[LeArc] Forecast Discussion : MLI@ 5/3/2003 5:02:15 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 030956
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
445 AM CDT SAT MAY 3 2003

VORT SEEN ON LATEST W/V IMAGERY OVER EAST IA...INDUCING SOME AC
OVER CENTRAL AND EASTERN IA...AND EVEN A FEW SHOWERS TRYING TO
BLEED OUT OF CENTRAL IA AND INTO THE SOUTHWEST PORTION OF DVN
CWA. BUT SFC ANTICYCLONE DROPPING OVER THE GRT LKS WILL CONTINUE TO
HAVE ITS DRYING...NORTHEAST FETCH INFLUENCE AND KEEP ANY PRECIP AT
BAY FROM REACHING THAT FAR INTO THE WESTERN CWA. WILL LEAVE OUT
MORNING MENTION ACRS THE WEST...AS THE FEW STRAY SHOWERS THAT MAY
SURVIVE INTO THE WESTERN FRINGE OF THE CWA TO BE SHORT LIVED AND
DECAY ENOUGH NOT TO BE MENTIONABLE. AS VORT EVACUATES THE AREA AND
MOVES TO THE SOUTHEAST TODAY...DRYING SUBSIDING COLUMN BEHIND IT
SHOULD ALLOW FOR THE AC TO ERODE AND MAKE FOR A MOSTLY SUNNY
AFTERNOON. EVEN AFTER COOL START...MAY INSOLATION AND MIXING EAST
SOUTHEAST WINDS IN PROJECTED LLVL THERMAL PROFILE...ALTHOUGH LIGHT...
SHOULD ALLOW TEMPERATURES TO REACH THE MID TO UPPER 60S OVER MOST
LOCAL AREA OF CONCERN TODAY.

DYNAMICAL SITUATION TO EVOLVE OVERNIGHT TO THE WEST OF THE REGION.
L/W TROUGH TO ROLL OUT OF THE WESTERN CONUS AND ACRS THE CENTRAL-
NORTHERN ROCKIES...EVENTUALLY CUTTING OFF AND BECOMING NEG TILTED BY
MIDDAY SUNDAY. AGAIN GENERALLY PREFER LATEST UKMET HANDLING OF THIS
SYSTEM...ALTHOUGH GFS SIMILAR AND MAINTAINING SOME RUN-TO-RUN
CONFORMITY AS WELL. THIS FEATURE TO FAN OUT IMPRESSIVE DIFFLUENT
SOUTHWEST FLOW AT MID-HIGH LEVELS OVER THE AREA ON SUNDAY.
DIFFLUENT NOSE OF 100+ KT H3 JET MAX TO PUNCH UP OVER THE AREA ON
SUNDAY...ADDING UPPER DIVERGENT CHIMNEY AFFECT ALOFT OVER
IMPRESSIVE 40-60 KT H85-H7 JETS WITH ROBUST WAA AND POS OMEGAS BY
SUNDAY AFTERNOON. SHORT RANGE MODELS VARY ON EXTENT AND PLACEMENT OF
VORT SWEEPING UP ACRS THE CWA ON SUNDAY...BUT LIKE GFS AND UKMET
SOLUTION OF SUGGESTING MAIN VORT TO PULL UP AROUND DEEPENING
VORTEX AN ACRS NORTHWEST IA BY SUNDAY EVENING. WITH DEEPENING SFC LOW
INDUCING ENOUGH OF A SFC GRADIENT FOR BRISK SOUTHEAST WINDS ACRS
THE CWA BY SUNDAY AFTERNOON...AND OCCLUDED WARM FRONT FEATURE
REMAINING JUST TO THE SOUTH OF THE AREA OVER NORTHERN MO THROUGH
SUNDAY EVENING...FEEL STAGE SET UP FOR ELEVATED BAND OF RAIN AND
EMBEDDED THUNDERSTORMS. H85 WARM FRONT AND THTA-E GRADIENT TO SHIFT
FURTHER NORTH ALMOST INTO THE NORTHERN CWA BY 00Z MON...ALSO
SUPPORTING ELEVATED THREAT. BRISK SOUTHEAST FLOW TAPPING BACK INTO
DRIER AIRMASS MAY RETARD SOUTHWEST-TO-NORTHEAST ADVANCEMENT OF PRECIP
SOMEWHAT...AGAIN SUGGESTS MUCH OF THE ACTIVITY NO TO OCCUR TIL
SUNDAY AFTERNOON WITH BEST DYNAMICS AND LIFT. PARAMETERS COMING
TOGETHER FOR HEAVIER THUNDERSTORM COMPLEX/DEVELOPMENT JUST NORTH OF
THE WARM FRONT ACRS THE SOUTHERN CWA SUNDAY AFTERNOON...AND EXPECT
HEAVIER RAIN TOTALS AND BETTER SEVERE THREAT DOWN THERE THROUGH MID
SUNDAY EVENING. "SCARY" STORM REL HELICITIES EXTEND UP THROUGH THE
CENTRAL CWA BY 00Z MON...AND MAY SUPPORT ELEVATED ROTATING STORMS FOR
LARGE HAIL THREAT FURTHER NORTH THAN THE SPC DAY-2 SLIGHT RISK
SUGGESTS.

MODELS SUGGEST DRY SLOT TO WHIRL ACRS THE CWA FROM THE SOUTHWEST
LATE SUNDAY NIGHT AND MONDAY MORNING...LOOKING REASONABLE WITH
EXTENT OF CLOSED STACKED SYSTEM JUST TO THE NORTH. WARM SURGE AND
MIXING IN THIS IN-FEED MAY SUPPORT UPPER 70S...TO AROUND 80 DEGREES
ON MONDAY AND HAVE RAISED TEMPS. ADJACENT UPPER LOW...COOL POOL AND
ROTATING VORT SPOKE...FOLLOWING DRY WARM TONGUE OF AIR OVER THE
AREA...SUPPORT CHANCE OF SCATTERED INSTABILITY SHOWERS AND STORMS BY
MID MONDAY AFTERNOON.


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

$$

JDH