Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 010424
AFDILX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1124 PM CDT TUE JUN 30 2015

.UPDATE...
ISSUED AT 835 PM CDT TUE JUN 30 2015

8PM SURFACE ANALYSIS INDICATES A WEAK SURFACE TROF/WIND SHIFT LINE
FROM JUST NORTH OF PARIS WEST TO NEAR QUINCY. WIDELY SCATTERED
STORMS DEVELOPED ALONG THIS BOUNDARY LATE THIS AFTERNOON AND
EXCEPT FOR A FEW SHOWERS IN SOUTHEAST ILLINOIS...THE ACTIVITY
HAS DECREASED IN AREAL COVERAGE AND INTENSITY. OUR ATTENTION NOW
TURNS TO A COMPLEX OF STORMS FORECAST TO DEVELOP OUT TO OUR WEST
AND THEN IS FORECAST TO SHIFT EAST-SOUTHEAST INTO EAST CENTRAL
MO AND SOUTHWEST ILLINOIS BY DAWN. MOST OF THE MORE SIGNIFICANT
CONVECTION IS FORECAST TO REMAIN OUT TO OUR WEST AND SOUTHWEST
LATE TONIGHT NEAR THE NOSE OF THE LOW LEVEL JET WITH THE MORE
IMPRESSIVE SPEED CONVERGENCE AT 850 MB NOTED OVER NORTHWEST
MISSOURI AND SOUTHWEST IOWA.

BASED ON SEVERAL OF THE CONVECTIVE ALLOWING MODELS...IT APPEARS
OUR WEST AND SOUTHWEST AREAS STAND THE BEST CHANCE FOR SHOWERS AND
ISOLD STORMS BY MORNING WITH THE BULK OF THE ACTIVITY AFFECTING
MAINLY THE SOUTHERN HALF OF THE FORECAST AREA ON WEDNESDAY.
CURRENT FORECAST HAS THIS WELL IN HAND...SO OTHER THAN SOME MINOR
ADJUSTMENTS TO THE OVERNIGHT WORDING...NO MAJOR CHANGES WERE MADE
TO THE ZFP. WE SHOULD HAVE THE UPDATE OUT BY 900 PM ADDRESSING THE
WEAKENING TRENDS WITH THE SHOWERS IN THE SOUTHEAST.

&&

.SHORT TERM...(TONIGHT)
ISSUED AT 246 PM CDT TUE JUN 30 2015

18Z/1PM WATER VAPOR IMAGERY CONTINUES TO SHOW A DEEP TROUGH OVER THE
GREAT LAKES/OHIO RIVER VALLEY...WITH NORTHWESTERLY FLOW PREVAILING
FROM THE NORTHERN PLAINS TO THE TENNESSEE RIVER VALLEY.  TWO
DISTINCT SHORT-WAVES ARE EMBEDDED WITHIN THE FLOW...ONE OVER INDIANA
AND ANOTHER FURTHER UPSTREAM ACROSS SOUTHERN SASKATCHEWAN.  DESPITE
WEAK FRONTAL BOUNDARY DROPPING INTO NORTH-CENTRAL ILLINOIS THIS
AFTERNOON...UPPER SUPPORT IS VERY WEAK IN THE WAKE OF THE INDIANA
WAVE.  AS A RESULT...AM ONLY EXPECTING ISOLATED SHOWERS/THUNDER
AHEAD OF THE APPROACHING FRONT LATE THIS AFTERNOON INTO THE EARLY
EVENING.  MOST HIGH-RES MODELS SUGGEST THE GREATEST AREAL COVERAGE
OF PRECIP WILL BE ACROSS EAST-CENTRAL ILLINOIS.  HAVE INCLUDED 20-30
POPS EARLY THIS EVENING TO COVER ANY POTENTIAL CONVECTION ALONG THE
FRONT...BUT THINK THIS WILL QUICKLY DISSIPATE AFTER SUNSET.  FURTHER
NORTHWEST...A LARGE COMPLEX OF THUNDERSTORMS IS EXPECTED TO DEVELOP
AHEAD OF THE SASKATCHEWAN WAVE THIS EVENING...THEN TRACK
SOUTHEASTWARD TOWARD THE REGION OVERNIGHT INTO WEDNESDAY MORNING.
MODEL TRENDS HAVE BEEN SLOWING THIS SYSTEM AND TRACKING IT FURTHER
S/SW ACROSS MAINLY CENTRAL MISSOURI INTO SOUTHERN ILLINOIS.  HAVE
TRIMMED POPS CONSIDERABLY AFTER MIDNIGHT...WITH ONLY SLIGHT CHANCES
ALONG/SOUTHWEST OF A MACOMB...TO SPRINGFIELD...TO OLNEY LINE TOWARD
DAWN WEDNESDAY.  ELSEWHERE AROUND CENTRAL ILLINOIS...DRY CONDITIONS
WILL PREVAIL WITH PERHAPS SOME PATCHY FOG DEVELOPING.

