[LeArc] Forecast Discussion : MLI@ 4/18/2003 4:01:54 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 180859
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
400 AM CDT FRI APR 18 2003

CHALLENGING FORECAST THIS MORNING WITH LARGE DIFFERENCES IN MODEL 
SOLUTIONS LEADING TO LOW CONFIDENCE BEYOND IMMEDIATE SHORT TERM. AM 
FAIRLY CERTAIN MOST OF FORECAST AREA WILL GET SIGNIFICANT RAINFALL 
OVER WEEKEND. THAT...ALONG WITH THREAT OF SEVERE THUNDERSTORMS 
COMPRISE FORECAST CHALLENGE.

LONGWAVE TROUGH MOVING INTO WESTERN CONUS EARLY THIS MORNING WITH 
LEAD SHORTWAVE MOVING OUT OF CENTRAL ROCKIES. WATER VAPOR IMAGERY 
AND RADAR MOSAIC SHOWS THUNDERSTORMS OUT AHEAD OF THIS WAVE 
OCCURRING ON NOSE OF 60 KT JET AT H85 MOVING INTO HIGH PLAINS... 
WHICH IF NOT CONTAMINATED...WAS WELL ABOVE 06Z GUIDANCE VALUES IN 40 
TO 45 KT RANGE. SHORT TERM MODELS ARE IN FAIR AGREEMENT WITH THIS 
LEAD WAVE CLOSING INTO LOW OVER WESTERN SD BY THIS EVENING WITH 
ENERGY EXTENDING SE RIPPLING THROUGH FORECAST AREA AND MID AND UPPER 
FLOW BECOMING MORE DIFFLUENT THIS EVENING. AT SURFACE...EXTENSIVE 
STRATUS TRAPPED UNDER INVERSION FROM SURFACE RIDGE OVER AREA SHOWING 
LARGE HOLES AT 08Z...JUST AS DENSE CI STREAMING AHEAD OF PLAINS 
SYSTEM MOVES IN. 

IN SHORT TERM...WILL HOLD CLOUDY CONDITIONS THROUGH MIDDAY THEN HAVE 
SOME PARTIAL CLEARING IN SOUTHWEST AROUND MIDDAY AS APPROACHING 
ENERGY AND H85 JET BEGINS TO MIX LOW LEVELS. CONVECTION IN HIGH 
PLAINS SHOULD REACH INTO WESTERN AND N CENTRAL IA BY AFTERNOON...BUT 
SHOULD STAY TO WEST IN DAY PERIOD. TEMPERATURES KEPT ON COOL SIDE OF 
MOS GUIDANCE. 

THINGS STILL APPEAR TO BE COMING TOGETHER TONIGHT FOR ELEVATED 
THUNDERSTORMS TONIGHT AS H85 JET DEVELOPS WITH STRONG WARM ADVECTION 
AND DEWPOINTS ABOVE 10 DEG C. META SOUNDINGS INDICATE HIGH SURFACE 
TO 3 KM HELICITY VALUES AND PER SPC DAY 1 SLIGHT RISK...COULD SEE 
SOME HAIL PRODUCERS IN EVENING THEN MAINLY HIGH WIND POTENTIAL LATE. 
WILL LEAVE OUT SEVERE WORDING IN ZONES AND GRIDS TODAY INTO SATURDAY 
NIGHT FOR NOW...BUT OF COURSE FURTHER DESCRIBE IN HWO. KEPT LIKELY 
POPS GOING...WITH EVENING ONSET IN WEST AND MAINLY AFTER MIDNIGHT IN 
EAST. 

WIDE RANGE OF MODEL SOLUTIONS SATURDAY AND BEYOND WITH RESPECT TO 
LOCATION OF SURFACE LOWS. ETA AND ECMWF DEVELOP SECONDARY LOW OVER 
MN/SD...WITH MAIN SURFACE LOW IN SOUTHERN PLAINS. TRIED TO FOLLOW 
ENSEMBLE SOLUTION WITH ONE MAIN LOW OVER TX/OK RIDING NORTHEAST 
ALONG TROUGH AXIS INTO EASTERN IA VICINITY BY SUNDAY. AT MID 
LEVELS...ALL SHOW SIGNIFICANT VORT MAX PUSHING THROUGH LATE 
SATURDAY...THEN ANOTHER WAVE LATE SATURDAY NIGHT INTO SUNDAY. MAIN 
UPPER LOW FILLS AND MOVES INTO GREAT LAKES ON MONDAY. ALL THIS 
WARRANTS KEEPING LIKELY POPS THROUGH SUNDAY...THEN SCATTERED POPS 
INTO EARLY MONDAY. BEYOND...UPPER FLOW CONTINUES TO FORM BLOCKING 
OMEGA PATTERN TOWARD MIDWEEK AND MADE FEW CHANGES TO GRIDS BEYOND 
DAY 3.    

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

$$

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