[LeArc] Forecast Discussion : MLI@ 8/3/02 2:29:06 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 031930
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
230 PM CDT SAT AUG 3 2002

SYNOPTIC PICTURE THIS AFTERNOON SHOWS 90-110KT JET JUST NORTH OF THE
U.S.-CANADIAN BORDER FROM COAST TO COAST...WITH LIGHT 25KT WINDS OVER
DVN.  AT 500H...A LARGE HIGH IS CENTERED OVER EAST CENTRAL MISSOURI...
WITH NEAR ZONAL SOUTH SOUTHWEST FLOW ACROSS NORTHERN TIER...AND A WEAK
SHORT WAVE AND VORT MAX OVER CENTRAL MINNESOTA.  AT THE SURFACE A WARM
FRONT EXTENDS FROM A 1009MB SOUTH DAKOTA LOW ACROSS SOUTHERN MINNESOTA
AND CENTRAL WISCONSIN.  A COLD FRONT EXTENDS SOUTH INTO WESTERN NEBRASKA
AND EASTERN COLORADO.  CONVECTION EXTENDS NORTH OF THE WARM FRONT AND
AHEAD OF THE SHORT WAVE ACROSS EAST CENTRAL MINNESOTA AND NORTHERN
WISCONSIN...AND ALSO JUST NORTH AND WEST OF THE LOW ITSELF IN WESTERN
AND CENTRAL SOUTH DAKOTA.  A SECONDARY WARM FRONT EXTENDS FROM NORTH
CENTRAL MISSOURI INTO SOUTH CENTRAL ILLINOIS.  NO PRECIP IS CURRENTLY
ASSOCIATED WITH THIS FRONT.

THE PRIMARY FORECAST CONCERNS THIS PACKAGE ARE THREE-FOLD.  FIRST IS
PRECIP CHANCES OVER THE NEXT 48 HOURS...PRIMARILY ASSOCIATED WITH AND
BEHIND THE COLD FRONT MOVING THRU.  SECOND IS THE POTENTIAL FOR HEAT
ADVISORY CONDITIONS SUNDAY ACROSS THE SOUTHERN THIRD OF THE FORECAST
AREA.  THIRD IS TEMPERATURES ASSOCIATED WITH THE COOL DOWN INTO
MIDWEEK.

THE MODELS INITIALIZED MODERATELY SELL THIS MORNING...BUT ALL HAVE DONE
A RELATIVELY POOR JOB WITH QPF BETWEEN 12Z AND 18Z...ESPECIALLY THE
NGM...WHICH EXHIBITED ALMOST A PERFECT INVERSE RELATIONSHIP TO WHERE
CONVECTION WAS OCCURRING.

THE MODELS DIFFER SIGNIFICANTLY IN WHEN THEY BRING THE COLD FRONT THRU
THE FORECAST AREA...WITH THE ETA THE FASTEST...BRINGING IT THRU THE
FORECAST AREA BETWEEN 18Z AND 00Z SUNDAY...THEN HANGING IT UP AROUND
EOK THRU 18Z MONDAY.  THE AVN BRINGS IT THRU BETWEEN 00Z AND 06Z
SUNDAY NIGHT...AND BY 12Z IT IS SOUTH OF THE AREA AND BY 18Z WELL
SOUTH.  THE NGM IS THE SLOWEST...MOVING IT THRU BETWEEN 06Z AND 18Z
SUNDAY NIGHT AND MONDAY.  STRONGEST DYNAMICS DURING THIS PERIOD STAY
STAY JUST NORTHWEST AND NORTH OF THE FORECAST AREA...BUT VV'S AND
UPPER DIVERGENCE ARE ENOUGH TO TRIGGER SCATTERED PRECIP...ESPECIALLY
NORTH.

LOOKING FURTHER AHEAD...THE MEDIUM RANGE MODELS AGREE ON A STRONG
SURFACE HIGH SINKING FROM CANADA INTO THE CENTRAL GREAT LAKES MIDWEEK...
AND THEN SOUTH BY FRIDAY.  WE WILL HAVE A LONG FETCH OFF LAKE MICHIGAN
MONDAY AFTERNOON THRU TUESDAY NIGHT.  ON WEDNESDAY THE WINDS BECOME
STRAIGHT EASTERLY...THEN LIGHT SOUTHEAST ON THURSDAY...AND LIGHT SOUTH
ON FRIDAY.  IT'S NOT UNTIL SATURDAY THAT A GOOD SOUTH TO SOUTHWEST
BREEZE DEVELOPS...AHEAD OF THE NEXT FRONT.

WILL STAY CLOSE TO CURRENT FORECAST ON POPS.  WILL LOWER TEMPS BACK DOWN
A NOTCH FOR TUESDAY THRU THURSDAY...AS MEDIUM-RANGE MODELS AND FMR/MEX
ALL POINT TO SLIGHTLY COOLER REGIME.  WILL HOLD OFF ON HEAT ADVISORY
SOUTH...AS DEW POINTS SUNDAY MAY NOT BE HIGH ENUF TO PUSH AREA TO 105
HEAT INDEX FOR 3 HOURS IN MOST LOCATIONS.  WILL PROBABLY OPT INSTEAD
FOR 100 TO 105 MENTION.

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

REA