[LeArc] Forecast Discussion : MLI@ 9/28/02 2:29:45 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 280738
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
230 AM CDT SAT SEP 28 2002

LATEST 11-3.9 MICRON SATELLITE IMAGE SHOWS LOW CLOUDS HAVE ERODED 
OVER MUCH OF REGION DUE TO LLVL NORTHEAST FLOW WHICH
HAS BROUGHT IN SOMEWHAT DRIER AIR WITH DEWPTS LOWERING INTO THE M/U 40S.
RADIATIONAL COOLING IN CLOUD FREE AREAS HAS RESULTED IN FOG WITH
VISIBILITIES 1-4 MILES. FRONTOGENETICAL FORCING UNDERWAY IN THE NORTHERN 
PLAINS WITH CONVECTION DEVELOPING IN SD. 

MAIN CHALLENGE IS WITH TEMPS AND POTENTIAL FOR ELEVATED CONVECTION
LATE AFTN AND TNGT...THEN EXTENT OF WARMUP SUN-MON. 

NEAR TERM...AREAS OF LOW CLOUDS AND FOG (LOCALLY DENSE) TO START THE MORNING.
LLVL FLOW VERY LIGHT BUT SHOULD INCREASE WITH SFC RIDGE AXIS
PASSING EAST THIS MORNING. THIS COMBINED WITH LACK OF MID/HIGH CLOUDS SHOULD
RESULT IN MUCH OF FOG BURNING OFF MID/LATE MORNING. 
TEMPS WARMER TODAY WITH MORE SUNSHINE...AND GUIDANCE OFFERS SOME LARGE
SPREADS. MET HAS BEEN VERIFYING TOO WARM OF LATE...AND GIVEN COOL START AM
SIDING TOWARD BLEND OF MAV/FWC. NGM SURFACE PARCEL TRAJECTORIES 
SUGGEST POTENTIAL FOR U70S IN THE FAR SOUTH WITH TEMPS TAILORING OFF HEADING
NORTH. 

UPPER PATTERN DOMINATED BY WESTERN U.S. TROUGH AND SEVERAL WEAK WAVES
EJECTING INTO PLAINS. FIRST WAVE TO SHIFT THROUGH PLAINS
INTO MID MISSISSIPPI VALLEY TONIGHT. DECENT QG FORCING AND ISENT LIFT IN
CONJUCTION WITH WAVE AND CONVERGENT FLOW AT SURFACE EXPECTED TO
TRIGGER SHOWERS/TSTMS EASTERN NE AND WESTERN IA BY MIDDAY OR SO WITH
ACTIVITY SHIFTING E/NE. SOME LIFT PROGGED INTO CWA DURING AFTN BUT PROBABLY
ACCAS WITH SPRINKLES ESPECIALLY WEST GIVEN LACK OF DEEP MOISTURE.
CAN/T RULE OUT SOME PCPN SNEEKING INTO WESTERN ZONES LATE PM AND WILL INSERT
LOW POP. TONIGHT...SHORTWAVE (ALBEIT FAIRLY WEAK) WILL MOVE THROUGH
WITH STRONG THERMAL ADVECTION POINTED AT EASTERN IA ON NOSE OF VEERED LLJ. 
PW/S INCREASE TO AROUND 1.5 IN BY 12Z SUN. DESPITE SHEARED VORT MAX GIVEN 
STRENGTH OF ADVECTION BELIEVE THIS IS OUR BEST SHOT AT SEEING PCPN IN QUITE SOME
TIME WITH VARIOUS PARAMETERS SUGGESTING CWA COULD BE GENESIS REGION
FOR SMALL CONVECTIVE COMPLEX. ALL BEING SAID...WILL BE DARING AND NUDGE POPS
UP A BIT MORE INTO LIKELY CAT MOST AREAS.

ON SUNDAY...EXPECT CONVECTION TO DIMINISH DURING MORNING AND SHIFT EASTWARD
WITH WEAKENING LLJ. POST CONVECTIVE DEBRIS WILL PLAY HAVOC WITH
TEMPS. ETA 2M AND MET THROWN OUT WITH M/U 80S...AND WILL SIDE TOWARD BLEND
OF MAV/FWC. POSITION OF FRONT AND LLJ SUGGEST PCPN FOCUS SUN NIGHT WILL
BE TO OUR NORTH AND WILL CONTINUE WITH DRY FORECAST.   

RELATIVELY QUIET START TO WEEK WITH TEMPS WELL ABOVE NORMAL. NEXT FRONT PROGGED
LATE TUE BY AVN...WHICH HAS TRENDED A BIT SLOWER FROM 24 HRS AGO. 
CONCERN WILL BE IF FRONT SLOWS EVEN FURTHER WHICH IS CERTAINLY POSSIBLE GIVEN 
SOUTHWEST UPPER FLOW. THIS COULD RESULT IN WARMER TEMPS ON TUE WITH 
PRE FRONTAL COMPRESSIONAL HEATING.  

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