[LeArc] Forecast Discussion : MLI@ 4/25/2003 3:46:42 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 252039
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
335 PM CDT FRI APR 25 2003

RAIN HAS EXITED FAR SOUTH/EAST ZONES AS VERTICALLY STACKED UPPER LOW 
NEAR BOOTHEEL OF MO MOVES EAST...HEADING FOR THE CENTRAL 
APPALACHIANS BY 12Z SAT. SURFACE RIDGE AXIS EXTENDS FROM THE UPPER 
MIDWEST THROUGH THE PLAINS AND WILL BUILD INTO THE AREA OVER THE 
NEXT 24 HRS. WATER VAPOR AND UPPER AIR ANALYSIS SHOW CLOSED LOW JUST 
OFF THE OREGON COAST. THIS SYSTEM IS PROGGED NOT TO MOVE MUCH OVER 
NEXT FEW DAYS. SPOKES OF ENERGY WILL BE EJECTED FROM THE SYSTEM 
THROUGH THE INTERMOUNTAIN WEST AND INTO THE UPPER MIDWEST. 

SHORT TERM...FOCUS IS WITH TEMPS AND CLOUDS. SURFACE RIDGE AXIS 
WILL BUILD INTO THE AREA DURING THE NEXT 24 HRS. MID/HIGH CLOUDS 
ACROSS THE SOUTH WILL EXIT BY EARLY EVE. NEXT BATCH OF HIGH 
CLOUDINESS OVER SOUTHWEST MN MOVING S/E...DEPICTED BEST BY GFS. THIS 
MAY SPELL BRIEF PERIOD OF PTCLDY SKIES THIS EVE INTO FIRST PART OF 
OVERNIGHT. MODELS ALSO INDICATE SOME MOISTURE OVERNIGHT AROUND H85 
BUT DON/T SEE MUCH IN THE WAY OF FORCING TO GENERATE CLOUDS. 
SO...OVERALL FEEL MOSTLY CLEAR WILL SUFFICE. MINS WILL BE 
CHALLENGING TONIGHT...WITH PLENTY OF DRY AIR WITH DEWPTS IN THE 
MID/UPPER 20S BEING ADVECTED IN ON LLVL NORTHEAST WINDS. TRICK WILL 
BE EXTENT OF HIGH CLOUDINESS AND ANY IMPACTS...AS WINDS BECOME LIGHT 
BY MID-LATE EVE. FEEL IMPACT FROM HIGH CLOUDINESS SHOULD BE RATHER 
MINIMAL AND WILL SIDE AT OR JUST BELOW COOL END OF GUIDANCE. ON 
SATURDAY...EXPECT SOME CIRRUS AND MODELS CONTINUE TO SHOW SOME 
MOISTURE AROUND H85...BUT AGAIN LACKING TRIGGER FOR MUCH CLOUD 
DEVELOPMENT AND FEEL MOSTLY SUNNY IS THE WAY TO GO. WILL NEUTRAL 
ADVECTION...EXPECT MAXES SIMILAR TO THOSE OF TODAY. SURFACE RIDGE 
SHIFTS EAST SATURDAY NIGHT WITH RETURN FLOW DEVELOPING. WENT WITH 
WEST TO EAST GRADIENT ON MINS WITH EASTERN CUTS IN LLVL SOUTHEAST 
FLOW TAPPING COOLER AIRMASS BENEATH HIGH IN THE OHIO VALLEY. 
THEREFORE...WENT AT OR JUST BELOW GUIDANCE IN THE EAST AND TOOK A 
BLEND IN THE WEST. 

SUNDAY AND MONDAY THE MAIN CONCERN WILL BE THE THE WEAK COLD FRONT 
SAGGING SOUTHEAST THROUGH THE REGION.  BOTH THE GFS AND THE ETA 
BRING THE FRONT THROUGH CWA SUNDAY EVENING AND EARLY MONDAY 
MORNING...WITH THE ETA A LITTLE SLOWER THAN THE GFS.  MODELS HAVE 
SHIFTED THE NORTHERN STREAM S/W ASSOCIATED WITH THIS 
FEATURE...FURTHER NORTH...LIMITING MID LEVEL DYNAMICS WITH THE 
SYSTEM.  SURFACE MOISTURE WILL ALSO BE SOMEWHAT LIMITED WITH THE GFS 
PULLING LOW 60 SURFACE DEWPOINTS NORTH AHEAD OF THE FRONT WITH THE 
ETA KEEPING DEWPOINTS IN THE MID 50S. BASED ON LIMITED MOISTURE AND 
INSTABILITY AND A WEAK TRIGGER...FEEL ANY CONVECTION THAT DEVELOPS 
WILL BE SCATTERED.  CURRENT FORECAST REFLECTS THIS THINKING WITH CHC 
POPS IN WESTERN CWA LATE SUNDAY AFTERNOON AND CWA WIDE OVERNIGHT 
MONDAY.  SURFACE BOUNDARY STALLS OVER NRN MO EARLY MONDAY MORNING.  
GFS RIDES A S/W ALONG THE BOUNDARY MONDAY...GENERATING SUBSTANTIAL 
QPF ALONG MO BORDER.  ETA IS LESS IMPRESSIVE BUT STILL
SUPPORT THIS SCENARIO.  WILL UP POPS TO 50S OVER THE SOUTHERN THIRD 
OF CWA SUNDAY NIGHT AND MONDAY TO ACCOUNT FOR THIS POSSIBILITY.

WILL GO ABOUT A CATEGORY OVER MOS FOR HIGHS ON THE SUNDAY WITH 
SOMEWHAT DRY SW FLOW AHEAD OF APPROACHING FRONT.  CLOUDS AND PCPN 
NEAR THE BOUNDARY OVERNIGHT WILL KEEP MINS NEAR THE MAV NUMBERS IN 
THE SOUTH...AND WILL GO A LITTLE COOLER THAN THE MAV OVER THE NORTH 
WHERE CLOUDS WILL HAVE LESS OF AN IMPACT.  MONDAY MAXES WILL BE 
GREATLY INFLUENCED BY PCPN EXPECTED IN THE SOUTH AND WILL KEEP TEMPS 
IN THE SOUTH ABOUT A CATEGORY LOWER THAN THE MEX.

EXTENDED (TUE-FRI)
SIGNIFICANT DIFFERENCES STILL EXIST NEXT WEEK BETWEEN THE GFS AND 
THE EUROPEAN MODELS.  ALL MODELS SUGGEST A SIMILAR SCENARIO WITH 
CYCLOGENISIS AHEAD OF LARGE UPPER TROF OVER THE WESTERN U.S. THE 00Z
GFS IS MUCH STRONGER WITH SURFACE MOVING THROUGH CANADA DURING THE 
PERIOD AND SUPRESSES THE SURFACE LOW FURTHER SOUTH THAN THE 
UKMET/ECMWF.  THE GFS SETS UP THE WARM FRONT TO OUR SOUTH CLOSE TO 
I70 WHICH WOULD KEEP CWA IN A COOLER/RAINY PATTERN UNTIL SYSTEM 
MOVES TO THE EAST LATE IN THE WEEK.  THE EUROPEAN MODELS OFFER 
WARMER SCENARIO...FAVORING MORE CONVECTIVE PCPN WITH WARM FRONT 
SETTLING IN NEAR I80.  GOING EXTENDED IS LINE WITH THE GFS...AND
WILL CONTINUE THIS THINKING UNTIL MODEL CONTINUITY IS ESTABLISHED.

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

$$

DLF/MWM