[LeArc] Forecast Discussion : MLI@ 7/25/2003 4:39:42 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 250937
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
420 AM CDT FRI JUL 25 2003

AS LARGE SFC RIDGE SHIFTS EAST ACRS THE OH RVR VALLEY...INCREASING
PRESSURE GRADIENT BETWEEN IT AND ORGANIZING TROUGH AND SFC WAVE OVER
THE NORTHERN PLAINS TO INDUCE BRISK RETURN FLOW FOR WARM UP TODAY.
EXTRAPOLATING UPSTREAM THERMAL PROFILES AND EXTENT OF EXPECTED MIXING
SUGGESTING WIDESPREAD MID TO UPPER 80S FOR HIGHS TODAY...WITH EVEN
A 90 POSSIBLE ACRS THE FAR SOUTHWEST CWA. FCST SOUNDINGS AND
WIND FIELDS AT HIGHEST MIXING HEIGHTS SUGGEST BREEZY DAY ON TAP...
ESPECIALLY THIS AFTERNOON. DEVELOPING SOUTHWEST 20-25KT H85 FLOW TO
TAP INTO THERMAL RIDGE OVER THE WESTERN PLAINS...AND BOOST H85
TEMPS AT LEAST INTO THE UPPER TEENS CELSIUS ACRS THE CWA BY 00Z SAT.

WESTERLIES WILL STRENGTHEN ALONG THE NORTHERN MID CONUS/CANADIAN
BORDER THIS AFTERNOON...WITH RESULTANT STORM TRACK AND UPPER LEVEL
DISTURBANCE PROPAGATION MAKING FOR POTENTIAL STORMY UPPER MS RVR
VALLEY. BUT BUILDING UPPER RIDGING OVER IA AND IL...AS WELL AS LOBE
OF LOW TO MID LEVEL WARM DOME GETTING DRAWN EAST ACRS IA TONIGHT...
SUGGEST LOCAL AREA TO BECOME CAPPED AND LESS CONDUCIVE OF
EXPERIENCING ANY STORM ACTIVITY. THUS HAVE REMOVED POPS FOR TONIGHT.
BOTH GFS AND ETA INDICATE MCS SPAWN PARAMETERS TO COME TOGETHER THIS
EVENING ACRS THE EAST HALF OF SD AND INTO SOUTHWEST MN...WITH
THICKNESS PARAMETERS THEN SUGGESTING ACTIVITY TO MOVE EAST. SOME
MID TO HIGH LEVEL DEBRIS CLOUDS TO PROBABLY MAKE IT DOWN ACRS AT
LEAST THE NORTHERN THIRD TONIGHT AND WILL WORD PARTLY CLOUDY IN
THOSE AREAS...OTHERWISE A MOSTLY CLEAR BUT MILD NIGHT IS IN STORE
WITH CONTINUING SOUTHERLY BREEZE.

LATEST SHORT RANGE MODEL ENSEMBLE NOW SUGGESTS EVEN SLOWER EVENTUAL
FROPA NOT TIL LATER SAT NIGHT...THUS BEST FORCING FOR CAP PENETRATION
AND RESULTANT CONVECTION PROBABLY DELAYED UNTIL THEN. 100+ KT WEST-
TO-EAST ALIGNED JET MAX TO SAG SOUTH SAT NIGHT AS WELL...AS
DEEPENING TROUGH CYCLE COMMENCES AGAIN OVER THE GRT LKS. AS THE
SOUTHERN GRADIENT OF THE JET MAX IMPINGES ON THE LOCAL CWA WITH SOME
DIVERGENT INFLUENCE...LIFTING MOTIONS WILL BE AIDED. UNTIL THEN...
DVN CWA MAY REMAIN DRY DURING THE DAY SAT...BUT SAT AFTERNOON STILL
WARRANTS CHANCE POPS FOR AN EARLIER POTENTIAL OF CAP WEAKENING FROM
THE NORTH AND OUTFLOW BOUNDARIES FORM MN/WI COMPLEXES POSSIBLY MAKING
THEIR WAY DOWN INTO THE AREA. IF CONVECTION HOLDS OFF FOR MOST OF
SATURDAY...CONTINUED PRE-FRONTAL WARMING AND PROGGED THERMAL PROFILES
SUGGEST SOME MID 90S POSSIBLE. BUT FEEL ALSO INCREASING SFC DPTS
INTO THE 70S AND RESULTANT LLVL RH INCREASE MAY LIMIT HIGH
TEMPERATURE POTENTIAL TO AROUND 90/LOWER 90S. AS PREVIOUS SHIFT
INDICATED...PLENTY OF BUOYANCY PENT UP BY CAP TO FUEL SVR CONVECTION
ON SAT...BUT AGAIN TRIGGER MECHANISM AT QUESTION TIL LATER SAT NIGHT.


NO CHANGE TO LONGER RANGE FOR NOW...


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

$$

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