[LeArc] Forecast Discussion : MLI@ 5/10/2003 5:09:26 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 101005
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
440 AM CDT SAT MAY 10 2003

SIGNIFICANT OUTBREAK OF SEVERE WEATHER EXPECTED FOR PORTIONS OF THE
CWA THIS AFTERNOON AND EVENING. DETAILS TO FOLLOW...BUT
PER COORDINATION WITH SPC (THANKS!) THEY WILL BE UPGRADING TO
HIGH RISK IN FAR SOUTHEAST. DANGEROUS SITUATION WITH POTENTIAL FOR SEVERAL
TORNADOES OF WHICH A COUPLE COULD BE MODERATE TO STRONG IN 
INTENSITY WITH LONG TRACKS. WILL BE DOING AN 18Z UPPER AIR RELEASE.
EXPECT SEVERE WEATHER WATCHES TO BE ISSUED BY MID AFTERNOON.

EARLIER CONVECTION WHICH PRODUCED SOME GUSTY WINDS AND A FEW HAIL 
REPORTS OF UP TO NICKEL SIZE HAS WEAKENED AND MOVED WELL OFF TO THE 
EAST INTO PORTIONS OF THE OHIO VALLEY. NEXT SURGE OF CONVECTION 
FAST APPROACHING FROM THE SOUTHWEST. SOME WEAKENING IS EXPECTED BUT
POTENTIAL STILL EXISTS FOR ISOLATED SEVERE HAIL MAINLY IN THE
FAR SOUTH. MAIN SHOW STILL ON TAP FOR LATER THIS AFTERNOON AND EVENING
AS 100-120 KT H3 JET INDUCES STRONG UPPER LEVEL DIVERGENCE 
TOWARD 00Z.

LATEST SURFACE ANALYSIS PLACES LOW IN SOUTHWEST KS. EARLIER CONVECTION
HAS CONTAMINATED WIND FIELDS SOME...BUT THERMAL/MOISTURE FIELDS
INDICATE FRONTAL ZONE EXTENDS EAST/NORTHEAST FROM LOW THROUGH CENTRAL KS 
INTO WEST CENTRAL IL ROUGHLY FROM JUST SOUTH OF SALINA TO 
NEAR QUINCY. CONVECTION RE-ENERGIZING FROM PORTIONS OF KS/NE INTO NORTH
CENTRAL MO ON NOSE OF 40-50 KT LLJ AND IN REGION OF STRONG MOISTURE
CONVERGENCE. SOME SURFACE BASED CONVECTION ALONG FRONTAL ZONE WHICH WILL
BECOME ELEVATED AS IT RACES EAST/NORTHEAST. LLVL NORTH WINDS
BRINGING INFLUX OF SOMEWHAT DRIER AIR WITH DEWPTS IN THE U40S/50S...THUS
SOME WEAKENING OF CONVECTION IS ANTICIPATED. 

EXPECT SOME BREAKS IN THE CLOUDS BEFORE NEXT ROUND OF CONVECTION DEVELOPS
THIS AFTERNOON...ROUGHLY IN THE 20Z-21Z TIMEFRAME.
UPPER LOW OVER ROCKIES TO EJECT AS NEG TILT WAVE...WHILE SURFACE LOW
PROGGED TO MOVE NORTHEAST WITH MODELS IN DECENT AGREEMENT
ON PLACEMENT NEAR KIRKSVILLE MO BY 00Z...DEEPENING AND SHIFTING EAST/NORTHEAST
TOWARD THE QUAD CITIES DURING THE EVENING TO NEAR LAKE MI 12Z SUN.
MODELS STILL SHOW PRESSURE DROP OF NEARLY 10 MBS IN THIS TIMESPAN...WHICH
WILL TRANSLATE INTO MORE VIGOROUS CONVECTION. ATMOSPHERE TO BECOME
VERY UNSTABLE IN THE SOUTH/EAST THIS AFTERNOON WITH TEMPS EXPECTED TO BE
PUSHING L80S AND DEWPTS NEAR 70...LI/S OF -4 TO -8...AND CAPES 
APPROACHING 3000 J/KG. SHEAR IS QUITE IMPRESSIVE THUS HAVE NO REAL CONCERNS
OF SEVERE THREAT DIMINISHING SHOULD DEBRIS FROM MORNING CONVECTION
HANG ON LONGER THAN EXPECTED. RUNNING BEHIND...BUT FIRST GLANCE AT NICHOLS
BLEP TECHNIQUE SUGGESTS LITTLE CHANGE FROM DAY SHIFT COMPUTATIONS.
USING INFLOW OF ROUGHLY 82/70...STRAIGHT LINE POTENTIAL WILL BE 60 KTS WITH
ROTATIONAL UPDRAFT VELOCITY OF ABOUT 140 KTS OR SO SUGGESTING
TORNADIC STRENGTH OF LOW END F3. IF SURFACE WINDS CAN CLIMB ANOTHER 5-7 KTS
AND TEMPS ANOTHER FEW DEGS THEN F4 POTENTIAL. ANTICIPATE SUPERCELLS
DEVELOPING IN NORTHEAST MO AROUND 20-21Z. ACTIVITY WILL THEN SHIFT EAST WITH
PRESSURE FALLS AND ADVECTION. THIS IS A DANGEROUS SITUATION WITH 
POTENTIAL FOR ONE OR TWO LONG TRACKED TORNADOES. GREATEST RISK WITH AND
JUST EAST OF SURFACE LOW...WHICH WOULD BE ROUGHLY KEOSAUQUA...TO
BURLINGTON...TO GALESBURG AND POINTS SOUTH. CAUTION THOUGH AS ANY SLIGHT
DEVIATION IN TRACK OF LOW WILL CHANGE GREATEST RISK AREA. WILL BE
UPDATING HWO WITH LATEST INFORMATION AND ATTEMPTING TO NAIL DOWN GREATEST
THREAT AREA AND TIMING...ETC. ASIDE FROM POTENTIAL FOR TORNADOES...LARGE
HAIL AND DAMAGING WINDS...FLOODING ALSO SOMEWHAT OF A CONCERN. 
FFG VALUES STILL 1.5 TO 2.5 INCHES OVER MOST OF THE AREA FOR 3 HRS.
WOULDN/T BE SUPRISED TO SEE A FEW 3 INCH AMOUNTS IN SOUTHERN PORTIONS
OF CWA...WITH FLOODING LIKELY WITH SUPERCELLS. HOWEVER...DON/T 
BELIEVE HEAVY RAINS OF THIS MAGNITUDE WILL BE WIDESPREAD ENOUGH TO WARRANT
A FLOOD WATCH. WILL CONTINUE TO HIGHLIGHT HEAVY RAIN IN ZONES AND
IN HWO.    

SURFACE LOW CONTINUES TO DEEPEN WHILE LIFTING THROUGH THE GREAT LAKES
ON SUN. STRONG PRESSURE GRADIENT TO RESULT IN WINDY CONDITIONS
WITH STILL SOME POTENTIAL FOR WIND ADVISORY. LOTS OF CLOUDS AND SOME
DRIZZLE IN WRAP AROUND WITH CHANCE OF RAIN NORTHERN 1/3RD OR SO.
CLOUDS WILL KEEP HOLD TEMPS MAINLY IN THE 50S...SO OVERALL UNFORTUNATELY NOT
THE BEST OF DAYS FOR MOM. 

NO CHANGES TO EXTENDED...DUE TO TIME CONSTRAINTS. 

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

$$

05