[LeArc] Forecast Discussion : MLI@ 11/3/02 2:53:28 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 030902
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
300 AM CST SUN NOV 3 2002

SHORT RANGE MODELS IN DECENT AGREEMENT IN SOLUTION OF RATHER INTENSE
CO/WY VORT COMPLEX SHEARING THROUGH CONFLUENT ZONE OF SPLIT FLOW
PATTERN. MODELS PROPAGATE BULK OF THIS FEATURE ACRS TO THE SOUTH
OVER MO TODAY IN AN OPENING WAVE FASHION. LATEST W/V IMAGERY AND 00Z
UA ANALYSIS INDICATES THIS REASONABLE AND MAKES SENSE...BUT MODELS
STILL MAY BE TYPICALLY TOO QUICK IN OPENING UP AND WEAKENING SUCH A
VIGOROUS FEATURE.  THIS WAVE PROPAGATION AND PHASING SOLUTION
SUGGESTS BULK OF PRECIP TO REMAIN SOUTH OF LOCAL AREA OF CONCERN
TODAY...AND LATEST MODEL RUNS HAVE DIMINISHED THE POPS. BETTER H7-H5
MB CONVERGENT QG FORCING...H3 JET DIFFLUENCE...AND H7 POS OMEGAS ARE
FORECAST BY THE AVN AND ETA TO REMAIN OVER MO TODAY...SUPPORTING
SOUTHWARD SHIFT IN PRECIPITAL AXIS. NGM DOES PUT 2 -UBARS/S
OMEGA BULLSEYE ACRS THE SOUTHERN CWA THIS AFTERNOON THOUGH...WHICH
LEAVES THE DOOR OPEN...BARELY. AVN...NGM AND ETA/META ALL SKIRT LIGHT
PRECIP ACRS MAINLY THE SOUTH THIRD OF THE CWA TODAY...AND THATS
PROBABLY WHAT WILL HAPPEN DUE TO FORECAST LACK OF FORCING OVER THE
IMMEDIATE AREA.

CONCEPTUALLY THE NOSE AND NORTHERN EDGE OF VORT AND MAIN CVA PUSH
SHOULD SPREAD PRECIP UP TO AND JUST NORTH OF THE I-80 CORRIDOR BY
THIS AFTERNOON...BUT AGAIN MAY BE NOTHING MORE THAN SPRINKLES. 295 K
ISENTROPIC ANALYSIS SHOWS DECENT LIFT ACRS THE SOUTH HALF OF THE
CWA BY MIDDAY...BUT STRONG COND P-DEF GRADIENT FROM NORTH TO THE
SOUTH HALF...ALSO INDICATES NORTHERN THIRD OF CWA MAY NOT SEE MUCH
PRECIP REACHING THE SURFACE AT ALL. QUICK LOOK AT H7-H4 THERMAL
WIND LAYER AND ITS PVA SUGGESTS THAT BETTER POS OMEGA/UVV POTENTIAL
FROM 18Z SUN-00Z MON OVER AT LEAST THE SOUTHERN THIRD OF THE CWA
...THAN MODELS NOW INDICATE. SO AM TORN WHETHER TO DOWNGRADE
LIKELY POPS ACRS THE SOUTH TO A CHANCE. ISENTROPIC LIFT QUICKLY GETS
SHUNTED TO THE EAST THIS EVENING...WITH CENTRAL IL/IN LOOKING TO HAVE
A BETTER SHOT AT MORE ORGANIZED PRECIP BY THIS EVENING THAN THE DVN
CWA. INCOMING SUBSIDENCE AND BRISK DOWN-GLIDE BEHIND DEPARTING SYSTEM
SHOULD ACT AS A CLEARING AGENT...ALTHOUGH WOULDN'T BE SURPRISED IF
SOUTH REMAIN PARTLY TO MOSTLY CLOUDY ADJACENT TO MID LEVEL VORT SHEAR
AXIS.

AS FOR PRECIP TYPE...FORECAST 925 MB TEMPS AND OTHER CRITICAL
THICKNESSES COMBINED WITH CLOUD BASES AROUND 3-4K FT SUGGEST ALL
LIQUID FORM BY TIME SATURATION ALLOWS PRECIP TO REACH SURFACE. SOME
CONCERN THAT IF VERTICAL MOTIONS UNDERDONE WITH SUCH A VIGOROUS
SYSTEM...MAY ALLOW MIXING DOWN OF COLD AIR FOR PRECIP MIX OR
TEMPORARY SWITCH OVER TO SNOW BY LATE MORNING. CLOUD COVER AND
POTENTIAL OF SOME EVAPORATIVE COOLING MAKES FOR A PREFERENCE OF THE
COOLER MAV TODAY. INCOMING SFC AND UPPER RIDGING TO MAKE FOR NICE
START TO WEEK...AND EXPECTED LLVL THERMAL PARAMETERS AND SUNSHINE
COULD BOOST MONDAY HIGHS TO NEAR YESTERDAYS/SATURDAYS VALUES EVEN
WITH LIMITED MIXING...THUS PREFER FWC HIGHS FOR TOMORROW(OR JUST
BELOW).

NO CHANGE TO LONGER RANGE FOR NOW...ALTHOUGH SOME MIXED SIGNALS IN
VARIOUS MODEL RUNS FOR THIS COMING TUE...MAKE FOR EAGERNESS AWAITING
THE ARRIVAL OF NEW RUNS. LATEST UKMET SUGGESTS POTENTIAL FOR LIGHT
ACCUMULATING SNOWS ON ELECTION/TUESDAY...WHILE ETA/META COMPLETELY
DRY.


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

JDH