Severe Thunderstorm Warning 105, NWS Lincoln, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
834 PM CDT FRI JUN 18 2010

.DISCUSSION...
ISSUED 834 PM CDT FRI JUN 18 2010

A SEVERE THUNDERSTORM WATCH IS IN EFFECT FOR THE MAJORITY OF
CENTRAL AND SOUTHEAST ILLINOIS THROUGH MIDNIGHT TONIGHT.

INITIAL BOW ECHO THAT RACED ACROSS NORTHERN ILLINOIS EARLIER THIS
AFTERNOON/EVENING MISSED THE BULK OF THE FORECAST AREA. THIS STORM
COMPLEX LEFT BEHIND AN OUTFLOW BOUNDARY THAT EXTENDS WEST TO EAST
ACROSS ILLINOIS FROM ABOUT MACOMB TO DANVILLE. THE AREA TO THE
NORTH OF THIS BOUNDARY HAS STABILIZED A BIT...BUT LOCATIONS TO THE
SOUTH OF THE BOUNDARY ARE STILL VERY UNSTABLE WITH 2-3K J/KG OF ML
CAPE. BULK SHEAR VALUES HAVE INCREASED AS WELL SINCE THIS
AFTERNOON...WITH AROUND 35 KTS NORTH OF THE BOUNDARY AND 30 KTS TO
THE SOUTH.

A SECOND MCS HAS BEEN DEVELOPING UPSTREAM OVER IOWA AND IS RACING
TOWARD THE FORECAST AREA ALONG THE INSTABILITY AXIS. THIS COMPLEX
HAS A HISTORY OF DAMAGING WINDS...AND THIS SHOULD CONTINUE TO BE
THE CASE AS THE CLUSTERS OF STORMS CONTINUE TO EVOLVE INTO A NEW
BOW ECHO. DAMAGING WINDS WILL BE THE PRIMARY THREAT...BUT THE
THREAT FOR A TORNADO WILL ALSO NEED TO BE MONITORED AS THE BOW
ENCOUNTERS THE BACKED LOW LEVEL FLOW ON THE OLD OUTFLOW BOUNDARY.

BAK
&&

.AVIATION...
ISSUED 632 PM CDT FRI JUN 18 2010

GENERALLY QUIET/VFR AVIATION WEATHER CONDITIONS EXPECTED THROUGH
THE 00Z TAF PERIOD. MAIN CONCERN CENTERS ON THE CHANCES FOR
THUNDERSTORMS TO IMPACT THE TERMINALS THOUGH EARLY SATURDAY. A
WEAK BOUNDARY CURRENTLY EXTENDS SOUTHEAST FROM CENTRAL IOWA...
ALONG A LINE FROM KPIA TO KCMI. THE AIR MASS IN THE VICINITY OF
THIS BOUNDARY IS CONDUCIVE FOR ADDITIONAL THUNDERSTORM DEVELOPMENT
AS IS SLOWLY SINKS SOUTH TONIGHT. HOWEVER...THE SPECIFIC THREAT AT
ANY ONE TERMINAL IS TOO LOW TO GO ABOVE A VCTS OR CB MENTION AT
THIS TIME. SOUTHERLY WINDS...OR VARIABLE WHERE PREVIOUS
THUNDERSTORM OUTFLOWS HAVE MOVED THROUGH...WILL TREND WESTERLY
SATURDAY MORNING ONCE THE BOUNDARY SETTLES SOUTH OF THE TERMINALS.

BAK
&&

.PREV DISCUSSION...
ISSUED 252 PM CDT FRI JUN 18 2010

MAIN FORECAST CONCERNS FOR MUCH OF THE NEXT SEVERAL DAYS REVOLVE
AROUND SHOWER/THUNDERSTORM CHANCES...AND HOW HOT IT WILL BE. THE
OVERALL PATTERN IS WELL AGREED UPON BY THE FORECAST MODELS.
SURFACE FRONTAL AND/OR OUTFLOW BOUNDARIES WILL BE IN OUR VICINITY
THROUGH THE NEXT WEEK...WITH TROFFING IN THE WESTERN U.S. AND FLAT
RIDGING IN THE EASTERN U.S. ALOFT. SHORT WAVES OR CONVECTIVELY
INDUCED DISTURBANCES RIPPLING THROUGH THE FLAT MEAN RIDGE WILL
PROVIDE A PERIODIC RISK OF SHOWERS/STORMS. HOWEVER...NOT
SURPRISINGLY...MODEL AGREEMENT IN THE SMALLER SCALE FEATURES THAT
ARE EXPECTED TO INITIATE CONVECTION IS NOT AS GOOD. THIS MAKES THE
CONVECTIVE THREAT IMPOSSIBLE TO PIN POINT UNTIL THE VERY NEAR TERM
OF THE FORECAST...GENERALLY NO MORE THAN 12-24 HOURS OUT. ONE
SIGNIFICANT EXAMPLE OF THIS DILEMMA IS THE CURRENT STORM COMPLEX
MOVING ACROSS NORTHERN ILLINOIS...WHICH WAS NOT FORECAST BY ANY OF
THE ROUTINE FORECAST MODELS. OVERALL...SEE NO REAL REASON TO
DEVIATE FROM THE DAILY CHANCES OF SHOWERS/STORMS CURRENTLY IN THE
FORECAST.

