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000
FXUS63 KILX 181719
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1219 PM CDT TUE JUN 18 2013

.DISCUSSION...
ISSUED 1010 AM CDT TUE JUN 18 2013

FRONTAL BOUNDARY HAS SETTLED SOUTHWARD TO AROUND THE I-74
CORRIDOR. VIGOROUS SHORTWAVE CURRENTLY IN NORTHEAST IOWA WILL
CONTINUE TO MOVE SOUTHEAST...AND WILL HELP TRIGGER SOME
THUNDERSTORMS OVER CENTRAL ILLINOIS BY MID AFTERNOON. CURRENTLY
HAVE A SLIGHT RISK OF SEVERE WEATHER FROM ABOUT PEORIA TO
WINCHESTER EASTWARD. LATEST RAP MODEL SHOWING ABOUT 40-50 KNOTS OF
0-6KM BULK SHEAR WITH THIS SHORTWAVE...WITH OVER 2000 J/KG OF
SBCAPE...SO THIS RISK AREA APPEARS WARRANTED. COULD SEE SOME
HEAVIER RAINS WITH THE STORMS...ALTHOUGH THE SOUTH HALF OF THE CWA
APPEARS MORE LIKELY FOR ANY SIGNIFICANT RAINS AS PWAT VALUES IN
THAT AREA ARE CLOSE TO 1.5 INCHES BY MID AFTERNOON.

HAVE SENT SOME MINOR ZONE/GRID UPDATES...MAINLY TO ADJUST THE
CLOUD AND WIND TRENDS. HIGH TEMPERATURES STILL APPEAR REASONABLE.

GEELHART


&&

.AVIATION...
ISSUED 1218 PM CDT TUE JUN 18 2013

MAIN CONCERN FOR THIS TAF SET IS TIMING OF CONVECTION THIS
AFTERNOON. SEVERAL HIGH-RESOLUTION MODELS POINTING TO SCATTERED
STORM DEVELOPMENT IN CENTRAL ILLINOIS BEGINNING AROUND 19-20Z AND
MOST NUMEROUS DURING THE MID TO LATE AFTERNOON HOURS. HAVE KEPT
VCTS WORDING AT ALL TAF SITES FOR THIS AFTERNOON...BUT HAVE
FOCUSED ON THE KSPI-KDEC-KCMI CORRIDOR BY ADDING TEMPO PERIODS OF
TSRA AND VARIABLE/GUSTY WINDS WITH THE STORMS...AS THIS AREA IS
NEAR A FRONTAL BOUNDARY. SHOULD SEE THE CONVECTION FADE OUT WITH
SUNSET. DRIER NORTHEAST FLOW WILL CLEAR OUT MUCH OF THE AREA
OVERNIGHT. HAVE HELD OFF ON ANY OVERNIGHT MVFR FOG CONDITIONS...
BUT ANY AREAS THAT GET EXCESSIVE RAINFALL DURING THE DAY MAY SEE
SOME DEVELOP ALTHOUGH CONFIDENCE IS NOT HIGH AT THE MOMENT.

GEELHART

&&

.PREV DISCUSSION...
ISSUED 254 AM CDT TUE JUN 18 2013

SHORT TERM...TODAY THROUGH THURSDAY

07Z/2AM SURFACE ANALYSIS SHOWS A WEAK COLD FRONT EXTENDING FROM
NORTHEAST IOWA E/SE ACROSS NORTH-CENTRAL ILLINOIS. THIS BOUNDARY
WILL BE THE PRIMARY FOCUSING MECHANISM FOR WIDELY SCATTERED
CONVECTION AS IT SAGS SLOWLY SOUTHWARD LATER TODAY. VIGOROUS
SHORT-WAVE TROUGH CURRENTLY NOTED ON WATER VAPOR IMAGERY OVER
SOUTHERN MINNESOTA WILL TRACK SOUTHEASTWARD AS WELL...PROVIDING
ENHANCED LIFT ACROSS THE AREA DURING PEAK HEATING. WITH SURFACE
DEWPOINTS ALONG/SOUTH OF THE BOUNDARY IN THE MIDDLE TO UPPER
60S...CAPE VALUES WILL REACH THE 1500 TO 2500J/KG RANGE. IN
ADDITION...0-6KM SHEAR WILL INCREASE TO AROUND 40KT ON THE SOUTHERN
PERIPHERY OF THE APPROACHING WAVE. ALL THESE INGREDIENTS WILL COME
TOGETHER TO PRODUCE SCATTERED THUNDERSTORMS THIS AFTERNOON...A FEW
OF WHICH COULD PRODUCE GUSTY WINDS AND HAIL. WILL CARRY 30-40 POPS
ACROSS THE ENTIRE AREA ACCORDINGLY. AS DAYTIME INSTABILITY IS
LOST...CONVECTION WILL DISSIPATE AFTER SUNSET. WILL LINGER A
SLIGHT CHANCE POP ACROSS THE S/SW KILX CWA THIS EVENING...THEN
WILL GO DRY ACROSS THE BOARD OVERNIGHT.

