[LeArc] Forecast Discussion : MLI@ 8/18/02 2:32:14 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 181935
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
230 PM CDT SUN AUG 18 2002

ALL SIGNALS POINT TO ACTIVE NIGHT...WITH POTENTIAL FOR HEAVY RAIN AND SOME
LARGE HAIL WITH ELEVATED CONVECTION...ESPECIALLY SOUTHERN HALF OF CWA.  

STRONG SHORTWAVE MOVING INTO NORTHERN PLAINS EARLY THIS AFTERNOON. 
18Z SURFACE ANALYSIS SHOWS FRONTAL ZONE EXTENDING ROUGHLY FROM NORTHERN MO 
INTO CENTRAL IL NEAR A LINE FROM MCI TO UIN. STRONG THERMAL AND
MOISTURE GRADIENT OVER THE FRONTAL ZONE WITH TEMPS IN THE L70S AND DEWPTS
IN M/U40S IN NORTHEAST IA...WHILE TEMPS IN 90S AND DEWPTS IN 70S
IN CENTRAL/SOUTHERN KS AND SOUTHWEST MO. MODELS AGREE ON SHORTWAVE DIVING
E/SE ACROSS THE PLAINS AND MIDWEST NEXT 24 HRS...INDUCING WAVE ALONG
FRONTAL ZONE. DISCREPANCIES EXIST WITH QPF (AMOUNTS/PLACEMENT) AND
LOCATION OF FRONT AND WAVE. OVERALL LEANING TOWARD FURTHER SOUTH
POSITIONING INDICATED BY AVN AND UKMET. PRESSURE FALLS AT 18Z WOULD SUGGEST 
FRONTAL ZONE TO LIFT INTO THE FAR SOUTH. INDICATIONS ARE STRONG
CONVECTION LIKELY TO GO IN THE NEXT COUPLE OF HOURS OVER PORTIONS OF SOUTHEAST 
NE...NORTHWEST MO...SOUTHWEST IA AND NORTHEAST KS AS SHORTWAVE BEGINS
TO EXERT INFLUENCE. CONVECTION SHOULD ORGANIZE WHILE TRACKING E/SE ON COOL
SIDE OF FRONTAL ZONE ON NOSE OF VEERING AND STRENGTHENING LLJ. 
HEAVIEST QPF WOULD APPEAR TARGETED FOR THE SOUTH...AND COULD POSSIBLY FALL
JUST SOUTH OF OUR CWA. MUCH OF REGION SHOULD SEE PCPN WITH DECENT 
ISENTROPIC LIFT AND UPPER LEVEL DIVERGENCE. EXPECT MAINLY RAIN WITH EMBEDDED 
THUNDER HEADING NORTH OF I-80 AS PCPN STRATIFIES IN COOLER AIRMASS. PW/S 
CLIMBING TO NEAR 2 INCHES AND FORCING CERTAINLY SUGGEST THREAT FOR HEAVY RAIN...
BUT WILL HOLD OFF ON ANY HIGHLIGHTS AS FFG VALUES GENERALLY AROUND 
2 INCHES IN SOUTH. COULD GET INTO SOME PROBLEMS WITH ANY BACKBUILDING...BUT
OVERALL THINK POTENTIAL MAINLY NUISANCE OR MINOR FLOODING.  
WILL CONTINUE MENTION HEAVY RAIN IN SOUTH. PRECIPITATION SHOULD BE ENDING
IN THE SOUTH AND EAST BY MID MORNING ALTHOUGH CONFLUENT FLOW WOULD
KEEP CLOUDS AND POSSIBLY -DZ LINGERING UNTIL MIDDAY...WITH SOME SUNSHINE 
RETURNING IN THE AFTERNOON. TEMP FORECAST WILL BE TRICKY WITH
WET GROUND AND CONCERNS WITH EXTENT OF SUNSHINE. OVERALL...CURRENT FORECAST
LOOKS GOOD...STAYING ON LOW END OF GUIDANCE MINUS COUPLE FEW DEGS. SURFACE HIGH
BUILDS IN MON NIGHT WITH QUIET CONDITIONS. SOME FOG POSSIBLE WITH WET GROUND
BUT WILL LET LATER SHIFTS RE-EVALUATE POTENTIAL. 
 
TUE-TUE NIGHT...
GREAT LAKES HIGH IN CONTROL WITH RIDGE AXIS THROUGH CWA. LLVL E/SE FLOW NOT
CONDUCIVE FOR MUCH WARMING...THUS WILL REMAIN ON LOW END OF GUIDANCE.
WARM FRONT LIFTS NORTH OVER REGION TUE NIGHT-EARLY WED WITH
POTENTIAL FOR CONVECTION. MAIN FOCUS APPEARS TO OUR WEST THROUGH THE PLAINS
ON NOSE OF LLJ AND WARM ADVECTION WITH MCS POTENTIAL. IF MCS DEVELOPS
IT SHOULD TRY TO RIDE E/SE ALONG BAROCLINIC ZONE WHICH WILL BE ADVANCING
NORTHWARD THROUGH CWA...THUS NORTHERN SECTIONS WOULD STAND BEST SHOT AT SEEING 
RAIN. FOR NOW WILL GO WITH CHANCE POPS HIGHEST IN THE NORTH.  

VERY WARM AND HUMID CONDITIONS RETURN MIDWEEK WITH FRONTAL ZONE TO THE NORTH.

EXTENDED (THU-SUN)...
MODELS IN REASONABLE AGREEMENT ON OVERALL PATTERN...WITH SOME TIMING
ISSUES. NEXT SHORTWAVE DIVES SOUTH FROM CANADA LATE WEEK.
IN RESPONSE...FRONTAL ZONE TO OUR NORTH WILL MOVE BACK SOUTH ACROSS THE
REGION PROVIDING FOCUS FOR SHOWERS/TSTMS. AVNX SLOWEST WITH FRONTAL
PASSAGE WITH PCPN LINGERING INTO SAT. STAYED WITH WARM
FMR GUIDANCE AHEAD OF FRONT TACKING ON A COUPLE DEGS...THEN POST FRONTAL 
SIDED TOWARD COOLER MEX GUIDANCE. MODELS ADVERTISE REX BLOCK IN THE
WESTERN US OVER THE WEEKEND WITH TROUGH OVER EASTERN CONUS. 
MRF LOOKS TOO QUICK TO BUILD UPPER HEIGHTS AND WARMING INTO THE REGION IN
THIS PATTERN...THUS WILL STAY BELOW GUIDANCE WITH DECENT COOLING
POTENTIAL BY SUN. 
  
COORD FROM ILX AND LSX...THANX!

.DVN...
IA...NONE.
IL...NONE.
MO...NONE.