Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 272234 CCA
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
257 PM CDT SAT JUN 27 2015

.SHORT TERM...(TONIGHT)
ISSUED AT 253 PM CDT SAT JUN 27 2015

ISOLATED SHOWERS AND POSSIBLE THUNDERSTORMS WEST OF A GALESBURG TO
BEARDSTOWN TO JACKSONVILLE LINE AT MID AFTERNOON FROM VERY WEAK
SHORT WAVE MOVING SOUTH NEAR MS RIVER VALLEY WILL DISSIPATE BY 00Z/7
PM LEAVING DRY CONDITIONS ACROSS CWA TONIGHT. DIRUNALLY DRIVEN
SCATTERED CUMULUS CLOUDS TO DISSIPATE AT SUNSET AS WELL LEAVING FAIR
SKIES TONIGHT ACROSS CENTRAL/SE IL. STRONGER NORTHERN STREAM SHORT
WAVE ALONG THE SOUTHERN ONTARIO AND MANITOBA PROVINCE LINE WITH
CONVECTION AS FAR SOUTH AS NORTHERN MN AND EASTERN ND WILL DIVE SE
ACROSS MN/IA BY DAWN SUNDAY AND INCREASE CLOUDS LATER TONIGHT OVER
IL RIVER VALLEY...MAINLY NW OF IL RIVER. ANY CONVECTION FROM THIS
SYSTEM SHOULD STAY NW OF CWA THROUGH AT LEAST 12Z/7 AM SUNDAY. WEAK
SURFACE HIGH PRESSURE RIDGE OF 1017 MB OVER THE MO VALLEY TO DRIFT
OVER IL OVERNIGHT. SO BREEZY NORTH WINDS WITH GUSTS 15-25 MPH SHOULD
DIMINISH LIGHT AND VARIABLE LATER THIS EVENING. DEWPOINTS HAVE
SLIPPED INTO THE MID 50S TO NEAR 60F AT MID AFTERNOON AND THIS
SHOULD BE WHERE LOWS REACH CLOSE TO OVERNIGHT. LOWS IN MID 50S OVER
EASTERN IL AND UPPER 50S OVER THE IL RIVER VALLEY.

&&

.LONG TERM...(SUNDAY THROUGH SATURDAY)
ISSUED AT 253 PM CDT SAT JUN 27 2015

MAIN CHALLENGE WILL BE TIMING OF INDIVIDUAL SHORTWAVES AND ASSOCIATED
PRECIPITATION CHANCES IN THE NORTHWEST FLOW ALOFT OVER THE EASTERN
U.S. AS A RATHER AMPLIFIED PATTERN TAKES HOLD ACROSS THE AREA THRU
THE WEEK. FIRST OF THE UPPER WAVES WAS TRACKING SSE ACROSS THE
NORTHERN PLAINS THIS AFTERNOON AND WILL BRING AN INCREASING CHANCE
FOR SHOWERS AND STORMS BACK INTO THE REGION SUNDAY AFTERNOON AND
NIGHT. MIXED LAYER CAPES AROUND 1500 J/KG BY AFTERNOON ACROSS THE
WEST...HOWEVER...STRONGER DEEP LAYER FLOW REMAINS JUST TO OUR WEST
INTO THE EVENING HOURS WITH MARGINAL LAPSE RATES...DEPENDING ON
WHICH MODEL YOU LOOK AT. THE NAM HAS SLOWED THE ONSET OF THE PRECIP
AND IS KEEPING THE DEEP LAYER SHEAR AND BETTER INSTABILITY JUST TO
OUR WEST. STILL COULD SEE STRONG WIND GUSTS WITH SOME OF THE MORE
ORGANIZED STORMS TOMORROW AFTERNOON INTO THE EVENING AS THE UPPER
WAVE TRACKS ACROSS OUR AREA. DUE TO THE PROGRESSIVE NATURE OF THE
SYSTEM...IT APPEARS QPF VALUES WILL BE HELD IN CHECK WITH MOST
AREAS SEEING A QUARTER TO ONE HALF INCH AMOUNTS LATE SUNDAY
AFTERNOON INTO THE OVERNIGHT HOURS.

