRNG WITH READINGS AT OR BELOW GUID VALUES...IN THE 25 TO 30 DEGREE RANGE. THE ACTUAL SFC RIDGE AXIS DOES NOT SHIFT EAST OF OUR AREA UNTIL WEDNESDAY NIGHT WHICH WILL ALLOW A WEAK SOUTHERLY RETURN FLOW TO DEVELOP ACRS THE AREA BY THEN. INCREASING SOUTHERLY FLOW ON THURSDAY SHOULD SET THE STAGE FOR A NICE WARMUP ACRS THE MIDWEST WITH AFTN READINGS IN THE MID OR UPPER 60S. LONG TERM...FRIDAY THROUGH MONDAY MEDIUM AND LONGER RANGE MODELS IN GOOD OVERALL AGREEMENT WITH THE PATTERN OVER THE LOWER 48. THE DEEP TROF OVER THE LAKES SHIFTS EAST OF THE AREA AFTER WEDNESDAY WITH OUR FLOW BECOMING MORE ZONAL BY THE END OF THE WEEK. A WEAK SHORTWAVE CONTINUES TO PUSH ACRS THE REGION LATE THU INTO EARLY FRIDAY BUT WITH NO APPARENT WX ACRS OUR AREA. A MORE SIGNIFICANT SHORTWAVE WILL PROGRESS ACRS THE NRN PLAINS AND UPPER LAKES LATER ON FRIDAY WHICH WILL HELP TO DRAG A WEAK COLD FRONT ACRS THE AREA. MODELS CONTINUE TO SUGGEST ANY PRECIP ASSOCIATED WITH THE UPPER WAVE AND FRONTAL BOUNDARY WILL REMAIN TO THE NORTH OF THE AREA. ANOTHER FAIRLY LARGE COOL HIGH PRESSURE SYSTEM WILL AFFECT THE AREA FOR THE START OF THE WEEKEND. HOWEVER...WITH THE HIGH FORECAST TO DRIFT EAST ACRS THE UPPER LAKES RATHER THE SOUTHEAST INTO OUR AREA...IT APPEARS THE COLDEST TEMPERATURES WL REMAIN TO OUR NORTH OVR THE WEEKEND. 850 TEMPS DO COOL OFF SOME 3 TO 6 DEGREES C SUGGESTING AFTN HIGHS ON SATURDAY WILL DROP BACK INTO THE UPPER 50S NORTH TO THE MIDDLE 60S SOUTH. WITH UPPER TROFS LOCATED OFF THE EAST AND WEST COASTS AND RIDGING OVR THE CENTER OF THE COUNTRY SUNDAY AND MONDAY...IT LOOKS AS THOUGH TEMPS WILL BE AVERAGING OUT ABOVE NORMAL STARTING SUNDAY AFTN AND CARRYING INTO EARLY NEXT WEEK. THE NEXT CHANCE FOR ANY SIGNIFICANT PRECIP APPEARS TO BE HOLDING OFF UNTIL AFTER THIS FORECAST PERIOD. SMITH && .ILX WATCHES/WARNINGS/ADVISORIES... FREEZE WARNING UNTIL 9 AM CDT TUESDAY FOR ILZ027>031-036>038- 040>057-061>063-066>068-071>073. && $$
