Flash Flood and Hail in Illinois, May 29, 2006

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LINCOLN IL
1220 PM CDT MON MAY 29 2006

.UPDATE...
UPON FURTHER REVIEW... CU FIELDS GROWING NICELY ACROSS ENTIRE CWA...
WITH A FEW ISOLATED CONVECTIVE SHOWERS AND THUNDERSTORMS POPPING UP
ACROSS NORTHERN AND EASTERN ILLINOIS.  THERE IS NO CLEAR TRIGGER FOR
THESE STORMS.  APPEARS WE HAVE SIMPLY REACHED CONVECTIVE TEMP... AND
WITH NO CAPPING ALOFT... WE ARE TAPPING INTO 3000-4000 J/KG OF CAPE
PER MODIFIED ILX SOUNDING.  THIS IS ALLOWING CONVECTION TO SIMPLY
FIRE UP ALONG HORIZONTAL CONVECTIVE ROLLS WITH NO LARGER SCALE
FORCING NEEDED.

THEREFORE... CANNOT OUT RULE SOME CONVECTION ACROSS THE NORTHWESTERN
PART OF THE CWA.  WILL UPDATE THE FORECAST FOR SLIGHT CHANCE TSRA IN
THE NORTHWEST... ISOLATED TO SCATTERED ELSEWHERE.  COVERAGE WILL
OVERALL BE LOW... WITH PULSE CELLS PREVAILING ACROSS MOST OF THE
AREA... PERHAPS SOME CLUSTERS IN THE SOUTH AND SOUTHEAST AS UPPER
VORT APPROACHES FROM THE SOUTH.

&&

.PREVIOUS UPDATE...
 /ISSUED 1040 AM CDT MON MAY 29 2006/
OVERALL THE FORECAST LOOKS IN GOOD SHAPE FOR TODAY.  SHOULD SEE
TEMPS A COUPLE DEGREES COOLER THAN YESTERDAY WITH MAIN THERMAL AXIS
NOW OFF TO OUR WEST OVER THE EASTERN PLAINS.  ALSO LOW LEVEL FLOW
AROUND HIGH PRESSURE IS MORE FROM THE SOUTH TODAY... BRINGING IN
SLIGHTLY MORE MODIFIED AIRMASS FROM THE LOWER MISSISSIPPI VALLEY.
THE KEY WORD HERE IS SLIGHTLY... STILL EXPECT LOWER 90S ACROSS
MUCH OF THE AREA.

CONVECTION QUESTION IS THE MAIN ISSUE TODAY.  ETA/GFS CONTINUE TO
PLASTER PRECIP ACROSS THE AREA THIS MORNING AND AFTERNOON... WHICH
HAS ALREADY TURNED OUT TO BE WRONG.  MOST RECENT MET GUIDANCE
NUMBERS HAVE ALSO BEEN LED ASTRAY BY THE FAUX PRECIP... WE HAD
ALREADY SURPASSED MET GUIDANCE NUMBERS FOR THE DAY BEFORE THEY EVEN
CAME OUT.  RUC APPEARS TO BE SUFFERING FROM THE SAME FATE BUT TO A
LESSER DEGREE... AT LEAST ITS PRECIP AT 15Z MATCHES UP WITH A PATCH
OF CU IN NORTHEASTERN IOWA.  WRF RUNS FROM THE UNIVERSITY OF
ILLINOIS USING THE KAIN-FRITSCH CONVECTIVE SCHEME ALSO IN THE SAME
BOAT.  OTHER U OF I RUNS HOWEVER... AS WELL AS THE 4KM NCEP WRF ARE
MUCH MORE TAME... INDICATING SOME ISOLATED CONVECTION ACROSS THE
SOUTHERN AND EASTERN REACHES OF THE CWA THIS AFTERNOON.  THIS
MATCHES UP WELL WITH THE CURRENT POPS.

ALL MODELS ASIDE... GIVEN MOIST/UNSTABLE AND LARGELY UN-CAPPED
ATMOSPHERE OVER US... A FEW ISOLATED CELLS CANNOT BE RULED OUT.
WATER VAPOR IMAGERY INDICATES A SMALL VORT MAX OVER CENTRAL ARKANSAS
WHICH IS LIFTING NORTHWARD AROUND THE STRONG RIDGING OVER THE
EASTERN STATES. THIS COULD PROVIDE THAT LITTLE BIT OF LIFT NEEDED TO
SPARK OFF A FEW CONVECTIVE SHOWERS AND STORMS.  RUC SEEMS TO HAVE A
ROUGH HANDLE ON THIS FEATURE... SHOWING A COOL POCKET AND VORT LOBE
AT 700 MB LIFTING INTO SOUTHERN ILLINOIS BY 21Z.

