Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 012303
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
603 PM CDT FRI MAY 1 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 240 PM CDT FRI MAY 1 2015

A 1022 MB HIGH PRESSURE OVER IL WILL SETTLE INTO THE MID MS AND OHIO
RIVER VALLEYS BY SATURDAY MORNING AND CONTINUE FAIR WEATHER OVER
CENTRAL AND SOUTHEAST IL INTO SATURDAY. MID AND HIGH CLOUDS OVER IA
AND NW PARTS OF MO AND IL INCLUDING THE IL RIVER VALLEY WILL DRIFT
EASTWARD ACROSS THE REST OF CENTRAL AND SOUTHEAST IL THE REST OF
TODAY WITH SKIES BECOMING PARTLY TO MOSTLY CLOUDY TONIGHT. LOWS OF
45-50F TONIGHT WITH COOLEST READINGS FROM I-57 EAST WHERE WINDS WILL
BE LIGHTER CLOSER TO HIGH PRESSURE RIDGE AND LESS CLOUD COVER. LIGHT
WINDS TO BECOME SSW TONIGHT AS HIGH PRESSURE SLIPS OFF TO THE
SOUTHEAST OF CENTRAL IL.

.LONG TERM...(SATURDAY THROUGH FRIDAY)
ISSUED AT 240 PM CDT FRI MAY 1 2015

LATEST GUIDANCE CONTINUES TO SUPPORT A MAINLY DRY WEEKEND ACROSS THE
AREA...ALTHOUGH A FEW SHOWERS MAY BE ABLE TO MAKE IT EAST ACROSS
THE MISSISSIPPI RIVER LATE TONIGHT/SATURDAY MORNING JUST AHEAD OF
A WEAKENING SHORTWAVE BEFORE DISSIPATING AS THEY ENCOUNTER A DRIER
AIR MASS. THE SURFACE HIGH PRESSURE SYSTEM THAT BROUGHT THE CHILLY
TEMPERATURES OVER THE REGION LAST NIGHT WILL BE SLOWLY PUSHING
AWAY FROM OUR AREA ON SATURDAY ALLOWING SOUTHERLY WINDS TO
RETURN...WHICH SHOULD HELP PUSH AFTERNOON TEMPERATURES INTO THE
MIDDLE 70S MOST AREAS. A STRONGER NORTHERN STREAM SHORT WAVE IS
THEN FORECAST TO TRACK ACROSS THE UPPER GREAT LAKES LATE SUNDAY
INTO MONDAY DRAGGING A COLD FRONT SOUTHEAST INTO THE LOWER GREAT
LAKES ALONG WITH AN INCREASING THREAT FOR SHOWERS AND
THUNDERSTORMS ALONG THE BOUNDARY.

AS THE UPPER WAVE SHIFTS WELL OFF TO OUR EAST ON MONDAY...THE
FRONTAL BOUNDARY WILL BECOME PARALLEL TO THE UPPER FLOW WHICH
SHOULD RESULT IN VERY LITTLE IF ANY SOUTHWARD PUSH TO THE FRONT.
LATEST MODEL SOLUTIONS HAVE TRENDED A BIT FURTHER SOUTH WITH THE
LOCATION OF THE FRONT ON MONDAY RESULTING IN A BIT OF A SOUTHWARD
ADJUSTMENT TO THE HIGHER POPS DURING THE DAY. OUR BEST CHANCES FOR
MORE WIDESPREAD SHOWERS AND THUNDERSTORMS WILL PUSH IN TO THE
NORTHWEST AREAS LATE SUNDAY NIGHT AND OVER THE NORTHERN HALF OF
THE FORECAST AREA DURING THE DAY MONDAY AND THRU MOST OF MONDAY
NIGHT. SEVERE THREAT AT THIS POINT LOOKS RATHER LIMITED WITH 500
MB WINDS OF LESS THAN 30 KTS EARLY NEXT WEEK. CAPES MONDAY/TUESDAY
AFTERNOON WILL BE AROUND 1300 J/KG WITH PRECIPITABLE WATER VALUES
OF AROUND 1.5 INCHES SO THE THREAT FOR HEAVY RAINFALL WILL HAVE TO
BE WATCHED... ESPECIALLY ALONG THE STALLED FRONTAL BOUNDARY WHERE
THE STORMS WILL HAVE A TENDENCY TO TRAIN. 850 MB JET NOT PARTICULARLY
STRONG OR ALIGNED JUST RIGHT INTO OUR AREA DURING THIS PERIOD AS
THE STRONGER WIND FIELDS AT THAT LEVEL AND THETA-E ADVECTION REMAIN
OUT TO OUR WEST BEFORE WEAKENING ON TUESDAY AS THE UPPER RIDGE STARTS
TO BUILD ACROSS THE REGION SHIFTING THE BETTER LOW LEVEL FLOW WELL
OUT TO OUR WEST.

PRECIP CHANCES WILL REMAIN THRU TUESDAY MORNING BEFORE UPPER HEIGHTS
BEGIN TO BUILD NORTHWARD AGAIN IN RESPONSE TO A DEEPER TROF PUSHING
ACROSS THE ROCKIES AND SOUTHERN PLAINS MID-WEEK. THIS SHOULD HELP TO
PUSH THE SURFACE BOUNDARY BACK NORTH AS A WARM FRONT TUESDAY AFTERNOON
AND EVENING WITH POPS RELEGATED TO THE NORTHERN PORTION OF THE
FORECAST AREA TUESDAY NIGHT INTO WEDNESDAY. IN FACT...THE LATEST
MEDIUM RANGE GUIDANCE INDICATES AFTER THE LEAD TROF EJECTS
NORTHEAST THROUGH THE CENTRAL PLAINS MID-WEEK...WE MAY HAVE TO
WAIT UNTIL LATE THUR OR FRIDAY BEFORE THE NEXT BEST CHANCE FOR
SHOWERS MOVES IN. LOOK FOR MORE SPRING- LIKE TEMPERATURES TO
PREVAIL THRU THE EXTENDED PERIOD AS OUR UPPER FLOW WILL TRANSITION
MORE INTO THE SOUTHWEST.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 603 PM CDT FRI MAY 1 2015

HIGH PRESSURE OVER CENTRAL IL THIS EVENING WILL SHIFT SOUTHEAST
OVERNIGHT, ALLOWING LIGHT/VARIABLE WINDS TO BECOME LIGHT
SOUTHWEST, AND INCREASE TO NEAR 10 KTS BY MIDDAY SATURDAY. A WEAK
UPPER LEVEL DISTURBANCE WILL BRING SCATTERED TO BROKEN MID LEVEL
CLOUDS OVERNIGHT, BEFORE DISSIPATING AROUND SUNRISE.

&&

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

$$

SHORT TERM...07
LONG TERM...SMITH
AVIATION...25



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