FXUS63 KILX 270207
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
807 PM CST THU NOV 26 2009

.DISCUSSION...
ISSUED 807 PM CST THU NOV 26 2009

CLEARING CONTINUES TO PROGRESS STEADILY EASTWARD INTO CENTRAL
ILLINOIS THIS EVENING...WITH 02Z SATELLITE IMAGERY/SURFACE OBS
SHOWING CLEAR SKIES ALONG AND WEST OF A MACOMB TO SPRINGFIELD
LINE. SUBSIDENCE BEHIND DEPARTING UPPER LOW WILL ALLOW SKIES TO
CLEAR ACROSS THE BOARD BY SHORTLY AFTER MIDNIGHT. COLDER/DRIER
AIRMASS IS FILTERING INTO THE AREA...WITH TEMPS ALREADY SLIPPING
INTO THE LOWER TO MIDDLE 30S. UPSTREAM DEWPOINTS ACROSS IOWA ARE
ONLY IN THE MIDDLE 20S...SO BELIEVE OVERNIGHT LOWS WILL BE A BIT
COLDER THAN PREVIOUSLY FORECAST ACROSS THE WESTERN KILX CWA. HAVE
THEREFORE TIGHTENED THE LOW TEMP GRADIENT TONIGHT...WITH READINGS
RANGING FROM THE MIDDLE 20S IN THE ILLINOIS RIVER VALLEY...TO
AROUND 30 DEGREES ALONG THE INDIANA BORDER.

BARNES
&&

.AVIATION...
ISSUED 533 PM CST THU NOV 26 2009

LOW CLOUDS CURRENTLY BLANKET CENTRAL ILLINOIS...BUT WILL BEGIN
CLEARING OUT FROM WEST TO EAST ACROSS THE AREA THIS EVENING.
SATELLITE IMAGERY SHOWS CLEARING LINE JUST WEST OF THE MISSISSIPPI
RIVER...WITH TIMING TOOL SUGGESTING CLEARING REACHING KSPI BY
02Z...THEN FURTHER EAST TO KCMI BY AROUND 05Z. NAM-WRF 1000-850MB
LAYER RH FIELD SUPPORTS THIS TREND AS WELL. ONCE THE LOW CLOUDS
DISSIPATE...WILL STILL SEE SCT-BKN HIGH CLOUDS OVERNIGHT INTO
FRIDAY...AS WEAK SHORT-WAVE DROPS THROUGH THE MIDWEST. WINDS WILL
INITIALLY BE GUSTY FROM THE NORTHWEST...BUT WILL GRADUALLY
DIMINISH AND BACK TO WESTERLY OVERNIGHT AND THEN TO SOUTHERLY BY
FRIDAY AFTERNOON.

BARNES
&&

.PREV DISCUSSION...
ISSUED 238 PM CST THU NOV 26 2009
SFC LOW SLOWLY MOVING THRU THE GREAT LAKES...AND REMAINING PRECIP
MOVING OUT OF THE EASTERN PORTIONS OF THE STATE. CLOUDY CONDITIONS
CONTINUE FOR THE FA AS THE REGION IS IN A RATHER DEEP TROF OF COLD
AIR ALOFT. MODEL AGREEMENT IN THE SHORT RANGE IS DECENT ENOUGH
THAT A BLEND IS JUST FINE. GOING WITH A MORE GFS SOLUTION FOR THE
SUN/MON SYSTEM...AS THE ECMWF IS SLOWLY GOING THE SAME WAY.
IN THE LONGER RANGE...THE ECMWF IS A LITTLE TOO AMPLIFIED AND
INCONSISTENT WITH THE HANDLING OF ANOTHER WAVE MOVING OUT OF THE
DESERT SW...AND FORECAST WILL BE A CONSERVATIVE BLEND...WITH FAVOR
TO THE GFS.  

SHORT TERM...TONIGHT THROUGH SATURDAY... CHILLY TEMPS AND GRAY
CONDITIONS LIKELY TO CONTINUE THROUGH THE EARLY EVENING...THOUGH
CLOUDS WILL CLEAR LEAVING THE FA WITH SOME VERY CHILLY TEMPS BY
MORNING...IN THE UPPER 20S. COULD DROP EVEN MORE IF CLOUDS CLEAR
EARLIER THAN EXPECTED. HIGH PRESSURE MOVES IN FOR A RATHER QUIET
SATURDAY. RIDGE AXIS SHIFTS A BIT TO THE EAST THROUGH THE
WEEKEND...AND A SOUTHERLY COMPONENT TO THE SFC WINDS BRINGS
MODERATING TEMPS AHEAD OF THE NEXT SYSTEM.

LONG TERM...SUNDAY THROUGH WEDNESDAY...
ECMWF HAS FINALLY COME AROUND TO THE GFS SOLUTION OF A MORE CUT
OFF LOW IN THE SW...AND SLOW TO FORM THE PRECIP PREDOMINANTLY IN
THE SOUTH AND PASS THE FRONT ON SUN/MON. WILL KEEP THE POPS LOW AS
MUCH OF THE QPF IS A BIT OVERBLOWN IN RESPONSE TO PREVIOUS RUNS.
NEXT SYSTEM IS THE LOW ITSELF...MOVING OUT MID WEEK. ECMWF IS
INCONSISTENT AND CHOPPY WITH THE MOVEMENT OF THE LOW...AS WELL AS
HIGH QPF. GFS IS MAINTAINING A SLOWER MEANDERING OF THE LOW ACROSS
THE SRN TIER OF THE CONUS IN THE SPLIT FLOW WITH A LESS AMPLIFIED
PATTERN OVERALL. FAVORING THE GFS...BUT STARTING A POTENTIAL TREND
IN THE GRIDS FOR POPS WED/THU.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$