FXUS63 KILX 252055
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
255 PM CST WED NOV 25 2009

.DISCUSSION...
ISSUED 232 PM CST WED NOV 25 2009
SFC LOW MAKING ITS WAY THROUGH THE GREAT LAKES TODAY...POST
FRONTAL TROF IS EXITING ILLINOIS TO THE EAST. YET ANOTHER WAVE OF
PRECIP IS MOVING ACROSS NRN IL THIS AFTERNOON...WITH VERY LIGHT
PRECIP FALLING. CLOUDS ARE THINNING AND MIGHT SEE A GLIMPSE OF
SUNLIGHT BEFORE SUNSET. THO MORE PRECIP IS ANTICIPATED FOR THE
HOLIDAY...POSSIBLY SOME SNOW AND RAIN MIXED...BUT NOTHING IN THE
WAY OF ACCUMULATION IS EXPECTED. BLACK FRIDAY SHOPPERS SHOULD
ALSO BE AWARE THAT BEHIND THE PRECIP IS A PRETTY STOUT SHOT OF
COLD AIR TO MAKE ANY CAMPING OUT FOR SALES A RATHER COLD AND DAMP
ENDEAVOR THURSDAY NIGHT/FRIDAY MORNING.

MODELS ARE STILL A BIT OF A WRECK...DIVERGING CONSIDERABLY AT MON
00Z. ECMWF HAS BEEN STRUGGLING WITH WHAT LOOKS LIKE A SPLIT FLOW
PATTERN SHIFT FOR THE PAST FEW RUNS...DEEPENING A STRANGE TROF
FROM THE DESERT SW TO THE MIDWEST...BUT FIGHTING SPLITTING OFF OF
A LOW IN BOTH THE GREAT LAKES AND THE SW. ALSO...FROM YESTERDAY TO
TODAY...ENSEMBLES WERE PUTTING THE NAO IN A NEGATIVE PHASE.
NEGATIVE VALUES FOR THE NAO POINTS TO A WEAKER ICELANDIC HIGH/LESS
AMPLIFIED FLOW. WITH A LESS AMPLIFIED FLOW...PHASING OF THE TWO
ENERGIES IS LESS LIKELY...AND COULD RESULT IN THE SECONDARY LOW
SPINNING OUT OVER THE SW AS THE OTHER MOVES THRU THE GREAT LAKES.
CERTAINLY...THERE ARE STILL MANY TIMING ISSUES AND OTHER PROBLEMS
TO DEAL WITH...BUT AM FAVORING THE SPLIT FLOW/CUT OFF LOW GFS
SOMEWHAT FOR THIS FORECAST.

SHORT TERM...TONIGHT THROUGH FRIDAY...
WILL KEEP THE LIKELY POPS IN THE NORTH TONIGHT...BUT SLIGHTS IN THE
SE TO HANDLE THE MORE SHOWERY ACTIVITY THAT WILL STILL BE
POSSIBLE. AFTER MIDNIGHT...COULD SEE A MIX OF SNOW/RAIN...BUT
WARMER AIR AT THE SFC SHOULD KEEP THE SNOW FROM ACCUMULATING...AND
2" SOIL TEMPS ARE STILL IN THE MID 40S. THANKSGIVING...THE
SHOWERS CONTINUE ON THE BACKSIDE OF THE LOW AS THE COLD AIR WRAPS
AROUND THE SYSTEM KEEPING THE SHOWERS A SNOW/RAIN MIX. BUT THE
GROUND SHOULD BE WET/WARM ENOUGH TO AVOID ANY SIGNIFICANT
ACCUMULATION. WILL CLEAR UP ENOUGH FOR THU EVENING TO WORK IN
COMBO WITH COLDER AIR TO BRING THE COLDEST TEMPS IN THE FORECAST
FOR THU NIGHT/FRI MORNING.

LONG TERM...SATURDAY THROUGH TUESDAY...
SATURDAY THROUGH SUNDAY SHOULD BE A BIT OF TEMP MODERATING...ESP
SAT AS THE FLOW GETS A MORE SOUTHERLY COMPONENT ON THE BACKSIDE OF
THE DEPARTING RIDGE AXIS. MODELS HAVING A MAJOR TIMING ISSUE WITH
THE NEXT PATTERN SHIFT. GFS IS A BIT MORE ADVANCED...TAKING THE
CHANGE OF A SPLIT FLOW BEFORE THE ECMWF HAS COME AROUND...THOUGH
THE ECMWF HAS BEEN HINTING FOR THE LAST COUPLE OF DAYS. WILL BE
WATCHING CLOSELY...AND KEEPING THE MAJORITY OF PRECIP TO THE SOUTH
PER THE GFS..AND LEAVE OPTIONS OPEN FOR ANOTHER WET END OF
WEEKEND/BEGINNING OF WORK WEEK.

HJS
&&

.AVIATION...
ISSUED 1155 AM CST WED NOV 25 2009

MVFR CEILINGS AND VISIBILITIES WILL PREVAIL ACROSS THE CENTRAL IL
TERMINALS THROUGH THU MORNING. VFR CONDITIONS WILL PROBABLY WORK
INTO SPI AND DEC SITES FOR A TIME THIS AFTERNOON WITH A DRY SLOT
WORKING EASTWARD FROM WEST CENTRAL IL. IFR CEILINGS AND
VISIBILITIES WILL BE POSSIBLE WITH SCATTERED RAIN SHOWERS WHICH
WILL MIX WITH OR CHANGE TO LIGHT SNOW SHOWERS LATE TONIGHT INTO
THU MORNING ESPECIALLY ALONG I-74.

MIDDAY SURFACE MAP SHOWS 1003 MB LOW PRESSURE OVER NORTHERN LAKE
MI WITH A SURFACE TROF EXTENDING SW INTO SE IA AND FAR NW MO.
STRONG 537 DM 500 MB CUTOFF LOW WAS OVER NW IA. BROKEN TO OVERCAST
MVFR TO LOCALLY IFR CEILINGS OVER CENTRAL/NORTHERN IL WITH LARGE
BREAKS/CLEARING AREAS IN SW/SOUTHERN IL. SCATTERED SHOWERS WILL
MOVING EAST FROM IA AND NORTHERN MO INTO THE IL RIVER VALLEY OVER
NW IL. MODELS DIG STRONG UPPER LEVEL LOW/TROF INTO IL BY 12Z/6 AM
THU AND INTO INDIANA BY 18Z/NOON THU. MODELS TRENDING A BIT
QUICKER WITH THIS. SCATTERED LIGHT RAIN SHOWERS WILL LIKELY SPREAD
ACROSS EASTERN IL THIS AFTERNOON AND CONTINUE TONIGHT ESPECIALLY
FROM I-74 NE WHERE LIGHT SNOW SHOWERS POSSIBLE LATE TONIGHT INTO
MID MORNING THU. BREEZY WSW WINDS WILL TURN WNW THU MORNING.

HUETTL
&&

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

$$