[LeArc] Forecast Discussion : MLI@ 6/8/2003 4:23:25 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 082110
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
410 PM CDT SUN JUN 8 2003

UPPER LOW POSITIONED OVER SOUTHERN WI. VORT MAX SHOWS UP NICELY IN RADAR AND
SATELLITE PICS OVER NORTHEAST IL NEAR KORD. SOME BREAKS IN CLOUDS COUPLED
WITH COLD POOL ALOFT HAS RESULTED IN SCATTERED CONVECTION 
THROUGOUT CWA...ESPECIALLY NORTH OF HIGHWAY 34. NEXT SHORTWAVE TO IMPACT
REGION CURRENTLY POSITIONED OVER WESTERN CAN IN SOUTHERN BC. 

MAIN FORECAST CONCERNS FOCUS ON POTENTIAL FOR CLEARING AND FOG...AND LOW TEMPS
TONIGHT...THEN PRECIPITATION CHANCES LATE MON-TUE...AND POTENTIAL
FOR ACTIVE PATTERN FEATURING LOCALLY EXCESSIVE RAINS AND STRONG CONVECTION
BY WEEKS END. 

SCATTERED CONVECTION OVER AREA DRIVEN LARGELY BY SOLAR INSOLATION...THUS
ONCE THE SUN SETS SHOULD SEE IT DIE OUT QUICKLY. ALSO...EXPECT SOME 
PARTIAL CLEARING...AND WITH WINDS DYING OFF AND WET GROUND NOT OUT OF THE 
QUESTION TO SEE SOME FOG. LOWS WILL BE TRICKY...AS THERE IS 
POTENTIAL TO BE COLDER THAN GOING FORECAST SHOULD CLEARING BECOME MORE 
DOMINANT AND OCCUR SOONER THAN EXPECTED...SIMILAR TO A FEW NIGHTS AGO. 

MONDAY WILL BE QUIET WITH SURFACE RIDGE MOVING THROUGH. RIDGE SHIFTS 
QUICKLY EAST MONDAY NIGHT WITH WARM ADVECTION DEVELOPING AHEAD
OF NEXT SYSTEM. SOME PRETTY BIG DIFFERENCES BETWEEN MODELS ON TIMING AND
LOCATION OF SURFACE LOW AND DYNAMICS...WITH GFS BEING FURTHEST NORTH...THOUGH
TRENDING SOUTH FROM 06Z RUN...AND NGM FURTHEST SOUTH. 
18Z META NOW SHIFTING SURFACE LOW FURTHER NORTH INTO WI FROM 12Z RUN...SO
SYSTEM GIVING MODELS FITS TO SAY THE LEAST. REGARDLESS...STRONG
WARM ADVECTION SHOULD BE ENOUGH TO FUEL NOCTURNAL CONVECTION...AND DEPENDING 
UPON WHICH MODEL POTENTIAL EXISTS FOR MCS TO AFFECT PORTIONS OF CWA.
BASED ON LATEST META WITH A JUMP TO THE NORTH...SUGGESTS NORTHERN SECTIONS
MOST AT RISK FOR DECAYING MCS AND HEAVY RAINS. CAN/T RULE OUT
SOME ELEVATED HAILERS MON NIGHT...BUT OVERALL GIVEN TIMING BELIEVE SEVERE
THREAT MINIMAL. LIKELY POPS LOOK GOOD ATTIM. 

FRONT SWINGS THROUGH ON TUE...WITH TIMING SUGGESTING BEST SEVERE POTENTIAL
WILL BE IN OUR EAST AND SOUTH ZONES...THOUGH LOTS OF UNCERTAINTY
ON CLOUD COVER WITH IMPACTS ON DESTABILIZATION. IF WE CAN GET SOME SUN
AND ENOUGH INSTABILITY THEN SOME POTENTIAL FOR A FEW SUPERCELLS EARLY ON BEFORE
ACTIVITY COALESCES INTO SQUALL LINE. LEFT LINGERING LOW CHANCE POPS
TUE EVENING TO ACCOUNT FOR ANY DEFORMATION ZONE RAIN GRAZING THE NORTH AND
FOR POSSIBILITY OF POST FRONTAL SHOWERS IN SOUTH. MID CREW WILL WANT
TO TAKE A CLOSER LOOK AT THIS...ESPECIALLY WITH 18Z META TRENDING
NORTH WITH SURFACE LOW WHICH WOULD SHIFT THREAT FOR DEF ZONE PRECIPITATION
FURTHER NORTH. 

FRONT SHIFTS SOUTH INTO MO TUE NIGHT AND WEDNESDAY AS HIGH PRESSURE BUILDS
IN DRYING THINGS OUT. HIGH PRESSURE LOOKS TO HOLD FIRM INTO THURSDAY
PROVIDING DRY AND QUIET CONDITIONS. 

EXTENDED (THU-SUN)...BROAD MEAN FRONTAL ZONE PROGGED IN VICINITY OF THE
MID MISSISSIPPI VALLEY EARLY ON GIVING 12Z/08 GFS LOTS OF FITS. MODEL GENERATES
SPURIOUS CONVECTIVE CLUSTERS...AND STRUGGLES WITH H5 HEIGHTS AND 
SHORTWAVES. THE CONVECTIVE FEEDBACK ISSUE RESULTS IN A NOISY UPPER PATTERN.
SO...HAVE OPTED TO SIDE WITH BLEND OF UKMET AND ECMWF. GOOD 
AGREEMENT EXISTS EARLY IN FORECAST PERIOD WITH FRONT LYING TO OUR SOUTH IN
WEST/SOUTHWEST UPPER FLOW. FRONT WILL BE FOCUS FOR SEVERAL CONVECTIVE
COMPLEXES...WITH OUTFLOW BOUNDARIES CLOUDING UP MESOSCALE PICTURE.
UKMET AND ECMWF SHOW NEXT SHORTWAVE EJECTING FROM THE SOUTHWEST LATE FRI/SAT. 
HAVE PUSHED BACK POPS TO LATE THURS NIGHT AND CONTINUE THEM THROUGH SAT. 
POTENTIAL FOR FRONT TO LINGER IN THE VICINITY ON SUNDAY...SO HAVE INTRODUCED 
POPS. 

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

$$

05