[LeArc] Forecast Discussion : MLI@ 7/14/2003 4:50:08 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 140947
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
435 AM CDT MON JUL 14 2003

SFC RIDGE TO SHIFT TO THE EAST TODAY...ALLOWING INCREASING GRADIENT
TO INDUCE A WARMING SOUTHEAST BREEZE. AT THE H85 LEVEL...INCREASING
SOUTH-SOUTHWEST FLOW TAPS INTO WARM THERMAL POOL OVER WESTERN MO AND
AR TODAY...WITH H85 TEMPS BEING BOOSTED INTO THE UPPER TEENS OR
AROUND 20 C BY 00Z TUE. BUT THESE TEMPS WILL NOT BE FULLY REALIZED
AT THE SFC WITH FETCH FROM THE SOUTHEAST BACK INTO DEPARTING RIDGE
FROM SOUTHERN IL. CI DEBRIS FROM THE NORTH ALSO TO FILTER INSOLATION
AT TIMES...AND FEEL HIGHS TO RANGE FROM MID TO UPPER 80S OVER MOST OF
THE CWA. THIS SOUTHEAST SFC FLOW SHOULD KEEP HIGHER DPTS SHUNTED TO
THE WEST AS WELL TODAY...AND MAYBE INTO TONIGHT. THUS FEEL PROGGED
CAPES AND INSTABILITIES FOR TONIGHT AHEAD OF APPROACHING FRONT MAY
BE OVERDONE SOMEWHAT...BUT STILL ENOUGH TO FUEL POSSIBLE SEVERE
CONVECTIVE EVENT.

1ST VORT/MCV FROM OVERNIGHT NORTHERN PLAINS ACTIVITY WILL ROLL ACRS
MN AND WI TODAY...TOUCHING OFF SHOWERS AND STORMS AS IT DOES. MAIN
WAVE IN NORTHERN CONUS WESTERLIES TO DIG ACRS THE UPPER MS RVR
VALLEY/WESTERN GRT LKS TONIGHT...AS NOSE OF H25 MB 110+ KT JET MAX
PUNCHES DOWN ACRS THE UPPER MIDWEST. DIFFLUENT STRUCTURE OF THIS
FEATURE TO ADD UPPER SUPPORT...AS WELL AS MAIN VORT SHEARING DOWN
INTO DEEPENING TROUGH. SHORT RANGE MODELS HAVE COME CLOSER IN THEIR
FROPA TIMING...GENERALLY EXITING THE CWA JUST BEFORE 12Z TUE...BUT
VARY ON WHAT'S TO COME BEFORE THEN...INCLUDING AREAL CONVECTION
PLACEMENT AND INTENSITY. ETA/META PAINT TWO AREAS OF BEST FORCING AND
THTA-E ADVECTION AND CONVERGENCE IN AREAS OF INCREASING LLJ FOR MAIN
"FLASH POINTS" THIS EVENING. ONE OVER CENTRAL AND SOUTHERN MN...AND
THE OTHER OVER SOUTHEAST NE INTO NORTHWEST MO. ETA THEN PROPAGATES
MN FORCING AND LLVL CONVERGENCE TO THE EAST OVER WI AHEAD OF MAIN
WAVE....WHILE NORTHWEST MO PARAMETERS SHIFT EAST-SOUTHEAST OVER
CENTRAL MO AS THE NIGHT PROGRESSES. THIS WOULD LEAVE DVN CWA IN-
BETWEEN THE TWO MAJOR AREAS OF CONVECTIVE SYSTEMS TONIGHT...BUT AM
NOT BUYING IT. FAVOR UKMET AND GFS SOLUTIONS WHICH DEVELOP
CONVECTION IN SOUTH CENTRAL MN/FAR NORTHERN IA THIS AFTERNOON...AND
DEVELOP AND EVOLVE STORMS TO THE SOUTHEAST OVER THE DVN CWA THIS
EVENING AND ESPECIALLY OVERNIGHT. LOBE OFF H7 MB WARM DOME TO THE
WEST WILL LOOK TO GET DRAWN OVER MUCH OF THE CWA TODAY AND ACT AS A
LID...ONLY TO BE ERODED FROM THE NORTH AS CONVECTION AND MID LEVEL
SATURATION/COOLING MIX SOUTH.

