[LeArc] Forecast Discussion : MLI@ 6/21/2003 3:55:45 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 212049
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
350 PM CDT SAT JUN 21 2003

SURFACE RIDGE ON LATEST SURFACE ANALYSIS DRAWING EAST AWAY FROM THE 
AREA...WITH PRESSURES FINALLY BEGINNING TO FALL ACROSS MUCH OF THE 
CWA.  SURFACE LOW OVER NW SOUTH DAKOTA SHIFTING ONLY VERY SLOWLY 
EAST...WITH TROUGHING SOUTH FROM IT OVER THE HIGH PLAINS.  SOME 
INTERESTING CONVECTIVE ACTIVITY OVER EASTERN NEBRASKA...TRIGGERED BY 
A SHORTWAVE/VORT LOBE MOVING NORTHEAST ACROSS EASTERN KANSAS. ON 
UPPER AIR ANALYSIS THIS IS A RATHER MORE AMPLIFIED PATTERN THAN IS 
USUAL FOR SUMMER...WITH A STRONG RIDGE OVER THE MISSISSIPPI VALLEY 
AND A STRONG TROUGH JUST COMING ON SHORE OVER THE NORTHWEST COAST. 

MAIN CONCERNS THIS FORECAST INCLUDE TIMING OF PRECIPITATION CHANCES 
FOR SUNDAY THROUGH THE REMAINDER OF THE FORECAST...AND HOT AND MUGGY 
CONDITIONS FOR THE EARLY PART OF THE WEEK.  

12Z MODELS APPEAR TO HAVE INITIALIZED REASONABLY WELL...WITH 
GENERALLY SIMILAR SOLUTIONS ON THE MAJOR FEATURES...AND HAVE GONE 
FOR THE MOST PART WITH A BLEND. TONIGHT...CONDITIONS REMAIN 
DRY...WITH ONLY CIRRUS STREAMING OVERHEAD AND A LITTLE AC TOWARDS 
MORNING.  WITH DEWPOINTS RISING ACROSS THE AREA AND WARM AIR 
ADVECTION FINALLY STARTING...TEMPS OUGHT TO BE SIGNIFICANTLY WARMER 
THAN THEY HAVE BEEN LAST FEW MORNINGS.  

SUNDAY PRECIPITATION MAY BREAK OUT IN THE LATE AFTERNOON OVER 
CENTRAL AND WESTERN PORTIONS OF NORTHERN IA...AND THERE IS A SLIGHT 
CHANCE OF IT MAKING IT INTO THE WESTERN CWA BEFORE EVENING.  
HOWEVER...THE MCS THAT DEVELOPS OVER NORTHERN IA/SOUTHERN MN DURING 
THE NIGHT...WILL MOVE ACROSS MAINLY THE NORTHERN PORTIONS OF THE 
CWA...OVERNIGHT AND EARLY MONDAY MORNING.  HAVE GONE WITH CHANCE 
POPS FOR NOW...BUT AS THE DETAILS BECOME MORE DEFINED...MAY BE ABLE 
TO UP POPS FOR A FEW LOCATIONS INTO THE LIKELY CATEGORY.  MONDAY TO 
BE A GRUNGY...HOT AND HUMID DAY WITH PRECIPITATION LIKELY TO RE-FIRE 
ALONG AN OUTFLOW BOUNDARY TO BE SENT OUT BY THE EARLY MORNING MCS.  
HAVE JUST GONE WITH BLANKET CHANCE POPS. 
...LE

LONG TERM...(MONDAY NIGHT THROUGH SATURDAY)

HOT AND HUMID WEATHER BEGINNING LATE MONDAY AS THE WARM SECTOR FLOWS 
UNINHIBITED NORTH INTO THE REGION.  THE MAIN FORECAST QUESTION WILL 
BE TIMING SEVERAL CHANCES FOR THUNDERSTORMS THROUGH THE TIME A COLD 
FRONT PASSES THROUGH THE AREA THURSDAY.  THERE WILL BE ANOTHER 
SMALLER THREAT OF SHOWERS AND SOME THUNDERSTORMS FRIDAY AS A THE 
MAIN UPPER TROF ROTATES THROUGH THE MISSISSIPPI VALLEY. MONDAY 
THROUGH THURSDAY MORNING...TO START...INSTABILITY IS NOT IN 
QUESTION...AS HOT AND HUMID AIR WILL BE WELL ENTRENCHED FROM IOWA ON 
SOUTH.  MODELS CONTINUE TO PROVIDE LITTLE CONSISTENCY AS TO WHETHER 
THE AREA WILL BE CAPPED OR ON THE EDGE OF THE CAP.  THE PLACEMENT OF 
THE CAP WILL LIKELY BE CRITICAL TO THE FORECAST AS SEASONALLY STRONG 
INSTABILITY IS RELEASED ON ITS NORTHERN/EASTERN EDGE DURING THIS 
PERIOD.  MID LEVEL SHORT WAVE TROF PASSING THROUGH THE AREA MONDAY 
EVENING WILL ALLOW FOR THE THREAT OF AN MCS MOVING IN FROM NORTHERN 
IOWA. WILL SHADE HIGHES POPS NORTH...TO SLIGHT CHANCES SOUTH.  FOR 
NOW...WILL KEEP TUESDAY DRY WITH MAIN FOCUS WELL NORTH OF THE AREA. 
NOCTURNAL CONVECTION IS TOO CLOSE TO CALL AGAIN TUESDAY NIGHT...SO 
WILL LEAVE CHANCE GOING CENTRAL AND NORTH.  BY WEDNESDAY 
AFTERNOON...THE MAIN UPPER TROF APPROACHES ALONG WITH A FORMITABLE 
COLD FRONT.  WILL GO 40-50% WEDNESDAY THROUGH 12Z THURSDAY AS THIS 
PASSES THROUGH THE AREA.  MORE THAN ANOTHER OTHER PORTION OF THE 
FORECAST...WEDNESDAY AFTERNOON AND NIGHT HAVE THE BEST POTENTIAL FOR 
WIDESPREAD PRECIPITATION AND SEVERE WEATHER.  IN 24 HOURS OR 
SO...CONFIDENCE SHOULD ALLOW ONE OF THESE TWO PERIODS TO BUMPED UP 
TO LIKELY OR CATEGORICAL AS THE TIMING OF THE FRONT GAINS 
CONFIDENCE. 

WILL GO DRY SATURDAY WITH TEMPERATURES NEAR MEX GUIDANCE. 

ERVIN...


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

$$