Severe Thunderstorm Warning 52, NWS Lincoln, IL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
220 AM CDT THU MAY 17 2001

PLENTY OF CONCERNS THIS RUN WITH MAIN FOCUS ON THUNDERSTORM
ACTIVITY...SEVERE POTENTIAL...HEAVY RAINFALL...AND TEMPERATURES.

LATEST 06Z SURFACE ANALYSIS DEMONSTRATES SURFACE LOW ACROSS
NORTHWEST MISSOURI/SOUTHERN IOWA. SURFACE STATIONARY FRONT
EXTENDS FROM SOUTHERN IOWA EAST INTO CENTRAL ILLINOIS AND EAST
INTO INDIANA. SFC COLD FRONT EXTENDS ACROSS CENTRAL PLAINS STATES
...WITH ANOTHER COLD FRONT ACROSS NORTHERN PLAINS STATES. LATEST
0645Z IR-SATELLITE IMAGE DEMONSTRATES THUNDERSTORMS ACROSS
IOWA...EASTERN ILLINOIS...AND INTO WESTERN INDIANA.  ALSO
STRONG THUNDERSTORMS ACROSS IOWA WITH IR-SATELLITE DEMONSTRATING
CLOUD TOPS COOLING. LATEST IR-SATELLITE ALSO DEMONSTRATING PLENTY OF
MID AND HIGH LEVEL CLOUDS ACROSS PARTS OF ILLINOIS. LATEST 0645Z
WATER VAPOR IMAGE DEMONSTRATING SEVERAL S/W ACROSS MID MS VALLEY...
PLAINS STATES...AND WESTERN US.  STRONG S/W WAS ACROSS WESTERN
ND/EASTERN MONTANA. LATEST 0656Z KILX RADAR INDICATING SCATTERED
THUNDERSTORMS ACROSS SOUTHEAST CWA WEAKENING AND STRONG
THUNDERSTORMS APPROACHING NORTHWEST CWA. AN OUTFLOW BOUNDARY
EXTENDED FROM JUST EAST OF BMI TO MOUNT PULASKI LINE AND MOVING WEST.
LATEST 0659Z KDVN RADAR INDICATING STRONG TSTMS JUST SOUTHWEST OF DVN
MOVING EAST-SOUTHEAST.

MODELS AGAIN DIVERGING SOME THIS RUN. PREFER TO USE MAINLY AN ETA
SOLUTION WHICH APPEARS TO ALREADY HAVE SOME PROBLEMS WITH SOME
OF THE CURRENT SITUATION. MODELS AGAIN APPEAR TO MOVE MAIN COLD
FRONT ACROSS CWA THIS EVENING INTO OVERNIGHT. RIDGE ACROSS CWA
DAMPENS NEXT 48 HRS WITH SERIES OF UPPER LEVEL DISTURBANCES. ETA
BRING IN 80-90 PERCENT 925MB RH BY 06Z FRI ACROSS CWA AND MAINTAINS
IT THROUGH 12Z FRI WEST AND 18Z SOUTHEAST. ETA KEEPS ABOUT 60-70
PERCENT 700MB RH ACROSS CWA THRU 00Z FRI WITH A DRY PUNCH 20 PERCENT
700MB RH IN UPPER MIDWEST BY 00Z FRI. ETA BRINGS IN DRY AIR INTO NW
CWA BY 12Z FRI AND THEN HAS STEEP GRADIENT OF 700MB RH FROM 20
PERCENT IN NW CWA TO 70 PERCENT 700MB RH IN SOUTHEAST CWA BY 06Z SAT.
 THEN BY 12Z SAT DRIER 700MB RH ACROSS ENTIRE CWA. ETA MOVES THE
110KT 300MB JET INTO UPPER MIDWEST BY 18Z THU...THEN INTO NORTHERN
GREAT LAKES BY 00Z FRI...THEN ACROSS NEW ENGLAND STATES BY 00Z SAT.
ETA T/H CROSS SECTIONS DEMONSTRATES HIGH MID LEVEL MOISTURE BY 12Z
THU THRU 00Z SAT. HIGH LOW LEVEL MOISTURE IN PLACE BY 06Z FRI. ETA
HAS +18 TO +20 850MB TEMPS THRU 18Z THU...+16 TO +18 850 TEMPS BY 00Z
FRI...+13 TO +14 850 TEMPS BY 12Z FRI...+12 TO +14 BY 00Z SAT. ETA
310K ISENTROPIC SFC INDICATING SOME WEAK ISENTROPIC LIFT AND COND
PRES DEF ACROSS CWA NEXT 42 HRS...18Z FRI. LATEST ETA MODEL SOUNDINGS
DEMONSTRATES FAIRLY STRONG INSTABILITY THIS AFTERNOON WITH MUCAPES OF
3000-4000 J/KG AND LI/S -6 TO -9. HOWEVER SOUNDINGS SUGGEST WEAKER
CAP. PWS OF 1.5 TO 1.75 WILL PRODUCE COPIOUS AMOUNTS OF RAIN IN
THUNDERSTORMS. ALSO SEVERAL OUTFLOW BOUNDARIES CURRENTLY NEAR CWA.
EXPECT SCATTERED THUNDERSTORMS TODAY. WILL MONITOR CURRENT RADAR AND
MAY LEAVE POPS OUT OF FIRST PERIOD ZONES IF TSTMS ARE ONGOING OR SOON
TO ARRIVE. WILL BRING IN CHANCE OF PRECIPITATION TO MOST OF CWA ON
FRIDAY.

FWC/FAN/MAV SEEM REASONABLE. CONVECTIVE ACTIVITY AND STATIONARY
FRONT WILL DETERMINE HIGHS. WILL USE A BLEND.

WILL KEEP EXTENDED WITH NO CHANGES EXPECTED AT THIS TIME.

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

SPI TE 087/059 075/054 074 13563
PIA TE 085/058 074/052 073 13542
DEC TE 087/060 075/053 074 13563
CMI TE 088/060 075/052 073 13563
MTO TE 088/061 076/054 074 13564
LWV TE 089/063 076/056 075 13564

.ILX...NONE.

EH