.LONG TERM...(WEDNESDAY THROUGH TUESDAY)
ISSUED AT 246 PM CDT TUE JUN 30 2015

DESPITE A LONG WAVE TROUGH REMAINING ACROSS THE EASTERN HALF OF THE
CONUS FOR MUCH OF THE NEXT WEEK, THERE STILL APPEAR TO BE A FEW DRY
PERIODS, ESPECIALLY FOR THE NORTHERN HALF OF ILLINOIS.

WEDNESDAY WILL START OUT WITH A STRONG MCS DEVELOPING IN NEBRASKA
AND A WARM FRONT EXTENDING EAST AHEAD OF THE LOW ACROSS MISSOURI AND
SOUTHERN ILLINOIS. THE 12Z MODELS HAVE ALL SLOWED DOWN THE
PROGRESSION OF THE LOW CENTER, WITH THE LOW PASSAGE NOW DELAYED
UNTIL THURSDAY. INCREASING WARM FRONTAL CIRCULATION ACROSS SOUTH-
CENTRAL ILLINOIS WILL BE THE FOCUS FOR SHOWERS AND STORMS TO DEVELOP
WELL AHEAD OF THE LOW, AS EARLY AS 12Z/7AM WEDNESDAY IN OUR SW
COUNTIES. SHOWERS AND STORMS WILL EXPAND EASTWARD DURING THE DAY,
WITH THE BEST CHANCES OF RAIN COMING WED NIGHT AS LOW CENTER REACHES
FAR SW IL BY 12Z/7AM THURSDAY. SHOWERS WILL BE CONFINED TO AREAS
SOUTH OF I-70 THURSDAY, AS THE LOW PROGRESSES INTO WESTERN KENTUCKY.

A STATIONARY FRONT LINGERING BEHIND THE LOW ACROSS SOUTHERN IL WILL
KEEP PRECIP CHANCES ACROSS OUR FAR SOUTHEASTERN COUNTIES FRIDAY
THROUGH SATURDAY NIGHT, WHILE THE REMAINDER OF OUR COUNTIES SEE A
POTENTIALLY DRY START TO THE WEEKEND. THE DRY TREND MAY END ON
SUNDAY AS A LOBE OF THE UPPER TROUGH SWINGS ACROSS IL. THE 12Z
ECMWF IS MORE AGGRESSIVE WITH PRECIP WITH THAT FEATURE, WITH THE
CANADIAN DRY AND THE GFS IN THE MIDDLE, SHOWING SCATTERED
AFTERNOON CONVECTION. WE KEPT CHANCE POPS FOR AREAS SOUTHEAST OF
THE IL RIVER FOR NOW.

A COLD FRONT ARRIVING FROM THE NORTHWEST ON MONDAY WILL PROMPT STORM
CHANCES ACROSS ALL OF IL. AS THE FRONT STALLS OUT ACROSS THE AREA,
RAIN CHANCES WILL LINGER THROUGH TUESDAY.

TEMPS ARE PROJECTED TO REMAIN BELOW NORMAL THROUGH FRIDAY, THEN
THE GFS ADVERTISES A WARMING TREND THIS WEEKEND INTO EARLY NEXT
WEEK AS AN UPPER LEVEL RIDGE TRIES TO BUILD INTO ILLINOIS. THE
ECMWF HAS CONTINUED TO DIFFER WITH THAT SOLUTION, INDICATING THE
ARRIVAL OF ANOTHER TROUGH FROM THE NORTHERN PLAINS EARLY NEXT
WEEK, AND A CONTINUATION OF BELOW NORMAL TEMPS. THE END RESULT IN
HIGHS WAS TO CLIMB TOWARD NORMAL EACH DAY SATURDAY THROUGH MONDAY,
WITH NORMAL BEING MID 80S.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1115 PM CDT TUE JUN 30 2015

MVFR VSBYS IN FOG/HZ OVERNIGHT WITH OUR NEXT WEATHER SYSTEM
PUSHING INTO MISSOURI BY MORNING. MODELS HAVE TRENDED FURTHER
WEST AND SOUTH WITH THE PRECIP SHIELD SO FOR NOW WILL CONTINUE
WITH VCSH OVER OUR SOUTHERN TAF SITES WITH LITTLE IF ANY PRECIP
FURTHER NORTH WITH LOW VFR CIGS SETTLING IN DURING THE MORNING
BASED ON THE LATEST FORECAST SOUNDINGS. SURFACE WINDS WILL NOT
BE MUCH OF A FACTOR THROUGH THIS FORECAST PERIOD WITH A LIGHT
AND VARIABLE WIND TONIGHT AND GENERALLY A LIGHT EASTERLY
DIRECTION ON WEDNESDAY WITH SPEEDS OF LESS THAN 10 KTS.

&&

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

$$

UPDATE...SMITH
SHORT TERM...BARNES
LONG TERM...SHIMON
AVIATION...SMITH


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