[LeArc] Forecast Discussion : MLI@ 4/24/2003 3:31:51 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 242025
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
325 PM CDT THU APR 24 2003

SHORT TERM...88D MOSAIC SHOWS TWO DISTINCT BANDS OF SHOWERS ROTATING
AROUND STACKED WESTERN KS LOW. INITIAL BAND...FROM KFOD TO JUST
NORTH OF KPIA AT 19Z PUSHING NORTH THROUGH CWFA HAVING A DIFFICULT
TIME SATURATING DRY LOWER LEVELS SO FAR TODAY...BUT STILL MANAGING TO
SQUEEZE OUT A FEW HUNDREDTHS ON METARS. SECOND BAND MORE CONVECTIVE
WITH LIGHTNING STRIKES PUSHING NORTH ACROSS NORTHERN MO...ABOUT TO
ENTER OUR MO ZONES WILL BE INITIAL CHANCE FOR SHOWERS THIS EVENING.
AT LEAST ONE MORE SPOKE OF ENERGY APPARENT ON SATELLITE IMAGERY IN
WEST CENTRAL MO TO ROTATE NORTHEAST INTO SOUTHERN ZONES LATER
TONIGHT. THUS SHORT TERM FORECAST CHALLENGE IS PRECIP CHANCES TONIGHT
INTO EARLY FRIDAY AS DEEP KS VORTEX SLIDES EAST.

MODELS ARE IN CLOSE AGREEMENT WITH FEATURES THROUGH 36 HOURS WITH
QPF UP TO ABOUT I-80 TONIGHT INTO THE FIRST HALF OF FRIDAY.
STRONGEST MID LEVEL Q VECTOR CONVERGENCE IS OVER FAR SOUTHERN ZONES
AND THUS WILL KEEP HIGHEST POPS...70 PERCENT...GOING THERE TONIGHT.
DO NOT EXPECT CURRENT THUNDERSTORMS TO HOLD TOGETHER MUCH LONGER AS
BAND MOVES INTO MORE STABLE AIRMASS OVER SOUTHEAST IA/W CENTRAL IL
LATE THIS AFTERNOON AND EARLY EVENING. TONIGHT...MUCH LIKE
TODAY...MODELS PLACING QPF TOO FAR NORTH INTO DRY LOW LEVEL AIRMASS.
THUS TRIMMED BACK CENTRAL TO SCATTERED TONIGHT...WITH NORTH CUT TO
SLIGHT. ON FRIDAY...LOW PASSES TO SOUTH. MAIN DEFORMATION ZONE AROUND
UPPER LOW PASSES AROUND 12Z...THEN LOW MOVES TO WESTERN KY BY 00Z.
MODEL TRENDS OF ENDING PRECIP IN MORNING LOOKS GOOD AND IS IN
AGREEMENT WITH TRENDS IN HIGH PLAINS...MINUS THE UPSLOPE ENHANCED
PRECIP. POPS CUT TO SCATTERED AND MAINLY SOUTH OF I-80 FOR MORNING.
NOT MUCH CHANGE TO TEMPERATURE GRIDS...40S TONIGHT AND ENOUGH THIN
SPOTS IN OVERCAST AND DRYING TREND TO SUPPORT AROUND 60 FRIDAY...
CLOSE TO COOL END OF GUIDANCE.

FRIDAY NIGHT...HIGH BUILDS INTO GREAT LAKES WITH LLVL NORTHEAST FLOW
ADVECTING IN DRIER AIR. MODEL GUIDANCE TYPICALLY TOO WARM IN
THIS PATTERN...SO WILL UNDERCUT BY 2-4 DEGS SIDING CLOSER TO UKMET
SURFACE TEMPS.

SATURDAY...SURFACE RIDGE AXIS DOMINATES AND STARTS TO SHIFT EAST
LATE. LIMITED MIXING SUPPORTS LEANING TOWARD COOL END OF GUIDANCE.

SATURDAY NIGHT...RETURN FLOW BECOMES ESTABLISHED...AS HIGH PULLS
EAST AND NEXT SYSTEM ORGANIZES IN THE PLAINS.
EXPECT WEST TO EAST GRADIENT ON MINS WITH EASTERN CUTS STILL DRAWING
IN COOL AIRMASS BENEATH SURFACE RIDGE ON LLVL E/SE WINDS.

SUNDAY...FRONTAL ZONE PROGGED INTO CENTRAL IA LATE DAY. TWO MAIN
AREAS OF PCPN EXPECTED...ONE ACROSS UPPER MIDWEST IN
ASSOCIATION WITH NORTHERN STREAM ENERGY AND SURFACE WAVE...WHILE THE
OTHER WILL BE ACROSS SOUTHERN PLAINS IN DEEPER MOISTURE WITH
CONVECTION ASSOCIATED WITH SURFACE WAVE AND DRYLINE.
THAT LEAVES LITTLE FOCUS FOR PCPN FOR OUR AREA...WITH CONVERGENCE
LOOKING SOMEWHAT WEAK ALONG FRONT AT THIS TIME. NONETHELESS...HARD
TO ARGUE LOW CHANCE POPS. WILL TRIM BACK DAYTIME POPS TO WEST
OF THE MISSISSIPPI RIVER. TEMPS CHALLENGING AS DON/T EXPECT ANY REAL
HELP FROM PRE-FRONTAL COMPRESSIONAL HEATING. FELL THOUGH WITH
WARMER START AND SOME LATE APRIL SUNSHINE...THAT MEX GUIDANCE IS IN
THE BALLPARK. WILL CONTINUE WITH CHANCE POPS SUN NIGHT AS FRONT
PUSHES SLOWLY INTO AREA.

EXTENDED (MON-THU)...VERY CHALLENGING PERIOD TO SAY THE LEAST WITH
MIXED SIGNALS FROM MEDIUM RANGE MODELS. UKMET/NOGAPS/GFS DEPICT
MORE AMPLIFICATION TO OVERALL PATTERN AND SHOW LARGE TROUGH
OVER EASTERN 1/2 OF COUNTRY BY MIDWEEK. ECMWF NOT AS AMPLIFIED...AND
DEPICTS BIT MORE RIDGING IN THE EAST. OVERALL...FAVOR UKMET
AS 12Z GFS IS TRENDING TOWARD IT/S SOLUTION. WILL DEFINITELY BE
A CHALLENGING TEMP FORECAST DURING THE PERIOD...WITH
STRONG SUGGESTIONS OF INFAMOUS LLVL LAKE ENHANCED NORTHEAST FLOW
BY MIDWEEK WITH LARGE SURFACE HIGH SHIFTING FROM GREAT LAKES
INTO OHIO VALLEY. THERE IS A LOT OF UNCERTAINTY ON PLACEMENT OF FRONT
TO OUR SOUTH AND HOW FAR NORTH IT RETURNS BUT FOR NOW WILL KEEP CHC
POPS IN FAR SOUTH TUE NIGHT AND AREAWIDE ON WED. NEXT SYSTEM
ADVERTISED BY UKMET TO PASS TO OUR SOUTH (NO SURPRISE THERE)...THUS
EXPECT MAINLY RAIN WITH SOME THUNDER POSSIBLE IN FAR SOUTH.
SYSTEM LOOKS A LOT LIKE CURRENT ONE. SCALED BACK TEMPS WITH LLVL E
FETCH.

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

$$

DLS/MWM