THE OTHER BIG STORY OF THE NEXT SEVERAL DAYS IS THE SUMMERTIME
HEAT/HUMIDITY THAT WILL REMAIN OVER THE REGION. DAILY HIGHS WILL
AVERAGE AROUND 90...OVERNIGHT LOWS AROUND 70...WITH DEW POINT
TEMPERATURES MAINLY IN THE 70S. THESE CONDITIONS ARE SUPPORTIVE OF
AFTERNOON HEAT INDEX VALUES AROUND 100 DEGREES WHICH IS HEAT
ADVISORY CRITERIA. HOWEVER...DUE TO THE LOCAL IMPACTS ON
TEMPERATURES/DEW POINTS THAT WILL BE CAUSED BY THE PERIODIC
THUNDERSTORMS...DO NOT HAVE A HIGH CONFIDENCE ON WHICH PORTIONS OF
THE FORECAST AREA WILL REQUIRE AN ADVISORY ON ANY GIVEN DAY. AT
THIS POINT...WILL CONTINUE THE GOING HEAT ADVISORY INTO THIS
EVENING...AND CARRY ANOTHER ONE TOMORROW IN THE SAME AREA /SOUTH
OF THE I-70 CORRIDOR/ FOR SATURDAY. THIS AREA IS LEAST LIKELY TO
BE SIGNIFICANTLY IMPACTED BY CONVECTION IN THE NEXT 24 HOURS.
DEPENDING ON CONVECTIVE TRENDS THROUGH THIS EVENING...THE ADVISORY
MAY NEED TO BE EXPANDED NORTHWARD FOR SATURDAY AFTERNOON.

BAK

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
HEAT ADVISORY FROM NOON TO 7 PM CDT SATURDAY FOR ILZ062-063-
066>068-071>073.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LINCOLN IL
331 PM CDT FRI JUN 18 2010

ILZ027>031-037-038-191100-
KNOX-MARSHALL-MCLEAN-PEORIA-STARK-TAZEWELL-WOODFORD-
331 PM CDT FRI JUN 18 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL
ILLINOIS.

.DAY ONE...TONIGHT

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS INTO THIS EVENING...
AS A SQUALL LINE ACROSS NORTHERN ILLINOIS. SIGNIFICANT WIND DAMAGE
IS POSSIBLE FROM THIS LINE OF STORMS...WITH LARGE HAIL ALSO
POSSIBLE.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

A WEAK FRONTAL BOUNDARY IS EXPECTED TO REMAIN OVER THE AREA THE
NEXT SEVERAL DAYS. THERE WILL BE A DAILY CHANCE FOR THUNDERSTORMS
ALONG THIS BOUNDARY...WITH THE BETTER CHANCE FOR MORE ORGANIZED
THUNDERSTORMS COMING ALONG EITHER LATE SATURDAY NIGHT OR SUNDAY.

SUMMER LIKE HEAT AND HUMIDITY WILL PRODUCE AFTERNOON HEAT INDICES
AROUND 100 DEGREES DURING MUCH OF THE UPCOMING WEEK.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS LIKELY INTO EARLY EVENING... PRIMARILY
BETWEEN NOW AND 7 PM.

ILZ036-040-041-047-049-050-191100-
CASS-FULTON-MASON-MORGAN-SCHUYLER-SCOTT-
331 PM CDT FRI JUN 18 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL
ILLINOIS.

.DAY ONE...TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS INTO THIS EVENING...
AS A SQUALL LINE ACROSS NORTHERN ILLINOIS. WIND DAMAGE IS POSSIBLE
FROM THIS LINE OF STORMS...WITH LARGE HAIL ALSO POSSIBLE. THE BEST
SEVERE WEATHER CHANCES WILL BE A BIT FURTHER NORTH.

FOR INTERESTS ALONG THE ILLINOIS RIVER...FLOODING WILL CONTINUE
ALONG THE ILLINOIS RIVER DOWNSTREAM FROM HAVANA FOR THE NEXT
SEVERAL DAYS.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

A WEAK FRONTAL BOUNDARY IS EXPECTED TO REMAIN OVER THE AREA THE
NEXT SEVERAL DAYS. THERE WILL BE A DAILY CHANCE FOR THUNDERSTORMS
ALONG THIS BOUNDARY...WITH THE BETTER CHANCE FOR MORE ORGANIZED
THUNDERSTORMS COMING ALONG EITHER LATE SATURDAY NIGHT OR SUNDAY.

SUMMER LIKE HEAT AND HUMIDITY WILL PRODUCE AFTERNOON HEAT INDICES
AROUND 100 DEGREES DURING MUCH OF THE UPCOMING WEEK.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED INTO THIS EVENING...PRIMARILY
BETWEEN NOW AND 7 PM.