LOOKS LIKE THE CURRENT POP GRID HANDLES THIS WELL... SO NO CHANGES
TO IT ARE NECESSARY.  THEREFORE... NO UPDATE TO THE ZFP IS NEEDED
EITHER.

&&

.PREV DISCUSSION...
 /ISSUED 155 AM CDT MON MAY 29 2006/
FORECAST CHALLENGES OVER THE NEXT COUPLE OF DAYS WILL REVOLVE AROUND
POPS...AS UPPER RIDGE BEGINS TO BREAK DOWN AND COLD FRONT SLOWLY
APPROACHES FROM THE WEST.

06Z SURFACE CHART CONTINUES TO SHOW HIGH PRESSURE ANCHORED OVER THE
MID-ATLANTIC STATES...PROVIDING AN UNSEASONABLY WARM SOUTHERLY FLOW
ACROSS THE MIDWEST.  FURTHER NORTHWEST...COLD FRONT STRETCHES FROM
THE NORTHERN PLAINS INTO THE SOUTHERN ROCKIES.  ALOFT...STRONG UPPER
RIDGE REMAINS IN PLACE ACROSS THE EASTERN CONUS...WHILE TROUGHING
PREVAILS ALONG AND WEST OF THE ROCKIES.

SHORT TERM...TODAY THROUGH WEDNESDAY...
FIRST CONCERN WILL BE LOW POPS TODAY...AS PLUME OF DEEPER
LOW/MID-LEVEL MOISTURE ADVECTS NORTHWARD FROM THE GULF OF MEXICO.
00Z 700MB ANALYSIS SHOWS HIGHER DEWPOINT AIR REACHING AS FAR NORTH
AS WESTERN KENTUCKY...AND EXPECT THAT TO CONTINUE WORKING ITS WAY
NORTHWARD INTO CENTRAL ILLINOIS TODAY.  WITH LITTLE IN THE WAY OF
FORCING AND A DECENT CAP REMAINING IN PLACE...DO NOT FORESEE MUCH IN
THE WAY OF PRECIP...OTHER THAN A FEW ISOLATED AFTERNOON/EVENING
THUNDERSTORMS.  BEST FORCING WILL REMAIN FURTHER SOUTH ACROSS THE
LOWER MISSISSIPPI VALLEY IN CONJUNCTION WITH WEAK MID-LEVEL WAVE.
DEEPEST MOISTURE PROFILE AND WEAKEST CAP WILL EXIST ACROSS THE
SOUTHERN KILX CWA...SO WILL PLACE HIGHEST POPS THERE.  WILL GO WITH
30S ACROSS THE SE...TAPERING TO 20S ALONG THE I-72 CORRIDOR.  ANY
ACTIVITY WILL BE DIURNAL IN NATURE...THUS HAVE DROPPED ANY MENTION
OF POPS FOR TONIGHT.

00Z MODELS NOW IN EXCELLENT AGREEMENT CONCERNING TIMING OF
APPROACHING FRONT.  NAM/GFS/CANADIAN ALL KEEP MAIN SYNOPTIC BOUNDARY
NORTHWEST OF THE AREA UNTIL WEDNESDAY AFTERNOON/EVENING.
INCREASINGLY MOIST FLOW AHEAD OF BOUNDARY...AS WELL AS WEAKENING
MID-LEVEL CAP...WILL LEAD TO INCREASING RAIN CHANCES ON TUESDAY.
BEST CHANCES WILL REMAIN FURTHER WEST ACROSS THE WEST AND NORTHWEST
CWA...IN CLOSER PROXIMITY TO BOUNDARY.  COLD FRONT BEGINS MAKING ITS
MOVE INTO THE AREA ON WEDNESDAY...WITH MODEL CONSENSUS PLACING
BOUNDARY ACROSS THE HEART OF CENTRAL ILLINOIS BY 00Z THU.  EXPECT
BEST RAIN CHANCES AT THAT TIME...SO HAVE THEREFORE BUMPED POPS UP TO
50.

