Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 301203
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
703 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 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 700 AM CDT SAT MAY 30 2015

LOW PRESSURE APPROACHING FROM THE SW AND A COLD FRONT FROM THE NW
WILL COMBINE TO KEEP RAIN AND STORM CHANCES ACROSS ALL THE
TERMINAL SITES TODAY AND INTO THIS EVENING. LOCALLY HEAVY RAINFALL
WILL BE POSSIBLE, WITH PONDING OF WATER IN LOW SPOTS AT TIMES.

IFR/LIFR CLOUD HEIGHTS WILL AFFECT THE TERMINAL SITES AT LEAST
THIS MORNING, BUT POSSIBLY THROUGH THE AFTERNOON AS THE LOW
PRESSURE CROSSES SOUTHERN IL LATER TODAY AND IT PULLS MOISTURE AND
LOW CLOUDS INTO IL. PERIODS OF MVFR AND EVEN VFR COULD DEVELOP
BETWEEN RAIN AND STORMS TODAY, BUT OVERALL CLOUD HEIGHTS ARE
EXPECTED TO RETURN TO IFR/LIFR OVERNIGHT TONIGHT.

ONCE THE COLD FRONT PASSES TO THE SOUTHEAST OF THE TERMINAL SITES
THIS AFTERNOON, WINDS WILL SHIFT FROM SOUTHEAST TO NORTH-
NORTHEAST. WIND SPEEDS WILL INCREASE DRAMATICALLY AS THE LOW
CROSSES SOUTHEAST IL EARLY THIS EVENING, WITH SUSTAINED NORTH
WINDS OF 15-20KT AND GUSTS AROUND 3OKT. WIND GUSTS SHOULD DIMINISH
AFTER 06-08Z TONIGHT.

&&

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

$$

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


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