[LeArc] Forecast Discussion : MLI@ 5/11/2003 5:17:58 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 111012
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
500 AM CDT SUN MAY 11 2003

LATEST SURFACE ANALYSIS SHOWS DEEP CYCLONE (985 MBS) OVER WESTERN WI WITH
CENTRAL PRESSURE DROPPING ABOUT 2 MBS/HR. DEEPENING TREND EXPECTED 
TO SLOW AND EVENTUALLY COME TO HALT THIS MORNING AS SYSTEM
BECOMES VERTICALLY STACKED AND OCCLUDES. REGIONAL RADAR LOOP SHOWS RAIN
ASSOCIATED WITH DEFORMATION ZONE INTO FAR NORTHERN IA ATTIM.
ISALLOBARIC MAX PUSHED THROUGH AROUND MIDNIGHT PRODUCING WIND GUSTS 
OF 40-45 KTS. SECOND SURGE NOTED AT PRESENT TIME WITH TIGHTENING PRESSURE 
GRADIENT PRODUCING VERY WINDY CONDITIONS WITH SEVERAL SITES 
AT/ABOVE WIND ADVISORY CRITERIA (SUSTAINED 30 MPH FOR 1 HR OR GUSTS OF 45 MPH 
OR GREATER FOR ANY DURATION).

MAIN CHALLENGES RESIDE WITH WINDS...AND PCPN CHCS NEXT 12-18RS WITH BACKLASH.
BEYOND...CONCERNS WITH PCPN CHANCES MIDWEEK. 

NEAR TERM...DEEPENING CYCLONE WILL MOVE INTO THE GREAT LAKES AND BECOME
VERTICALLY STACKED...ESSENTIALLY SLOWING FORWARD SPEED WITH
FAR NORTHERN ZONES ON THE EDGE OF DEFORMATION BAND. WEAK SHORTWAVE ALSO
PROGGED TO DROP DOWN BACKSIDE OF SYSTEM AND ACROSS THE NORTH...SO
WILL PLACE HIGH CHANCE POPS IN THE NORTH TAPERING OFF AS YOU HEAD SOUTH.
DMX/DVN RADARS SHOW INCREASE IN BANDING OF WEAK RETURNS NORTH OF HWY 34.
OVERALL...HIGH POP/LOW QPF EVENT. FEEL BEST WORDING WILL BE WITH
OCCASIONAL DRIZZLE/LIGHT RAIN NORTH...WITH MAINLY DRIZZLE IN THE SOUTH.
CLOUDS AND LIGHT PCPN TO TEMPER MAXES AND UNDERCUT GUIDANCE BY A FEW DEGS.
NEXT CONCERN IS WITH WIND. INITIAL SURGE OF ADVISORY CRITERIA WINDS
BLASTED THROUGH AROUND MIDNIGHT WITH ISALLOBARIC MAX...NOW SEEING OVERALL
WIND FIELD INCREASE DUE TO TIGHTENING PRESSURE GRADIENT. 
VERY IMPRESSIVE HEIGHT FALL CENTER OF OVER 200 M IN WESTERN WI...MORE
TYPICAL OF LATE WINTER/EARLY SPRING. MODELS SHOW PRESSURE GRADIENT
MAXIMIZED ACROSS STATE OF IA THIS MORNING AT ROUGHLY 18 MBS!!!
USING RULE OF MAXIMUM WIND (GUSTS) OF 10 MPH FOR EVERY 4 MBS MSLP GRADIENT
THIS SUGGESTS MAX GUSTS JUST OVER 40 KTS...WHICH LOOKS TO BE
VERIFYING PRETTY WELL. 
 
TONIGHT...VERTICALLY STACKED SYSTEM MOVES SLOWLY EAST THROUGH THE
GREAT LAKES. ANY DRIZZLE OR LIGHT RAIN LOOKS TO BE END IN 
THE EVENING AS WEAK SHORTWAVE ON BACKSIDE OF SYSTEM PULLS EAST.
SURFACE RIDGING BUILDS INTO WESTERN IA WITH FLOW BECOMING
BIT MORE ANTICYCLONIC WEST OF THE MISSISSIPPI. MODELS SHOW DEEP COLUMN
DRYING INTO WESTERN 1/3RD OR SO BY 12Z MON. WILL BE OPTIMISTIC 
AND GO WITH PARTIAL CLEARING FOR NOW...EXCEPT EAST WHERE LLVL CYCLONIC 
FLOW SHOULD KEEP CLOUDS AROUND FOR MUCH OF THE NIGHT. MIN TEMPS 
CHALLENGING WITH CLOUDS TRENDS DIFFICULT...AND AMPLE MIXING IN BL WITH
WINDS STAYING UP IN RANGE OF 10-20 MPH OR SO. POTENTIAL TO BE
COLDER IN THE WEST AND WARMER IN THE EAST. 

MUCH NEEDED REST FROM ACTIVE PATTERN IN STORE TO START THE WORK WEEK.
 
ETA...UKMET AND GFS INDICATE NEXT CHANCE OF RAIN LATE TUE THOUGH MIDWEEK WITH 
CONVECTION DEVELOPING IN PLAINS ON NOSE OF STRONG WARM ADVECTION. 
ACTIVITY WILL BLEED SOUTHEAST WITH MEAN STEERING FLOW FROM THE 
NORTHWEST...HOWEVER ATMOSPHERE FAIRLY STABLE...SO EXPECT STRATIFICATION 
AND MAINLY JUST RAIN INTO WED...THOUGH CAN/T RULE OUT SOME THUNDER WITH
ELEVATED INSTABILITY WED AFTERNOON/NIGHT AS FRONTAL ZONE FIRMS UP TO 
OUR SOUTH. WENT AHEAD AND INTRODUCED POPS TUE NIGHT THROUGH WED SINCE ALL 
MODELS ARE POINTING TOWARD THIS SCENARIO...WITH MAIN DIFFERENCE 
WITH TIMING/SATURATION AS LLVL FLOW WILL BE FROM THE EAST AND NORTHEAST. 

COORDINATED WITH DMX...LOT...ILX...THANX!

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

$$

05