Heat in Illinois, July 7 to 9, 2001

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
215 PM CDT SAT JUL 7 2001

FORECAST CHALLENGES WILL BE PRECIP CHANCES AND HEAT INDICES.

LOOKING AT THE 07/12Z UPPER AIR MAPS THE FOLLOWING WAS NOTED.
100-110 KT 25H JET WAS POSITIONED ALONG THE U.S/CAN BORDER FROM
MONTANA TO LAKE SUPERIOR. A SHORT WAVE TROUGH WAS RIDING ALONG THIS
JET IN THE VICINITY OF NORTH DAKOTA. COMING ON SHORE BRITISH
COLUMBIA WAS ANOTHER...BUT WEAKER...JET STREAK OF 70-80 KTS WITH ITS
OWN ASSOCIATED SHORT WAVE TROUGH. POSITIONED OVER THE CENTRAL AND
SOUTHEAST PARTS OF CONUS WAS A BROAD WARM RIDGE. AT 7H A BAROCLINIC
ZONE WAS NOTED JUST SOUTH OF THE U.S/CAN BORDER WITH ITS SOUTHERN
MOST EXTENT INTO THE PA/NJ AREA. OVER THE FORECAST AREA /FA/ A 7H
HIGH WAS OVER THE MO/AR REGION WITH THE +10 C ISOTHERM COINCIDENT TO
THE IL/IN BORDER THEN SOUTHEAST THROUGH CENTRAL KENTUCKY. THE 8H
BAROCLINIC ZONE HAD A SC...OH...MI ORIENTATION BEFORE HEADING WEST
NEAR THE U.S./CAN BORDER. 8H TEMPS ACROSS THE FA WERE +19 C EAST AND
+23 C WEST. AT THE SURFACE AT 07/16Z...DEW PTS WERE IN THE MID TO
UPPER 70S ACROSS SOUTHEAST MO WITH READINGS AROUND 70 ACROSS THE
REST OF THE FA. A CIRRUS VEIL WAS OVER SOUTHEAST IN...SOUTHERN IL
AND NORTHWEST KY IN ASSOCIATION WITH AN MCS PROGRESSING SOUTHEAST
THROUGH CENTRAL IN AND WESTERN OH.

COMPARING HAND ANALYSIS OF THE UPPER 07/12Z UPPER MAPS WITH 0 HR
INITIALIZATION OF THE NGM/ETA/AVN SHOWED THE AVN AS THE LEAST
FAVORABLE MODEL TODAY. GIVEN TEMPERATURES WILL BE OF MOST CONCERN
FOR THIS FORECAST PACKAGE...THE NGM/ETA DID VERY WELL WITH THEIR
INITIALIZATION WHILE THE AVN TENDED TO BE ABOUT 2 DEG C TOO COOL IN
THE LOWER LEVELS. ALSO...AVN WAS NOT AT ALL IMPRESSIVE WITH ITS MID
40S DEW PT INITIALIZATION OVER IN/TN WHEN IN ACTUALITY LOWER 60S
PREVAILED IN THESE AREAS AT 07/12Z. HERE AGAIN THE NGM/ETA HIT THESE
VALUES ON THE HEAD.

RULE OF THUMB OF CONVECTION NOT CROSSING THE 7H +10 C ISOTHERM SEEMS
TO BE HOLDING TODAY AS NOTED BY THE PATH OF THE IN/OH ACTIVITY.
AGREE WITH LATEST SWODY1 THAT INITIATION POINT OF OVERNIGHT MCS WILL
BE NORTH OF THE FA NEAR CHICAGOLAND. WHETHER THIS SYSTEM WILL HOLD
TOGETHER AND AFFECT NORTHEAST PARTS OF THE FA IS THE QUESTION. I
CAN/T COMPLETELY RULE THIS POSSIBILITY OUT...BUT GIVEN THE
EXPECTATION OF A STRENGTHENING CAP...BELIEVE BIGGEST RISK WILL BE
NORTH AND EAST OF THE FA...OR A PATH SIMILAR TO THAT OF THE CURRENT
IN/OH MCS.

