[LeArc] Forecast Discussion : MLI@ 11/7/02 2:47:32 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 072058
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
258 PM CST THU NOV 7 2002

SYNOPTIC PICTURE THIS AFTERNOON SHOWS 500H FLOW TRENDING TOWARDS
ZONAL...WITH THE EAST COAST TROF AND ROCKIES RIDGE DE-AMPLIFYING.
DEEP 500H LOW IN CENTRAL CANADA OVER CHURCHILL...WITH ANOTHER DEEP
LOW OFF BRITISH COLUMBIA COAST.  A WEAK MID LEVEL SHORT WAVE IS
MAKING ITS WAY ACROSS KANSAS THIS AFTERNOON WITH NO MOISTURE TO WORK
WITH. IN THE UPPER LEVELS...A 120KT JET UNDER-RIDES THE CHURCHILL LOW
WITH A STRONG 170KT JET COMING UNDER PACIFIC LOW AND HEADING TOWARDS
THE WEST COAST. AT 850MB TEMPS HAVE WARMED DRAMATICALLY FROM -3C 30
HOURS AGO TO +5C OVER US AT 12Z...WITH UPSTREAM READINGS OF +10C AT
OMA AND +14C AT DDC.  AT THE SURFACE A TROF EXTENDS SOUTH FROM
SURFACE CHURCHILL LOW INTO WESTERN NEBRASKA. A STRONG HIGH WAS
CENTERED OVER EAST TEXAS...WITH A 955MB LOW OFF THE BC COAST.  SKIES
ARE CLEAR ACROSS THE MIDWEST AND CENTRAL PLAINS.

THE PRIMARY FORECAST CONCERN IS TWO-FOLD.  FIRST IS PRECIP IN THE
SATURDAY-SUNDAY TIME FRAME ASSOCIATED WITH A MAJOR NORTHERN STREAM
TROF MOVING THRU...AND SECOND IS PRECIP WITH A SECOND SOUTHERN STREAM
TROF IN THE MONDAY NIGHT-TUESDAY TIME FRAME. PRECIP TYPE WILL NOT BE
A CONCERN...DUE TO MILD TEMPS...UNTIL THE LAST HALF OF THE SECOND
EVENT.  DIFFERENCES IN THE 12Z MODEL RUNS...AND DIFFERENCES FROM
PREVIOUS RUNS...ARE THE MAIN CHALLENGE.

THE SHORT-TERM MODELS INITIALIZED MODERATELY WELL AT 12Z...WITH THE
AVN A LITTLE BETTER THAN THE ETA/NGM WITH SURFACE PRESSURE AND
SIGNIFICANTLY BETTER WITH 850MB TEMPS.

THE SHORT-TERM MODELS BRING A SHORT WAVE THRU LATE FRIDAY NIGHT-
EARLY SATURDAY...BUT WITH NO MOISTURE TO WORK WITH.  AFTER THAT...
GETTING INTO THE MEDIUM-RANGE MODELS...A LOBE OFF THE INCOMING 500H
TROF MOVES THRU SUNDAY EVENING...GIVE-OR-TAKE DEPENDING ON THE
MODEL...WITH THE PRIMARY TROF AXIS MOVING OVER DVN BETWEEN 06Z AND
12Z TUESDAY.  THIS IS SIGNIFICANTLY SLOWER THAN PREVIOUS RUNS. JET
LEVEL DIVERGENCE WILL ENHANCE PRECIP CHANCES SUNDAY AND SUNDAY
NIGHT.  AT THE SURFACE ENERGY OFF THE PACIFIC LOW HEADS EAST INTO THE
NORTHERN PLAINS SATURDAY...WITH THE SURFACE LOW MOVING THRU OR NEAR
DVN AROUND 12Z OR 15Z SUNDAY.  THEN A SECOND LOW LIFTS NORTH OUT OF
THE SOUTHERN PLAINS THRU STL OR MEM MONDAY NIGHT...AND LIFTS INTO
INDIANA TUESDAY.  THICKNESSES WILL STAY ABOVE 540 THROUGH
MONDAY...THEN HEAD DOWNHILL MONDAY NIGHT...PRESENTING SNOW
POSSIBILITIES MONDAY NIGHT AND TUESDAY...ESPECIALLY NORTH FROM CID TO
DBQ. BUT NORTH IS ALSO WHERE QPF WILL BE LEAST FOR THE SECOND WAVE.

WILL STAY CLOSE TO CURRENT FORECAST...WITH BROAD BRUSH ON PRECIP AND
TEMPS COOLING BACK DOWN AGAIN MONDAY.

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

REA