ILZ042-043-048-051>053-061-191100-
CHRISTIAN-DE WITT-LOGAN-MACON-MENARD-SANGAMON-SHELBY-
331 PM CDT FRI JUN 18 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL
ILLINOIS.

.DAY ONE...TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS INTO THIS EVENING...
AS A FRONTAL BOUNDARY BECOMES STATIONARY OVER NORTHERN ILLINOIS.
WIND DAMAGE AND LARGE HAIL WILL BE THE PRIMARY THREATS...AS WELL
AS VERY HEAVY RAIN.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

A WEAK FRONTAL BOUNDARY IS EXPECTED TO REMAIN OVER THE AREA THE
NEXT SEVERAL DAYS. THERE WILL BE A DAILY CHANCE FOR THUNDERSTORMS
ALONG THIS BOUNDARY...WITH THE BETTER CHANCE FOR MORE ORGANIZED
THUNDERSTORMS COMING ALONG EITHER LATE SATURDAY NIGHT OR SUNDAY.

SUMMER LIKE HEAT AND HUMIDITY WILL PRODUCE AFTERNOON HEAT INDICES
AROUND 100 DEGREES DURING MUCH OF THE UPCOMING WEEK.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED INTO THIS EVENING...PRIMARILY
BETWEEN NOW AND 7 PM.

ILZ044>046-054>057-191100-
CHAMPAIGN-COLES-DOUGLAS-EDGAR-MOULTRIE-PIATT-VERMILION-
331 PM CDT FRI JUN 18 2010

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

.DAY ONE...TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS INTO THIS EVENING...
AS A FRONTAL BOUNDARY BECOMES STATIONARY OVER NORTHERN ILLINOIS.
WIND DAMAGE AND LARGE HAIL WILL BE THE PRIMARY THREATS...AS WELL
AS VERY HEAVY RAIN.

FOR INTERESTS ALONG THE SANGAMON RIVER...ESPECIALLY NEAR
MONTICELLO...MINOR FLOODING WILL BE POSSIBLE THE NEXT SEVERAL DAYS.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

A WEAK FRONTAL BOUNDARY IS EXPECTED TO REMAIN OVER THE AREA THE
NEXT SEVERAL DAYS. THERE WILL BE A DAILY CHANCE FOR THUNDERSTORMS
ALONG THIS BOUNDARY...WITH THE BETTER CHANCE FOR MORE ORGANIZED
THUNDERSTORMS COMING ALONG EITHER LATE SATURDAY NIGHT OR SUNDAY.

SUMMER LIKE HEAT AND HUMIDITY WILL PRODUCE AFTERNOON HEAT INDICES
AROUND 100 DEGREES DURING MUCH OF THE UPCOMING WEEK.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED INTO THIS EVENING...PRIMARILY
BETWEEN 5 PM AND 8 PM.

ILZ062-063-066>068-071>073-191100-
CLARK-CLAY-CRAWFORD-CUMBERLAND-EFFINGHAM-JASPER-LAWRENCE-RICHLAND-
331 PM CDT FRI JUN 18 2010

...HEAT ADVISORY IN EFFECT UNTIL 7 PM CDT THIS EVENING...
...HEAT ADVISORY IN EFFECT FROM NOON TO 7 PM CDT SATURDAY...

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

.DAY ONE...TONIGHT

ISOLATED TO WIDELY SCATTERED THUNDERSTORMS WILL BE POSSIBLE
INTO THIS EVENING. A FEW OF THE STORMS WILL BE CAPABLE OF PRODUCING
GUSTY WINDS AND HEAVY RAINFALL. ANY RISK OF SEVERE WEATHER IS MOST
LIKELY TO BE NORTH OF I-70.

EXTENSIVE FLOODING IS EXPECTED ALONG MUCH OF THE WABASH RIVER THE
NEXT SEVERAL DAYS. MINOR FLOODING ALONG PORTIONS OF THE LITTLE
WABASH AND EMBARRAS RIVERS WILL CONTINUE INTO THE FIRST PART OF
THE WEEKEND.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

A WEAK FRONTAL BOUNDARY IS EXPECTED TO REMAIN OVER ILLINOIS THE
NEXT SEVERAL DAYS. ISOLATED TO WIDELY SCATTERED THUNDERSTORMS WILL
BE POSSIBLE...AS LONG AS THE FRONT REMAINS IN THE AREA. SOME OF
THE STRONGER STORMS MAY PRODUCE STRONG WINDS AND VERY HEAVY
RAINFALL. THE THREAT OF SEVERE WEATHER BEYOND SATURDAY IS
UNCERTAIN AT THIS TIME.

SUMMER LIKE HEAT AND HUMIDITY WILL PRODUCE AFTERNOON HEAT INDICES
OF 100 TO 105 DEGREES DURING MUCH OF THE UPCOMING WEEK.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH TONIGHT.

BAK

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