Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 300828
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
328 AM CDT SAT MAY 30 2015

.SHORT TERM...(TODAY)
ISSUED AT 328 AM CDT SAT MAY 30 2015

LOW PRESSURE IS PROJECTED TO TRACK IN A NORTHEAST DIRECTION ACROSS
SOUTHEAST ILLINOIS TODAY, WITH A COLD FRONT PUSHING ACROSS ILLINOIS
FROM NW TO SE DURING THE DAY. BOTH FEATURES WILL PROVIDE A FOCUS FOR
AN EXTENDED PERIOD OF RAIN SHOWERS AND SCATTERED THUNDERSTORMS IN
CENTRAL AND SOUTHEAST ILLINOIS. AN INTENSIFYING SOUTHERLY LOW LEVEL
JET WILL PROGRESS ACROSS SOUTHERN IL AHEAD OF THE LOW...WITH SPEED
CONVERGENCE MAXIMIZED ON AN AXIS FROM SW TO NE ACROSS OUR FORECAST
AREA. THAT LLJ WILL AID IN MOISTURE TRANSPORT PUSHING PRECIP WATER
VALUES INTO THE 1.5 TO 2 INCH RANGE. FLASH FLOOD GUIDANCE FOR ONE
HOUR IS GENERALLY 2 TO 2.5 INCHES IN AREAS THAT ARE EXPECTED TO SEE
THE HIGHER PRECIP TOTALS. SOME CONCERN FOR A FLASH FLOOD WATCH
SOUTHEAST OF THE ILLINOIS RIVER, BUT MOST OF THAT AREA SHOULD BE
ABLE TO HANDLE THE RAINFALL THAT OCCURS WITH THIS SYSTEM. PEAK
INSTABILITY THIS AFTERNOON IS FORECAST TO REACH TO AROUND 1500 J/KG
MUCAPE SE OF I-55, WHICH WILL INCREASE RAINFALL RATES WITH STRONGER
UPDRAFT DEVELOPMENT. SEVERE STORMS ARE NOT EXPECTED, BUT A FEW
STORMS CLOSER TO THE TRACK OF THE LOW SE OF I-55 COULD SEE SOME
SMALL HAIL AND GUSTY WINDS.

HIGH TEMPS WILL BE HELD IN CHECK BY THE WIDESPREAD CLOUD COVER AND
PERIODIC RAIN. HIGHS WILL STRUGGLE TO REACH 70 AROUND GALESBURG,
WITH LOW 80S FOR 80S SE OF I-70 WHERE SOME PEEKS OF SUN MAY OCCUR
THIS MORNING TO HELP BOOST TEMPS.

&&

.LONG TERM...(TONIGHT THROUGH FRIDAY)
ISSUED AT 328 AM CDT SAT MAY 30 2015

SURFACE LOW PROJECTED TO RIDE JUST NORTH OF THE OHIO RIVER AND THEN
INTO CENTRAL INDIANA TONIGHT...WITH MOST OF THE MODELS FAVORING A
POSITION IN EAST CENTRAL INDIANA BY SUNDAY MORNING. SOME HEAVIER
RAINS SHOULD CONTINUE TO AFFECT EASTERN ILLINOIS INTO THE FIRST PART
OF THE EVENING WITH THIS TRACK...WHERE CATEGORICAL POP`S WILL BE IN
PLACE FOR THE FIRST FEW HOURS. WITH THE CHANGES TO THE TRACK...HAVE
HAD TO RE-ORIENT THE ORIGINAL POP GRIDS TO FAVOR A MORE WEST-EAST
TAPERING OF THE RAIN VS A CLEARING FROM THE NORTHWEST. THUS...POP`S
WILL LINGER EAST OF I-57 PAST MIDNIGHT. TOTAL QPF FOR TODAY AND
TONIGHT EXPECTED TO BE IN THE 1.5 INCH RANGE IN AREAS FROM EFFINGHAM
NORTHEAST TO DANVILLE. STIFF NORTH/NORTHEAST WIND WILL DRIVE IN MUCH
COOLER AIR INTO THE AREA...ALTHOUGH THERE WILL BE A TIGHT
TEMPERATURE GRADIENT ACROSS THE FAR EAST DEPENDING ON THE SPEED OF
THE DEPARTING LOW.

