Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 021721
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1221 PM CDT WED SEP 2 2015

.UPDATE...
ISSUED AT 946 AM CDT WED SEP 2 2015

UPPER WAVE CURRENTLY TRACKING ACROSS IOWA IS RESPONSIBLE FOR AN
AREA OF SHOWERS AND ISOLATED THUNDERSTORMS WEST OF THE MISSISSIPPI
RIVER. NORTHEAST EDGE OF THIS AREA IS IN SOUTHEAST IOWA BUT
SHOWING SOME DIMINISHMENT AS OF LATE...AND HIGH-RESOLUTION MODELS
IN AGREEMENT THAT THIS WILL DIE OUT BEFORE REACHING OUR AREA...SO
WILL LEAVE THE FORECAST DRY. HOWEVER...HAVE BEEFED UP THE CLOUD
COVER SOMEWHAT...PRIMARILY OVER THE NORTHWEST CWA THROUGH
MIDDAY...WITH THE ASSOCIATED CLOUD SHIELD STARTING TO APPROACH THE
ILLINOIS RIVER. TEMPERATURES STILL LARGELY ON TRACK TO REACH THE
LOWER 90S...BUT WILL HAVE TO WATCH THE NORTHWEST CWA IN CASE THESE
CLOUDS REMAIN THICK TOO LONG.

&&

.SHORT TERM...(TODAY)
ISSUED AT 307 AM CDT WED SEP 2 2015

UPPER RIDGE ORIENTED FROM THE SOUTHERN PLAINS TO THE EASTERN GREAT
LAKES WILL CONTINUE TO BE THE DOMINANT WEATHER FEATURE ACROSS
CENTRAL ILLINOIS TODAY...PROVIDING MOSTLY SUNNY AND HOT CONDITIONS.
VIGOROUS SHORT-WAVE THAT HAS TRIGGERED SCATTERED HEAVY DOWNPOURS
ACROSS PORTIONS OF EAST-CENTRAL ILLINOIS OVER THE PAST TWO DAYS HAS
SHIFTED FURTHER EAST INTO OHIO AND WILL NOT BE A FACTOR.
MEANWHILE...A SECOND WAVE ACROSS SOUTHERN MINNESOTA WILL STAY WELL
TO THE N/NW OF THE AREA.  MAY SEE SOME HIGH/THIN CLOUDS FROM
CONVECTIVE DEBRIS ASSOCIATED WITH THIS FEATURE...BUT OVERALL SKY
CONDITION WILL REMAIN MOSTLY SUNNY. HIGH TEMPERATURES WILL BE
SIMILAR TO YESTERDAY...MAINLY IN THE LOWER 90S.

.LONG TERM...(TONIGHT THROUGH Tuesday)
ISSUED AT 307 AM CDT WED SEP 2 2015

MINNESOTA SHORT-WAVE TROUGH WILL TRACK E/NE ACROSS WISCONSIN
TODAY...THEN WILL DROP SOUTHEASTWARD INTO MICHIGAN/NORTHERN INDIANA
ON THURSDAY.  WITH THIS PARTICULAR TRACK...ANY ASSOCIATED CONVECTION
SHOULD STAY MAINLY TO THE N/NE OF THE AREA...HOWEVER LOCATIONS
ALONG/NORTHEAST OF I-74 COULD POTENTIALLY SEE AN ISOLATED
THUNDERSTORM THURSDAY AFTERNOON/EVENING.  THE NAM CONTINUES TO BE
THE MOST AGGRESSIVE WITH PRECIP FURTHER SOUTH INTO PORTIONS OF THE
KILX CWA...WHILE THE LATEST ECMWF KEEPS THE CONVECTION MUCH FURTHER
NORTH ACROSS MICHIGAN.  THINK A MIDDLE-OF-THE ROAD APPROACH IS BEST
HERE...WITH SHOWERS/THUNDER REMAINING JUST N/NE OF THE CWA.  HIGH
TEMPERATURES WILL ONCE AGAIN REACH THE LOWER 90S.

THE UPPER RIDGE WILL REMAIN IN PLACE ACROSS THE REGION THROUGH THE
WEEKEND...ENSURING A CONTINUATION OF VERY WARM AND LARGELY DRY
CONDITIONS.  AN ISOLATED THUNDERSTORM CANNOT COMPLETELY BE RULED OUT
ON ANY PARTICULAR DAY...HOWEVER SYNOPTIC FORCING WILL REMAIN WEAK AT
BEST...SO WILL MAINTAIN A DRY FORECAST WITH HIGHS IN THE LOWER
90S THROUGH SUNDAY.

AFTER THAT...THINGS GET A LITTLE MORE INTERESTING AS THE RIDGE
GRADUALLY BEGINS TO BREAK DOWN.  MODELS ARE STRUGGLING WITH THE
PATTERN CHANGE...WITH THE GENERAL TREND SUGGESTING A SLOWER
WEAKENING OF THE RIDGE AND A DELAYED ARRIVAL OF A COLD FRONT.  THINK
00Z SEP 2 ECMWF MAY HAVE THE MOST REASONABLE HANDLE ON THE
SITUATION...SHOWING A DEEP UPPER LOW DIVING INTO THE PACIFIC
NORTHWEST THIS WEEKEND THEN LIFTING INTO SOUTHERN CANADA EARLY NEXT
WEEK.  THIS WILL PUSH A DISSIPATING COLD FRONT INTO CENTRAL ILLINOIS
ON MONDAY.  DUE TO HIGH UPPER HEIGHTS AND WEAK CONVERGENCE ALONG THE
BOUNDARY...WILL ONLY CARRY SLIGHT CHANCE POPS WITH HIGHS IN THE
UPPER 80S TO AROUND 90 ON MONDAY.  THE ECMWF THEN SHOWS ANOTHER
STRONG SHORT-WAVE TRACKING SOUTHEASTWARD OUT OF WESTERN CANADA NEXT
WEEK THAT WILL EVENTUALLY PUSH A STRONGER COLD FRONT INTO THE
REGION.  TIMING REMAINS IN QUESTION...BUT IT APPEARS FROPA WILL
OCCUR DURING THE TUESDAY/WEDNESDAY TIME FRAME.  WILL THEREFORE CARRY
CHANCE POPS ON TUESDAY...WITH HIGHS DROPPING BACK INTO THE MIDDLE
80S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z Thursday AFTERNOON)
ISSUED AT 1217 PM CDT WED SEP 2 2015

CENTRAL ILLINOIS REMAINING ON THE PERIPHERY OF SURFACE HIGH
PRESSURE OVER THE OHIO VALLEY...RESULTING IN LITTLE CHANGE IN
TRENDS FROM THE PAST COUPLE DAYS. AREAS OF MVFR VISIBILITIES
POSSIBLE ONCE AGAIN THURSDAY MORNING WITH THE WARM AND HUMID AIR
MASS IN PLACE. MAIN CONCERN WILL BE WITH POTENTIAL FOR CONVECTION
ON THURSDAY...AS AN UPPER DISTURBANCE DROPS SOUTHEAST ACROSS THE
GREAT LAKES. AT THE MOMENT...ISOLATED SHOWERS/STORMS WOULD BE A
CONCERN AROUND KBMI/KCMI LATE THURSDAY MORNING...BUT COVERAGE IS
TOO SMALL TO WARRANT A VCTS MENTION AT THIS POINT.

&&

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

$$

UPDATE...Geelhart
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Geelhart



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