116 
FXUS63 KILX 312319
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
619 PM CDT SUN JUL 31 2011

.DISCUSSION...
ISSUED 234 PM CDT SUN JUL 31 2011

MAIN CONCERN WITH THIS FORECAST PACKAGE WILL BE THE INCREASING
HEAT/HUMIDITY OVER THE NEXT COUPLE OF DAYS.

SHORT TERM...TONIGHT THROUGH WEDNESDAY

WITH HIGH PRESSURE REMAINING IN PLACE ACROSS THE AREA...DIURNAL CU
WILL DISSIPATE TOWARD SUNSET AND WINDS WILL BECOME LIGHT/VARIABLE.
THANKS TO ABUNDANT LOW-LEVEL MOISTURE CHARACTERIZED BY SURFACE
DEWPOINTS IN THE LOWER 70S...THINK FOG WILL ONCE AGAIN FORM LATE
TONIGHT. FORECAST SOUNDINGS AND NUMERIC GUIDANCE SUPPORT FOG
DEVELOPMENT...ALTHOUGH WITH DECENT MIXING THIS AFTERNOON...DO NOT
THINK VISBYS WILL DROP QUITE AS LOW AS LAST NIGHT. EVEN
STILL...FEEL MENTION OF PATCHY FOG IS WARRANTED.

AFTER ANY EARLY MORNING FOG BURNS OFF...MOSTLY SUNNY SKIES WILL
PREVAIL ACROSS CENTRAL ILLINOIS ON MONDAY. AS CENTER OF HIGH
SHIFTS INTO THE OHIO RIVER VALLEY...WINDS WILL BEGIN TO SWITCH TO
A MORE SOUTHERLY DIRECTION...WHICH WILL ALLOW AFTERNOON HIGH TEMPS
TO CLIMB A COUPLE OF DEGREES HIGHER THAN TODAY. MOST LOCATIONS
WILL SEE READINGS IN THE LOWER 90S...ALTHOUGH MIDDLE 90S WILL BE
LIKELY ALONG/SOUTH OF I-70. CORRESPONDING HEAT INDEX VALUES WILL
GENERALLY BE IN THE 100 TO 105 DEGREE RANGE.

ANOTHER VERY HOT AND HUMID DAY WILL BE IN STORE ON TUESDAY...AS
HIGHLY CAPPED AIRMASS BENEATH UPPER RIDGE WILL ALLOW AMPLE
SUNSHINE ACROSS THE AREA. GIVEN STRONG S/SW FLOW AHEAD OF WEAK
COLD FRONT APPROACHING FROM THE NORTHWEST...THINK MOISTURE
POOLING AHEAD OF THE BOUNDARY WILL CREATE DEWPOINTS IN THE MIDDLE
TO UPPER 70S ALONG/NW OF THE I-55 CORRIDOR. RESULTING HEAT INDEX
READINGS WILL LIKELY CLIMB INTO THE 105 TO 110 RANGE ACROSS THE
WESTERN KILX CWA...AND SHOULD HOVER AROUND 105 FURTHER EAST. DUE
TO THE EXPECTED HEAT AND HUMIDITY OVER THE NEXT COUPLE OF
DAYS...HAVE DECIDED TO ISSUE A HEAT ADVISORY FOR ALL OF CENTRAL
AND SOUTHEAST ILLINOIS FOR MONDAY AFTERNOON THROUGH EARLY TUESDAY
EVENING. EVEN THOUGH HEAT INDEX READINGS WILL BE BORDERLINE
MONDAY AFTERNOON...THINK GETTING THE ADVISORY OUT NOW TO LET
PEOPLE KNOW ABOUT THE DANGEROUS HEAT/HUMIDITY IS PRUDENT.

MODEL CONSENSUS KEEPS WEAK COLD FRONT NORTH OF THE KILX CWA UNTIL
TUESDAY EVENING...WITH A FEW OF THE MODELS TRYING TO DEVELOP
CONVECTION ACROSS THE FAR NORTH AS EARLY AS TUESDAY AFTERNOON.
FORECAST SOUNDINGS INDICATE STRONG LOW/MID-LEVEL CAPPING...WITH
850MB TEMPS AROUND 25C. THIS SHOULD PREVENT STORMS FROM FIRING
WELL AHEAD OF THE FRONT...WITH CONVECTION LIKELY CONFINED
IMMEDIATELY ALONG THE BOUNDARY. AS SUCH...HAVE OPTED TO GO WITH A
DRY FORECAST THROUGH TUESDAY AFTERNOON. RAIN CHANCES ENTER THE
PICTURE TUESDAY NIGHT ACROSS THE CENTRAL AND NORTHERN ZONES...THEN
LINGER INTO WEDNESDAY ACROSS THE CENTRAL AND SOUTH AS THE FRONT
DROPS THROUGH THE REGION. WITH BOUNDARY WEAKENING AS IT MOVES
FURTHER SOUTH AND UPPER SUPPORT REMAINING WELL TO THE
NORTH...PRECIP CHANCES LOOK TO REMAIN RATHER LOW WITH FROPA. HAVE
THEREFORE KEPT POPS AT ONLY 30 PERCENT. BEHIND THE FRONT...SLIGHTLY
COOLER/DRIER CONDITIONS WILL ARRIVE BY WEDNESDAY AFTERNOON AND
NIGHT.

