[LeArc] Forecast Discussion : MLI@ 6/27/2003 4:32:30 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 270930
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
420 AM CDT FRI JUN 27 2003

BACKING LLVL FLOW TODAY TO BRING ABOUT BOUT OF WAA...ESPECIALLY AT
THE H85 LEVEL. H85 ACTUALLY WARM AIR ADVECTS FROM THE WEST-NORTHWEST
TODAY AS TAP INTO WARMER POOL OVER THE NORTHERN PLAINS COMMENCES.
WITH ADEQUATE INSOLATION AND MIXING IN MODERATED THERMAL PROFILE
AND LOWER DPT/MORE HEATABLE SFC AIR...FCST SOUNDINGS SUGGEST THAT
REBOUND INTO THE LOWER TO MID 80S ON TAP FOR MOST OF THE AREA HIGHS
TODAY. DBQ AND NORTHWEST IL TO REMAIN CLOSER TO THE 80 DEGREE MARK.
L/W OVER THE NORTHERN GRT LKS TO CONTINUE TO SHIFT EAST TODAY...WITH
RESULTANT NORTHWEST FLOW USHERING VORT PIECES AND MAXES DOWN ACRS THE
UPPER MS RVR VALLEY THROUGH FIRST HALF OF THE WEEKEND. SOME CONCERN
THAT "SATELLITE" VORT ROTATING AROUND EXITING GRT LKS MAIN VORT TODAY
MAY SET OFF WIDELY SCATTERED SHOWERS AND THUNDERSTORMS IN AN
INCREASINGLY UNSTABLE AIRMASS ACRS PORTIONS OF THE CWA...ESPECIALLY
IN THE NORTHEAST 2/3'S. MAY INCLUDE LOWER POPS FOR THIS LATE
AFTERNOON POSSIBILITY....WITH SOME POS OMEGA FIELDS BEING INDUCED BY
WAA AND GLANCING CVA. FEEL SAME PROCESSES TO ALSO PRODUCE AT LEAST
PARTLY CLOUDY SKIES ACRS THE NORTHERN HALF THIS AFTERNOON FROM
MORNING SUNSHINE.

BETTER CHANCE OF PRECIP TO COME LATER TONIGHT AND SATURDAY...AS
STRONGER ALBERTA CLIPPER TYPE VORT WILL LOOK TO SKIRT DOWN ACRS MN
AND WI FRI NIGHT. MODELS OF COURSE VARY IN TIMING AND STRENGTH OF
THIS WAVE WITH GFS STRONGER BUT MORE PROGRESSIVE. IN ANY CASE
FEATURE TO KICK UP SCATTERED CONVECTION OVER MN...WHICH MAY
COALESCE INTO A TYPE OF CONVECTIVE COMPLEX AND PROPAGATE DOWN ALONG
TIGHTENING WARM FRONT AHEAD OF DEEPENING SFC REFLECTION OF UPPER
FEATURE. MOST MODELS AGREE HEAVIEST CONVECTION TO DROP DOWN JUST
NORTH OF WARM FRONT ACRS SOUTHERN MN AND SOUTHERN WI THROUGH SAT
MORNING. BUT...SHORT RANGE MODEL ENSEMBLE SUGGESTS EXTENT OF FORCING
...MID LEVEL JET PUNCH...AND THTA-E ADVECTION AND CONVERGENCE TO
"TAIL" DOWN ENOUGH ACRS THE LOCAL CWA FOR LATE NIGHT THREAT TO MOST
OF THE CWA...BUT WEST CENTRAL IL MAY ESCAPE ACTIVITY UNTIL SAT
MORNING.

SFC LOW PUSHING ACRS SOUTHEAST MN AND WI ON SAT TO WHIRL COLD FRONT
ACRS THE CWA FROM THE WEST BY LATE IN THE DAY. THIS FACT ALONG WITH
ANY OUTFLOW BOUNDARIES...SHOULD ACT AS FOCAL POINTS FOR FORCING
AND LLVL THTA-E FEED ACRS THE AREA TO KEEP SHOWER AND STORM THREAT
GOING INTO SAT. SOME DISCONTINUITY ON TIMING AND EXITING OF PRECIP
LATER IN THE DAY SAT...WITH SOME MODELS CLEARING MOST OF THE CWA OUT
BY AFTERNOON AND PAINTING A FAIR SAT NIGHT. OTHERS LINGER PRECIP
ACRS MOST OF THE CWA INTO SAT EVENING BEFORE CLEAR OUT. WILL
DEFINE DAY BETTER IN LATER PACKAGES...WITH UPCOMING MODEL RUNS
HOPEFULLY SHOWING MORE CONFORMITY. WILL BANK ON CONVECTIVE DEBRIS
KEEPING SAT TEMPS DOWN IN THE UPPER 70S TO LOWER 80S...ALTHOUGH
THERMAL POTENTIAL WARMER BY A FEW CATEGORIES.   ..12..

SUNDAY THROUGH THURSDAY...
NOT A LOT OF CHANGES DURING THIS TIME FRAME.  SUNDAY A BIT OF A
QUANDARY...AS LOW CHANCE POPS BASED MAINLY ON THE PROXIMITY OF A
TROUGH TO THE SOUTH OF THE CWA.  THIS APPEARS TO BE DEPENDENT ON HOW
FEATURES PLAY OUT ON SATURDAY...AND THE WEAK CLIPPER LIKE SYSTEM DUE
THROUGH THEN...AND THIS WILL NEED TO BE WATCHED.  A SURFACE RIDGE
BUILDS IN FOR MONDAY...AND CONDITIONS REMAIN QUIET.  A WARMING TREND
STARTS ON TUESDAY...AND ENOUGH OF A WEAK FEATURE MOVES THROUGH ON
TUESDAY TO CREATE A CHANCE OF SHOWERS AND THUNDERSTORMS...THOUGH
AFTERWARDS THERE DOESN'T APPEAR TO BE ENOUGH OF A TRIGGER DESPITE
INCREASING SOUTHERLY FLOW FOR PRECIPITATION UNTIL A WEAK FRONT DROPS
SOUTH ACROSS THE AREA ON THURSDAY.   ...LE...


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

$$

12/LE