[LeArc] Forecast Discussion : MLI@ 8/14/2003 3:40:44 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 140837
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
337 AM CDT THU AUG 14 2003

UPPER LOW THAT ORIGINATED IN GREAT LAKES REGION EARLIER THIS WEEK 
WAS OVER CENTRAL TEXAS THIS MORNING WITH INVERTED TROUGH EXTENDING 
NORTHEAST INTO EASTERN IA EARLY THIS MORNING. VORT LOBES IN UNUSUAL 
S-SE FLOW DRIFTING TOWARD AREA. THIS...ALONG WITH ABUNDANT LOW LEVEL 
MOISTURE AND WEAK TROUGH TO SOUTH...HAS RESULTED IN SHOWERS AND FEW 
TSRA DRIFTING NORTH-NW ACROSS CENTRAL IL THIS MORNING. MAIN FORECAST 
CHALLENGE IS POPS IN SHORT TERM AND AGAIN OVER WEEKEND. 

GFS SEEMS TO HAVE BEST HANDLE ON THE LOCATION AND INTENSITY OF MID 
LEVEL FEATURE MOVING INTO CENTRAL IL. STRONGER VORT MAX WAS AT TIP 
OF TROUGH MOVING THROUGH CENTRAL IA...BUT THIS FEATURE WILL REMAIN 
TO WEST AS INVERTED TROUGH DRIFTS WEST. AT SURFACE...A WEAK TROUGH 
AXIS WAS FROM SOUTHEAST MO TO SOUTHERN IL AT 06Z. AREA 88DS SHOW 
ISOLATED SHOWERS MOVING NORTH APPROACHING SOUTHEAST ZONES...BUT 
CONTINUE TO WEAKEN WITH BETTER COVERAGE SHOWING UP FURTHER EAST 
HEADING TOWARD CHI. WENT AHEAD AND THREW IN SCATTERED TO ISOLATED 
MORNING SHOWERS...BUT BETTER CHANCES FOR SHOWERS AND TSRA WILL BE IN 
AFTERNOON AS SURFACE TROUGH APPROACHES ALONG WITH THE WEAK MID LEVEL 
FORCING. WITH SURFACE DEWPOINTS FROM 65 TO 70 AND AT LEAST PARTIAL 
SUNSHINE...WE SHOULD SEE CAPES APPROACH META VALUES EXCEEDING 1000 
J/KG IN SOUTHEAST. RAISED POPS TO 40 PERCENT SOUTHEAST FOR AFTERNOON 
SHOWERS/TSRA...TAPERING TO 20 PERCENT IN FAR NORTHWEST FOR 
AFTERNOON. 

TONIGHT...THE UPPER TROUGH SHIFTS TO WEST WITH FLAT UPPER RIDGE 
REBUILDING FROM SOUTH TO END PRECIP CHANCES. LIGHT FLOW AND 
LINGERING LOW LEVEL MOISTURE WILL SET STAGE FOR FOG...AS WE HAVE 
SEEN MUCH OF THIS WEEK. DIFFERENCE TONIGHT WILL BE ADDED GROUND 
LEVEL MOISTURE WHERE SHOWERS OCCURED. HAVE PUT IN AREAS OF FOG...AND 
WILL LET DAYSHIFT EVALUATE DENSE FOG THREAT AS DAYTIME RAIN COVERAGE 
BECOMES MORE APPARENT AND AMOUNT OF CLOUDS TONIGHT IS MORE EASILY 
DISCERNED. FRIDAY AFTERNOON...BOTH ETA AND GFS SHOW SHORTWAVE IN NW 
FLOW AROUND DEVELOPING UPPER RIDGE AND THIS COULD PRODUCE MORE TSRA 
DURING PEAK HEATING...ESPECIALLY IN EAST. WILL LET ANOTHER MODEL RUN 
VERIFY THIS TREND AND NOT INTRODUCE YET AND ALSO KEEP GRID 
COORDINATED WITH SURROUNDING WFOS.

SATURDAY EVENING...CANNOT IGNORE GFS AND ETA BRINGING COLD FRONT AND 
DECENT SHORTWAVE IN MID LEVEL THROUGH AREA IN AFTERNOON AND BROUGHT 
IN CHANCE AFTERNOON POPS FOR EAST. WITH FOCUS ON SHORT TERM 
CHALLENGES...MADE FEW CHANGES TO EXTENDED BEYOND SATURDAY NIGHT... 
BUT QUICK LOOK AT LATEST MEDUIM RANGE GUIDANCE SHOWS SUNDAY 
NIGHT/MONDAY PRECIP CHANCES IN DOUBT WITH UPPER RIDGE RETURNING FOR 
DRY WEATHER THROUGH MID WEEK.  

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

$$

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