Severe Thunderstorm Warning 128, NWS Lincoln, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
330 AM CDT WED JUL 18 2001

FORECAST CONCERNS ARE WITH RESPECT TO PCPN CHCS AND PSBLTY OF STRONG
STORMS/HEAVY RAIN.

CONVECTION CURRENTLY IN ERN PARTS OF FORECAST AREA IS ELEVATED IN
NATURE AS 20-25 KT LOW LEVEL JET INTERSECTS A BOUNDARY THAT WAS
ROUGHLY FROM SOUTH OF DSM-UIN-XTRM SW IND. THIS CONVECTION IS XPCTD
TO CONTINUE PAST DAYBREAK...THEN DISSIPATE AS LOW LEVEL WINDS AND
CONVERGENCE FCST TO WEAKEN. MCS IN IOWA IS HOLDING TOGETHER AND WILL
BE THE FOCUS FOR DEVELOPING T-STORMS IN WCENT IL TODAY. THE MID
LEVEL SHORTWAVE ASSOCIATED WITH IT/MCS REMNANTS WILL SLIDE INTO CENT
IL LATE THIS MORNING/ERLY AFTN. PLENTY OF INSTABILITY WITH CAPES
OVER 4000 AND LI/S UP TO -9. LOW LEVEL SHEAR/DEEP LAYER SHEAR NOT
VERY IMPRESSIVE...BUT HIGH INSTABILITY AND PROXIMITY OF NW-SE
ORIENTED SFC BOUNDARY FROM SW IA-CENT/SE IL COULD PRODUCE STORMS WITH
STRONG WIND GUSTS.

AM ALSO CONCERNED THAT WITH AFOREMENTIONED BOUNDARY...LOW LEVEL
CONVERGENCE...INCRSG UPR LEVEL DIVERGENCE AND DEEP MOISTURE
(PRECIPITABLE WATER VALUES GRTR THAN 2 INCHES) TRAINING CELLS WITH
LOCALLY HEAVY RAIN A DISTINCT POSSIBILITY. FLASH FLOOD GUIDANCE IS
RELATIVELY HIGH...SO WILL HOLD OFF ON HEADLINE BUT WILL MENTION
LOCALLY HEAVY RAIN ACROSS FORECAST AREA.

TEMPS WILL BE TRICKY TODAY DUE TO ONGOING CONVECTION IN ERN IL AND
ADVANCING CONVECTIVE COMPLEX/ASSOCIATED CLOUD COVER. WILL FOLLOW THE
LEAD OF THE NUMERICAL GUIDANCE AND LOWER TEMPS A FEW DEGREES FROM
YESTERDAYS HIGHS...WITH UPR 80 AND HEAT INDICES AROUND 100.

WILL BUMP UP POPS FOR SRN PARTS OF FORECAST AREA TONIGHT...AND KEEP
40 POPS GOING IN NRN SECTIONS AS A BOUNDARY SLIDES SOUTH IN RESPONSE
TO INCREASING NE FLOW IN GRT LAKES STATES. MODELS INDICATE AN MCS
XPCTD TO DEVELOP IN NRN MO TRACKING INTO SCENT IL OVERNIGHT. THE
BOUNDARY IS XPCTD TO SLIDE A BIT FARTHER SOUTH THURSDAY...BUT WILL
KEEP CHC POPS GOING FOR WHOLE CWA SINCE TEMPS/MOISTURE NOT XPCTD TO
CHANGE MUCH AND UNCERTAINTY OF BOUNDARY POSTIONS COULD PROVIDE FOCUS
FOR CONVECTION.

WILL UPDATE EXTENDED FORECAST TO DROP PCPN MENTION FOR FRIDAY AND
SATURDAY AS UPR RIDGE BUILDS IN UPR MIDWEST...WHICH SHOULD CAUSE
CONVECTION TO STAY FAR ENOUGH WEST AND NORTH OF REGION.

THANKS TO LOT/LSX FOR COORDINATION.

...PRELIMINARY CCF FOR COORDINATION PURPOSES ONLY...

SPI TB 089/073 088/073 087 23664
PIA TB 088/072 088/073 087 23643
DEC TB 087/073 088/072 087 23664
CMI TB 088/072 087/072 086 23643
MTO TB 086/072 087/072 086 23664
LWV TB 087/073 088/073 087 23664

.ILX...NONE.

MILLER

ILZ027>031-036>038-040>057-061>063-066>068-071>073-181200-

HAZARDOUS WEATHER OUTLOOK FOR CENTRAL ILLINOIS
NATIONAL WEATHER SERVICE LINCOLN IL
600 AM CDT WED JUL 18 2001

...LOCALLY HEAVY RAIN AND GUSTY WINDS POSSIBLE TODAY...

THUNDERSTORMS ARE EXPECTED TO MOVE INTO CENTRAL ILLINOIS THIS
MORNING. THESE THUNDERSTORMS WILL BE CAPABLE OF PRODUCING HEAVY
RAINFALL AMOUNTS AND GUSTY WINDS AS THEY SPREAD ACROSS THE REGION.
THUNDERSTORMS IN SOUTHEAST ILLINOIS EARLY THIS MORNING WILL ALSO
PRODUCE LOCALLY HEAVY RAIN. ADDITIONAL THUNDERSTORMS ARE
ANTICIPATED IN CENTRAL AND SOUTHEAST ILLINOIS THIS AFTERNOON INTO
TONIGHT. THESE STORMS WILL BE CAPABLE OF PRODUCING DAMAGING WINDS
AND HEAVY| RAINFALL AMOUNTS.

MILLER