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000
FXUS63 KILX 160137
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
837 PM CDT WED MAY 15 2013

.DISCUSSION...
ISSUED 837 PM CDT WED MAY 15 2013

STATIONARY FRONTAL BOUNDARY BISECTS CENTRAL ILLINOIS THIS
EVENING...WITH COOLER/SLIGHTLY DRIER AIR FILTERING INTO THE FAR
NORTHERN KILX CWA WHERE DEWPOINTS HAVE DROPPED INTO THE UPPER 40S
AND LOWER 50S. FURTHER SOUTH...MOISTURE POOLING ALONG THE BOUNDARY
HAS RESULTED IN DEWPOINTS IN THE LOWER 60S ALONG THE I-72
CORRIDOR. 01Z/8PM IR SATELLITE IMAGERY IS BEGINNING TO SHOW AC
DEVELOPING ALONG THE FRONT...WITH REGIONAL RADAR SHOWING SCATTERED
THUNDERSTORMS DEVELOPING FURTHER WEST ACROSS NORTHERN MISSOURI.
23Z HRRR SUGGESTS CONVECTION WILL DEVELOP EASTWARD ALONG THE
FRONT INTO WEST-CENTRAL ILLINOIS AFTER 03Z/10PM. BASED ON POSITION
OF FRONT AND LATEST HIGH-RES MODEL DATA...HAVE LOWERED POPS TO
JUST SLIGHT CHANCE ACROSS THE SE CWA ALONG/SOUTH OF I-70. FURTHER
NORTH...WENT WITH SCATTERED WORDING ACROSS THE CENTRAL AND
NORTHERN ZONES IN CLOSER PROXIMITY TO THE BOUNDARY. ALSO ADJUSTED
OVERNIGHT LOWS UP A FEW DEGREES...WITH LOWER TO MIDDLE 60S IN MOST
LOCATIONS...EXCEPT COOLER UPPER 50S FAR NORTH. ZONE UPDATE HAS
ALREADY BEEN ISSUED.

BARNES
&&

.AVIATION...
ISSUED 632 PM CDT WED MAY 15 2013

STATIONARY FRONTAL BOUNDARY CURRENTLY DRAPED ACROSS THE AREA WILL
BE THE MAIN FOCUSING MECHANISM FOR WIDELY SCATTERED SHOWERS/THUNDER
THROUGH THE ENTIRE 00Z TAF PERIOD. LATEST RADAR IMAGERY SHOWS VERY
LITTLE PRECIP OCCURRING NOW...ALTHOUGH MOST HIGH-RES MODELS TEND
TO DEVELOP CONVECTION ALONG THE I-72 CORRIDOR AFTER 03Z. WHILE
SOME MODEL SOLUTIONS DIMINISH THIS SCATTERED CONVECTION
OVERNIGHT...OTHERS KEEP IT GOING RIGHT THROUGH THE NIGHT INTO
THURSDAY. DUE TO UNCERTAINTIES CONCERNING EXACT TIMING AND
LOCATION OF ANY CONVECTION...HAVE OPTED TO CARRY ONLY VCTS AT THE
TAF SITES FOR THIS FORECAST ISSUANCE. WILL MENTION THUNDER BETWEEN
03Z AND 08Z AT THE I-72 TERMINALS...WITH DRY CONDITIONS FURTHER
NORTH. AFTER THAT...WILL BRING BACK VCTS AFTER 14Z AS DAYTIME
INSTABILITY RETURNS AND SCATTERED SHOWERS/STORMS DEVELOP IN THE
VICINITY OF THE BOUNDARY. WILL KEEP THUNDER OUT OF THE TAF FOR
BOTH KPIA AND KBMI UNTIL THURSDAY AFTERNOON ONCE FRONT SLOWLY
BEGINS TO RETREAT BACK NORTHWARD. WINDS WILL BE LIGHT/VARIABLE
THROUGHOUT THE PERIOD.

BARNES
&&

.PREV DISCUSSION...
ISSUED 259 PM CDT WED MAY 15 2013

FORECAST CONCERN TODAY IS THE POPS ASSOCIATED WITH THE STALLING
FRONT OVER THE REGION INTO THE WEEKEND...AND THEN THE APPROACH OF
THE MAIN UPPER WAVE AND FRONT THE FIRST PART OF NEXT WEEK.

.SHORT TERM...TONIGHT THROUGH FRIDAY NIGHT.
MORNING UPPER AIR DATA AND SPC INSTABILITY ANALYSIS SHOWS THE
EAST-WEST FRONTAL ZONE HAD MADE INTO THE NORTH CENTRAL PART OF IL
TODAY...WITH ENOUGH CONVERGENCE ON THE BOUNDARY TO CONTINUE THE
TREND THAT BEGAN OVERNIGHT...OF ELEVATED CONVECTION FORMING AND
MOVING EAST ALONG THE FRONTAL ZONE. THIS TREND HAS BEEN THE CASE
ALL DAY...AS THE UPPER AIR SHOWED A TONGUE OF LOW LEVEL MOISTURE
SURGING NORTH FROM TX OVER MO INTO THE BOUNDARY ZONE. SPC MESODATA
CONTINUED TO SHOW AIR SOUTH OF THE BOUNDARY CAPPED AND THE PCPN
REMAINING ELEVATED. EXPECT THIS TREND TO REMAIN OVERNIGHT...WITH
THE FRONT SAGGING A LITTLE SOUTH.

WITH THE FRONT PROGGED TO BE IN THE REGION BY ALL THE MODELS ON
THURSDAY...WILL KEEP POPS IN THE LIKELY CAT THROUGH CENTRAL REGION.
ADDITIONAL SUPPORT FOR DEVELOPMENT WITH UPPER LEVEL REMAINS OF THE
WEAKENING UPPER WAVE THAT IS OVER TX TODAY. THAT SYSTEM WILL BE
DRIFTING TO THE EAST NORTHEAST OVER OK TO AR. THIS SYSTEM IS
FORECAST TO WASH OUT THURSDAY NIGHT AND THEN THE UPPER RIDGE
BEGINS TO START TO BUILD OVER AREA. LOWERING POPS THEN FRIDAY AND
INTO FRIDAY NIGHT.

.LONG TERM...SATURDAY THROUGH WEDNESDAY.
THE APPROACH OF THE DEEPENING UPPER LOW/WAVE ON SUNDAY GRADUALLY
INCREASES POPS OVER WEST SUNDAY. GFS AND NEW EUR ARE DIFFERENT IN
THE DETAILS ON THE APPROACHING FRONT AND THE UPPER LOW/TROUGH
CONFIGURATION. TODAYS RUN DOES NOT DISPLAY A CLEAR SYSTEM MOVING
THROUGH...BUT A MORE GRADUAL MOVEMENT OF THE UPPER SYSTEM...WHICH
RESULTS IN A LONGER PERIOD OF POPS...FOR SUNDAY INTO THE DAY
WEDNESDAY. WILL STILL HAVE TO WATCH MONDAY FOR SIGNIFICANT
CONVECTION...AS SOUNDING AND HODOGRAPH ON THAT DAY STILL SHOW
POTENTIAL FOR STRONG STORMS.

GOETSCH
&&

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

$$