[LeArc] Forecast Discussion : MLI@ 9/4/02 2:32:09 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 041937 CCA
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
237 PM CDT THU SEP 4 2002

ANOTHER QUIET AND SUNNY DAY ACROSS CWA...WITH NOT TOO MUCH TO GET 
EXCITED ABOUT HERE.  SURFACE RIDGE AS OF 18Z SHIFTING TO EAST OF 
CWA...OVER LAKE MICHIGAN.  VERY LIGHT SOUTHEASTERLY FLOW PICKING UP 
...WITH STRONGER WINDS OVER WESTERN IA.  DEVELOPING LOW OVER WESTERN 
ND...WITH GOOD FALLS ACROSS NRN MN.  UPPER LEVELS SHOW 850MB WARM 
FRONT EXTENDING FROM ND TO JUST WEST OF CWA...WITH STRONG SOUTHERLY 
FLOW TO ITS SOUTH.  WINDS ARE AS STRONG AS 40KTS OVER NEBRASKA.  
THERE IS A POCKET OF VERY WARM AIR AT BOTH 850 AND 700 MB JUST WEST 
OF THE RIDGE AXIS...BUT THIS AIR IS ALSO ON THE DRY SIDE FOR THE 
MOST PART.  MAIN FEATURE TO WATCH NEXT 24-36 HRS IS THE WAVE MOVING 
NORTHEAST OUT OF THE CO/WY AREA.

MAIN CONCERNS THIS FORECAST INCLUDE TEMPS TONIGHT AND PRECIP CHANCES 
WITH THE ABOVE MENTIONED WAVE.  

12Z MODELS APPEAR TO HAVE INITIALIZED FAIRLY WELL...THOUGH ETA SEEMS 
TO HAVE BEST HANDLE ON VORT MAX POSITION AT 12 AND 18Z.  AVN TOO FAR 
SW.  TONIGHT THE AVN APPEARS TO SUFFER FROM CONVECTION PROBLEMS AS 
IT OVERLY DEEPENS THE VORT MAX...AND OVERDOES THE QPF FIELDS.  SO 
FOR AT LEAST TONIGHT AND SOME OF THURSDAY MUCH PREFER THE ETA 
FIELDS.  AVN RETURNS TO SOME SENSE BY THURSDAY...AND THE ETA THEN 
APPEARS TO BE OUT.  BOTH MODELS SPLIT THE VORT MAX IN TWO...WITH THE 
AVN GOING VERY STRONG WITH THE NORTHEN FEATURE...AND THE ETA THE 
SOUTHERN FEATURE.  CONSIDERING WHERE THE LOWER LEVEL CONVERGENCE... 
MOISTURE...UPPER LEVEL JET STRUCTURE...AND OTHER FACTORS LINE 
UP...IT MAKES MORE SENSE THAT THE NORTHERN FEATURE WOULD BE THE 
STRONGER.  SO...AFTER MID-DAY THURSDAY...WILL SHIFT TO AVN.  

TEMPS TONIGHT NOT TOO BAD AS WAA FINALLY BEGINS TO KICK IN OVER 
CWA...AND SOME CIRRUS STREAMS OVER THE AREA.  USING TRAJECTORY 
METHOD YIELDS LOW TEMPS THIS MORNING IN THE MID 50S TO LOW 60S. 
HOWEVER CONDITIONS FOR RADIATION NOT QUITE SO GOOD AS LAST NIGHT SO 
WILL GO A LITTLE WARMER.  GOING TEMP FORECAST NOT TOO FAR OFF 
INTENTIONS.

CONDITIONS THIS FAR SOUTH ARE TOO DRY FOR EVEN THIS RATHER VIGOROUS 
SHORT WAVE TO SQUEEZE OUT SOME PRECIP...THOUGH AT LEAST PARTLY 
CLOUDY FOR FRIDAY IN ORDER.  LAPSE RATES APPROACH 7 ON FRIDAY ACROSS 
CWA...ESPECIALLY ACROSS THE NORTHERN PARTS OF CWA.

EXTENDED...SUN-WED
UPPER LEVEL RIDGE REMAINS OVER AREA SUNDAY AND MONDAY...SO DRY AND 
WARM FCST LOOKS GOOD.  TUESDAY AND WEDNESDAY STILL LOOK IN LINE FOR 
THE FROPA OF A SIGNIFICANT COLD FRONT...BRINGING A PRETTY GOOD COOL 
DOWN FOR LATER IN THE WEEK.  SYSTEM IS DELAYED A LITTLE FROM 
YESTERDAYS MODEL RUNS...SO MAY WORK IN LATE WORDING FOR TUESDAY 
PRECIPITATION.  

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

LRE