[LeArc] Forecast Discussion : MLI@ 5/18/2003 2:42:48 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 181942
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
240 PM CDT SUN MAY 18 2003

PLENTY OF CLOUD COVER ACROSS FORECAST AREA THIS AFTERNOON THANKS TO 
SURFACE TO H7 EAST TO SOUTHEAST FLOW PULLING IN MOISTURE FROM 
WEAKENING CYCLONE OVER LOWER MISS VALLEY. THIS HAS LIMITED 
TEMPERATURES TO LOWER 70S SO FAR THIS AFTERNOON. THIS SCENARIO WILL 
CONTINUE INTO MONDAY MORNING WITH LINGERING MOISTURE AND CLOUDS. LOW 
LEVEL WINDS GRADUALLY BECOMING MORE SOUTHERLY...WHICH WILL ADVECT 
LOWER 60S DEWPOINTS NORTHWARD ACROSS AREA. MAIN SHORT TERM CHALLENGE 
IS TEMPERATURES THROUGH MONDAY WITH FOCUS ALSO ON COLD FRONT AND 
ASSOCIATED THUNDERSTORM CHANCES AFTERNOON INTO MONDAY NIGHT.

AT 18Z...COLD FRONT WAS FROM NEAR KGFK TO NEBRASKA PANHANDLE. 12Z 
ANALYSIS HAD LONGWAVE TROUGH WEST OF CONTINENTAL DIVIDE WITH 
DOWNSTREAM RIDGE OVER EASTERN CANADA INTO GREAT LAKES. FORECAST 
MODELS IN FAIR AGREEMENT FILLING UPSTREAM TROUGH AND SCOOTING IT 
BY TO OUR NORTH TUESDAY MORNING. SURFACE COLD FRONT SLIDES EAST TO 
CENTRAL IOWA BY 18Z MONDAY...SHIFTING EAST OF FORECAST AREA BY 06Z. 
SOME MINOR DIFFERENCES APPEAR IN TIMING OF FRONT AND FOLLOWED 
ETA/GFS BLEND. RAISED POPS TO LIKELY FOR LATE AFTERNOON SHOWERS AND 
THUNDERSTORMS WITH SUFFICIENT MOISTURE IN PLACE...MID LEVEL FORCING 
AND FRONTAL CONVERGENCE. KEPT EARLY AFTERNOON ONSET IN FAR WEST. 
LOCAL TECHNIQUES SHOW SEVERE CHANCES MUCH LESS THAN EARLIER 
THINKING...MAINLY DUE TO LIMITED INSOLATION AND RESULTING DECREASE 
IN LOW LEVEL INSTABILITY AND HWO IS BEING UPDATED. HAVE BUMPED HIGHS 
BACK AT LEAST ONE CATEGORY INTO MID TO UPPER 70S...IN MID RANGE OF 
MOS GUIDANCE. IN SHORTER TERM...CLOUD COVER AND INCREASING LOW LEVEL 
MOISTURE TONIGHT WILL PREVENT MUCH COOLDOWN...WHICH ON-GOING GRIDS 
HAVE HANDLED WELL. 

TUESDAY AND BEYOND...CANADIAN SURFACE HIGH SETTLES SOUTHEAST OVER 
AREA THROUGH END OF WEEK WITH COLDEST PERIOD BEING WEDNESDAY MORNING 
WITH HIGH NEARLY OVERHEAD. LOWS IN 40S AND POSSIBLY SOME UPPER 30S 
LOOKS REASONABLE. UPPER LEVEL LOW DEVELOPS OVER GREAT LAKES ON 
FRIDAY WITH UPSTREAM RIDGE OVER WESTERN CONUS RESULTING IN  DEEP 
NORTHWEST FLOW. THIS WILL KEEP TEMPERATURES BELOW SEASONAL NORMALS 
INTO FRIDAY. SATURDAY POPS TRIMMED BACK TO SUNDAY...BUT EVEN THEN 
CONFIDENCE NOT HIGH ON TIMING OF WEAK IMPULSES ROUNDING TOP OF 
WESTERN CONUS RIDGE.  

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

$$

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