LONG TERM...THURSDAY THROUGH SUNDAY...
IN THE EXTENDED...00Z GFS/CANADIAN BOTH DROP FRONT INTO SOUTHERN
ILLINOIS BY 12Z THU...HOWEVER 12Z ECMWF IS ABOUT 12 HOURS SLOWER.
WILL FOLLOW THE CONSENSUS HERE...QUICKLY ENDING PRECIP CHANCES FROM
NORTH TO SOUTH ACROSS THE AREA ON THURSDAY.  WILL HOLD ON TO 30S
ACROSS THE SE INTO THE AFTERNOON...HOWEVER THESE MAY NEED TO BE
DROPPED IF CURRENT TRENDS CONTINUE.  AFTER THAT...UPPER RIDGING IS
REPLACED BY A W/NW FLOW ACROSS THE MIDWEST FRIDAY THROUGH
SUNDAY...RESULTING IN A RETURN TO NEAR NORMAL TEMPS.

&&

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

&&

HARDIMAN/BARNES

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE LINCOLN IL
1243 PM CDT MON MAY 29 2006

ILZ027>031-036>038-040-041-301100-
KNOX-STARK-PEORIA-MARSHALL-WOODFORD-FULTON-TAZEWELL-MCLEAN-
SCHUYLER-MASON-
1243 PM CDT MON MAY 29 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL
ILLINOIS.

.DAY ONE...THIS AFTERNOON AND TONIGHT

ISOLATED SHOWERS AND THUNDERSTORMS CAN BE EXPECTED THROUGH THE
REMAINDER OF THE AFTERNOON. THESE STORMS WILL BE VERY LOCALIZED
AND NATURE... AND NO SEVERE WEATHER IS EXPECTED. HOWEVER... THE
RESULTING LIGHTNING THREAT MAY BE A CONCERN WITH OUTDOOR
ACTIVITIES FOR THE MEMORIAL DAY HOLIDAY.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

A COLD FRONT WILL MOVE INTO THE REGION ON TUESDAY AND COMBINE WITH
THE WARM AND HUMID AIR MASS TO PRODUCE THUNDERSTORMS ACROSS THE
AREA FOR TUESDAY AND TUESDAY NIGHT. THIS FRONT WILL BE SLOW TO
MOVE THROUGH ILLINOIS...SO THUNDERSTORMS WILL REMAIN POSSIBLE
THROUGH WEDNESDAY NIGHT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH TONIGHT.

ILZ042>057-061>063-066>068-071>073-301100-
LOGAN-DE WITT-PIATT-CHAMPAIGN-VERMILION-CASS-MENARD-SCOTT-MORGAN-
SANGAMON-CHRISTIAN-MACON-MOULTRIE-DOUGLAS-COLES-EDGAR-SHELBY-
CUMBERLAND-CLARK-EFFINGHAM-JASPER-CRAWFORD-CLAY-RICHLAND-LAWRENCE-
1243 PM CDT MON MAY 29 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL
ILLINOIS...EAST CENTRAL ILLINOIS AND SOUTHEAST ILLINOIS.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SCATTERED SHOWERS AND THUNDERSTORMS CAN BE EXPECTED THROUGH THE
REMAINDER OF THE AFTERNOON. THESE STORMS ARE NOT EXPECTED TO REACH
SEVERE LIMITS. HOWEVER... THE RESULTING LIGHTNING THREAT MAY BE A
CONCERN WITH OUTDOOR ACTIVITIES FOR THE MEMORIAL DAY HOLIDAY.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

A COLD FRONT WILL MOVE INTO THE REGION ON TUESDAY AND COMBINE WITH
THE WARM AND HUMID AIR MASS TO PRODUCE THUNDERSTORMS ACROSS THE
AREA FOR TUESDAY AND TUESDAY NIGHT. THIS FRONT WILL BE SLOW TO
MOVE THROUGH ILLINOIS...SO THUNDERSTORMS WILL REMAIN POSSIBLE
THROUGH WEDNESDAY NIGHT. SOME THUNDERSTORMS COULD LINGER INTO
THURSDAY...MAINLY IN SOUTHEASTERN ILLINOIS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH TONIGHT.

HARDIMAN/AUTEN