FXUS63 KILX 160248
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
848 PM CST TUE DEC 15 2009

.DISCUSSION...
ISSUED 848 PM CST TUE DEC 15 2009

A BROAD AREA OF HIGH PRESSURE...CURRENTLY CENTERED NEAR THE
INTERSECTION OF IL/IA/MO...WILL DRIFT EAST ACROSS THE FORECAST AREA
OVERNIGHT. THE DRY/COLD AIR MASS ASSOCIATED WITH THIS FEATURE WILL
PROVIDE QUIET...BUT CHILLY...CONDITIONS THROUGHOUT CENTRAL AND
SOUTHEAST ILLINOIS.

WEAK DISTURBANCES IN THE NORTHWEST FLOW ALOFT MAY PROVIDE A FEW
WISPS OF HIGH CLOUDS...BUT ANY CLOUD COVER WILL BE TOO MINIMAL TO
SIGNIFICANTLY REDUCE RADIATIONAL COOLING OVERNIGHT. SINGLE DIGIT
LOWS SHOULD BE PRETTY COMMON OVERNIGHT...ESPECIALLY IN LOCATIONS
THAT WILL BE NORTHWEST OF THE SURFACE RIDGE AXIS BY MORNING...
WHICH INCLUDES MOST OF THE FORECAST AREA NORTH OF I-70. IF WE HAD
SNOW COVER...SUB ZERO READINGS WOULD BE COMMON...MUCH LIKE IS
OCCURRING UPSTREAM ACROSS IOWA.

GOING FORECAST IS IN GOOD SHAPE OVERALL. PLAN ON MAKING A FEW
MINOR TWEAKS FOR THE LATEST AND EXPECTED TRENDS...MOST NOTABLY TO
DECREASE OVERNIGHT LOWS A FEW DEGREES IN MANY AREAS.

BAK
&&

.AVIATION...
ISSUED 510 PM CST TUE DEC 15 2009

ARCTIC HIGH PRESSURE CENTERED IN NRN MO TO DRIFT EAST INTO CENTRAL
IL BY 12Z WED. LIGHT WINDS WILL GRADUALLY SWITCH TO THE SOUTH
AROUND 5 KTS AS THE HIGH DRIFTS FARTHER EAST AFTER 15Z WED.
MAINLY SKC WITH SOME SCATTERED HIGH CLOUDS STREAMING IN FROM THE
NW WED MORNING AND AFTN.

25
&&

.PREV DISCUSSION...
ISSUED 150 PM CST TUE DEC 15 2009

FORECAST PROBLEM TODAY IS THE EXTENDED PERIODS...AS WEAK WAVE TO
BRING CHANCE OF PCPN FRIDAY INTO WEEKEND.

SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT.
SURFACE DATA SHOWS RIDGE OF HIGH PRESSURE OVER THE CENTRAL PLAINS.
AIR MASS IS COOL AND DRY AND SO WITH LIGHT WINDS AND HIGH PRESSURE
MOVING INTO AREA TONIGHT...TEMPS SHOULD DROP OFF INTO THE SINGLE
DIGITS NORTH AND TEENS SOUTH. ALL THREE MODELS IN GOOD AGREEMENT
ON HIGH PRESSURE MOVEMENT. 

HIGH PRESSURE WEAKENS AND DRIFT OFF TO THE EAST SOME...AS A WEAK
INVERTED TROF OF SURFACE LOW PRESSURE DEVELOPS BY MIDDAY THURSDAY
IN THE PLAINS. 

LONG TERM...FRIDAY THROUGH TUESDAY. 

NEW EUR AND GFS MODELS ARE DIFFERENT IN PROGGED DEVELOPMENT AND
MOVEMENT OF THE UPPER TROF AND ASSOCIATED SURFACE FEATURE EARLY IN
THE EXTENDED PERIOD. EUR MODEL SEEMS TO CONTINUE TO BE THE MODEL
OF CHOICE. UPPER LEVEL DYNAMICS AND AVAILABLE MOISTURE ARE SOMEWHAT
LIMITED WITH THE SYSTEM. THEREFORE THE SYSTEM SHOULD BE A SOMEWHAT 
LIMITED PCPN MAKER. HAVE INCREASED POPS FOR FRIDAY AND FRIDAY
NIGHT TO CHANCE CATEGORY ONLY. 

WITH UPPER LEVEL TROUGHING IN PLACE...REST OF THE EXTENDED 
TIME FRAME SHOULD REMAIN COOL. THERE MAY BE SOME PERIODS OF LIGHT
SHOWERY PCPN THAT WILL NEED TO BE ADDED LATER.

GOETSCH
&&

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

$$