Area Forecast Discussion
Issued by NWS Central Illinois

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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 281727
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1227 PM CDT FRI AUG 28 2015

.UPDATE...
ISSUED AT 1034 AM CDT FRI AUG 28 2015

EXTENSIVE MID/HIGH CLOUD SHIELD HAS OVERSPREAD THE FORECAST AREA
IN CONJUNCTION WITH THE STORM SYSTEM TO OUR WEST. MUCH OF THE
RAIN IN IOWA WAS TRACKING TO THE EAST-NORTHEAST ON A TRAJECTORY
THAT WOULD PASS NORTH OF OUR FORECAST AREA. CONVECTION FURTHER
SOUTHWEST ALONG THE BOUNDARY, ACROSS NORTHWEST MISSOURI, IS MORE
LIKELY TO GET HERE LATER THIS EVENING. THEREFORE, HAVE NOT CHANGED
POP`S TOO MUCH, WHICH ORIGINALLY WERE CONFINED TO MAINLY SLIGHT
CHANCES. HOWEVER, HAVE BUMPED THEM UP A TAD AROUND GALESBURG, AS
THE SOUTHERN FLANK OF THE RAIN SHIELD IN SOUTHEAST IOWA MAY CLIP
THAT AREA IN A COUPLE HOURS. HAVE ALSO LOWERED TEMPERATURES BY A
DEGREE OR TWO MOST AREAS, BUT WILL HAVE TO MONITOR THE NORTHWEST
CWA CLOSELY AS THE THICKER CLOUD COVER WILL PERSIST THERE THROUGH
THE DAY, AND TEMPERATURES THERE HAVE ONLY REACHED THE MID 60S AS
OF 10 AM.

&&

.SHORT TERM...(TODAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

LATEST SURFACE ANALYSIS HAD AN AREA OF HIGH PRESSURE CENTERED OVER
WESTERN PA & NY, WITH A RIDGE EXTENDING WEST ACROSS NORTHERN
ILLINOIS. MEANWHILE, WEAK LOW PRESSURE WAS CENTERED OVER THE CENTRAL
PLAINS. THIS AREA OF LOW PRESSURE, AND ITS DRIVING UPPER LEVEL SHORT
WAVE, WILL SLOWLY DRIFT EAST OVER THE NEXT FEW DAYS. MAIN CONCERN
FOR THE FORECAST TODAY IS IF ANY OF THE RAINFALL CURRENTLY
ASSOCIATED WITH THE LOW CAN MAKE IT EAST INTO THE FORECAST AREA
BEFORE TONIGHT.

FORECAST SOUNDINGS SUGGEST THE AIRMASS ACROSS CENTRAL AND SOUTHEAST
ILLINOIS SHOULD REMAIN RATHER DRY TODAY. WHILE CLOUDS WILL BE ON THE
INCREASE WITH THE APPROACH OF THE LOW/UPPER WAVE, THE DEEPER
MOISTURE SHOULD REMAIN WEST OF ILLINOIS THROUGH THE DAY. IN FACT,
SURFACE FLOW IS PROGGED TO REMAIN SOUTHEASTERLY ON THE SOUTH SIDE OF
THE HIGH PRESSURE RIDGE, CERTAINLY NOT A DIRECTION CONDUCIVE TO
SIGNIFICANT LOW LEVEL MOISTURE INCREASES. IN ADDITION TO THE
APPARENT LACK OF MOISTURE, DO NOT ANTICIPATE MUCH IN THE WAY OF
FORCING IN THE AREA TODAY. THE LOW LEVEL FLOW IS EXPECTED TO REMAIN
ANTICYCLONIC, WITH THE BETTER FORCING WITH THE UPPER WAVE STAYING
WELL WEST OF THE AREA TODAY FROM THE CENTRAL PLAINS INTO WESTERN
PORTIONS OF THE MIDWEST.

WITH THIS THINKING IN MIND, EXPECT DRY CONDITIONS TO PERSIST
ACROSS THE CENTRAL AND SOUTHEAST ILLINOIS TODAY. WILL HOLD ONTO A
SLIGHT CHANCE OF SHOWERS/STORMS ACROSS FAR NORTHWEST PORTION OF
THE FORECAST AREA, CLOSEST TO THE APPROACHING SYSTEM, BUT THE ODDS
ARE CERTAINLY BETTER THAT THIS AREA WILL STAY DRY. THE LOCAL
AIRMASS WILL CONTINUE TO MODIFY TODAY, UNDER PERSISTENT SOUTHERLY
FLOW, BECOMING A LITTLE WARMER AND MORE HUMID THAN YESTERDAY, BUT
THESE CONDITIONS WILL CERTAINLY REMAIN SEASONABLE FOR LATE AUGUST.

