[LeArc] Forecast Discussion : MLI@ 9/28/02 2:22:57 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 281927
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
227 PM CDT SAT SEP 28 2002

VISIBLE SATELLITE IMAGERY SHOWED STRATUS HAD LIFTED OVER ENTIRE CWA 
EARLY THIS AFTERNOON. 18Z SURFACE ANALYSIS HAD MAIN SURFACE LOW OVER 
EASTERN CO WITH SECONDARY LOW OVER NORTH CENTRAL KS WITH WARM FRONT 
EXTENDING E-SE THROUGH NORTHERN MO TO NEAR STL. WEAKER WARM 
FRONT/TROF AIDED BY DIFFERENTAL HEATING FROM STRATUS FIELD STRETCHED 
FROM SW IA INTO NW IL. BROAD SW FLOW DOMINATING UPPER LEVELS HAD A 
COUPLE SIGNIFICANT SHORTWAVES THAT WILL HELP TRIGGER CONVECTION 
MAINLY NORTH OF MAIN FRONT TO IMPACT CWA TONIGHT. INITIAL FORECAST 
CHALLENGE IS SHOWER AND THUNDERSTORM POTENTIAL TONIGHT AND EARLY 
SUNDAY...THEN HOW WARM TEMPERATURES WILL SOAR AS ENTIRE AREA GETS 
INTO WARM SECTOR SUNDAY THROUGH MONDAY. 

META HAD BEST DEPICTION OF DOUBLE LOW STRUCTURE IN HIGH PLAINS AT 
18Z....BUT ALL WERE NOT FAR OFF WITH ONE LOW IN VICINITY AND TROF 
EXTENDING NE. WATER VAPOR IMAGERY SHOWED TWO SIGNIFICANT 
SHORTWAVES...ONE PRODUCING SCATTERED TSRA IN MN WITH TAIL END 
AIDING ELEVATED CONVECTION IN SW IA...AND OTHER CHURNING INTO SW 
NEB. AVN HAD BEST HANDLE ON THE STRENGTH AND LOCATION OF THE HIGH 
PLAINS VORT AND THUS FAVOR ITS SLIGHTLY FASTER MOVEMENT OF 
FEATURE...WHICH SENDS UPPER FORCING ACROSS CWA AROUND 06Z AND 
EXITING EAST BY 12Z. 18Z PRESSURE FALL AXIS AND ETA/AVN BLEND POINT 
TOWARD ONE MAIN WARM FRONT FROM SW IA TO NEAR DBQ BY 06Z TONIGHT. 
CONVERGENCE ALONG FRONT AND LOW LEVEL JET JUST TO ITS SOUTH WILL BE 
ENOUGH FOR CONTINUED LIKELY POPS FOR SHRA/TSRA OVER ALL BUT FAR 
SOUTHERN ZONES...WHERE WILL CONTINUE CHANCE POPS. WILL CONFINE 
POSSIBILITY OF LINGERING SUNDAY MORNING SHOWERS TO NW IL ZONES 
FOLLOWING AVN TIMING.
 
WARM FRONT LIFTS N OF CWA AND WASHES OUT SUNDAY WITH DEEP S-SW FLOW 
AND WARM ADVECTION CONTINUING. LOOKING AT TEMPERATURE TRENDS 
TODAY...FORECAST H85 TEMPERATURES...AND WHAT IS HAPPENING IN 
SOUTHERN PLAINS...GUIDANCE TEMPERATURES SHOOTING TO NEAR 90 IN FAR 
NW MO ZONES DO NOT LOOK TOTALLY OUT OF QUESTION. WILL RAISE ONE OR 
TWO CATEGORIES TO RANGE OF NEAR 80 NE TO UPPER 80S SW. SOME CONCERN 
FOR NOCTURNAL TSRA AS VORT MOVES THROUGH LATE MONDAY NIGHT WITH LOW 
LEVEL JET POSSIBLY A PLAYER...BUT WILL LEAVE OUT MENTION FOR NOW. 
MONDAY NOT AS WARM WITH MORE CLOUDS EXPECTED...BUT STILL MILD AND 
ABOVE NORMAL. SOUTHERN CANADIAN SHORT WAVE TO PUSH SURFACE COLD 
FRONT THROUGH TUESDAY FOR NEXT SIGNIFICANT RAIN CHANCES THAT WILL 
CONTINUE INTO WEDNESDAY AS WAVE MOVES ALONG STALLED FRONT TO SOUTH. 
MID TO LATE WEEK WILL BE MUCH COOLER AND DID NOT STRAY FAR FROM 
GUIDANCE HIGHS IN 60S. STILL SOME MEDIUM RANGE MODELS DISAGREEMENT 
ON TIMING OF NEXT WESTERN CONUS UPPER TROUGH KICKING OUT AROUND 
FRIDAY AND SATURDAY. FOR NOW WILL CONTINUE WITH MRF RAIN CHANCES FOR 
FRIDAY AND INTRODUCE SATURDAY AS DRY AND COOL.  

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

DLS