[LeArc] Forecast Discussion : MLI@ 7/2/2003 4:39:07 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 022113
AFDMLI

AREA FORECAST DISCUSSION...RETRANSMISSION...
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
330 PM CDT WED JUL 02 2003

TONGUE OF DEEPER MOISTURE ACROSS THE SOUTH YESTERDAY HAS OVERSPREAD 
MUCH OF THE AREA...ESPECIALLY ALONG AND WEST OF THE MISSISSIPPI 
RIVER. WITH SLIGHTLY DRIER AIR IN THE FAR EAST IN PROXIMITY TO LAKE 
BOUNDARY WHICH SHOWS UP NICELY ON SATELLITE FROM NEAR FORT WAYNE 
INDIANA TO BLOOMINGTON ILLINOIS. RESULTING CU FIELD SHOWING SOME 
MODERATE EXTENT ESPECIALLY ACROSS THE NORTH AND EAST...WITH SIGNS OF 
TRYING TO DEVELOP FURTHER. THIS WILL BE THE IMMEDIATE SHORT TERM 
CONCERN (PCPN CHCS). EARLIER MCS HAS FINALLY DISSIPATED OVER SOUTH 
CENTRAL WISCONSIN...THOUGH WELL DEFINED OUTFLOW BOUNDARY LINGERS 
FROM EAU CLAIRE TO BARABOO. SECOND CONVECTIVE COMPLEX MARCHING 
EASTWARD INTO NORTHWEST MINNESOTA. ALL EYES ARE ON THIS CONVECTION 
AND SUBSEQUENT DEVELOPMENT THIS EVENING...AND INTERACTION WITH 
OUTFLOW BOUNDARY TO OUR NORTH...WITH POTENTIAL PROPAGATION INTO 
NORTHERN ZONES. 12Z UPPER AIR ANALYSIS SHOWS UPPER LOW OVER WESTERN 
CANADA WITH DECENT 100 KT H25 JET LIFTING INTO NORTHERN ROCKIES. 
MAIN WESTERLIES LIE FROM PACIFIC NORTHWEST THROUGH SOUTHERN CANADA. 
H7/H85 THERMAL GRADIENTS EXTEND ROUGHLY FROM NORTHERN NORTH DAKOTA 
THEN ARC THROUGH EASTERN MINNESOTA INTO NORTHERN ILLINOIS. THIS WILL 
BE KEY THE NEXT 24 HRS WITH CONVECTION GENERALLY FOLLOWING ALONG AND 
ON THE COOL SIDE OF THE GRADIENT. 

TONIGHT...LATEST MSAS SHOWING WEAK SURFACE MOISTURE FLUX CONVERGENCE
OVER ALL BUT FAR EAST. HOWEVER...THERE CONTINUES TO BE LITTLE 
DEVELOPMENT ATTIM OVER CWA WITHIN MODERATE CU BUILDUP. 
WILL MONITOR RADAR AND SATELLITE TRENDS...BUT ATTM PLANNING ON NOT 
MENTIONING ANY PCPN EARLY THIS EVENING. CAN/T RULE OUT ISOLD
DEVELOPMENT...BUT IT COULD BE HANDLED WELL WITH SHORT TERM FORECASTS.
WILL CONTINUE MENTION OF PATCHY FOG WITH LIGHT WINDS AND 
ABUNDANT LLVL MOISTURE. WITH THE INCREASE IN MOISTURE WILL SEE 
WARMER MINS...BUT BELIEVE THEY COULD END UP BEING A COUPLE 
OF DEGREES COOLER THAN GUIDANCE WITH RADIATIONAL COOLING WITH LIGHT 
WINDS AND MAINLY CLEAR SKIES.

THE MAIN CHALLENGE LATER TONIGHT WILL BE WITH PRECIPITATION CHANCES 
MAINLY ACROSS THE NORTHERN 1/3RD OR SO. CONVECTIVE COMPLEX 
MARCHING EASTWARD THROUGH NORTHWEST MINNESOTA ATTIM...AND SHOULD 
CONTINUE DOING SO FOR THE NEXT FEW HOURS. HOWEVER...LATER THIS 
EVENING AS IT INTERACTS WITH ARCING OUTFLOW BOUNDARY AND LLJ... 
ANTICIPATE NEW DEVELOPMENT ON THE SOUTHERN FLANK WITH A CHANGE IN 
FORWARD PROPAGATION TO MORE SOUTH/SOUTHEAST ALONG H7/H85 THERMAL 
GRADIENT AND SURFACE THETA-E AND LI GRADIENTS. H3/H5 DIFFLUENCE 
SUGGESTS CONVECTION PROPAGATING INTO OR TOWARD SOUTHERN MN/NORTHEAST 
IA/NORTHWEST IL AND SOUTHERN WI LATER TONIGHT. SO WITH ALL BEING 
SAID...WILL INTRODUCE CHANCE POPS ALONG AND NORTH OF HIGHWAY 30 FOR 
LATE TONIGHT.

THURSDAY...CONVECTION POTENTIAL DURING DAYTIME DEPENDS A LOT ON 
MESOSCALE DETAILS. HAVE PLACED CHANCE POPS IN THE NORTH TO ACCOUNT 
FOR TWO THINGS 1) MORNING DEBRIS FROM DECAYING COMPLEX...AND 2) 
POSSIBILITY OF REDEVELOPMENT DURING THE AFTERNOON ALONG OUTFLOW... 
DESPITE WARM MID LEVEL TEMPS (+11 C). MOISTURE AND RESULTANT CU 
FIELD COULD KEEP MAXES IN CHECK AND POTENTIAL IS THERE TO BE FEW 
DEGS COOLER THAN ADVERTISING.   ..05..

