[LeArc] Forecast Discussion : MLI@ 11/24/02 2:10:53 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 242023
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
225 PM CST SUN NOV 24 2002

NEAR TERM CONCERN IS WITH SNOW AMOUNTS...THEN POTENTIAL CLEARING TONIGHT
AND TEMPS. BEYOND...CONCERN REMAINS WITH TEMPS WITH
MODELS OFFERING BIG DIFFERENCES OF SOME 10 TO 15 DEGS TUE-WED! ALSO OF CONCERN
IS CLIPPER TYPE SYSTEM ON TUE AND POTENTIAL FOR -SN. 

SNOW FALLING NOW IN BAND FROM CID TO NORTH OF FEP WITH REPORT OF 1/4-1/2
INCH 4 W OF MAQUOKETA FROM COOP OBSERVER. ALSO RECEIVED REPORT OF -SN 
(SOME SNOW GRAINS MIXED IN) FROM COOP OBSERVER IN WASHINGTON WHERE RADAR ALSO 
DEPICTING RETURNS. CID ASOS REPORTING VISIBILITY RECENTLY OF 1/2 MI 
IN MODERATE SN. VISIBLE SATELLITE SHOWS NICE BAROCLINIC LEAF EXTENDING FROM 
NORTHWEST MISSOURI THROUGH SOUTHEAST WISCONSIN. RIGHT ENTRANCE 
REGION OF UPPER JET...APPROACHING SHORT WAVE AND FRONTOGENETICAL FORCING WITH 
TIGHT BAROCLINIC ZONE DRAPED OVER REGION ALL LEADING TO INCREASE IN UVV/S 
THIS AFTN AND EVE. WILL MONITOR LATEST RADAR/OBS BUT LOOKS AS THOUGH
CURRENT AMOUNTS ARE ON TRACK WITH AROUND 1 INCH...WITH FEW SPOTS 2 INCHES AND
POSSIBLY NEARING 3 INCHES WITHIN BANDED SEGMENTS EXPECTED OVER NEXT FEW
HOURS FROM CID AND FEP SOUTH THROUGH QUAD CITIES TO NEAR PRINCETON AND ALEDO. 
SUBSIDENCE SETTLES IN FROM WEST TO EAST IN 03Z-08Z TIMEFRAME WITH 
SOME CLEARING. LOWS WILL BE QUITE TRICKY WITH SOME AREAS LIKELY TO HAVE
AN INCH OR SO OF SNOW COVER. TRAJECTORIES POINT TO NORTH CENTRAL MN
AS SOURCE REGION FOR SOUTHERN IA WHERE READINGS THIS MORNING WERE IN THE
UTEENS TO NR 20 DEGS. OVERALL LEANING TOWARD MET GUIDANCE MAKING
NECESSARY TWEAKS. 

MON...CYLCONIC FLOW TO START TRENDING ANTICYLCONIC DURING AFTN AS SURFACE
RIDGES BUILDS IN. EXPECT SOME CLOUDS MAINLY OF MID/HIGH TYPE.
MODELS INDICATE VORT MAX SHEARING EASTWARD FROM PLAINS INTO GREAT LAKES
DURING MORNING WITH SOME PVA...SO CAN/T RULE OUT SOME FLURRIES.
BIG MODEL DIFFERENCES ON MAX TEMPS BY SOME 10+ DEGS. MAV GUIDANCE LOOKS COLD
WITH ANTICIPATION OF SUNSHINE...DESPITE SOME LIGHT SNOW COVER IN
AREAS. SEEMS THE TREND OF LATE IS MIDDLE OF ROAD FWC BEEN PERFORMING BEST
SO WILL TREND THAT DIRECTION. THIS MATCHES WELL WITH THICKNESS AND
18Z OBS UPSTREAM. 

MODELS HAVE COME AROUND TO UKMET SOLUTION OF LAST FEW DAYS BRINGING 
SHORTWAVE THROUGH MIDWEST ON TUE. ETA KEEPS BULK OF FORCING
WEST MON NIGHT-TUE. HOWEVER...DISCARDING ETA SOLUTION AND GOING WITH BLEND 
OF UKMET AND AVN/GFS ON SYSTEM GIVEN RECENT TRENDS. STILL THROUGH 
DIFFERENCES IN THE TWO WITH UKMET FURTHER N WITH VORT MAX WHICH IS CRITICAL
TO PCPN CHCS. GIVEN UKMET/S PERFORMANCE OF LATE WILL LEAN TOWARD
AND MAINTAIN LIKELY POPS SOUTHERN 1/3RD TO 1/2 WITH POSITIVE VORTICITY ADVECTION
ALTHOUGH MOISTURE LIMITED SO LIGHT PCPN AND AMOUNTS.

SURFACE RIDGE BUILDS IN WED NIGHT WITH MOCLEAR SKIES AND LIGHT WINDS AND
DRY AIR SETTING UP FAVORABLE RADIATIONAL COOLING. SHOULD BE PLENTY COLD
AND WILL TRIM BACK TEMPS SOME FROM CURRENT FORECAST.  

EXTENDED (THU-SUN)
PERIOD BEGINS WITH UPPER RIDGE BUILDING FROM WESTERN STATES INTO PLAINS
RESULTING IN RISING HEIGHTS AND MODERATING TEMPS. SYSTEM PASSING NORTH OF GREAT
LAKES DRAGS WEAK FRONT THROUGH LATE THU-FRI. MOISTURE LIMITED WITH 
SURFACE HIGH ALONG GULF AND BEST DYNAMICS AIDING SATURATION PASSING WELL NORTH 
SO WILL REMOVE MENTION OF PRE-FRONTAL PCPN ON THANKSGIVING. SYSTEM BRINGS 
SHOT OF COLD AIR BY WEEKEND WITH CHC OF SNOW AND FLURRIES WITH WAVES 
IN NORTHWEST UPPER FLOW. 

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

05