[LeArc] Forecast Discussion : MLI@ 7/7/2003 3:38:18 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 072029
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
330 PM CDT MON JUL 7 2003

CONVECTIVE INITIATION AND PROPAGATION OF THUNDERSTORMS AND WHAT THEY 
MAY PRODUCE AGAIN THE MAIN NEAR TERM CONCERNS FOR TONIGHT. FIRST 
CONCERN LOCALLY IS POTENTIAL FOR THUNDERSTORM INITIATION ALONG LLVL 
COOL FRONT EXTENDING FROM SOUTHWEST WI...TO DSM VCNTY...AND ACRS 
SOUTHWEST IA. BOUNDARY IS POOLING MID 70 DPTS IN SOUTH CENTRAL TO 
EASTERN IA ATTM...AND WITH INSOLATION CAUSING TEMPS TO REACH THE 
UPPER 80S TO LOWER 90S EVEN IN SUCH A HUMID ENVIRONMENT...THE DVN 
CWA HAS BECOME UNSTABLE AND "LOADED". LAPS INDICATED CAPES HAVE 
GROWN TO AROUND AROUND 5K J/KG OVER THE ENTIRE CWA. KDVN SPECIAL 18Z 
SOUNDING SHOWS GOOD CAP AT AROUND H85-H7 MB CURRENTLY KEEPING LID ON 
DEVELOPMENT...BUT VEERING FLOW NOTED ON SAME SOUNDING AT AROUND 10K 
FT TROUBLESOME...AS NORTHWEST FLOW AT THIS LEVEL WOULD EVENTUALLY 
TAP INTO COOLER TEMPS AT CAP LEVEL FOR WEAKENING MIX-OUT. ALSO 
WATCHING SOME CU ENHANCEMENT ALONG THE BOUNDARY IN NORTHEAST AND 
CENTRAL IA ON CURRENT VIS SATELLITE LOOP. THUS POTENTIAL THERE FOR 
INITIATION RIGHT OVER THE LOCAL AREA THIS EVENING AS WEAK VORT SEEN 
ON W/V IMAGERY OVER SD PUSHES TOWARD NORTHERN IA FOR SOME UPPER 
SUPPORT.

SECOND AREA OF CONCERN AND MAIN LIFTING/FORCING THAT SHOULD TAKE 
PLACE THIS EVENING INDICATED BY BOTH THE GFS AND ETA/META...WILL 
LOOK TO BE FROM SOUTHEAST NE INTO WEST CENTRAL AND SOUTHWEST IA. 
MODELS INDICATE 30-40 KT LLVL JET TO IMPINGE ON LLVL BOUNDARY OUT 
THERE FROM 00Z-06Z TUE...FOR PROBABLE MCS DEVELOPMENT. THICKNESS 
PARAMETERS AND SECONDARY H85 THTA-E GRADIENT SUGGEST THIS ACTIVITY 
WILL PROPAGATE TOWARD THE SOUTH HALF OF THE DVN CWA LATER TONIGHT 
...FEEDING ON VEERING H85 JET AND ASSOCIATED THTA-E INFLUX AND 
CONVERGENCE. UNCERTAINTY WITH WHAT MAY HAPPEN LOCALLY THIS EVENING 
...AND POSSIBLE RESULTANT COOL POOL AND LOCAL AIRMASS MODERATION IF 
SOME CONVECTION WERE TO TAKE PLACE...WOULD HAVE AFFECT ON 
THIS LATE NIGHT POTENTIAL. IF LITTLE OR NOTHING OCCURS THIS 
EVENING LOCALLY IN VIEW OF FRONT(THAT SHOULD SAG ACRS THE NORTHERN 
CWA IN A WEST-TO-EAST FASHION OVERNIGHT AND ALMOST WASH-OUT) 
...INCOMING MCS SHOULD BE OF THE SVR STRAIGHT LINE WIND PRODUCING 
VARIETY FEEDING ON BOTTLED-UP INSTABILITY. BLEP TECHNIQUE SUGGESTS 
80 MPH WINDS POSSIBLE IF THIS COMPLEX CAME INTO CURRENT UNMODIFIED 
AIRMASS. WITH UNCERTAINTIES ON LOCATION AND STORM DEVELOPMENT...WILL 
SIDE AGAINST FLOOD WATCH FOR TONIGHT...ALTHOUGH SOME NORTHERN 
COUNTIES THAT RECEIVED HEAVY RAINFALL EARLY THIS MORNING WARRANT A 
WATCH IF IT WAS DETERMINED THAT THEY WOULD LIKELY GET HIT AGAIN. 
WILL STILL WORD HEAVY RAINFALL POTENTIAL IN ZONES. OVERNIGHT LOWS 
WILL RANGE FROM THE 60S NORTH...BUT MAY BE KEPT UP WELL INTO THE 70S 
ACRS THE SOUTH AHEAD OF BOUNDARY. COOLING STORM OUTFLOW MAY BE A 
FACTOR THOUGH IN TEMPERING LOWS EVEN IN THE SOUTH TO AROUND 70 OR 
UPPER 60S.    ...HLADIK...


