Area Forecast Discussion
Issued by NWS Central Illinois

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KILX 020155
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
855 PM CDT SAT AUG 1 2015

.UPDATE...
ISSUED AT 855 PM CDT SAT AUG 1 2015

A BROAD TROUGH OVER THE EASTERN U.S. WITH NORTHWESTERLY FLOW ALOFT
OVER CENTRAL ILLINOIS...A SHORTWAVE TO THE NORTHWEST WILL BRING
CHANCES OF THUNDERSTORMS DEVELOPING WEST OF THE ILLINOIS RIVER BY
EARLY MORNING...SPREADING EASTWARD ACROSS AREAS FROM AROUND I-72
NORTHWARD THROUGH THE DAY. MODELS SUGGESTING CONVECTION WILL
DEVELOP OVER SOUTHERN MN/IOWA THE NEXT FEW HOURS...PROPAGATING ESE
OVERNIGHT...WHILE CONVECTION ONGOING OVER NORTHERN MISSOURI WILL
WEAKEN AND MOVE SOUTHEAST OVERNIGHT. PREDOMINANT MODEL SOLUTIONS
PROPAGATE STRONGER CONVECTION ACROSS THE GREAT LAKES WITH STRONGER
UPPER LEVEL FORCING...LEAVING WEAKENING CONVECTIVE REMNANTS
MOVING INTO CENTRAL IL EARLY IN THE MORNING. WITH MODEST AMOUNTS
OF MOISTURE CHARACTERIZED BY DEWPOINTS IN THE 60S...EXPECTING LOWS
TO REACH THE MID-UPPER 60S TONIGHT. CURRENT FORECAST DEPICTS THE
SITUATION WELL AND NO SIGNIFICANT UPDATES PLANNED THIS EVENING.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 314 PM CDT SAT AUG 1 2015

A SHORT-WAVE TROUGH EVIDENT ON 19Z/2PM WATER VAPOR IMAGERY OVER THE
WESTERN DAKOTAS WILL BE THE PRIMARY TRIGGERING MECHANISM FOR
THUNDERSTORMS THIS AFTERNOON INTO TONIGHT.  AS THIS FEATURE TRACKS
EASTWARD...STORMS WILL INCREASE IN COVERAGE ACROSS THE EASTERN
DAKOTAS INTO MINNESOTA THIS EVENING...THEN WILL SPREAD INTO THE
GREAT LAKES BY SUNDAY MORNING.  FURTHER SOUTH...HIGH-RES MODELS SUCH
AS THE RAPID REFRESH ARE SUGGESTING ANOTHER AREA OF SCATTERED
CONVECTION WILL DEVELOP ALONG THE REMNANTS OF AN OLD FRONTAL
BOUNDARY ACROSS SOUTHERN IOWA/NORTHERN MISSOURI AFTER MIDNIGHT.
SOME OF THIS ACTIVITY MAY SPILL INTO WEST-CENTRAL ILLINOIS TOWARD
DAYBREAK.  HAVE ADJUSTED POPS TO GO WITH DRY CONDITIONS ACROSS THE
BOARD THIS EVENING...THEN HAVE INTRODUCED LOW CHANCE POPS ALONG/WEST
OF THE ILLINOIS RIVER WELL AFTER MIDNIGHT.  OVERNIGHT LOW
TEMPERATURES WILL RANGE FROM THE LOWER 60S SOUTH OF I-70 WHERE WINDS
WILL REMAIN LIGHTEST BENEATH A SLOWLY DEPARTING HIGH PRESSURE
SYSTEM...TO THE UPPER 60S IN THE ILLINOIS RIVER VALLEY.

.LONG TERM...(SUNDAY THROUGH SATURDAY)
ISSUED AT 314 PM CDT SAT AUG 1 2015

FORECAST MODELS ARE COMING INTO A BIT BETTER AGREEMENT WITH THE
EVOLVING UPPER LEVEL PATTERN FOR NEXT WEEK AS WESTERN RIDGE AND
EASTERN TROUGH FLATTEN OUT INTO A SEMI-ZONAL FLOW BY LATE IN THE
WEEK. HOWEVER...AS THIS EVOLUTION TAKES PLACE...A PERIOD OF
UNSETTLED WEATHER WILL BE IN STORE FOR CENTRAL AND EASTERN IL IN THE
TUE-THU TIMEFRAME.

