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000 FXUS63 KILX 250816 AFDILX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LINCOLN IL 216 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 1151 PM CST TUE NOV 24 2009 LOW PRESSURE OVER EASTERN IOWA WILL SLOWLY TRACK NORTHEASTWARD OVERNIGHT...SPREADING SCATTERED SHOWERS ACROSS CENTRAL ILLINOIS. BASED ON LOW TRACK AND LATEST RADAR MOSAIC...SHOWERS WILL BE MOST NUMEROUS AT THE NORTHERN TERMINALS. HAVE THEREFORE INCLUDED PREDOMINANT SHOWERS AT BOTH KPIA AND KBMI...WITH ONLY A TEMPO GROUP FOR SHOWERS FURTHER SOUTH AT THE REMAINING SITES. LOWEST CEILINGS OF UNDER 1000FT WILL ALSO BE NOTED ACROSS THE NORTH...WHILE CEILINGS WILL GENERALLY STAY ABOVE 1000FT THROUGH THE NIGHT AT THE I-72 TERMINALS. ONCE LOW MOVES FURTHER NORTHEAST...SCATTERED SHOWERS WILL COME TO AN END WEDNESDAY MORNING...AND CEILINGS WILL RISE TO AROUND 2500FT BY MIDDAY. UPPER DISTURBANCE CURRENTLY DIVING SOUTHWARD THROUGH THE DAKOTAS WILL APPROACH BY WEDNESDAY AFTERNOON...BRINGING ANOTHER CHANCE FOR SHOWERS. HAVE HANDLED THIS WITH VCSH AT THIS TIME. WINDS WILL INITIALLY BE SOUTHWESTERLY TONIGHT...BUT WILL VEER TO WESTERLY AND BECOME GUSTY ON WEDNESDAY. BARNES && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$