TUESDAY MORNING THROUGH THURSDAY MORNING
MODELS ARE IN GOOD AGREEMENT SHOWING NORTHWEST FLOW DEVELOPING OVER 
THE REGION DURING THE PERIOD.  NW MID LEVEL FLOW WILL FINALLY PUSH 
BOUNDARY SOUTH OF CWA.  ETA/NGM ARE MORE AGRESSIVE WITH THE 
SOUTHWARD PUSH OF THE FRONT BY WEDNESDAY.  THE GFS/UKMET HOLD THE 
FRONT OVER CENTRAL/SOUTHERN IOWA UNTIL WELL INTO THE DAY WEDENSDAY.
THE MODEL TREND WITH THIS BOUNDARY HAS BEEN TO MOVE THE FRONT TO 
FAST TO THE SOUTH AND WILL FAVOR THE MORE NORTHERN SOLUTION OF THE 
GFS/UKMET.  THE GFS/UKMET ARE ALSO IN GOOD AGREEMENT WITH THE 
SURFACE LOW MOVING ALONG THE BOUNDARY TUESDAY NIGHT AND WEDNESDAY.  
THE GFS HAS BEEN POINTING TO THIS SCENARIO FOR THE LAST SEVERAL 
RUNS.  THE ETA IS COMING AROUND TO THE GFS SOLUTION BUT AGAIN...IT 
APPEARS TO BE TO FAR SOUTH. TIMING OF MCS ACTIVITY TONIGHT SHOULD 
PUT TSRA OVER THE NORTHERN HALF OF THE CWA AROUND EARLY TUESDAY 
MORNING AND WILL BUMP POPS UP TO LIKELY CATEGORY.  WITH BOUNDARY 
SETTLING IN THE VICINITY OF HWY 34 DURING THE DAY AND GFS SHOWING H7 
TEMPS COOLING SIGNIFICANTLY REDUCING THE CAP...WILL CONTINUNE CHANCE 
POPS CWA WIDE DURING THE AFTERNOON AND EVENING. SURFACE LOW DROPPING 
OUT OF THE PLAINS WILL FORCE THE FRONT BACK NORTH SOME...FOCUSING 
TSRA MORE OVER THE NORTHERN HALF OF THE CWA.  WILL GO WITH LIKELY 
POPS...ESPECIALLY AFTER MIDNIGHT.  WILL CONTINUE CHANCE POPS ALL 
AREAS WEDNESDAY AND WEDNESDAY NIGHT AS SURFACE LOW TRACKS ACROSS 
NORTHERN MISSOURI INTO ILLINOIS. IF GFS/UKMET SOLUTION IS 
CLOSE...THEN FFA MAY BE NEEDED BY MID WEEK.  GOING TEMP FORECAST 
THROUGH THE PERIOD IS ON TRACK AND AGREES WITH CURRENT THINKING...SO 
ONLY MINOR ADJUSTEMENTS WERE MADE.

THURSDAY THROUGH MONDAY
MODELS IN GOOD AGREEMENT IN MAINTAINING NW FLOW OVER CWA THROUGH 
MOST OF THE PERIOD.  BASED ON GFS...HAVE BACKED OFF ON TEMPS SOME 
THROUGH THE WEEKEND...BUT NOT QUITE AS COOL AS THE MEX NUMBERS.  
GFS AND EUROPEAN MODELS STILL SHOWING A WEAK FRONTAL BOUNDARY
MOVING THROUGH THE CWA SUNDAY AND WILL CONTINUE WITH LOW CHANCE 
POPS.  STRONG H5 TROF PROGGED TO MOVE INTO NORTHWEST U.S. BY 
MONDAY.  GFS WINDS UP A STRONG SURFACE LOW TO OUR WEST WHICH PULLS A 
WARM FRONT NORTH INTO THE MID MISSISSIPPI VALLEY.  THIS SYSTEM LOOKS 
TO STRONG FOR MID JULY. FOR NOW WILL GO WITH LOW CHANCE POPS MONDAY 
AND WAIT TO SEE HOW LATER RUNS HANDLE SYSTEM.  DLF


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


$$