EXTENT OF INSTABILITY...MOISTURE...SHEAR...AND TRIGGER PARAMETERS
(BLEP TECHNIQUE) SUGGEST ABOVE MENTIONED MCV OVER SOUTHERN MN TO SET
OFF CONVECTION AS CAP ERODES IN A SUPERCELLULAR FORM OVER NORTH
CENTRAL INTO NORTHEAST IA...WHICH COULD GET INTO THE NORTHWEST CWA BY
LATE AFTERNOON/EARLY EVENING. THIS ACTIVITY COULD THEN FORM INTO A
SEVERE MCS AND MAINLY DAMAGING WIND EVENT AS IT EVOLVES TO THE SOUTH
AND SOUTHEAST AS NIGHT PROGRESSES. WILL BE INTERESTING TO SEE WHAT
COMES OUT OF THIS AND IF SPC'S MODERATE RISK FOR THE ENTIRE CWA IS A
HIT. IF CAP BECOMES STRONGER THAN CURRENTLY EXPECTED...IT MAY KEEP A
LID ON CONVECTION UNTIL CLOSER TO FROPA FORCING LATER TONIGHT.
   ..12..

EXTENDED (THURSDAY THROUGH SUNDAY)
EUROPEAN MODELS AND GFS ARE IN GOOD AGREEMENT LATE NEXT WEEK AND
INTO THE WEEKEND.  AT THE BEGINNING OF THE PERIOD MODELS SHOW
IOWA/NORTHERN ILLINOIS ON THE SOUTHERN EDGE OF THE STRONGER WESTERLY
FLOW WITH STRONG MID LEVEL RIDGE CENTERED OVER THE CENTRAL ROCKIES.
WARM/STATIONARY FRONT SHOULD BE SOUTH OF CWA FROM THE LOWER OHIO
VALLEY INTO THE CENTRAL PLAINS.  STRONG S/W TOPPING RIDGE ACROSS THE
SOUTHERN CANADA THURSDAY NIGHT/FRIDAY SHOULD PULL FRONT NORTH AS
COLD FRONT TRAVERSES NORTHERN PLAINS...REACHING WESTERN GREAT LAKES
BY LATE FRIDAY.  TIMING DIFFERENCES SHOW UP BETWEEN GFS AND UKMET
WITH MOVEMENT OF FRONT THROUGH THE MID MISSISSIPPI VALLEY FRIDAY
NIGHT...WITH THE GFS BEING THE QUICKEST.  BUT THE END RESULT BY
SATURDAY IS THAT THE BOUNDARY WILL BE WELL TO THE SOUTH OF THE CWA.
CURRENT FORECAST IS IN GENERAL AGREEMENT WITH THE 14/00Z MODEL RUNS
AND WILL NOT MAKE ANY CHANGES AT THIS TIME.  THE DAY SHIFT WILL HAVE
TO RE-ASSES THE TIMING ISSUES FOR THE FRONTAL PASSAGE FRIDAY
NIGHT/SATURDAY MORNING.  IF THE 14/12Z RUNS TREND TOWARD THE SLOWER
UKMET...THEN POPS WILL HAVE TO BE EXTENDED INTO SATURDAY.
ALSO...MODELS ARE SUGGESTING THAT TEMPS THURSDAY MAY BE ABOUT A
CATEGORY LOWER THAN CURRENTLY FORECAST WITH MODELS HOLDING BOUNDARY
JUST TO OUR SOUTH.    ..DLF..


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

$$

12/DLF