THU AFTERNOON PRECIP CHANCES TO EXTEND INTO THE EVENING...BUT BETTER 
CHANCE COMES LATER IN THE NIGHT WHEN POTENTIAL COMPLEX MIGRATES FROM 
UPSTREAM ALONG SLIGHTLY DIFFLUENT MID LEVEL THICKNESS PATTERN INTO 
INCREASED 1000-H85 THTA-E ADVECTION AND CONVERGENCE ZONE ACRS THE 
LOCAL AREA. TIME PERIOD OF INCREASED POPS FOR THIS POTENTIAL FROM 
05Z ON. PARAMETERS STILL THERE FOR MCS TO MAINTAIN STRENGTH AND BE A 
WIND PRODUCER INTO THE CWA THU NIGHT. OF COURSE...THU NIGHT OUTCOME 
TO INFLUENCE FRI AND FRI NIGHT POTENTIAL WITH LINGERING OUTFLOW 
BOUNDARIES AND LLVL COOL POOL FOR RENEWED INFLAMMATION OF 
CONVECTION. BOTH ETA AND GFS SUGGEST BUILDING SWATH OF GOOD DEEP 
CONVECTIVE INDICES RIGHT OVER THE CWA ON FRI...AND IMPINGING 25 KT 
H85 FLOW IN UNSTABLE AND THTA-E RICH AIRMASS SPELLS POTENTIAL OF 
STRONG STORMS AND HEAVY RAINFALL POTENTIAL. CONVECTIVE DEBRIS FROM 
THU NIGHT ACTIVITY AND HOW FAST IT CAN ERODE FOR ATMOSPHERIC 
RECHARGE THE MAIN WILD CARD FOR THIS POTENTIAL. SOUTHERN EDGE OF 
WESTERLIES TO USHER IN VORT/UPPER SUPPORT...OR LINGERING MCV ALSO 
COULD BE A RE-IGNITER(GFS DOES BECOME FEEDBACK POLLUTED THOUGH ON 
FRI WITH VORT STRENGTH). AS FOR FRI HIGH TEMPS...THERMAL PROFILES 
SUGGEST UPPER 80S TO LOW 90S TAKING INTO ACCOUNT DEBRIS EROSION 
PROCESS AND AFTERNOON REDEVELOPMENT. AS CONVECTION MATURES INTO FRI 
EVENING...LIKELY POPS WARRANTED OVER MUCH OF THE CWA...BUT GFS 
SUPPORTS THE NORTH HALF WHILE ETA/META FAVORS THE THE SOUTH HALF TO 
SOUTHERN THIRD. AGAIN MUCH DEPENDS ON BOUNDARY LAYOUT AND CONVECTIVE 
OCCURRENCES BEFORE THEN.

.LONGER RANGE(SATURDAY THROUGH WEDNESDAY)...WILL GO ALONG WITH 
LATEST MRF...XGFS...AND ECMWF IN WALKING OUT DECAYING CONVECTION 
FROM AT LEAST THE SOUTH HALF OF THE CWA SAT MORNING...WITH INCOMING 
BUT TEMPORARY WEAK SFC RIDGE BUILDING ACRS THE AREA FOR FAIR REST 
OF THE DAY. WITH THINNING DEBRIS AND PROJECTED THERMAL PARAMETERS TO 
BE REALIZED...RECOVERY BACK INTO THE MID TO UPPER 80S. MEDIUM RANGE 
MODELS THEN SUGGEST NEXT MAIN WAVE OF CONSEQUENCE IN WESTERLIES ACRS 
THE NORTHERN CONUS...TO DEEPEN ACRS THE NORTHERN ROCKIES ON SUNDAY. 
THIS WILL START MIGRATION OF SECONDARY(PRIMARY ONE NEAR THE 
U.S./CANADIAN BORDER)WEST-TO-EAST ORIENTED THERMAL BOUNDARY NORTH 
INTO SOUTHERN IA. WILL KEEP CHANCE OF CONVECTION FOR MAINLY FOR LATE 
IN THE DAY AS WARM FRONT CONTINUES TO GET DRAWN NORTH BACK ACRS THE 
CWA. BOTH THE MRF AND EURO SWEEP TRAILING FRONT...EXTENDING OFF 
VIGOROUS SFC LOW PUSHING ACRS NORTHERN MN AND WI...INTO THE CWA/WARM 
UNSTABLE AIRMASS ON MONDAY FOR CONTINUING THREAT OF PRECIPITATION. 
QUESTIONS ARISE ON TUE WITH HOW FAR FRONT MAKES IT TO THE SOUTH OF 
THE CWA. MRF FAR ENOUGH SOUTH TO KEEP THUNDERSTORM CHANCE AND WARMER 
TEMPS JUST TO THE SOUTH OF THE CWA...WHILE EURO FURTHER NORTH WITH 
BOUNDARY GETTING HUNG UP ACRS SOUTHERN AND CENTRAL IA. MAY KEEP 
CHANCE GOING ACRS THE SOUTH WITH BOUNDARY PLACEMENT UNCERTAINTIES. 
THESE UNCERTAINTIES EXTEND INTO WED...BUT WILL BANK ON BACKDOOR HIGH 
TO DROP ACRS LK MICHIGAN AND SHUNT PRECIP THREAT SOUTH AND KEEP CWA 
DRY FOR THE DAY.   ..12..

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

$$

05/12