[LeArc] Forecast Discussion : MLI@ 10/19/02 2:14:14 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 190717
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
215 AM CDT SAT OCT 19 2002

06Z SURFACE ANALYSIS SHOWS COLD FRONT EXTENDING FROM CHI-SPI-COU LINE.
LOW PRESSURE WAS LOCATED OVER NORTHERN LAKE MI WITH 
EXTENSIVE COLD ADVECTION ST/SC CLOUDS DROPPING SOUTH IN LLVL CYLCONIC
FLOW WITH LEADING EDGE ENTERING NORTHERN ZONES. 
UPPER PATTERN CONSISTS OF LONGWAVE TROUGH OVER EASTERN HALF OF CONUS WITH
SOUTHERN STREAM CLOSED LOW IN SOUTHEAST NM.

MAIN FORECAST CONCERNS NEXT 24-36 HRS ON CLOUDS AND TEMPS...THEN PCPN 
CHCS SUN NIGHT THROUGH MON...AND PHASING ISSUES IN EXTENDED WITH
SIGNIFICANT MODEL DIFFERENCES.
 
COLD ADVECTION LOW CLOUDS WILL CONTINUE TO MOVE ACROSS THE REGION THIS 
MORNING WITH MAIN QUESTION ON HOW FAR SOUTH. SATELLITE SHOWS
EXTENSIVE CLOUD SHIELD ALL THE WAY INTO SOUTHERN CAN. LLVL FLOW MORE
ANTICYCLONIC ESPECIALLY SOUTHERN HALF OF CWA AND BANKING ON THIS
TO EAT AWAY OR SLOW PROGRESS OF CLOUDS...SO WILL GO WITH MORE CLOUDS NORTHERN
HALF TO START. LLVL FLOW NORTH SHOULD BECOME MORE ANTICYCLONIC
AS DAY PROGRESSES...WHICH MEANS EVEN NORTHERN SECTIONS SHOULD SEE SOME
HOLES ALLOWING SOME SUNSHINE TO PEEK THROUGH. WITH THIS IN MIND
WILL GO CLOSER TO COLDER MAV GUIDANCE NORTH HALF WITH CLOUDS...AND LEAN
TOWARD FWC/MET BLEND IN SOUTH WITH MORE SUNSHINE. GRADIENT SUPPORTIVE
OF GUSTY WINDS THIS MORNING...BUT THEN SHOULD WEAKEN THIS AFTN ALLOWING
DROP OFF.  

TONIGHT...IDEAL RADIATIVE COOLING TONIGHT AS SURFACE RIDGE SETTLES IN
PROVIDING CLEAR SKIES...AND LIGHT WIND. EXPECT FREEZE JUST ABOUT 
ENTIRE AREA AND WILL HOIST HIGHLIGHTS IN SOUTHEAST SECTIONS ROUGHLY E OF LINE
FROM MOLINE TO FORT MADISON TO KAHOKA MO...WHICH ARE THE LAST REMAINING
AREAS IN CWA THAT HAVE YET TO SEE WIDESPREAD FREEZE. WILL BE SIDING TOWARD 
COLDER MAV GUIDANCE BUT SHAVING A DEG OR TWO. 

SUNDAY...WEAK COLD FRONT MOVES QUICKLY THROUGH REGION BY EARLY EVE WITH
INCREASE IN CLOUDS. TEMPS CONTINUE ON COOL SIDE...AND WILL 
STAY THE COURSE FAVORING COOLER MAV GUIDANCE NORTH WITH CLOUDS AND MET/FWC
BLEND SOUTH WITH MORE SUNSHINE. 

SUN NIGHT...MOISTENING DEEPENS WITH SHORTWAVE ACTING ON TIGHT BAROCLINIC 
ZONE FOR LOW POPS FOR PCPN NORTH IN CLOSER PROXIMITY TO 
THERMAL GRADIENT. H85 TEMPS OF -1C TO -2C SUGGEST/S MAINLY RAIN ALTHOUGH WITH 
EVAP COOLING CAN/T RULE OUT FEW FLAKES. LOWS NEAR BLEND OF GUIDANCE.

MON...PCPN CHCS PERSIST INTO MON NIGHT WITH BETTER CHCS NORTH NEAR MAIN 
BAROCLINIC RIBBON AND EFFECTS OF SHORTWAVE. TEMPS COLDER WITH
LOTS OF LOW CLOUDS AND LIGHT E/NE LLVL WIND...AND MAV GUIDANCE LOOKS 
REASONABLE.

EXTENDED (TUE-FRI)...
AVN SHOWING SOME RUN-RUN CONTINUITY WITH WAVE WITH PCPN THROUGH WED...THOUGH
BIG DISCREPANCIES WITH UKMET WHICH CONTINUES IT/S TREND OF BEING 
MORE PROGRESSIVE WITH COLD CANADIAN HIGH OVERHEAD WED-THU. GIVEN UNCERTAINTIES 
WILL NOT MAKE CHANGES TO GOING EXTENDED.

.DVN...
IA...FREEZE WARNING TONIGHT EAST OF A MEDIAPOLIS TO DONNELLSON LINE.
IL...FREEZE WARNING TONIGHT ALONG AND SOUTH OF I-80 AND EAST OF A MOLINE TO 
ALEDO TO CARTHAGE LINE.
MO...FREEZE WARNING TONIGHT EAST OF A KAHOKA TO NEEPER LINE.