[LeArc] Forecast Discussion : MLI@ 7/28/02 3:04:56 AM

[learc@mailman.qth.net]

The following weather message is provided by McDonough County E.S.D.A.


FXUS63 KDVN 280805
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
300 AM CDT SUN JUL 28 2002

LATEST SFC AND MSAS ANALYSIS INDICATING UPPER MIDWEST AWASH IN A
COMPLEX MAZE OF WEAK TROUGHS AND OUTFLOW BOUNDARIES. ONE SUCH SFC
BOUNDARY OF CONSEQUENCE TO LOCAL CWA IS ALIGNED FROM SOUTHWEST
INTO NORTHEAST IA ATTM...WITH SOUTH TO SOUTHWEST WINDS INTO THIS
FEATURE MAINTAINING MOISTURE CONVERGENCE AND HIGHER DPT POOL OVER
MUCH OF EASTERN IA INTO NORTHWEST IL. 00Z UA ANALYSIS INDICATED
STRONG MID LEVEL CAP INHIBITING OR KILLING ANYTHING THAT TRIES TO GET
GOING...BUT PULSING ACCAS FIELDS OVER THE CWA STILL MAKES FOR A
NERVOUS WATCH.

FIRST BIG QUESTION IS FOR POSSIBLE NEED OF HEAT ADVISORY FOR CWA
TODAY INTO TONIGHT. FORECAST SOUNDINGS AND MIXING POTENTIAL...H85 AND
CRITICAL THICKNESS TEMPS AND ADVECTION...PLUS TRAJECTORIES FROM
SOUTHWEST MO/NORTHEAST OK SUGGEST HIGHS IN MID TO UPPER 90S...AND
WITH POOLED SFC DPTS AT LEAST IN MID 70S...ADVISORY CRITERIA SHOULD
BE MET AND HELD BOTH TODAY AND TONIGHT BEFORE COOLING CONVECTION
HITS. BUT...THE CWA IN LINE AGAIN FOR CONVECTIVE DEBRIS/BLOW-OFF FROM
KS MCS...COMBINED WITH ANY LOCAL LINGERING MID LEVEL CLOUDS...SHOULD
TEMPER FULL INSOLATION AFFECT. ALSO HIGH AMBIENT MOISTURE ALSO HARDER
TO HEAT...AND MAY LIMIT HIGH TEMPERATURE POTENTIAL. SOUTHWEST SFC
FLOW TODAY MAY ALSO ADVECT SOMEWHAT LOWER DPT AIR OUT OF CENTRAL
MO...AS WELL AS HELP MIX OUT HIGHER DPT POOL IN PLACE. SO IT WILL BE
CLOSE EITHER WAY...BUT WILL BANK ON HIGHS IN LOW TO MID 90S WITH MID
70 DPTS...THUS WILL GO WITH HEAT ADVISORY.

SHORT RANGE MODELS SUGGEST SECONDARY WARM FRONTAL-TYPE BOUNDARY TO
LIFT UP AND ENHANCE OVER NORTHEAST MO AND WESTERN IL TODAY...WITH
PRECIP THREAT ALONG AND NORTH OF IT. WITH ONGOING MID LEVEL WARM DOME
AND WEAK FORCING ALONG THIS FEATURE...DON/T THINK MUCH WILL HAPPEN...
BUT SINCE POPS ALREADY IN PACKAGE ACRS THE SOUTH WILL KEEP LOWER
CHANCES GOING EVEN WITH LIMITED POTENTIAL. AVN REALLY APPEARS TO BE
OVERDOING PRECIP THREAT TODAY OVER SOUTH HALF OF THE CWA...THANKS IN
PART TO FEEDBACK ENHANCED VORT BALL ROLLING OUT ACRS THE AREA FROM
THE CENTRAL PLAINS.

STILL APPEARS MAIN CONVECTIVE SHOW TONIGHT AS MORE SIGNIFICANT SHORT
WAVE ROLLS OUT OF THE NORTHERN ROCKIES AND DIGS ACROSS THE MIDWEST
TONIGHT. MAIN NORTH-TO-SOUTH ORIENTED COLD FRONT ASSOCIATED WITH THE
UPPER LEVEL FEATURE MAY NOT CROSS THE MS RVR TO MID MONDAY MORNING...
IF SLOWING MODEL PROGS AND TIMING KEEP THEIR TRENDS. WITH WARM
CAPPING DOME IN PLACE...CONVECTION MAY BY LIMITED TO PROXIMITY OF
FRONTAL FORCING...AND MAY PUSH BEST CONVECTIVE CHANCES TO AFTER
MIDNIGHT AND ESPECIALLY MONDAY MORNING.


.DVN...
IA...HEAT ADVISORY FOR EASTERN IOWA TODAY AND TONIGHT.
IL...HEAT ADVISORY NORTHWEST AND WEST CENTRAL ILLINOIS TODAY AND
     TONIGHT.
MO...HEAT ADVISORY FOR FAR NORTHEASTERN MISSOURI TODAY AND TONIGHT.

JDH