FOR TONIGHT/S LOW TEMPERATURES...THE ETA/MESOETA TREND MAY BE THE
WAY TO GO. CONCERNED ABOUT THE NGM/S DEW PT FORECAST INTO THE
OVERNIGHT HOURS...THAT OF DROPPING READINGS INTO THE LOWER 60S. THE
ETA/MESOETA KEEPING READINGS IN THE LOW TO MID 70S. WITH THESE DEW
PT READINGS...WOULD EXPECT LOW TEMPERATURES AT MOST 3 DEGREES
WARMER...OR LOWS IN THE MID TO UPPER 70S. CURRENT POOL OF HIGHEST
DEW PTS ARE CURRENTLY CENTERED OVER SOUTHEAST MO. GUIDANCE SUGGESTS
A PUSH OF THESE HIGHER VALUES INTO WESTERN KY/SOUTHERN IL BY MORNING
WITH A CONTINUED PUSH INTO SOUTHERN INDIANA AND CENTRAL KENTUCKY
DURING THE DAY SUNDAY. CONCERNED SOUTHEAST MISSOURI AND A GOOD
PORTION OF WESTERN KENTUCKY AND SOUTHERN ILLINOIS WILL BE FLIRTING
THE A MINIMUM HEAT INDEX OF 80 TONIGHT WITH DEW POINTS IN THE MID
70S AND LOWS IN THE UPPER 70S. SUNDAY BELIEVE THIS SAME AREA WILL
SEE HEAT INDEX VALUES MID-DAY AND AFTERNOON AROUND OR ABOVE THE 105
MARK. SOUTHWEST INDIANA SHOULD BE THE COOLEST AREA TOMORROW GIVEN
THE EXPECTED DEBRIS CIRRUS SHIELD LEFT OVER FROM TONIGHT/S EXPECTED
UPSTREAM CONVECTION.

SUNDAY NIGHT INTO MONDAY...CONCERNS REMAIN ABOUT THE SAME...THAT OF
WHETHER UPSTREAM MCS DEVELOPMENT WILL PROPAGATE INTO ANY PART OF THE
FA. GUIDANCE SUGGESTS THAT THE TEMPERATURE AND DEW PT PROFILE OF THE
LOWER PORTIONS OF THE TROPOSPHERE WILL BE SIMILAR TO THOSE EXPECTED
TONIGHT AND SUNDAY. GIVEN THIS...WILL GO WITH A SIMILAR FORECAST.

HEADING INTO THE EXTENDED PORTION OF THE FORECAST...MODEL SOLUTIONS
SUGGEST AN AMPLIFICATION OF THE CENTRAL U.S. UPPER HIGH AND A
DEEPENING OF AN EAST COAST UPPER TROUGH. THIS ORIENTATION WILL HELP
TO LOWER HEIGHTS AND SUBSEQUENTLY WEAKEN THE CAP A LITTLE. THIS IN
TURN WOULD HELP INCREASE CHANCES OF OVERNIGHT MCS PROPAGATION ACROSS
AT LEAST THE NORTHERN AND EASTERN PORTIONS OF THE FA STARTING
PERHAPS AS EARLY AS MONDAY NIGHT WITH CHANCES CONTINUING THROUGHOUT 
THE WEEK.

.PAH...HEAT ADVISORY TONIGHT AND SUNDAY
ILZ080-081-084>086-088>094-KYZ001>013-016-017-021-022-MOZ076-086-087-
100-107>112-114.

SLEIGHTER

INZ081-082-085>088-KYZ010-014-015-018>020-071900-

THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE PADUCAH KY
1141 AM CDT SAT JUL 7 2001

THIS THUNDERSTORM OUTLOOK IS FOR SOUTHWEST INDIANA...AND PORTIONS OF
WEST KENTUCKY...VALID UNTIL 600 AM SUNDAY.

THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON ACROSS SOUTHWEST INDIANA
INTO PORTIONS OF WEST KENTUCKY...NORTH OF A LINE FROM MARION TO
CALHOUN.  THERE IS A SLIGHT CHANCE OF STORMS BECOMING SEVERE ACROSS
MAINLY SOUTHWEST INDIANA.

A WARM FRONT EXTENDED FROM EASTERN ILLINOIS INTO WEST KENTUCKY AND
WESTERN TENNESSEE.  AS THIS FRONT MOVES SLOWLY EAST...THE WARM
AND HUMID AIRMASS EAST OF THIS FRONT WILL REMAIN UNSTABLE. ISOLATED
THUNDERSTORMS MAY DEVELOP ACROSS SOUTHWEST INDIANA AND PORTIONS OF
WEST KENTUCKY THIS AFTERNOON.  ALTHOUGH THE BEST INSTABILITY IS TO
THE EAST AND NORTHEAST OF THE REGION...THERE IS A SLIGHT RISK OF ANY
STORMS THAT DO DEVELOP MAY BECOME SEVERE WITH LARGrE HAIL AND GUSTY
WINDS.

STORM MOTION WILL BE TO THE SOUTHEAST AT 20 TO 25 MPH.

SPOTTER ACTIVATION MAY BE NEEDED IF ANY STORMS DEVELOP ACROSS
MAINLY SOUTHWEST INDIANA THIS AFTERNOON.