Severe Thunderstorm Warning 176, NWS Lincoln, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
220 AM CDT MON AUG 19 2002

CONTINUE TO BE PLENTY OF FORECAST CHALLENGES WITH FOCUS ON CURRENT
PRECIPITATION AND TEMPERATURES.

LATEST 05Z SURFACE ANALYSIS PLACES SURFACE LOW PRESSURE ACROSS
SOUTHEAST ROCKIES/WESTERN SOUTHERN PLAINS STATES. A STATIONARY
BOUNDARY EXTENDED FROM CENTRAL PLAINS STATES NORTHEAST INTO NORTHERN
MISSOURI AND INTO NORTHWEST ILLINOIS.  SURFACE HIGH PRESSURE WAS
ACROSS NORTHERN PLAINS STATES.  LATEST 0530Z IR SATELLITE PLACES
AREA OF CONVECTION ACROSS NORTHERN KANSAS/SOUTHERN NEBRASKA AND
ACROSS EASTERN IOWA AND NORTH CENTRAL ILLINOIS.  PLENTY OF MID AND
HIGH LEVEL CLOUDS WERE ACROSS CENTRAL AND SOUTHERN ILLINOIS.
LATEST 0530Z W/V IMAGE PLACES SEVERAL S/WS ACROSS MIDWEST AND PLAINS
STATES REGION.  STRONG S/W WAS ACROSS UPPER MIDWEST NEAR SOUTHERN
MN.  OTHER SW/S WERE ALSO ACROSS WESTERN U.S.  LATEST 0537Z KILX
RADAR DEMONSTRATES THUNDERSTORMS FROM NEAR GALESBURG SOUTHEAST TO
BMI. STRONG/SEVERE THUNDERSTORMS WERE LOCATED NEAR BMI. LATEST 0542Z
KDVN RADAR INDICATES SHOWERS AND THUNDERSTORMS ACROSS SOUTHERN AND
EASTERN IOWA MOVING EAST.

LATEST 00Z MON MODELS DID NOT DETECT CLUSTER OF STORMS IN KANSAS
FAIRLY WELL.  AXIS OF HEAVY PRECIPITATION DIFFERS BETWEEN MODELS AND
WILL MAINLY USE AN AVN OVERALL SOLUTION.  CONFIDENCE NOT THAT GREAT
IN MODELS THIS RUN.

AVN MOVES H50 TROUGH ACROSS GREAT LAKES REGION WITH ANOTHER H50
TROUGH ACROSS PACIFIC NORTHWEST BY 00Z TUE. H50 TROUGH WAS ACROSS
PACIFIC NORTHWEST AND ANOTHER TROUGH ACROSS NORTHEAST U.S BY 00Z
WED. AVN AND ETA DEVELOPS STRONG H50 S/W NEAR IOWA BETWEEN 06Z WED
THRU 12Z WED. POSSIBLE CONVECTION AGAIN DEVELOPING WITH HEAVY
RAINFALL.  AVN MAINTAINS SURFACE LOW ACROSS SOUTHERN PLAINS STATES
WITH A SURFACE WAVE ALONG FRONT AND IS ACROSS EASTERN ILLINOIS BY
12Z MON.  SURFACE HIGH PRESSURE BUILDS ACROSS UPPER MIDWEST BY 18Z
MON AND PUSHES FRONT FURTHER SOUTH ACROSS REGION.  SURFACE HIGH
PRESSURE BUILDS ACROSS GREAT LAKES REGION BY 12Z TUE AND MOVES EAST
ACROSS NORTHEAST U.S BY 12Z WED.  SURFACE LOW PRESSURE DEVELOPS
ACROSS CENTRAL PLAINS STATES BY 12Z WED.  T/H CROSS SECTIONS
PROVIDING HIGH RH AT ALL LEVELS AND GOOD OMEGA THROUGH 15Z MON. THEN
T/H CROSS SECTIONS DECREASES RH AT ALL LEVELS BY 00Z TUE AND RETURNS
HIGH LOW LEVEL RH BETWEEN 06Z WED AND 12Z WED. MODEL SOUNDINGS
INDICATES DECENT INSTABILITY LI/S -4 AND P/WS 1.5 TO 2.0 INCHES
THROUGH 18Z MON THEN DECREASES RH AT ALL LEVELS BY 12Z TUE.  AVN
310K ISENTROPIC SURFACE INDICATES SOME ISENTROPIC LIFT AND COND PRES
DEF THROUGH 18Z ACROSS CENTRAL ILLINOIS. AVN 310K ISENTROPIC SURFACE
ALSO RETURNS COND PRES DEF AND LIFT ACROSS EASTERN IOWA AND
NORTHWEST ILLINOIS BETWEEN 06Z WED THROUGH 12Z WED.  850MB TEMPS
DECREASES TO +16C TO +18C BY 00Z TUE...TO 850MB TEMPS +18C TO +20C
BY 12Z WED.  AVN PLACES CWA IN FAVORABLE REGION OF 100KT 300MB JET
MAX THROUGH 18Z MON AND THEN SHIFTS IT EAST BY 00Z TUE.  CONTINUE NO
REAL CHANGES FROM CURRENT EXTENDED. WILL ALSO MONITOR CURRENT RADAR
TRENDS BEFORE ZONE ISSUANCE. WILL MENTION PERIODS OF OR OCCASIONAL
SHOWERS AND THUNDERSTORMS NORTH AND CENTRAL DEPENDING ON RADAR
TRENDS.

TEMPERATURES CONTINUE TRICKY...WITH CONVECTION AND BOUNDARY ACROSS
REGION. GUIDANCE NUMBERS FAIRLY SIMILAR AND LEAN ON COOLER TEMPS.

SPI TB 079/060 083/066 089 13+10
PIA TB 077/059 081/065 088 13+10
DEC TB 079/060 083/065 089 13+10
CMI TB 077/058 081/063 087 13+10
MTO TB 080/061 083/065 089 13810
LWV TB 082/063 086/066 090 13830

.ILX...NONE.

EH