[LeArc] Forecast Discussion : MLI@ 2/13/03 3:47:05 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 132154
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
315 PM CST THU FEB 13 2003

COMPLICATED FORECAST NEXT 36 HRS.  I'LL GET RIGHT TO THE POINT. THE 
WATCH HAS BEEN UPGRADED TO A WINTER STORM WARNING EFFECTIVE FROM 
FRIDAY MORNING THROUGH FRIDAY NIGHT.  AREAS ALONG AND SOUTH OF 
HIGHWAY 34 FOR A COMBINATION OF SIGNIFICANT ICE AND SOME SNOW 
ACCUMULATION. TO THE NORTH TO ALMOST HIGHWAY 20 MAIN THREAT WILL BE 
HEAVY SNOW WITH AREAS ALONG AND JUST SOUTH OF I80 EXPERIENCING SOME 
MINOR ICE ACCUMULATION.  WILL GO AHEAD AND HOIST A WINTER WEATHER 
ADVISORY WEST DBQ AND WEST FOR SNOW...MAINLY FOR FRIDAY AND FRIDAY 
EVENING.

THERE WERE SOME INITIALIZATION ISSUES WITH THE MODELS THIS MORNING.
SYSTEM LIFTING OUT OF SRN CA/NRN MEX TONIGHT AND NO MEXICAN RAOBS 
MADE IT INTO THE MODEL RUNS THIS MORNING.  IMPACT THIS HAS ON THE 
12Z RUNS REMAINS TO BE SEEN.  ETA APPEARS TO HAVE INITIALIZED THE H3 
JET MOVING INTO SRN CA STRONGER THAN THE AVN.  THE AVN ALSO HANDLED
THE WARMER H8 TEMPS OVER THE PLAINS BETTER THAN THE ETA.  ALSO IT 
LOOKS LIKE THE AVN HAS A BETTER HANDLE ON PCPN MOVING THROUGH SRN 
PLAINS THIS AFTERNOON.  ETA IS TO FAR SOUTH. GFS HOLDS THE WARMER 
AIR FURTHER SOUTH AS SYSTEM MOVES THROUGH THE PLAINS FRIDAY.  GFS 
MOVES THE 0C H8 ISOTHERM JUST N OF BRL BY 18Z FRIDAY WHILE ETA 
PUSHES IT TO ALMOST DBQ.  IT'S ALWAYS DIFFICULT TO PIN DOWN THE 
NORTHERN EXTENT OF THE WARM AIR IN THESE WAA SCENARIOS...BUT WITH 
MODELS DEPICTING  A MODERATE E WIND NORTH OF THE H8 WARM FRONT AND 
SW FLOW TO THE SOUTH...IT APPEARS ETA IS OVER DOING THE WARM AIR.  
ALSO ADDING TO THE MIX IS THE UKMET WHICH IS COLDER THAN THE GFS BUT 
ALSO KEEPS THE SIGNIFICANT PCPN SOUTH OF MOST OF THE CWA.  WILL RELY 
MAINLY ON THE GFS THIS ISSUANCE.  EXPECT ONSET OF PCPN IN SW CWA 
AROUND 12Z WITH PCPN SPREADING NW INTO NRN SCTNS BY LATE MORNING. AS 
LOW LEVEL FLOW BACKS TO THE NORTH EAST PCPN IN N WILL DIMINISH 
DURING THE EVENING...BUT WILL CONTINUE ACROSS THE SOUTH INTO SAT 
MORNING WITH BULK OF SYSTEM STILL OVER KS/WRN MO. SURFACE TEMPS IN 
THE SOUTH WILL BE BORDER LINE FRIDAY MORNING...BUT WITH AMOUNT OF 
PCPN EXPECTED FEEL WARNING IS WARRENTED.  MOST OF FORCING WILL BE 
DUE TO WAA ADVECTION AND GARCIA METHOD USING THE 295K SURFACE 
SUPPORTS SNOWFALL IN THE 4 TO 8 INCH RANGE OVER CENTRAL CWA...BUT 
WILL SHAVE A LITTLE OFF DUE TO SOME MIXED PCPN EARLY FRIDAY.  

EXPECT LIGHT SNOW TO LINGER OVER SERN HALF OF CWA INTO SATURDAY BUT 
ADDITIONAL ACCUMS WILL BE MINOR.  

FOR REST OF THE SHORT TERM FCST ONLY SIGNIFICANT CHANGE TO PREVIOUS 
FCST WILL BE TO LOWER TEMPS SUNDAY WITH EXPECTED SNOW COVER AND HIGH 
PRESSURE MOVING THROUGH SETTING UP GOOD RADIATIONAL COOLING 
CONDITIONS.


MODELS CONTINUE TO SHOW ZONAL TO SWLY U/A FLOW NEXT WEEK BRINGING 
MILDER AIR TO THE REGION.  UKMET/ECMWF CONTINUES TO BE MORE 
AMPLIFIED THAN THE GFS.  WEEK WILL GET OFF TO A COLD START
AS HIGH PRESSURE RIDGES SLIDES EAST EARLY MONDAY MORNING. RAPID 
SUCCESSION OF SYSTEMS MOVING ALONG THE CANADIAN BORDER WILL ALLOW 
WARMER AIR TO RETURN NORTH WITH LITTLE TIME BETWEEN SYSTEMS FOR A 
SIGNIFICAN COOL DOWN.  HIGH PRESSURE RIDGE ACROSS GULF COAST WILL 
BLOCK MOISTURE RETURN INITIALLY.  RIDGE BREAKS DOWN SOME BY MID WEEK
WITH UKMET SUGGESTING BEST MOISUTRE RETURN BY LATE TUESDAY.  BASED 
ON THIS WILL CONTINUE CHC POPS ALREADY IN EXTENDED FOR WEDNESDAY.  
THURSDAY LOOKS DRY WITH RIDGE MOVING THROUGH.  TEMPS WILL BE SIMILAR 
TO PREVIOUS FORECAST WITH THE EXCEPTION OF MONDAY'S MINS.  I'LL 
LOWER THESE FROM PREVIOUS PACKAGE AND GO A LITTLE UNDER MEX WITH 
STRONG HIGH PRESSURE MOVING THROUGH SUNDAY NIGHT.


.DVN...
IA....WINTER STORM WARNING FOR FRIDAY THROUGH SATURDAY MORNING SOUTH 
OF
HIGHWAY 20.
WINTER WEATHER ADVISORY FRIDAY AND FRIDAY NIGHT ALONG THE HIGHWAY 20 
CORRIDOR.      
IL...WINTER STORM WARNING FOR FRIDAY THROUGH SATURDAY MORNING SOUTH 
OF HIGHWAY 20.
WINTER WEATHER ADVISORY FRIDAY AND FRIDAY NIGHT ALONG THE HIGHWAY 20 
CORRIDOR.
MO...WINTER STORM WARNING FOR FRIDAY THROUGH SATURDAY MORNING.

$$

DLF