.LONG TERM...(TONIGHT THROUGH THURSDAY)
ISSUED AT 328 AM CDT FRI AUG 28 2015

TONIGHT`S TEMPERATURES CLOSE TO NORMALS FOR AUGUST FOR CENTRAL
ILLINOIS, AIDED PARTIALLY BY INCREASING CLOUDS WITH A SHORT WAVE
MOVING THROUGH THE MIDWEST. MODELS HAVE BEEN CONSISTENTLY
INCONSISTENT WITH THE TIMING OF THE ONSET OF THE PRECIP. HOWEVER,
MODELS HAVE BEEN IN AGREEMENT WITH THE GENERAL SLOWNESS OF THE WAVE,
RESULTING IN A SHOWERY WEEKEND FOR CENTRAL ILLINOIS.  BEST CHANCES
TOMORROW AND TOMORROW NIGHT, WITH A SLIGHTLY BETTER CHANCE IN THE
AFTERNOON WITH A DIURNAL ASSIST FROM MAX HEATING.  THAT BEING SAID,
TEMPERATURES WILL BE SLIGHTLY WARMER FOR SATURDAY WITH HIGHS IN THE
UPPER 70S NW OF THE ILLINOIS RIVER VALLEY, AND MORE SEASONABLE LOWER
80S SOUTH OF INTERSTATE 72. PRECIP CHANCES LINGER INTO SUNDAY
MORNING AND PROGRESSION OF THE WAVE TO THE EAST WILL HAVE A BIG
IMPACT ON CHANCES FOR PRECIP IN THE EAST SUN AFTERNOON.  FOR NOW,
ONLY SLIGHT CHANCES IN THE FORECAST ALONG THE INDIANA BORDER, BUT
WILL NEED TO KEEP AN EYE ON THE PROGRESSION OF THE SHORTWAVE IN THE
WEAK FLOW ALOFT.

THE REMAINDER OF THE FORECAST IS DOMINATED BY HIGH PRESSURE OVER
MUCH OF THE SOUTHEASTERN QUADRANT OF THE CONUS, REACHING ALL THE WAY
INTO THE MIDWEST/GREAT LAKES.  SOME SMALL WAVES MOVING THROUGH, BUT
GENERALLY TRACKING ALONG THE MORE PROGRESSIVE FLOW ACROSS THE GREAT
LAKES TO THE NORTH.  THE SHORTWAVE MOVING THROUGH THE REGION THIS
WEEKEND SHIFTS THE NORTHWESTERLY FLOW TO A SLIGHTLY LESS AMPLIFIED
PATTERN WITH A SOUTHWESTERLY TREND. HOT TEMPS UNDER THE RIDGE IN THE
SOUTHWESTERN CONUS DIFFUSE INTO THE REGION WITH THE PATTERN SHIFT
AND TEMPS THROUGH THE MIDDLE OF NEXT WEEK SIGNIFICANTLY ABOVE
NORMALS WITH MAX TEMPS APPROACHING THE 90 MARK BEFORE MIDWEEK.
GUIDANCE RUNNING ON BOTH SIDES OF THE 90 DEGREE MARK, SO WILL HAVE
TO KEEP AN EYE ON THE VARIANCE THERE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1227 PM CDT FRI AUG 28 2015

MAIN QUESTION FOR THIS TAF SET WILL BE THE ARRIVAL OF ANY
SHOWERS/STORMS. FORECAST SOUNDINGS ARE SHOWING QUITE A BIT OF DRY
AIR BELOW 10KFT MOST OF THE PERIOD...FINALLY MOISTENING UP AROUND
KPIA TOWARD SUNRISE. HOWEVER...INSTABILITY REMAINS RATHER
LIMITED...SO WILL KEEP MENTION OF THE VCSH THERE WITHOUT ANY
MENTION OF THUNDER. THE REMAINDER OF CENTRAL ILLINOIS WILL MAINLY
SEE A GRADUAL LOWERING OF HIGH CLOUDS THROUGH THE NEXT 24
HOURS...WITH SOUTH-SOUTHEAST WINDS TRENDING MORE SOUTH-SOUTHWEST
BY MID MORNING SATURDAY.

&&

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

$$

UPDATE...GEELHART
SHORT TERM...BAK
LONG TERM...HJS
AVIATION...GEELHART



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