[LeArc] Forecast Discussion : MLI@ 4/1/2003 4:31:40 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 012222
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
421 PM CST TUE APR 1 2003

DOWNRIGHT HOT DAY TODAY FOR THE FIRST OF APRIL...WITH VERY DRY
DEWPOINTS IN THE 30S TO LOW 40S...AND SOUTHWESTERLY WINDS OF 15 TO
25 MPH.  RECORDS HAVE ALREADY BEEN BROKEN AT A FEW SITES AROUND THE
CWA...AND THERE MAY BE A FEW MORE BEFORE THE END OF THE DAY.  850MB
TEMP UP TO PLUS 16 ON THIS MORNINGS SOUNDING...WITH EVEN WARMER
TEMPS UPSTREAM.

MAIN CONCERN OF THE DAY INCLUDES TEMPS THROUGH THURSDAY...AND THEN
POTENTIAL FOR SEVERE TSTMS ON THURSDAY LATE AFTERNOON/OVERNIGHT.

12Z RUNS APPEAR TO HAVE INITIALIZED RELATIVELY WELL. MOST MODEL MOS
GUIDANCE HAS BEEN FAR TOO COOL TODAY...SO THERE ARE SOME CONCERNS
ABOUT HOW THE LOW LEVEL TEMPS WILL BE HANDLED IN THE NEXT 24 TO 48
HOURS.  AS OF 18Z...THE AVN SEEMS TO HAVE THE BEST HANDLE ON THE
POSITION OF THE SURFACE STATIONARY FRONT ALONG THE IA/MN BORDER.
THE AVN HAS BEEN TRENDING TOWARDS AN EARLIER ETA SOLUTION...WITH
THE SURFACE FRONT THROUGH THE CENTRAL PORTIONS OF THE CWA.  FROM
PAST EXPERIENCE...WARM/STATIONARY FRONTS THIS TIME OF YEAR LIKE TO
HANG UP ALONG THE I-80 CORRIDOR...DUE TO EFFECTS FROM LAKE MICH.
AM RE-ASSURED BY THE NEW AVN BEGINNING TO PLACE THE FRONT ALONG THIS
AREA BY THURSDAY MORNING.  12Z ETA TOO FAR SOUTH...ACROSS NORTHERN
MISSOURI.

TEMPS TONIGHT WILL BE A BALANCE BETWEEN RADIATIONAL COOLING AND WARM
AIR ADVECTION CONDITIONS.  HAVE DECIDED TO GO CLOSE TO THE AVN MOS
GUIDANCE.  WEDNESDAY NIGHT OUGHT TO BE SIMILAR...BUT WITH MORE RANGE
ACROSS THE CWA AS THE FRONT DROPS TO THE SOUTH.  WEDNESDAY HIGHS
SIMILAR TO TODAY...WITH SIMILAR CONDITIONS AT THE MID LEVELS...AND
EXCEPT FOR COOLING TEMPS FOR THE NORTHERN COUNTIES A LITTLE...
FORECAST WILL BE VERY CLOSE TO PERSISTENCE FROM TODAY.  THURSDAY
TEMPS COOL OFF SOME AS CLOUDS MOVE IN AND FRONT SAGS FURTHER SOUTH.

THURSDAYS MAIN CONCERN IS THE POTENTIAL FOR SEVERE THUNDERSTORMS IN
THE AFTERNOON AND EVENING.  AS THE LOW PRESSURE CENTER MOVES
TOWARDS THE AREA...SHEAR INCREASES...LOW LEVEL DEWPOINTS INCREASE...
AND INSTABILITY WILL BE REASONABLY HIGH...WITH CAPES AS HIGH AS
1600 J/KG.  INITIAL THOUGHTS ARE LOOKING TOWARDS A FEW SUPERCELLS
DEVELOPING...WITH A BRN OF 25 TO 35. A CALCULATION OF THE BLEP
TECHNIQUE -SEE WEB PAGE FOR EXPLANATION OF THIS NEW TECHNIQUE-YIELDS
WIND SPEEDS OF UP TO 70 KTS WITH STRAIGHT LINE WIND GUSTS...AND UP TO
135 KTS ROTATIONAL...POSSIBLY F2 DAMAGE WITH ANY TORNADOES THAT DO
DEVELOP.  THIS IS THE EXTREME...SO HAVE NOT MENTIONED ANY MORE THAN
POSSIBLE SEVERE STORMS WITH STRONG WINDS IN THE ZONE PACKAGE.  BEST
CHANCE OF THESE SEVERE STORMS SHOULD BE ALONG AND SOUTH OF THE LOW
TRACK...SO BASICALLY ALONG AND SOUTH OF HIGHWAY 34 FROM MID
AFTERNOON ON.

EXTENDED...SATURDAY THRU TUESDAY
BUSY WEATHER PERIOD WITH A STRONG UPPER LEVEL LOW SYSTEM SWINGING
ACROSS THE REGION SUNDAY NIGHT THROUGH MONDAY.  IF THIS TIMING
CONTINUES...PRECIPITATION SHOULD START SATURDAY NIGHT...AND CONTINUE
UNTIL MONDAY NIGHT.  TUESDAY SHOULD BE QUIET AND DRY WITH A SURFACE
RIDGE BUILDING IN.  THE GFS IS THE STRONGEST WITH THIS SYSTEM...AND
PULLS IN THE MOST COLD AIR.  FEEL THAT THIS MAY BE A LITTLE OVER
DONE...BUT IT HAS CONTINUITY ON ITS SIDE...AND THE UKMET IS CLOSER
TO IT THAN IT IS TO THE MUCH WARMER ECMWF.  DUE TO THE UNCERTAINTIES
WITH THIS SYSTEM HAVE GONE ONLY WITH HIGH CHANCE POPS...AND HAVE
DECIDED TO GO WITH TEMPS A LITTLE WARMER THAN THE MEX MOS TEMPS.

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

$$

LRE