[LeArc] Forecast Discussion : MLI@ 8/25/02 2:14:32 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 251918
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
220 PM CDT SUN AUG 25 2002

SHEAR AXIS OVER WRN IA STILL EVIDENT ON 12Z UA ANALYSIS AT 500/250 MB.
AXIS ALONG WITH WEAK CIRCULATION OVER WRN IA AND SURFACE HEATING
CONTRIBUTING TO PERSISTENT TSRA JUST W OF CWA WITH ISOLATED SHRA/TSRA
JUST DEVELOPING OVER W HALF OF CWA.  WOULD EXPECT CONTINUED
DEVELOPMENT THROUGH THE REST OF THE AFTERNOON AS ADDITIONAL SURFACE
HEATING CAUSES FURTHER DESTABALIZATION. HOWEVER...COVERAGE WILL BE
SPOTTY AT BEST.  SURFACE PATTERN REMAINS WEAK WITH VERY LIGHT WNW WINDS
OVER MUCH OF AREA.

MAIN CONCERN WILL BE DEALING WITH FOG POTENTIAL AGAIN TONIGHT AND
LINGERING CONVECTION THIS EVENING.

MODELS SUGGEST SHEAR AXIS TO DRIFT NE OVERNIGHT TONIGHT...KEEPING SOME
SUPPORT FOR ISOLATED CONVECTION THIS EVENING.  BEST INSTABILITY WILL BE
OVER SOUTWEST HALF OF CWA...WHERE CURRENT FORECAST ALREADY HAS LOW POPS
AND WILL CONTINUE.  LAST NIGHTS FOG EVENT WAS SQUASHED BY CI SHIELD IN
VICINITY OF SHEAR AXIS WITH WEAK S/W ENHANCING COVERAGE.  HI LEVEL RH
PROGS FROM NGM/AVN SUGGEST THAT CI SHIELD WILL REMAIN OVER AREA
THROUGH THE NIGHT...ALTHOUGH IT SHOULDN'T BE A THICK AS LAST NIGHT.
CURRENT THINKING IS THAT SOME DENSE FOG WILL STILL BE POSSIBLE...BUT
ONSET WILL BE DELAYED UNTIL AFTER MIDNIGHT DUE TO HIGH CLOUDS.  ALSO
WITH TEMPS A LITTLE WARMER THAN YESTERDAY AND  SLIGHTLY LOWER
DEWPOINTS...ESPECIALLY IN NW IL...IT WILL TAKE LONGER FOR LOW LEVELS TO
SATURATE.

MODELS ARE CONSISTENT THROUGH MID WEEK KEEPING UPPER RIDGING OVER
CENTRAL U.S. AS TROUGH DIGS OVER NORTHERN ROCKIES AND UPPER LOW CUTS OFF
JUST TO OUR SOUTHEAST MONDAY...THEN MEANDERS AROUND THE OHIO VALLEY.
SURFACE PATTERN TO REMAIN WEAK...ALTHOUGH FLOW SHOULD BECOME EASTERLY BY
LATE MONDAY AS HIGH PRESSURE SLIDES ACROSS THE NORTHERN GREAT LAKES.
CURRENT FORECAST LOOKS REASONABLE WITH PERSISTENCE THE BEST TOOL
THROUGH TUESDAY.  WITH SHEAR AXIS NEARBY MONDAY AND UPPER DEVELOPING
OVER IL THERE IS SOME SUPPORT FOR LOW POPS. HOWEVER FEEL THREAT IS NOT
GREAT ENOUGH TO ADD POPS IN YET...ESPECIALLY AS LOW LEVELS BECOME MORE
STABLE WITH INCREASING EASTERLY FLOW.  TEMPS MONDAY WILL BE
SIMILAR TO TODAY'S READINGS.  TUESDAY TEMPS SHOULD BE A NOTCH LOWER
WITH LIGHT EAST WINDS.  SURFACE RIDGE WILL STILL BE IN PLACE THROUGH
WEDNESDAY.  MODELS ARE SUGGESTING S/W WILL MOVE THROUGH THE PLAINS
WEDNESDAY NIGHT. IT APPEARS THAT BEST SUPPORT WILL BE TO OUR NORTH.
WILL REMOVE MENTION SHOWERS FROM ALL BUT THE NORTHERN COUNTIES.


.EXTENDED (THU-SUN)...MODELS INDICATE STRONG RIDGING OVER SOUTHERN HALF
OF COUNTRY WILL BREAK DOWN LATE THIS WEEK...ALLOWING FAST FLOW OVER
CANADA TO SETTLE SOUTH.  INITIAL SYSTEM WILL MOVE THROUGH MID WEST
THURSDAY AND WILL CONTINUE CHANCE WORDING ALREADY IN EXTENDED.  MRF
SHOWING BETTER SHOT AT SHOWERS/TSRA LATE IN WEEKEND AS STRONG S/W
MOVING ACROSS NORTH CENTRAL U.S. PROVIDING GOOD DIFFLUENT FLOW OVER
REGION AND ASSOCIATED COLD FRONT MOVING THROUGH MISSISSIPPI VALLEY
LATE SUNDAY WILL PROVIDE SUPPORT IN THE LOW LEVELS.  TEMPS WILL BEGIN A
GRADUAL WARMUP OVER THE WEEKEND AS SURFACE RIDGING BREAKS DOWN.

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