[LeArc] Forecast Discussion : MLI@ 7/15/2003 3:38:32 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 152027
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
327 PM CDT TUE JUL 15 2003

LATEST SURFACE ANALYSIS INDICATING THAT SURFACE FRONT THAT PUSHED
THROUGH THE AREA THIS MORNING IS NOW WELL SOUTH OF THE AREA...WITH
A NICE SURFACE RIDGE BUILDING INTO THE AREA FROM THE NORTHWEST.
DEWPOINTS AS OF 19Z ARE DOWN INTO THE LOWER 60S FROM AROUND 70 RIGHT
BEHIND THE FRONT THIS MORNING.  FASCINATING LITTLE GRADIENT WINDS
EVENT HAPPENED RIGHT BEHIND THE FRONT THIS MORNING...WITH MANY
SITES BRIEFLY REPORTING GUSTS TO AROUND 50 MPH DURING THE EARLY
MORNING HOURS...AFTER PRESSURES FELL RAPIDLY 3-4MB/3HRS FOR A FEW
HOURS.  THIS WAS ACCOMPANIED BY SOME SHOWERS AND THUNDERSTORMS...
BUT WERE NOT CREATED BY THE CONVECTION...BUT THE PRESSURE GRADIENT.

MAIN CONCERN THIS FORECAST IS THE PRECIP CHANCES THROUGH THE
PERIOD.  12Z MODELS APPEAR TO BE IN REASONABLE SYNOPTIC SCALE
AGREEMENT...AND HAVE IN GENERAL GONE WITH A BLENDED FORECAST.

WEDNESDAY NIGHT/THURSDAY A FRONT DROPS THROUGH THE REGION...WHICH
COULD TRIGGER A BAND OF CONVECTION...WITH THE MAIN QUESTION BEING
WHERE AND WHEN.  GFS BRINGS THIS FRONT FURTHER SOUTH THAN THE ETA...
AND IS ALSO STRONGER ALOFT.  GFS LOOKS LIKE IT MIGHT BE GETTING A
LITTLE CONVECTIVE FEEDBACK...AND HAVE LEANED MORE TOWARDS THE ETA
SOLUTION IN THIS CASE.

NEXT CHANCE IS FRIDAY...WITH A NICE LITTLE VORT MAX DROPPING ACROSS
THE CWA...INTERACTING WITH THE SURFACE BOUNDARY THAT SLOWLY DROPS
SOUTHEAST ACROSS THE AREA.  AT THIS TIME...IT APPEARS THAT IT WILL
BE A DECAYING MCS THAT MOVES ACROSS THE AREA DURING THE MORNING...
WHICH IS EARLIER IN TIMING THAN THE GOING FORECAST.  DID NOT MOVE
IT INTO THURSDAY NIGHT...BUT IF THIS TREND CONTINUES THIS MAY NEED
TO BE DONE.

EXTENDED...SAT-TUE
MESSY SITUATION WITH THE UPPER LEVEL RIDGE REMAINING IN PLACE TO THE
WEST...AND BITS OF ENERGY MOVING OVER THE RIDGE AND DROPPING ACROSS
THE MIDWEST.  THE MAIN QUESTION IS HOW FAR SOUTH THE ENERGY WILL
GET...AND WHERE THE BOUNDARIES WILL BE.  AT THIS TIME...COULD PUT
PRECIP CHANCES IN NEARLY ALL PERIODS EXCEPT SATURDAY.  THE NEW GFS
AND UKMET BRING IN PRECIP CHANCES FOR SUNDAY AND MONDAY...WITH THE
ECMWF DELAYING INTO TUESDAY.  HAVE DECIDED NOT TO MAKE MANY
CHANGES...AND HAVE JUST PUSHED PRECIP INTO SUNDAY NIGHT FOR NOW.

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

$$

LE