[LeArc] Forecast Discussion : MLI@ 11/23/02 3:01:21 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 230914
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
310 AM CST SAT NOV 23 2002

IR FOG LOOP INDICATING MID DECK PUSHING/DEVELOPING SOUTH ACRS THE
CWA...A BY-PRODUCT OF A GOOD SURGE OF CONVERGENT MID LVL QG FORCING
AND UVV'S AHEAD OF INCOMING TROUGH. WILL AGAIN HAVE TO DEAL WITH THIS
EARLY MORNING DECK AND WALK OUT OF EASTERN ZONES WITH APPROPRIATE
WORDING...BUT AS MID LEVEL FORCING/WAA SHIFTS EAST...SKIES SHOULD
BECOME MOSTLY SUNNY OVER ALL OF CWA. RAPIDLY INCREASING SFC PRESSURE
FALLS OVER EASTERN IA SUGGEST TROUGH FEATURE TO MAINTAIN ITS CURRENT
PROGRESSIVE NATURE AND SWEEP COMPLETELY THROUGH THE CWA BY 19Z-20Z.
INCOMING(BUT TEMPORARY)SURGE OF WARMER LLVL THERMAL PARAMETERS AND
COLD AIR LAG BEHIND TROUGH...SUGGEST POTENTIAL FOR HIGHS TODAY TO
REACH THE 50 DEGREE MARK/LOWER 50S OVER MUCH OF THE SOUTHERN HALF OF
THE CWA.

TIMING AND SOUTHERN EXTENT OF NEXT COLD PUSH/LLVL BAROCLINICITY
TONIGHT AND SUNDAY THE MAIN CHALLENGE OF THIS FCST...ALONG WITH
INCOMING VORT AND SUNDAY SNOW POTENTIAL.

MAIN VORT SURGE TO THE NORTH TONIGHT TO BECOME CHANNELED ALONG AND
SOUTH OF CANADIAN CYCLONE OVER THE DAKOTAS THROUGH WI...AND WILL HAVE
NO EFFECT ON THE LOCAL AREA. BUT VORT NOW OVER B.C...WILL LOOK TO
SHEAR DOWN ACRS IA/SOUTHERN MN IN NORTHWEST FLOW BY SUNDAY
AFTERNOON. INTERACTION OF THIS FEATURE OVER LLVL BAROCLINICITY...
ALONG WITH EXTRA UPWARD VERTICAL MOTION SUPPORT FROM H3 JET COUPLING
BETWEEN INCOMING 95 KT MAX AND REAR OF EXITING 100 KT MAX...TO BRING
SNOW POTENTIAL TO AREA SUNDAY AFTERNOON AND EVENING. PROBLEM IS
SOUTH PUSH OF COLD AIR DIFFERENCE BETWEEN THE AVN-GFS...AND THE
ETA/META. ETA FURTHER SOUTH WITH BAROCLINIC SURGE...AND WEAKER(THIS
FAR NORTH ANYWAY) WITH ISENTROPIC LIFT AND SATURATION...LOOKING AT
290-295 K SFCS. GFS FURTHER NORTH WITH LLVL THERMAL RIBBON SUNDAY
MORNING ALONG MO/IA BORDER AND HANGS IT UP LONGER BEFORE RETURN
MIGRATION SOUTHWARD. GFS ALSO BUILDS BETTER OVERRUNNING/ISENTROPIC
LIFT SCENARIO OVER THE SOUTHERN HALF OF THE CWA AND BREAKS OUT 1-2
INCH ACCUMULATIONS BY MID SUNDAY EVENING ALONG AND NORTH OF THE I-80
CORRIDOR. OTHER MODELS(UKMET/NGM/META/ETA) ALL LIGHTER IN PRECIP
AMOUNTS SUNDAY AFTERNOON AND EVENING WITH JUST A FEW TENTHS OF AN
INCH OF SNOW ACCUMULATION...AND MAKE GFS ODD MAN OUT. STILL MAY
UPGRADE CURRENT FLURRY WORDING ACRS THE CENTRAL AND NORTHERN CWA...
TO CHANCE POPS FOR LIGHT SNOW. LATEST MODEL QPF NOT DISCRIMINATING
FROM NORTH TO SOUTH...BUT IF ETA HAS ITS WAY WITH COLD PUSH...
CURRENT ZONES WITH SNOW ACRS SOUTH AND JUST FLURRIES CENTRAL AND
NORTH PROBABLY WOULD BE ON THE MARK. WILL TAKE GFS/ETA COMPROMISE
THOUGH...AGAIN WITH UPGRADING FLURRIES TO LIGHT SNOW CHANCE WITH BEST
UVV'S THROUGH DEEPER LAYER CENTERED AROUND 00Z MON. SFC CAA IN
ERNEST ON SUNDAY..AS WELL AS CLOUD COVER WILL KEEP HIGHS IN LOW TO
MID 30S.


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

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