[LeArc] Forecast Discussion : MLI@ 3/17/03 3:16:46 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 172121 CCA
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
320 PM CST MON MAR 17 2003

NEAR RECORD WARMTH THIS AFTERNOON WITH TEMPERATURES IN THE LOWER TO 
MID 70S. THIN CI BLANKET WILL LIKELY KEEP READINGS FROM HITTING 
RECORDS AT MOST LOCATIONS. 18Z ANALYSIS SHOWED BROAD LOW LEVEL WARM 
ADVECTION FLOW INTO AREA WITH LOW CENTER OVER FAR SOUTHEAST CO. TO 
OUR NORTH...STATIONARY FRONT EXTENDED FROM NORTHERN LOWER 
MI...EXTENDING WEST ACROSS SOUTHERN MN WHERE STRATUS AND FOG 
LINGERED EARLY THIS AFTERNOON...THEN CURVING NW INTO SE MT. NEARLY 
STATIONARY AREA OF CONVECTION OVER EASTERN NEB AND KS LOCATED UNDER 
AREA OF FAVORABLE UPPER DIVERGENCE...LOW LEVEL MOISTURE RIDGE AND 
STREAM OF MID LEVEL STREAM OF SHORTWAVES KICKING OUT OF UPPER LOW. 
FORECAST CHALLENGE IS ONSET AND DURATION OF SHOWERS AND THUNDERSTORM 
POTENTIAL THROUGH LATE WEEK AS LARGE UPPER LOW CHURNING OVER 4 
CORNERS REGION MOVES VERY SLOWLY EAST.  

ALL MODELS IN SIMILAR AGREEMENT WITH UPPER LOW MOVING EAST TO 
WESTERN OK BY 12Z WED. MOST SIGNIFICANT DIFFERENCES SHOW UP IN 
HANDLING OF SURFACE LOW. GFS AND UK FAIRLY CONSISTENT PAST FEW MODEL
RUNS AND CONTINUE TO SLOW SYSTEM DOWN. UK AND ESPECIALLY GFS KICK 
OUT LOW TOO FAST TO NW IN COMPARISON TO UPPER LEVEL FEATURES LATER 
THIS WEEK. ETA TREND IN LINE WITH MODEL TRENDS AND MORE REALISTIC 
WITH COMPROMISE FOLLOWED BETWEEN GFS AND ETA IN THURSDAY/FRIDAY TIME 
FRAME WITH UPPER LOW OVER MO. IN SHORT TERM...MAINLY FOLLOWED META 
AS IT HAD BETTER HANDLE ON PRECIP AREAS AND FORCING SO FAR TODAY.

BIGGEST CHANGE IS TO BACK OFF ON CONVECTION TONIGHT AS VORT MAXIMA 
MOVING UP FROM SOUTHERN PLAINS STAY TO WEST THROUGH MORNING. STILL 
CHANCE OF STRAY CONVECTION DEVELOPING LATE AS NEXT UPSTREAM WAVE 
PUSHING UP INTO EASTERN OK STREAMS NORTH. BEST MID LEVEL LAPSE RATES 
AND LOW LEVEL MOISTURE FAVOR THE SOUTHWEST LATE. LOWERED POPS TO 
SLIGHT AND KEPT ONLY IN WEST AND SOUTH. OTHERWISE...PLENTY OF CI 
MOST OF TONIGHT WITH LARGE CLOUD SHIELD TO S-SE TO PUSH OVER 
FORECAST AREA TONIGHT. BACKDOOR FRONT TO NORTH TO PUSH INTO FAR 
NORTH BY MORNING AS INCREASING EASTERLY FLOW DEVELOPS AND WENT 
TOWARD COLDER END OF GUIDANCE OVER ENTIRE AREA. 

TUESDAY...BACKING H85 FLOW TAPS INTO MOISTURE OVER OHIO VALLEY WITH 
UPPER DIVERGENCE COMBINING FOR CLOUDY SKIES. THIS AND INCREASING 
EASTERLY FLOW TO HOLD TEMPERATURES DOWN...ESPECIALLY NORTH...AND 
STAYED CLOSER TO COOLER MAV GUIDANCE. ALL MODELS POINT TOWARD WEAK 
MID LEVEL FORCING FROM MID LEVEL VORT MAXIMA AROUND MIDDAY...COUPLED 
WITH STRONG UPPER DIVERGENCE TO BRING BETTER CHANCE FOR SHOWERS. 
WITH LOW LEVEL EASTERLY FLOW...THINK GUIDANCE IS BRINGING IN SHOWERS 
TOO FAST AND TRIMMED BACK POPS SOME IN NORTH WITH AFTERNOON WORDING. 
BEST THUNDER CHANCES IN SOUTH AND WEST. EVERYTHING COMES TOGETHER 
FOR EXTENDED RAIN EVENT WITH BRISK SURFACE EASTERLY WINDS TUESDAY 
NIGHT THROUGH WED NIGHT AS NEARLY STACKED UPPER LOW APPROACHES FROM 
SOUTHWEST. STRONG OVERRUNNING RAIN EVENT WITH THUNDER CHANCES LOW 
AND MAINLY IN FAR SOUTH EARLY WED. SYSTEM VERY SLOW AND WILL KEEP 
POPS GOING THURSDAY INTO FRIDAY AS UPPER LOW FILLS AND MOVES 
NORTHEAST.    

EXTENDED...
SIGNIFICANT DIFFERENCES BETWEEN GFS AND CANADIAN WITH UPPER FEATURES 
OVER AREA ON FRIDAY...CANADIAN HAS NRN STREAM LOW MOVING INTO 
DAKOTAS THURSDAY NIGHT...WHERE GFS HAS RIDGE. SURFACE FEATURES NOT 
THAT DIFFERENT WITH NORTHERLY SFC FLOW OVER REGION. ACTIVE NORTHERN 
STREAM WILL KEEP PLENTY OF CLOUDS AROUND THROUGH WEEKEND AND BELOW 
NORMAL TEMPERATURES GOING. CANADIAN ALONE WITH SUGGESTING SURFACE 
TROUGH PASSING TO NORTH ON SATURDAY...AND EVEN IF IT OCCURS...LOOKS 
TOO FAR NORTH TO IMPACT AREA AND WILL KEEP WEEKEND DRY AND NEAR TO 
BELOW NORMAL TEMPERATURES. GFS SHOWING GOOD WARMING SCENARIO FOR 
MONDAY WITH FRONT APPROACHING...AND WENT A BIT ABOVE GUIDANCE.  

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

$$

DLS