Issued by NWS Central Illinois
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000 FXUS63 KILX 252345 AFDILX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 645 PM CDT SAT OCT 25 2008 .DISCUSSION... ISSUED 140 PM CDT SAT OCT 25 2008 UPPER LOW THAT PLAGUED THE AREA WITH THE RAIN AT THE END OF THE WORK WEEK HAS WEAKENED AND LIFTED TO OUR NORTHEAST EARLY THIS AFTN. THE COLD POOL ASSOCIATED WITH THE UPPER LOW WAS ALSO SHIFTING AWAY FROM THE AREA AS A RESULT WE WERE SEEING A DECREASE IN CLOUD COVER FROM WEST TO EAST. A STRONGER SHORTWAVE WAS SEEN ON THE WATER VAPOR LOOP OVR SRN CANADA INTO THE DAKOTAS. THE ASSOCIATED COLD FRONT WAS RACING SOUTHEAST OUT OF NORTH DAKOTA AND IS SLATED TO PUSH ACRS OUR AREA SUNDAY MRNG...FOLLOWED BY THE COLDEST AIR MASS OF THE FALL SEASON SO FAR. SHORT TERM...TONIGHT THROUGH TUESDAY MODELS IN GENERAL AGREEMENT OVERALL AS THE UPPER TROF IS FORECAST TO DEEPEN IN ACRS THE LAKES REGION ON SUNDAY HELPING TO DRAW DOWN -6 TO -9C 850 MB TEMPS INTO CNTRL IL. AS THE TROF DEEPENS IN TO OUR NORTHEAST...THE SFC WAVE WL ALSO INTENSIFY NORTH OF THE LAKES REGION WITH ALL MODELS SHOWING A TIGHT PRESSURE GRADIENT ACRS OUR AREA LATE SUNDAY MRNG INTO THE EVENING HOURS. MODEL SOUNDINGS INDICATING DEEP MIXING WL OCCUR TMRW WITH BUFKIT MOMENTUM TRANSFER SUGGESTING WIND GUSTS OF 45 TO 50 MPH IN A FEW LOCATIONS. WL ISSUE A WIND ADVSY FOR ALL AREAS NORTH OF I-70 STARTING AT 15Z SUN AND RUNNING THRU THE EARLY EVENING HOURS. WITH THE LOW LEVEL THERMAL RIDGE FORECAST TO MOVE ACRS THE AREA TNT...AND COUPLED WITH SOUTHWEST WINDS ALL NIGHT...OVERNIGHT LOWS WL HAVE A TOUGH TIME FALLING OFF MUCH. HIGH TEMPS ON SUNDAY WL BE REALIZED IN THE MORNING ACRS THE NORTHWEST WITH STEADY OR SLOWLY FALLING TEMPS IN THE AFTN. NEXT CONCERN ONCE THE WINDS SUBSIDE SUNDAY EVENING WL BE WITH A HARD FREEZE MONDAY THRU WEDNESDAY MORNINGS. THE BEST SETUP FOR A HARD FREEZE WL BE TUESDAY AND WED MRNGS AS THE CENTER OF THE COLD AIR MASS IS FORECAST TO BE JUST TO OUR WEST. MODELS A BIT MORE AGGRESSIVE WITH THE SOUTHWARD MOVEMENT OF SOME COLD AIR STRATOCU INTO PARTS OF THE REGION BY MONDAY MRNG AHEAD OF A SECONDARY SHORTWAVE RACING SOUTHEAST ACRS THE MID-MISSISSIPPI VALLEY WHICH MAY KEEP TEMPS UP A BIT FROM GUID...IN ADDITION TO THE WINDS HOLDING UP DURING THE OVERNIGHT HOURS. MODELS SUGGEST ENOUGH LIFT AND MOISTURE ASSOCIATED WITH THIS WAVE TO PRODUCE TRACE AMOUNTS OF PRECIP (FLURRIES AND OR SPRINKLES) ON MONDAY SO WL INCLUDE SLIGHT CHANCES IN THE GRIDS (NOT MENTIONED IN THE ZFP) FOR NOW AND SEE HOW FUTURE MODEL RUNS HANDLE THIS FEATURE. MET GUID SEEMS TOO COLD... AT LEAST BASED ON THE ABOVE REASONING...WHILE THE MAV NUMBERS WERE A BIT TOO WARM SO WL TREND MORE TWDS A MAVMET BLEND MONDAY MRNG AND THEN GO WITH THE COLDER GUID NUMBERS TUESDAY AND WED MRNGS. DAYTIME HIGHS ON MONDAY AND TUESDAY...BASED ON 850 TEMP FORECASTS WL BE IN THE 40S WITH A FEW 50S PSBL ACRS THE SOUTHWEST TUE AFTN WITH FULL SUNSHINE. LONG TERM...WEDNESDAY THROUGH SATURDAY UPPER FLOW FORECAST TO DEAMPLIFY ACRS THE LOWER 48 WHICH WILL RESULT IN A MODERATING TREND DURING THIS PERIOD. THE COLD HIGH PRESSURE AREA WILL SHIFT TO OUR EAST BY WEDNESDAY AFTN RESULTING IN A RETURN FLOW SETTING UP ACRS THE MIDWEST FOR THE END OF THE WEEK. MODELS INDICATING +10C 850 MB TEMPS TRACKING IN FROM THE WEST BY THU AND FRIDAY WHICH SHOULD HELP PUSH TEMPERATURES BACK TO OR SLIGHTLY ABOVE NORMALS FOR THE END OF THE PERIOD. MEDIUM RANGE MODELS STILL NOT SHOWING ANY STRONG SIGNALS FOR PRECIP IN OUR AREA WITH THE WARM UP SO WL CONTINUE WITH A DRY FORECAST THRU THE END OF THE PERIOD. SMITH && .AVIATION... ISSUED 645 PM CDT SAT OCT 25 2008 A STRONG...BUT DRY...COLD FRONT WILL APPROACH THE REGION TONIGHT AND PASS THE TERMINALS BY MIDDAY SUNDAY. EXPECT SCATTERED MID CLOUDS FOR A FEW HOURS AHEAD OF FROPA...BUT NOT MUCH CLOUD COVER WITH OR AFTER FROPA. SOUTHWEST WINDS WILL SHIFT WEST NORTHWEST BEHIND THE FRONT AND GUST TO 30 KTS OR A BIT HIGHER BY AFTERNOON. BAK && .ILX WATCHES/WARNINGS/ADVISORIES... WIND ADVISORY FROM 10 AM TO 9 PM CDT SUNDAY FOR ILZ027>031- 036>038-040>057-061. && $$