MUCH QUIETER WEATHER EXPECTED SUNDAY AND MONDAY IN THE WAKE OF THE
DEPARTING SYSTEM. SURFACE HIGH TO BUILD SOUTHWARD THROUGH THE GREAT
LAKES...AND WILL NOT BE IN ANY PARTICULAR HURRY TO LEAVE. GFS AND
ECMWF TAKE UNTIL LATE WEDNESDAY/EARLY THURSDAY TO PUSH THIS SYSTEM
INTO THE EASTERN GREAT LAKES REGION...RESULTING IN DRY CONDITIONS
FOR OUR AREA. IN FACT...THEY BASICALLY KEEP THINGS DRY UNTIL LATE
THURSDAY OR FRIDAY AS UPPER LEVEL HEIGHTS BUILD DUE TO HIGH PRESSURE
IN THE PLAINS. TEMPERATURES WILL START OFF RATHER COOL WITH HIGHS IN
THE 60S TO AROUND 70 SUNDAY AND MONDAY...BUT 80S SHOULD RETURN BY
MID WEEK AS THE HIGH PUSHES FARTHER EAST.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)
ISSUED AT 1105 PM CDT FRI MAY 29 2015

NEXT WEATHER SYSTEM ALREADY STARTING TO MOVE INTO FAR WEST CENTRAL
ILLINOIS LATE TONIGHT AND WILL CONTINUE TO PUSH NORTH-NORTHEAST
INTO THE FORECAST AREA DURING THE EARLY MORNING HOURS. VFR CIGS
ARE EXPECTED TO GRADUALLY DETERIORATE TO MVFR WITH SOME LOCAL
IFR CIGS IN THE HEAVIER SHOWERS THAT WILL PUSH ACROSS THE WEST
AND NORTHERN AREAS LATE TONIGHT AND THRU A GOOD PORTION OF SAT.
BASED ON SOUNDING DATA...IT APPEARS SPI AND PIA WILL BE THE
FIRST TO GO TO MVFR CIGS IN THE RAIN AND ISOLD TSRA LATE
TONIGHT...ROUGHLY IN THE 08Z-11Z TIME FRAME...WITH ONLY A SLOW
SHIFT EAST DURING THE MORNING WITH CMI NOT SEEING THE LOWER
CIGS UNTIL AROUND 15 0R 16Z. VSBYS IN SOME OF THE HEAVIER
SHOWERS WILL DROP TO 1-2 MILES BUT TIMING OF THAT OCCURRENCE
HARD TO PINPOINT FROM THIS FAR OUT SO WILL LOWER TO 3-4 MILES
FOR NOW.

A COLD FRONT WILL SHIFT SOUTHEAST ACROSS THE AREA ON SATURDAY
AS LOW PRESSURE DRIFTS OVER SOUTH CENTRAL ILLINOIS LATE TOMORROW
MORNING INTO THE AFTERNOON HOURS. MOST MODELS DEPICTING THIS
NOW...SO FEEL MORE CONFIDENT ON THE WIND SHIFTS MOST AREA STARTING
AROUND 12-15Z AT PIA BUT NOT GETTING OVER TO CMI UNTIL AFTER 20Z.
LIGHT SOUTH TO SOUTHWEST WINDS TONIGHT INTO SATURDAY MORNING WILL
SHIFT INTO THE NORTH TO NORTHEAST ACROSS PIA IN THE MORNING AND
BMI IN THE EARLY AFTERNOON HOURS...WITH WINDS GOING MORE INTO
THE WEST TO NORTHWEST FOR OUR TAF SITES FURTHER SOUTH WITH CMI
SEEING THE WIND SHIFT IN THE 19-22Z TIME FRAME. ONCE THE FRONT
SHIFTS SOUTHEAST OF THE AREA LATE TOMORROW...LOOK FOR NORTH
TO NORTHEAST WINDS OF 15 TO 20 KTS...WITH SOME HIGHER GUSTS
POSSIBLE...ESPECIALLY EARLY IN THE EVENING.

LATEST SATELLITE DATA AND SURFACE OBSERVATIONS CONTINUE TO SHOW A
LARGE AREA OF MVFR AND IFR CIGS BEHIND THE COLD FRONT SO ONCE THAT
COLDER AIR STARTS TO FILTER IN LATE TOMORROW...IT APPEARS WE WILL
SEE A PERIOD OF LOW CIGS THRU AT LEAST THE EVENING HOURS OF SAT.


&&

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

$$

SHORT TERM...SHIMON
LONG TERM...GEELHART
AVIATION...SMITH


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