[LeArc] Forecast Discussion : MLI@ 10/24/02 2:36:06 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 240745
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
245 AM CDT THU OCT 24 2002

SYNOPTIC SCALE THIS MORNING SHOWS RIGHT REAR QUAD OF 100KT JET OVER
FORECAST AREA.  AT 500H ZONAL FLOW PREVAILS...WITH A SHARP EAST-WEST
TROF PERSISTING OVER MINNESOTA AND WISCONSIN.  AT THE SURFACE A 1034MB
HIGH IS CENTERED OVER MINNESOTA AND WISCONSIN...WITH A SHARP RIDGE
EXTENDING SOUTHWEST IN THE SOUTHERN HIGH PLAINS.  LIGHT TO
OCCASIONALLY MODERATE PRECIPITATION COVERS MOST OF IOWA...WITH
SCATTERED LIGHT PRECIP INCREASING ACROSS NORTHERN ILLINOIS...AND
EXTENDING INTO SOUTHERN MINNESOTA AND SOUTHERN WISCONSIN.  THIS IS
MAINLY IN RESPONSE TO WEAK TROP FOLD AND UPPER DIVERGENCE.
PRECIPITATION IS SNOW NEAR AND NORTH OF A LINE FROM DSM TO ALO TO JUST
NORTH OF DBQ.

THE PRIMARY FORECAST CONCERN THIS PACKAGE IS IN THE SHORT TERM...WITH
A SOUTHERN PLAINS DISTURBANCE PASSING SOUTH OF THE FORECAST
AREA TODAY AND TONIGHT.  PRECIP TYPE WILL BE A CONCERN FOR NORTHERN
AREAS THIS MORNING...AND AGAIN POSSIBLY THIS EVENING.

THE SHORT-TERM MODELS AGREE ON LIFTING THE SOUTHERN PLAINS LOW THROUGH
THE LOWER MISSISSIPPI VALLEY TODAY AND TONIGHT...WITH TROFING
EXTENDING NORTH IN THE DVN FORECAST AREA.  UPPER SUPPORT WILL COLLAPSE
THIS MORNING...AS PRECIP IN CENTRAL IOWA MOVES NORTHEAST INTO
NORTHEAST IOWA.  DEW POINTS IN THE NORTHWEST PORTION OF THE FORECAST
AREA WILL REMAIN NEAR 32 THROUGH THE MORNING COMMUTE...WITH TEMPS IN THE
MID 30S...NOT ALLOWING MUCH ROOM FOR EVAPORATIVE COOLING DESPITE -4C
TEMPS AT 850MB. COULD STILL SEE AN INCH OF SNOW ON GRASSY SURFACES
OVER THE NEXT SEVERAL HOURS NORTH AND WEST OF A LINE FROM CEDAR RAPIDS
TO DUBUQUE.  LIGHT  PRECIP WILL PICK UP AGAIN THIS AFTERNOON FROM WEST
TO EAST...AS UPPER SUPPORT RENEWS.  ISENTROPIC LIFT NOT A FACTOR EITHER
THIS MORNING OR THIS AFTERNOON...OR FOR THAT MATTER...TONIGHT EITHER.
PRECIPITATION WILL INCREASE IN COVERAGE AND INTENSITY THIS EVENING...
CONTINUE THRU THE NIGHT...AND END FROM WEST TO EAST IN THE MORNING.
THIS WILL BE IN RESPONSE TO UPPER SUPPORT AT THE JET LEVEL WHICH WILL
PRODUCE GOOD VV'S.  1000-500MB AND PARTIAL THICKNESSES NOT FAVORABLE
FOR SNOW THIS AFTERNOON...EVENING...OR OVERNIGHT...ALTHOUGH A MIX
NORTH CAN NOT BE RULED OUT.

LOOKING FURTHER AHEAD...MEDIUM-RANGE MODELS ARE NOW TAKING MONDAY WAVE
LIFTING OUT OF SOUTHERN PLAINS FURTHER SOUTH...DUE TO BLOCKING HIGH
OVER AND NORTH OF THE DVN AREA.

WILL KEEP CLOSE TO CURRENT FORECAST.

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

REA