[LeArc] Forecast Discussion : MLI@ 7/17/2003 3:31:37 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 172016
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
305 PM CDT THU JUL 17 2003

LATEST MSAS LOOP AND SFC ANALYSIS INDICATE BOUNDARY UNDULATING
SLOWLY SOUTHWARD SOUTHERN WI...ACRS NORTHERN IA...AND ACRS
NORTHEAST NE. LATEST LAPS INDICATING AIRMASS ALONG AND SOUTH OF
BOUNDARY HAS BECOME A LOADED POWDER KEG WITH SFC TEMPS IN THE MID TO
UPPER 80S AND DPTS OF MID 70S. CAPES ACRS THE LOCAL CWA HAVE
BREACHED 4K J/KG...WHILE JUST TO THE WEST AROUND DSM THE CAPES HAVE
GROWN TO AROUND 6K J/KG. BUT SFC BASED CONVECTION HAS BEEN HELD AT
BAY WITH ROBUST CAP IN PLACE. SHORT WAVE WITH ELEVATED PRECIP MOVING
SOUTHEAST OUT OF THE DAKOTAS TROUBLING IN THAT IT SHOULD BRING
MODERATION IN MID LEVELS ENOUGH TO ERODE CAP FOR EVENING CONVECTION
TO ERUPT FROM NORTH TO SOUTH. CAP MAY HOLD THROUGH EARLY EVENING
THOUGH...WITH PESKY ELEVATED CONVECTION CONTINUING ACRS SOUTHWEST IA
AND CENTRAL/NORTHEAST IL. MSAS PRESSURE FALLS/LLVL CONVERGENCE
AND MESOANALYSIS INDICATING FLASH POINT MAY ACTUALLY BE NORTHWEST OF
THE DSM AREA WITH INCOMING VORT...WITH CONVECTION THEN LIGHTING UP
IN A "ZIPPER" EFFECT BACK THROUGH SOUTHERN WI. WILL BE INTERESTING TO
SEE HOW CONVECTION TRANSPIRES. BLEP TECHNIQUE WITH CURRENT THERMAL
AND MOISTURE PARAMETERS SUGGEST SOME SUPERCELLULAR DEVELOPMENT ALONG
BOUNDARY/BOUNDARIES...THEN CONSOLIDATING INTO A SEVERE LINEAR MCS AND
PROPAGATE SOUTHWARD OFF THE BOUNDARY AND PRODUCE STRAIGHT LINE WINDS
POTENTIALLY OF UP TO 90 MPH OR HIGHER(IF IT CAN BECOME SFC BASED).
UNTIL THEN...THE CAP RULES.

WILL LEAN TOWARD UKMET WHICH LINGERS SHOWERS ACRS THE SOUTHERN CWA
FRIDAY MORNING...BEFORE INCOMING SFC HIGH SHUNTS BOUNDARY AND
PRECIP FURTHER SOUTHWARD TO ACRS CENTRAL MO AND SOUTHERN IL AS DAY
PROGRESSES. EXPECT DEBRIS AND MID LEVEL CLOUDINESS NORTH OF BOUNDARY
ACRS AT LEAST THE SOUTHERN HALF OF THE CWA ON FRI...COMBINED WITH
INCREASING NORTHEAST WINDS...HIGHS MAY NOT GET OUT OF THE 70S.
LOOKING AT EXTENT OF COOLING AIRMASS ASSOCIATED WITH SFC HIGH
BUILDING DOWN INTO THE AREA FRI NIGHT AND SAT...SAT MORNING LOWS MAY
APPROACH RECORD COOL LEVELS(LOW TO MID 50S) AND WILL MENTION "NEAR
RECORD' WORDING IN ZONES. "RIDGE AXIS SATURDAY" LOOKS TO BE A WINNER
WITH LIGHT WINDS AND FAIR SKIES...TEMPS TO REBOUND TO BACK AROUND 80
WITH INSOLATION BUT LIMITED MIXING.

.LONGER RANGE(SUN-THU)...LATEST MEDIUM RANGE MODEL ENSEMBLE STILL
SUGGESTS NEXT WEEK TO BE A REINFORCED ROUND OF STRONG NORTHEAST
FETCH/GRT LK EFFECT INLAND FAR ENOUGH TO HAVE IMPACT ON THE DVN CWA.
WILL SIDE WITH LATEST EURO AND UKMET SOLUTIONS WHICH ARE SIMILAR.
NORTHWEST FLOW TO USHER DIGGING WAVE INTO GRT LKS ON SUNDAY...WITH
INCOMING COLD FRONT OFF SFC LOW WARRANTING PRECIP CHANCE. DEPENDING
ON FROPA TIMING AND PRE-FRONTAL WARMING POTENTIAL ON SUNDAY...MEX
GUIDANCE HIGHS MAY BE UNDERDONE. AS UPPER LOW CONTINUES TO DEEPEN
OVER THE GRT LKS ON MONDAY...WRAP AROUND VORTS AND UPPER LEVEL COLD
POOL SHOULD GENERATE SCTRD SHOWERS AND EVEN A FEW STORMS OVER THE
LOCAL AREA. THEN LARGE CANADIAN HIGH CENTER AT THE SFC WILL LOOK TO
MAKE ITS WAY TOWARD LK SUPERIOR THROUGH MID WEEK...INDUCING
NORTHEAST FETCH TOWARD NORTHWEST IL AND EASTERN IA FOR COOLING LK
EFFECT. MEX HIGHS STILL LOOK TO BE OPTIMISTIC(TOO WARM) MON THROUGH
WED...LOOKING AT CURRENTLY INDICATED STRENGTH OF INCOMING RIDGE AXIS
AND NORTHEAST GRADIENT. UPPER MS RVR VALLEY TO BE BATHED IN STEEP
CYCLONIC FLOW ALOFT UNTIL UPPER RIDGING TRIES TO BUILD IN FROM
THE WEST ON THU FOR SOME SLIGHT TEMP MODERATION.


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

$$

12