[LeArc] Forecast Discussion : MLI@ 4/26/2003 3:06:25 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 262003
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
340 PM CDT SAT APR 26 2003

MSAS SHOWED SURFACE RIDGE AT 18Z EXTENDING FROM LAKE MI ACROSS CWFA 
TO EASTERN OK WITH ONLY FEW CI SPILLING OVER HIGH PLAINS UPPER RIDGE 
AXIS. IN BIGGER PICTURE...ONE UPPER LEVEL LOW TO NORTHEAST OVER 
HUDSON BAY WITH UPSTREAM VORTICES OVER OVER NW CONUS. LEE SIDE LOW 
AT SURFACE UNDER DIFFLUENT UPPER FLOW OVER EASTERN WY/WESTERN SD TO 
SWEEP BY TO NORTH SUNDAY NIGHT AND PUSH A COLD FRONT INTO FORECAST 
AREA EARLY MONDAY. SHORT TERM FORECAST CHALLENGE IS TEMPERATURES 
THROUGH SUNDAY NIGHT...THEN CHANCES FOR TSRA SUNDAY NIGHT AS FRONT 
APPROACHES.

SHORT TERM...THROUGH 12Z MONDAY...
MODELS SHOW SIMILAR SOLUTIONS AT UPPER LEVELS THROUGH 36 HOURS... 
WITH ONLY SMALL DIFFERENCES AT SURFACE TO IMPACT FORECAST AREA. ETA 
AND GFS HAVE SIMILAR TIMING OF COLD FRONT PUSHING INTO NW FORECAST 
AREA TOWARD 12Z MONDAY...WHILE NGM FASTER AND GENERATES SOUTHERN 
PLAINS LOW TOO FAR TO NORTH. MAINLY FOLLOWED ETA AND GFS...WITH META 
TEMPERATURES PREFFERED FOR TONIGHT. CLEAR SKIES...LOW DEWPOINTS... 
AND WEAK PRESSURE GRADIENT BEHIND SURFACE RIDGE TO EAST WILL ALLOW 
MOST OF AREA TO RADIATE BACK INTO 40S TONIGHT. SOME INCREASE OF MID 
TO HIGH CLOUDS SUNDAY AS WARM AIR ADVECTION COMMENCES AT H85. GOING 
FORECAST TREND AT UPPER END OF GUIDANCE...WITH MID TO UPPER 70S 
LOOKS GOOD. SUNDAY NIGHT...BEST MID LEVEL QG FORCING PASSES ACROSS 
NORTH...WHERE META HAS STEEPEST MID LEVEL LAPSE RATES. HOWEVER...LOW 
LEVEL INSTABILITY...MOISTURE...CONVERGENCE...AND LOW LEVEL JET 
FAVORS THE SOUTHWEST TOWARD MORNING. HAVE THUS PLACED BEST 
THUNDERSTORM CHANCES IN SOUTHWEST ZONES FOR LATE NIGHT...WITH SLIGHT 
CHANCE IN NORTH. CLOUDS AND COUPLED LOW LEVEL FLOW WILL KEEP 
TEMPERATURES IN LOW TO MID 50S.  

12Z MONDAY THROUGH 06Z WEDNESDAY...
MODELS STILL HAVING PROBLEMS DECIDING WHERE THE WARM FRONT WILL SET 
UP LATE MONDAY INTO TUESDAY.  MODELS HAVE DONE A FLIP FLOP SINCE 
YESTERDAYS RUN WITH THE UKMET NOW PLACING FRONT INTO CENTRAL MO BY 
00Z TUESDAY WITH GFS FAVORING SOUTHERN HALF OF IA AND ETA IN THE 
MIDDLE ACROSS NRN MO. I LIKE THE ETA SOLUTION FOR THIS SCENARIO 
SINCE IT HAS THE BEEN THE MOST CONSISTENT THE LAST COUPLE OF DAYS 
WITH THE MOVEMENT OF THE FRONT AND THE SURFACE HIGH  MOVING OUT OF 
CENTRAL CANADA. WITH FRONT EXPECTED TO STALL OVER NORTHERN MO 
MONDAY...WILL KEEP PCPN CHANCES CONFINED TO THE SRN HALF OF THE CWA 
THRU MONDAY NIGHT THEN SPREAD TSRA CHANCE NORTH WITH THE BOUNDARY 
TUESDAY. SHOULD SEE SOME MCS DEVELOPMENT ALONG THE BOUNDARY BOTH 
MONDAY NIGHT AND TUESDAY NIGHT.  HOWEVER...THE POTENTIAL FOR HEAVY 
RAINFALL SHOULD BE LIMITED TO TUESDAY NIGHT...WHEN A BETTER FEED OF 
LOW LEVEL MOISTURE EXISTS.  TEMPS THROUGH THE PERIOD WILL BE TRICKY 
GIVEN THE UNCERTAINTY ON THE FRONTAL POSITION AND ASSOCIATED CLOUD 
COVER AND PCPN.  I'LL KEEP TEMPS ABOUT THE SAME AS PREVIOUS FORECAST 
WITH THE EXCEPTION OF RAISING MINS A NOTCH MONDAY NIGHT.

EXTENDED...
WILL FOLLOW THE GFS SOLUTION THROUGH THE END OF THE WEEK.  SURFACE 
LOW WILL MOVE OUT OF THE PLAINS THROUGH THE MID MISSISSIPPI VALLEY 
AHEAD OF S/W ENERGY EJECTING OUT OF WRN U.S. TROF WED AND THURSDAY.
CURRENT TIMING HAS BEST UPPER DYNAMICS AND LOW LEVEL FORCING MOVING 
THROUGH CWA EARLY THURSDAY MORNING...WHICH SHOULD LIMIT SEVERE 
THREAT.  HOWEVER DUE TO APPARENT STRENGTH SYSTEM...A LOW END SEVERE 
EVENT IS NOT OUT OF THE QUESTION.  THE WEEK SHOULD END ON A DRY 
NOTE...AS SURFACE HIGH BUILDS OVER REGION.



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

$$

DLS/DLF