SURFACE HIGH PRESSURE BUILDING INTO THE REGION BEHIND THE
DEPARTING FRONT WILL PROVIDE WARM/DRY WEATHER ON WEDNESDAY...WITH
AFTERNOON HIGHS IN THE LOWER 80S AND OVERNIGHT LOWS IN THE LOWER
60S. NEXT APPROACHING UPPER WAVE WILL COME INTO THE PICTURE ON
THURSDAY...AS A PIECE OF ENERGY EJECTS EASTWARD FROM DEEP UPPER
LOW SPINNING OFF THE COAST OF THE PACIFIC NORTHWEST. THIS WAVE IS
PROGGED TO TRACK ACROSS CENTRAL ILLINOIS ON THURSDAY. DESPITE
SYNOPTIC LIFT ASSOCIATED WITH THIS FEATURE...AIR MASS WILL BE
RATHER DRY...SO AM NOT EXPECTING MUCH IN THE WAY OF PRECIP. HAVE
GONE WITH A PARTLY SUNNY FORECAST...WITH JUST A SLIM CHANCE FOR
SHOWERS/THUNDER WEST OF I-55 THURSDAY AFTERNOON.

LONG TERM...FRIDAY THROUGH MONDAY

UPPER RIDGE IS EXPECTED TO BUILD ACROSS THE MIDWEST BY THE END OF
THE WEEK...LEADING TO A HOT AND LARGELY DRY EXTENDED FORECAST.
STILL SOME QUESTION AS TO HOW QUICKLY THE RIDGE WILL BUILD AND
WHETHER ANY NOCTURNAL MCS ACTIVITY WILL IMPACT PARTS OF THE AREA
FRIDAY/SATURDAY...HOWEVER MODEL CONSENSUS CONTINUES TO SUGGEST
MOST OF THIS PRECIP WILL BE FOCUSED FURTHER NORTH ACROSS THE UPPER
MIDWEST INTO THE GREAT LAKES. WILL THEREFORE CONTINUE WITH A
MAINLY DRY FORECAST ACROSS CENTRAL ILLINOIS...WITH JUST SLIGHT
CHANCE POPS ACROSS THE FAR NORTH. MAIN STORY WILL BE THE HEAT...AS
HIGH TEMPS REACH THE 90S OVER THE WEEKEND. NEXT BIG QUESTION WILL
BE HOW QUICKLY THE RIDGE WILL FLATTEN EARLY NEXT WEEK. 00Z JUN 18
GFS/ECMWF ARE IN GOOD AGREEMENT THROUGH 168HR/00Z TUE...THEN
SOLUTIONS DIVERGE BY THE MIDDLE OF NEXT WEEK AS GFS HOLDS ONTO
RIDGING ACROSS THE MIDWEST...WHILE THE ECMWF SHIFTS THE RIDGE
FURTHER WEST INTO THE ROCKIES. BASED ON THE PATTERN WE HAVE BEEN
IN FOR MUCH OF THE SPRING...THINK ECMWF HAS A MORE REALISTIC
ANSWER. WILL THEREFORE GRADUALLY INTRODUCE SHOWERS/THUNDERSTORMS
INTO THE FORECAST ACROSS THE NORTHERN HALF OF THE CWA BY
MONDAY/MONDAY NIGHT...THEN EVERYWHERE TUESDAY AS THE RIDGE WEAKENS
AND A FRONTAL BOUNDARY SAGS SOUTHWARD INTO THE REGION.

BARNES


&&

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

$$