IN THE NEAR TERM...AN MCS/CLUSTER OF THUNDERSTORMS IS EXPECTED TO
DEVELOP IN SOUTHERN MN/NORTHERN IA OVERNIGHT...FARTHER NORTH THAN
PREVIOUSLY EXPECTED. THE REMNANTS OF THIS MAY BRING SCATTERED
SHOWERS AND T-STORMS TO AREAS NW OF THE UPPER IL RIVER VALLEY SUNDAY
MORNING. A WEAK COLD FRONT WILL ALSO GRADUALLY MOVE INTO NW IL
TOWARD EVENING. PLENTY OF WARM AIR AND MODERATE INSTABILITY SHOULD
LEAD TO SCATTERED T-STORMS NW OF A MACOMB-BLOOMINGTON LINE SUNDAY
AFTERNOON...REACHING A QUINCY-LINCOLN-DANVILLE LINE DURING THE
EVENING. AS THE FRONT CONTINUES TO MAKE PROGRESS THROUGH CENTRAL
IL SUNDAY NIGHT...THE POTENTIAL FOR SCATTERED T-STORMS WILL
INCREASE IN MOST AREAS NORTH OF I-70.

ON MONDAY THE FRONT WILL SLOW DOWN IN SOUTHERN IL. THE LOW LEVEL
WIND FLOW...HOWEVER...IS EXPECTED TO BECOME PARALLEL TO THE BOUNDARY
RESULTING IN A RAPID DROP IN LOW LEVEL CONVERGENCE. THIS COMBINED
WITH MARGINAL INSTABILITY SHOULD RESULT IN A FEW CLOUDS AND LITTLE
IN THE WAY OF CONVECTION IN SOUTHEAST IL.

THE GFS AND EUROPEAN MODELS ARE SIMILAR IN SHOWING A PIECE OF A
SHORTWAVE TROUGH CUTTING THROUGH THE UPPER RIDGE POSITION AND
APPROACHING THE MID MS AND LOWER OHIO VALLEY TUESDAY...WITH
ADDITIONAL SHORTWAVES EXPECTED TO FOLLOW THROUGH EARLY THURSDAY.
THIS UPPER LEVEL SUPPORT WILL COMBINE WITH THE NEARLY STATIONARY
FRONT IN SOUTHERN IL TO PRODUCE PERIODS OF SHOWERS AND T-STORMS.
WILL KEEP AN EYE ON THIS FOR A HEAVY RAIN POTENTIAL...BUT IT APPEARS
THAT THERE SHOULD NOT BE ENOUGH DEEP LEVEL MOISTURE FOR THIS TO
OCCUR. WITH MUCH OF THE FORECAST AREA EXPECTED TO BE ON THE COOL
SIDE OF THE FRONT...TEMPERATURES SHOULD BE BELOW SEASONAL NORMALS
MOST OF NEXT WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 615 PM CDT SAT AUG 1 2015

PREDOMINANTLY VFR CONDITIONS EXPECTED THROUGH THE 00Z TAF PERIOD.
LATEST MODEL GUIDANCE GENERALLY CONSISTENT WITH DRY CONDITIONS FOR
CENTRAL IL TERMINALS UNTIL 17Z...THEN BRINGING A CHANCE FOR
THUNDERSTORMS MAINLY FOR NORTHERN TERMINALS KPIA-KBMI. SEVERAL
CLUSTERS OF CONVECTION EXPECTED TO DEVELOP TO THE WEST...THEN
EITHER WEAKEN OR MOVE PAST CENTRAL IL TO THE NORTH MID-MORNING
THROUGH AFTERNOON SUNDAY...SO CHANCES FOR DISRUPTION OF VFR
CONDITIONS ARE MINIMAL AND HAVE ONLY INCLUDED VCTS AT TERMINALS
KPIA-KBMI AFTER 17Z. WINDS SW THROUGH THE PERIOD...4-7 KTS
OVERNIGHT...INCREASING TO 12-16 KTS AFTER 17Z WITH GUSTS AROUND 20
KTS POSSIBLE IN THE AFTERNOON.


&&

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

$$

UPDATE...ONTON
SHORT TERM...BARNES
LONG TERM...MILLER
AVIATION...ONTON


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.