LONG TERM...THURSDAY THROUGH SUNDAY

THE EXTENDED FORECAST WILL BE DOMINATED BY A FLAT UPPER RIDGE
ACROSS THE CENTRAL AND EASTERN CONUS...WHICH WILL ALLOW A SERIES
OF FAST-MOVING SYSTEMS TO TRACK ACROSS THE UPPER MIDWEST INTO THE
GREAT LAKES. THE FIRST WAVE HAS BEEN CONSISTENTLY SHOWING UP ON
MODEL RUNS FOR THURSDAY NIGHT INTO FRIDAY. LATEST ECMWF CONTINUES
TO SUGGEST MCS DEVELOPMENT NORTH OF THE STALLED SURFACE FRONT
ACROSS IOWA THURSDAY EVENING...WITH STORM COMPLEX PUSHING EASTWARD
ACROSS NORTH-CENTRAL ILLINOIS THURSDAY NIGHT INTO FRIDAY MORNING.
THIS SOLUTION HAS BEEN WELL ADVERTISED FOR SEVERAL RUNS NOW...SO
CONFIDENCE IS GROWING THAT A PRECIP EVENT WILL OCCUR DURING THAT
TIME FRAME. AS A RESULT...HAVE FOCUSED HIGHEST POPS ALONG/NORTH OF
A RUSHVILLE TO BLOOMINGTON-NORMAL LINE...WITH DECREASING CHANCES
FURTHER SOUTH TOWARD THE I-70 CORRIDOR. ONCE THIS FEATURE SLIDES
OFF TO THE EAST...SURFACE HIGH PRESSURE WILL BUILD INTO THE GREAT
LAKES. HOWEVER...PERSISTENT FRONTAL BOUNDARY WILL REMAIN NEARLY
STATIONARY FROM MISSOURI E/SE INTO THE TENNESSEE RIVER VALLEY.
WILL MAINTAIN A DRY FORECAST WITH NEAR NORMAL TEMPS IN THE MIDDLE
TO UPPER 80S OVER THE WEEKEND FOR NOW...BUT SLIM CHANCES FOR
PRECIP MAY NEED TO BE ADDED ACROSS THE S/SE CWA IF FRONTAL BOUNDARY
BECOMES ACTIVE.

&&

.AVIATION...
ISSUED 610 PM CDT SUN JUL 31 2011

SOME MVFR AND LOCAL IFR VSYBS/CIGS POSSIBLE IN FOG TOWARDS
DAYBREAK MONDAY...OTHERWISE...VFR CONDITIONS WILL PREVAIL. 

HIGH PRESSURE WILL HOLD OVER THE REGION THRU TUESDAY. DEEP
SUBSIDENCE ASSOCIATED WITH THE SURFACE HIGH WILL KEEP CLOUD
DEVELOPMENT TO A MINIMUM AND WINDS ON THE LIGHT SIDE. ONCE
ANY FOG OR STRATUS LIFTS AFTR 13Z MONDAY...EXPECT THE TYPICAL
SCATTERED DIURNAL CU TO FORM WITH BASES AROUND 4000 FEET MONDAY
AFTERNOON. THAT SHOULD QUICKLY DISSIPATE BY SUNSET WITH ANOTHER
THREAT FOR AT LEAST MVFR VSBYS IN FOG LATE MONDAY NIGHT. SFC
WINDS WILL BE NEARLY CALM TONIGHT INTO THE MID MORNING HOURS OF
MONDAY...AND THEN BECOME SOUTHWEST AT LESS THAN 10 KTS BY MONDAY
AFTERNOON. 

SMITH
&&

.ILX WATCHES/WARNINGS/ADVISORIES...
HEAT ADVISORY FROM 1 PM MONDAY TO 7 PM CDT TUESDAY FOR 
ILZ027>031-036>038-040>057-061>063-066>068-071>073.

&&

$$