[LeArc] Forecast Discussion : MLI@ 7/11/2003 4:10:18 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 112101
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
400 PM CDT FRI JUL 11 2003

VORT MAX EVIDENT ON WATER VAPOR IMAGERY EARLIER TODAY NOW MOVING 
ACROSS NORTHWEST ILLINOIS. THIS WAVE WAS ROTATING AROUND BACKSIDE OF 
NEARLY STACKED LOW OVER NORTHERN LAKE HURON. TSRAS BROKE OUT THIS 
MORNING OVER SW WI AND CONTINUE TO PROGRESS SOUTHEAST MAINLY ALONG 
AND EAST OF MISSISSIPPI RIVER. STRONGEST STORMS HAVE PRODUCED BRIEF 
3/4 INCH HAIL DUE TO RELATIVELY LOW WET BULB ZERO HEIGHTS AROUND 9  
KFT ON MORNING SOUNDINGS. THIS ACTIVITY SHOULD DISSIPATE BY EARLY 
EVENING AS MID LEVEL SUPPORT SLIDES SOUTHEAST AND WE PASS MAX 
HEATING.

TONIGHT THROUGH SATURDAY AFTERNOON...MAIN CHALLENGE IS TEMPERATURES.
MUCH LIKE LAST NIGHT...DIURNAL CLOUDS SHOULD DISSIPATE IN EVENING 
WITH ALL AREAS CLEAR BY MIDNIGHT. DEWPOINTS AND UPSTREAM LOWS 
SUPPORT ANOTHER COOL AND DRY JULY NIGHT WITH LOWS AGAIN IN UPPER 50S 
TO AROUND 60 AND THUS WENT CLOSE TO COOLEST GUIDANCE. 
SATURDAY...HIGH CURRENTLY OVER DAKOTAS SLIDES EAST AS LOW OVER GREAT 
LAKES PUSHED INTO CANADA. TRIMMED BACK GOING SCATTERED AFTERNOON TO 
SLIGHT CHANCE FOR NE HALF...AS AIRMASS PROGGED TO BE MORE STABLE 
THAN TODAY WITH MUCH WEAKER WAVE IN NW H5 FLOW AND ALSO LACKING THE 
FAVORABLE H25 JET LEVEL WINDS ASSISTING CURRENT CONVECTION. MORE 
SUNSHINE THAN ANTICIPATED OVER THE HAS PUSHED TEMPERATURES A BIT 
ABOVE WARMEST GUIDANCE HIGHS FOR TODAY...AND THUS WENT CLOSE TO 
PERSISTENCE AND SLIGHTLY ABOVE WARMER MAV GUIDANCE FOR SATURDAY.  
...SHEETS

SATURDAY NIGHT...
LINGERING SHOWERS WILL DISSIPATE AROUND SUNSET. SURFACE HIGH THEN 
BUILDS IN PROVIDING CLEAR SKIES AND LIGHT WINDS. WITH NEARLY IDEAL 
RADITIONAL COOLING SETUP...WENT AT OR JUST BELOW LOW END OF GUIDANCE 
ON MINS. 

SUNDAY AND SUNDAY NIGHT...
SOME MODERATION IN BL TEMPS...BUT LITTLE CHANGE ABOVE...SO TACKED ON
COUPLE 2 DEGS TO MAXES EXPECTED ON SAT. OTHERWISE...LITTLE 
WX OF CONSEQUENCE WITH PLENTY OF SUNSHINE AS SURFACE HIGH GRADUALLY 
SHIFTS EAST WITH RETURN FLOW SETTING UP LATE. 
SOUTH WINDS WILL BRING AN INCREASE IN MOISTURE SUNDAY NIGHT RESULTING
IN WARMER MINS.

MONDAY AND MONDAY NIGHT...
GFS APPEARS TO BE SUFFERING FROM CONVECTIVE FEEDBACK...THUS 
DISREGARDED CONVECTIVELY INDUCED VORT MAX AND QPF. 
PRESSURE GRADIENT INCREASES WITH SOUTH BREEZES USHERING IN 
WARMER AIR AHEAD OF NEXT FRONT DIVING THROUGH THE UPPER MIDWEST AND
PLAINS. PARAMETERS APPEAR IN PLACE FOR MCS DEVELOPMENT
ALONG THE FRONT MONDAY EVENING ACROSS PORTIONS OF MN/SD/NE WITH 
FAVORABLE MEAN FLOW AND FORWARD PROPAGATING CORFIDI VECTORS 
TO CARRY DEBRIS ACROSS THE NORTH LATE MONDAY NIGHT. THEREFORE
EXPANDED POPS TO INCLUDE AREAS ALONG AND NORTH OF I-80.   

EXTENDED (TUE-FRI)...
FRONTAL PASSAGE SLATED TUE WITH MEDIUM RANGE MODELS STILL OFFERING 
TIMING DIFFERENCES...THOUGH MINOR ENOUGH TO HAVE LITTLE 
IMPACT ON FORECAST. KEPT CHC POPS TUE/TUE EVE BUT BUMPED UP INTO THE
HIGHER END. GFS INDICATING DECENT DIFFLUENCE ALOFT AND LIFT FROM
RIGHT ENTRANCE REGION OF H3 JET. IF LATER RUNS CONTINUE 
ADVERTISING THESE DYNAMICS THEN WILL NEED TO CONSIDER RAISING POPS.
CANADIAN HIGH THEN BUILDS IN BEHIND THE FRONT MIDWEEK WITH 
MODELS VARYING SOME ON STRENGTH. ECMWF IS ADVERTISING 1030 MB HIGH!
UKMET IS A TAD WEAKER THOUGH STILL SHOWING A DECENT HIGH 
FOR MID JULY (1024 MB) ENSURING A NICE STRETCH OF WX WED INTO FRI.
DEPENDING UPON THE STRENGTH OF THE HIGH...TEMPS COULD BE
FEW DEGS COOLER THAN GOING FORECAST. THIS WILL NEED TO BE WATCHED.

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

$$