THE SHORTWAVE WILL SHIFT OFF TO OUR EAST BY MONDAY MORNING WITH THE
HIGHER POPS OVER THE EAST. STILL ENOUGH COLD AIR ALOFT ASSOCIATED
WITH THE DEPARTING WAVE TO KEEP AT LEAST LOW CHANCE POPS GOING
DURING THE AFTERNOON. POPS ARE IN THE SLIGHT CHANCE RANGE MONDAY
NIGHT IN THE WAKE OF THE SHORTWAVE WITH LOW POPS HOLDING INTO
TUESDAY BEFORE THE NEXT SHORTWAVE DROPS INTO THE REGION FOR MAINLY
TUESDAY NIGHT. IF THE SOUTHWARD TREND IN THE MODELS CONTINUES...THE
HIGHER THREAT FOR SHOWERS AND STORMS WOULD BE OVER OUR SOUTHERN
AREAS...BUT FOR NOW... WITH SOME SPREAD IN THE MODEL SOLUTIONS FOR
THAT TIME FRAME...WILL KEEP THE 30-40 POPS GOING TUESDAY NIGHT INTO
WEDNESDAY. ANOTHER FAST MOVING WAVE EMBEDDED IN THE NORTHWEST FLOW
WILL APPROACH THE AREA LATE WEDNESDAY/WEDNESDAY NIGHT WITH MORE
ORGANIZED SHOWER AND THUNDERSTORM CHANCES ADVERTISED OFF THE LATEST
ECMWF...WHILE THE 12Z GFS AND GEM GLOBAL SOLUTIONS NOT SHOWING MUCH
REFLECTION QPF-WISE FROM THAT SHORTWAVE.

PATTERN NOT EXPECTED TO MAKE MUCH OF A CHANGE UNTIL LATE NEXT WEEK
MEANING THE DAILY THREAT FOR SCATTERED SHOWERS AND STORMS WILL
CONTINUE INTO THE END OF THIS FORECAST PERIOD. THE LATEST ECMWF DOES
OFFER SOME HOPE IN THE EXTENDED PERIOD AS IT SHIFTS THE STRONGER
FLOW FURTHER NORTH AS AN UPPER LEVEL RIDGE EXPANDS NORTHWARD INTO
THE CENTRAL PLAINS AND MIDWEST NEXT WEEKEND. THIS WOULD SHIFT THE
BETTER CHANCES FOR SHOWERS AND STORMS FURTHER NORTH AND BRING SOME
VERY WARM TEMPS BACK INTO THE AREA. HOWEVER...WITH AS MUCH WATER
AS THERE IS IN THE SOIL OVER A LARGE PORTION OF THE CENTRAL
U.S...IT SEEMS HARD TO BUY THE IDEA OF ANY PERSISTENT RIDGING
OCCURRING ACROSS THE MIDDLE OF THE COUNTRY. IT`S NOT THE FIRST
TIME THIS MODEL HAS TRIED TO AMPLIFY THE RIDGE OVER THE CENTER OF
THE NATION...ONLY TO HAVE PERSISTENT CONVECTIVE ACTIVITY ACROSS
THE NORTH-CENTRAL PLAINS KEEP THE PATTERN MUCH LESS AMPLIFIED WITH
THE STRONGER FLOW DISPLACED FURTHER SOUTH THAN FORECAST. WE CAN
ONLY HOPE WE SEE AT LEAST A TEMPORARY SHIFT IN THE PATTERN HEADING
INTO THE SECOND WEEK OF JULY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1259 PM CDT SAT JUN 27 2015

VFR CONDITIONS ARE EXPECTED TO CONTINUE ACROSS THE CENTRAL IL
AIRPORTS NEXT 24 HOURS THROUGH 18Z/1 PM SUNDAY. SCATTERED CUMULUS
CLOUDS WITH BASES OF 3-5K FT WILL OCCUR THIS AFTERNOON WHILE
BROKEN CEILINGS MORE CONFINED TO AREAS WEST OF PIA/SPI AND SOUTH
OF I-72. ISOLATED SHOWERS AND THUNDERSTORMS THAT DEVELOP DURING
MID/LATE AFTERNOON TO STAY WEST OF PIA/SPI PER HRRR AND RAP13
MODELS. THESE DIURNALLY ENHANCED CUMULUS CLOUDS TO DISSIPATE AT
SUNSET LEAVING FAIR SKIES TONIGHT WITH JUST SCATTERED CIRRUS
CLOUDS. SCATTERED CUMULUS CLOUDS TO APPEAR AGAIN BY 15Z/SUNDAY
THOUGH ANY SHOWERS AND THUNDERSTORMS WILL NOT DEVELOP UNTIL AFTER
18Z/SUNDAY FROM I-55 NW. BREEZY NORTH WINDS 10-15 KTS AND GUSTS
16-23 KTS THIS AFTERNOON TO DIMINISH LIGHT AND VARIABLE BY SUNSET
AS WEAK HIGH PRESSURE RIDGE SETTLES OVER IL. WINDS BECOME SW AT
5-9 KTS AFTER 14Z/SUNDAY AS WEAK SURFACE RIDGE PASSES EAST OF IL
AND SHORT WAVE OVER NORTHERN PLAINS MOVES INTO THE UPPER MS RIVER
VALLEY SUNDAY MORNING.


&&

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

$$

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



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