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000 FXUS63 KILX 251144 AFDILX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 544 AM CST WED NOV 25 2009 .DISCUSSION... ISSUED 215 AM CST WED NOV 25 2009 SATELLITE AND RADAR IMAGERY SHOWS THE CENTER OF THE STACKED LOW JUST NORTHEAST OF GALESBURG. SHOWERS CONTINUE TO PINWHEEL AROUND THIS LOW...MAINLY AFFECTING AREAS NORTH OF I-72 OVER THE LAST FEW HOURS. A SECONDARY TROUGH WAS ASSOCIATED WITH THIS LOW...AND WAS POISED TO BEGIN MOVING INTO THE NORTHWEST CWA. MEANWHILE...WATER VAPOR IMAGERY SHOWED A SECOND UPPER LOW EGINNING TO CROSS THE MANITOBA/NORTH DAKOTA BORDER. THE LINGERING EFFECTS OF THESE TWO SYSTEMS THROUGH THANKSGIVING DAY...ALONG WITH ASSOCIATED PRECIPITATION TYPES...MAKE UP THE FORECAST CHALLENGES FOR THIS PACKAGE. SHORT TERM...TODAY THROUGH FRIDAY... CURRENT SURFACE LOW EXPECTED TO QUICKLY LIFT NORTHEAST INTO THE GREAT LAKES TODAY AND WEAKEN...AS THE NEW CLOSED UPPER LOW DIVES SOUTHEAST INTO CENTRAL ILLINOIS BY MIDNIGHT. SHOWERS ACROSS THE NORTHERN CWA EXPECTED TO TAPER OFF BY LATE MORNING...WITH A NEW ROUND MOVING IN TOWARD MID TO LATE AFTERNOON AS THE NEW UPPER LOW MOVES INTO THE AREA. TRICKY PART OF THE FORECAST IS WHEN THE TRANSITION FROM RAIN TO SNOW OCCURS. MODEL AND BUFKIT SOUNDINGS SHOW THIS TO BEGIN OCCURRING TOWARD MIDNIGHT...WITH A POTENTIAL SWITCH BACK TO RAIN AS THE PRECIPITATION ENDS THURSDAY MORNING ACROSS THE WESTERN CWA...AND IN THE EARLY AFTERNOON ACROSS THE EAST. GROUND TEMPERATURES IN THE 40-45F RANGE...AND THE BULK OF THE DEFORMATION ZONE PRECIP REMAINING JUST TO OUR NORTH...WOULD LIMIT ANY ACCUMULATIONS THAT MAY OCCUR. GUSTY WINDS TO NEAR 25-30 MPH EXPECTED ON THURSDAY AS A TROUGH ZIPS THROUGH THE AREA. WINDS WILL SUBSIDE THURSDAY NIGHT...WITH A HIGH PRESSURE RIDGE PUSHING EAST ACROSS THE MISSISSIPPI VALLEY. THIS RIDGE WILL RESULT IN QUIET WEATHER FOR FRIDAY...AND SOUTHWEST WINDS WILL HELP BOOST TEMPERATURES SEVERAL DEGREES FROM THANKSGIVING DAY HIGHS. LONG TERM...SATURDAY THROUGH TUESDAY... WEAK UPPER RIDGING TO MOVE EAST ACROSS THE CONUS THE FIRST PART OF THE WEEKEND. MAIN CONCERNS IN THE LONG TERM CONTINUE TO FOCUS ON TWO SYSTEMS IN THE NORTHERN AND SOUTHERN JET STREAMS. GFS IS STRONGER WITH THE NORTHERN SYSTEM...DROPPING IT INTO THE SOUTHERN PLAINS TO GREATLY ENHANCE THE SOUTHERN STREAM SYSTEM BY MIDWEEK...WHILE THE ECMWF GENERALLY KEEPS THE STREAMS SEPARATE. HOWEVER...THE MORE SIGNIFICANT DIFFERENCES COME BEYOND THE END OF THE CURRENT FORECAST PERIOD. GEELHART && .AVIATION... ISSUED 535 AM CST WED NOV 25 2009 LOW PRESSURE CURRENTLY OVER CENTRAL LAKE MICHIGAN...WILL CONTINUE TO MOVE AWAY FROM THE FORECAST AREA THIS MORNING. RADAR INDICATING THE BAND OF SHOWERS THAT ROTATED ACROSS THE AREA OVERNIGHT HAVE SHIFTED MOSTLY TO THE EAST OF THE TAF SITES THIS MRNG. WE SHOULD SEE THE LIFR/IFR CIGS GRDLY IMPROVE TO MVFR CIGS BY LATER THIS MRNG. HOWEVER...THAT WILL BE SHORT LIVED AS ANOTHER UPPER DISTURBANCE...CURRENTLY DIVING SOUTHEAST OUT OF EASTERN SOUTH DAKOTA...INTO OUR AREA LATER THIS AFTERNOON. THIS WEATHER SYSTEM WILL BRING ANOTHER CHANCE FOR SHOWERS LATE THIS AFTN INTO THIS EVENING...ESP ACRS THE NRN TAF SITES (PIA AND BMI). WINDS WILL MAINLY OUT OF THE WEST TODAY AT 15KTS WITH OCCASIONAL GUSTS APPRCHG 25 KTS...WITH SOME DECREASE IN THE SPEEDS TONIGHT. WINDS WILL PICK UP AGAIN ON THURSDAY OUT OF THE NORTHWEST WITH GUSTS ARND 25 KTS AT TIMES. SMITH && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$
