[LeArc] Forecast Discussion : MLI@ 10/18/02 3:05:15 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 180810
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
300 AM CDT FRI OCT 18 2002

SOMEWHAT STAGNANT UPPER PATTERN WITH REX BLOCK IN WEST AND LONGWAVE TROUGH
DOMINATING EASTERN HALF OF CONUS. SHORTWAVE DIVING SE 
ACROSS THE NORTHERN STATES WITH ASSOCIATED SURFACE COLD FRONT SWINGING
THROUGH LATE AFTN/EVE. STRONG WARM ADVECTION AIDING BAND OF PCPN
SHIFTING QUICKLY E THROUGH MN...NORTHERN IA INTO WESTERN WI AT 07Z AND
THIS IS IMMEDIATE CONCERN IS SHORT TERM...ALONG WITH WINDS
AND EXTENT OF WARMUP. CONCERNS BEYOND FOCUS ON TIMING OF COLD FRONT AND
BLAST OF UNSEASONABLY COLD AIR EARLY NEXT WEEK. 

SURFACE LOW AT 07Z NEAR ABERDEEN SD WITH MSAS PRESSURE FALL BULLSEYE 
IN SOUTHWEST MN...INDICATING E/SE TRANSLATION.
WARM FRONTAL ZONE EXTENDS FROM LOW THROUGH SOUTHEAST IA. RECENT OBS
INDICATE CEILINGS LOWERING NORTH WITH SOME -RA BEING
REPORTED AT MCW AND PDC. ISENTROPIC LIFT TO SHIFT QUICKLY EAST THIS
MORNING WITH COND PRESSURE DEFICITS AND TRACK OF SURFACE WAVE 
SUPPORTIVE OF CHC OF RAIN MAINLY NORTH OF HIGHWAY 20...WITH SPRINKLES
POSSIBLE AS FAR SOUTH AS 1-80 CORRIDOR. WARM FRONT LIFTS NORTH
BY 18Z WITH BREEZY/WINDY CONDITIONS WITH MIXING OF 40-50 KT WINDS ALOFT
AND TIGHTENING PRESSURE GRADIENT. TRAJECTORIES SUPPORT 60S MOST
LOCATIONS WITH FEW 70S NOT OUT OF QUESTION MAINLY SOUTH WHERE MORE SUNSHINE
EXPECTED. NEXT CONCERN IS TIMING OF COLD FRONT. ETA/META QUICKER 
THAN GFS AND UKMET WITH FRONT THROUGH ENTIRE CWA AT 00Z. THIS WOULD 
PRECLUDE PCPN CHCS AS NOT ENOUGH TIME FOR MOISTURE.
06Z META COMING IN AND HAS SLOWED ON FRONTAL TIMING SIMILAR TO GFS AND
UKMET. FORCING NOT GREAT FOR SURE...BUT PERHAPS ENOUGH
LLVL CONVERGENCE IN SOUTH WHERE BETTER MOISTURE FOR SMALL POP IN 
SOUTH LATE AFTN/EVE.  

SURFACE HIGH BUILDS IN LATER TONIGHT PROVIDING QUIET AND COOLER CONDITIONS
THROUGH SAT NIGHT. MAXES SAT CLOSER TO FWC/MEX BLEND WITH MINS 
SUN MORNING NEAR COOLER MAV GUIDANCE. 

FOCUS SUN SHIFTS TO COLD FRONT. GFS BLASTS FRONT THROUGH BY 00Z MON WHILE
UKMET HAS IT ENTERING NORTHERN ZONES AT 00Z...SO BIG 
DIFFERENCES WHICH WILL LOOM LARGE IN TEMP FORECAST. LEANING TOWARD 
GFS GIVEN SHALLOW NATURE OF AIRMASS...THUS WILL SCALE
BACK TEMPS A COUPLE DEGS. CAN/T RULE OUT EVEN SOME VERY LIGHT POST
FRONTAL PCPN. 

NO BIG CHANGES TO EXTENDED ATTIM. GFS WOULD SUGGEST BULK OF OVERRUNNING
PCPN STAYING OUT WEST FROM FRONT RANGE INTO CENTRAL PLAINS 
MON/TUE. BUT...SHORTWAVE STILL ADVERTISED TO DIVE SOUTH BRINGING REINFORCING
SHOT OF COLD AIR.

HARD FREEZE LIKELY EARLY NEXT WEEK. 

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