[LeArc] Forecast Discussion : MLI@ 8/15/02 2:06:53 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 151909
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
205 PM CDT THU AUG 15 2002

.OVERVIEW...STRONG AND CONTINUED CHANGEABLE LATE SUMMER PATTERN IN PLACE
WITH VIGOROUS UPPER JET STRADDLING CANADIAN/US BORDER WITH EMBEDDED
SHORT WAVES. LATEST WAVE WITH LEADING EDGE OF SFC BOUNDARY INTO NW IOWA
ALONG A MSP TO OMA AXIS AT 18Z MOVING SE ~15 MPH.  SYSTEM SHEARING EAST
WITH FAST ZONAL FLOW AS SIMILAR TO PAST FEW SYSTEMS. NOWCAST TOOLS
SUGGEST FROPA BETWEEN 05 AND 11Z AS FRONT SLOWS DOWN AND ULTIMATELY
STALLS IN FAR SOUTH AND SE SECTIONS TOWARD MORNING. APPEARS CONVECTIVE
TEMPERATURE TO BE REACHED TOWARD SUNSET WITH A FEW STORMS THAT MAY LAST
WELL INTO NIGHT DEPENDING ON STRENGTH OF LOW LEVEL JET ALONG BOUNDARY
SFC TEMPS BEHIND BOUNDARY ARE RUNNING ABOVE ALL GUIDANCE AS IT SHEARS
AND PLAN TO INCORPORATE INTO FRI TEMPS.

...TIMING POPS AND TEMPS WITH NEXT TWO SYSTEMS INTO WEEKEND MAIN
CHALLENGE WITH EMBEDDED DISTURBANCES INTO MID WEEK ALSO A FORECAST
ISSUE...

.DIAGNOSIS AND DAYS 1-3...MODELS CONTINUE TO VARY RUN TO RUN WITH THIS
FAST PATTERN AND ALSO INTER-MODEL DIFFERENCES AS WELL.  PLAINS SYSTEM
SLIGHTLY TOO STRONG AND COOL PER 18Z AND WILL USE MAINLY ETA DYNAMICS
WITH SOME INPUTS FROM FWC/MAV WITH ETA-M TEMPS STILL NOT RELIABLE EXCEPT
TRENDS.  THUS...PLAN TO KEEP CHANCE POPS THIS EVENING NW AND SLIGHTLY
HIGHER INTO OVERNIGHT HOURS TONIGHT SE WITH COOLER FAR NW AS LOWER
DEWPOINTS MOVE IN AND SLIGHTLY HIGHER SE WITH MORE CLOUDS AND HIGHER
DEWPOINTS FROM MOISTURE POOLING.  FOR NOW...WILL LEAVE OUT CHANCE OF
MORNING DEBRIS POPS BUT PASS TO LATER SHIFTS TO EVALUATE TONIGHT.  THEN
TEMPS ON HIGH SIDE OF MAV/FWC FRIDAY WITH LIGHT WINDS.  INCREASING
CHANCE OF POPS FRIDAY NIGHT AS STRONGER IMPULSE HEADS INTO REGION WITH
LOW LEVEL JET DEVELOPING FOR SOME CONVECTION DEVELOPING ALONG WARM
FRONT AS IT SLIDES NORTH.  TEMPS A MAJOR CHALLENGE SAT WITH TIMING OF
CLOUDS...PRECIP AND FROPA. FOR NOW...WILL PLAN FOR NEAR MAV/FWC FAR NW
AND SLIGHTLY ABOVE CENTRAL AND SE BUT OBVIOUS RISK OF BUST IF SOME SUN
DOESN/T OCCUR BEFORE FROPA. GO LIKELY OR HIGHER MOST AREAS WITH STRENGTH
OF BOUNDARY AND CHANCE EVENING POPS BEFORE MUCH COOLER COMES IN.  TIMING
ISSUE SUGGEST LEAVING SEVERE WORDING AND HEAVY RAINS OUT AT THIS TIME
FOR LATER SIFTS TO CONSIDER SATURDAY.  SUNDAY...TEMPS WILL GO ON LOW
SIDE BASED ON PERSISTENCE AND MODEL BLEND OF LOW LEVEL TEMPS INTO SUNDAY
NIGHT AS UPPER TROUGH MUCH STRONGER THAN PAST FEW SYSTEMS FOR SEASONABLY
COOL CONDITIONS.

.EXTENDED (MON-THU)...MODEL STILL VARY QUITE A BIT RUN TO RUN AND
BETWEEN THEM MON AND INTO TUESDAY.  PLAN WITH DISTURBANCES  TO KEEP
CHANCE POPS GOING INTO TUESDAY WITH TEMPS NEAR MEX.  LATEST UKMET ALSO
SUGGEST A PATTERN SIMILAR TO AVNXT AND MRF OF WARMER TEMPS MID WEEK AND
CHANCE OF PRECIPITATION WITH NEXT FRONT THURSDAY.

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

NICHOLS