[LeArc] Forecast Discussion : MLI@ 6/18/02 2:08:44 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 181908
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
208 PM CDT TUE JUN 18 2002

LATEST SURFACE ANALYSIS CONTINUES TO BE SOMEWHAT COMPLEX.  LOW
PRESSURE SYSTEM OVER CENTRAL NEBRASKA WITH TYPICAL DRY LINE
EXTENDING SOUTHWARD THROUGH WEST KANSAS INTO OKLAHOMA PANHANDLE.  A
BROAD WARM FRONT EXTENDS ACROSS IOWA INTO ILLINOIS...BUT BECOMES VERY
DIFFUSE.  WARMER AIR AND HIGHER DEW POINTS STILL IN THE MISSOURI
RIVER VALLEY REGION.  THIS IS WHERE EARLY MORNING CONVECTION FIRED...
ALONG THE 850 MB TEMPERATURE GRADIENT PRODUCING SOME FLOOD PROBLEMS
FOR NORTHWEST IOWA.  LOW LEVEL SOUTHWEST JET COMBINED WITH NORTHWEST
FLOW ALOFT...PRODUCED ENOUGH SHEAR TO PRODUCE A FEW LARGE HAIL EVENTS
IN SOUTHWEST IOWA.

MAIN FORECAST CHALLENGES ARE MANY TO PICK FROM IN THE EARLY GOING.
WILL ATTEMPT TO BREAK OUT THE SURFACED BASED OVERNIGHT CONVECTION
FROM THE ELEVATED CONVECTION WHICH SHOULD ARRIVE WITH THE NEXT SHORT
WAVE...NOW OVER SOUTH DAKOTA.  TRYING TO DETERMINE THE FOCUS FOR
SHOWER AND THUNDERSTORM CHANCES ON WEDNESDAY IS ALSO NOT CUT AND
DRIED.

MODELS ARE IN FAIRLY GOOD AGREEMENT WITH BUILDING UPPER RIDGE OVER
THE SOUTH CENTRAL U.S. TO THE NORTHEAST U.S.  ALSO WITH BRINGING
ENERGY ON LEADING EDGE OF PACIFIC NORTHWEST TROUGH TO THE
NORTHEAST INTO CANADA BY DAY 3.  AFTER DAY 4...TAKE YOUR PICK OF
MODELS...AS THEY TAKE SEPARATE PATHS.  THE AVN IS THE FASTEST AND
THE STRONGEST WITH THE NEXT UPPER SYSTEM WHICH THE MODELERS
CONTRIBUTE TO CONVECTIVE FEEDBACK PROBLEMS.  THE AVN AND ECMWF ARE
BOTH FAST WITH THE SURFACE FEATURES AS WELL...WHILE ALL OTHER MODELS
APPEAR TO BE SLOWER.  I TEND TO AGREE WITH THE SLOWER SOLUTIONS.

LOOKING AT THE EARLY PERIODS OF THE FORECAST...WILL ONCE AGAIN HAVE
TO GO WITH SOME 30 POPS TYPE WORDING FOR OUR WEST AND NORTH ZONES.
WILL TAKE CENTRAL ZONES DOWN TO SLIGHT CHANCE WORDING AND LEAVE SOUTH
ZONES DRY. TOMORROW...WILL GO WITH SOME MORNING POPS IN WEST ZONES...
ALL OTHERS WILL GO DRY.  700 MB TEMPERATURES PUSH A +10 ACROSS OUR
FORECAST AREA BY PM...WHICH IS NOT REALLY A CAP...BUT IT APPEARS THE
BEST SURFACE AND UPPER LEVEL FORCING WILL BE TO OUR NORTH.  WILL
LEAVE SLIGHT CHANCE WORDING IN FOR HIGHWAY 20 ZONES FOR WEDNESDAY
NIGHT...BUT CONFIDENCE NOT HIGH.  IN THE MID RANGE...MODELS CONTINUE
TO BRING SURFACE FRONT ACROSS FORECAST AREA THURSDAY AND FRIDAY WHICH
NOW IS LOOKING TO BE OUR BETTER CHANCE OF SHOWERS AND THUNDERSTORMS.

LOOKING AT THE EXTENDED...WILL MAKE SOME CHANGES IN THIS AREA...FOR
THE WEEKEND THROUGH MONDAY WILL TAKE OUT MENTION OF PRECIPITATION
AND THUNDER.  GUIDANCE IS THROWING SOME POPS AT US ON MONDAY BUT WILL
LEAVE PARTLY CLOUDY AND DRY FOR NOW.  AVN MRF DO BRING A 500 MB
TROUGH THROUGH OUR FORECAST AREA ON MONDAY...BUT RH NOT VERY
IMPRESSIVE AND BEST SURFACE CONVERGENCE APPEARS TO BE NORTH. MODELS
HAVE BEEN TO FAST WITH FEATURES IN THE PAST SO WILL BRING CHANCE OF
SHOWERS AND THUNDERSTORMS IN ON DAY 7.  STILL LOOKING TO BE A HOT
WEEKEND...BUT THE STORMS WILL LIKELY FIRE NORTH OF OUR FORECAST AREA
AROUND TOP OF BROAD UPPER RIDGE.  WILL BUMP TEMPERATURES UP TO AROUND
90 FOR THE SOUTHERN ZONES ON SATURDAY AND GO WITH MID AND UPPER 80S
ELSEWHERE.

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

MEYER