[LeArc] Forecast Discussion : MLI@ 7/26/2003 2:50:51 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 261947
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
247 PM CDT SAT JUL 26 2003

CAPPED WEATHER DAY TODAY WITH SOUNDING SO CAPPED WILL BE SURPRISED 
IF EVEN FLAT CU POP UP.  VERY HARD TO BREAK 700MB TEMPS OF 12+ WITH 
SURFACE FEATURE AND VORT MAX ALL TOO FAR NORTH TO INITIATE 
CONVECTION THIS AFTERNOON OR EARLY EVENING.  12Z UPPER AIR ANALYSIS 
SUPPORTIVE OF THIS...WITH BEST UPPER LEVEL FEATURES ACROSS MN AND 
WI...AND 300MB JET OVER SOUTHERN CANADA.  

MAIN CONCERNS THIS FORECAST INCLUDE PRECIPITATION POTENTIAL FOR 
TONIGHT...AND PRECIP CHANCES WITH THE FROPA SUNDAY.  LINGERING 
PRECIP POTENTIAL FOR SUNDAY NIGHT THROUGH MONDAY NIGHT ALSO IN 
QUESTION...WITH UPPER LEVEL LOW MOVING ACROSS BUT NO SURFACE FOCUS.

12Z MODELS APPEAR TO HAVE INITIALIZED REASONABLY WELL...AND ARE IN 
DECENT AGREEMENT WITH EACH OTHER ON MAIN FEATURES.  BY THIS 
EVENING....THE ETA SEEM TO DROP THE FRONT A LITTLE TOO FAR 
SOUTH...PERHAPS FROM CONVECTION FEEDBACK...WHICH DOES NOT CURRENTLY 
EXIST.  AVN AND NGM SEEM TO BE HANDLING THE FRONT A LITTLE 
BETTER...BUT ALL THREE MODELS HAVE TOO MUCH CONVECTION GOING ON 
RIGHT NOW.  AVN SEEMS TO BE THE LEAST OFF...AND HAVE IN GENERAL 
FOLLOWED ITS SOLUTION THIS AFTERNOON. 

TONIGHT AND SUNDAY BEST CHANCE OF PRECIP THROUGH TUESDAY...WITH 
FRONT MOVING THROUGH AND A FEW WEAK UPPER LEVEL VORT MAXES MOVING 
THROUGH.  CURRENT CONVECTION OVER EASTERN SOUTH DAKOTA ASSOCIATED 
WITH A VORT MAX THAT MOVES THROUGH TONIGHT AROUND MIDNIGHT.  A LINE 
OF CONVECTION ALSO DEVELOPING ALONG THE IA/MN BORDER RIGHT 
NOW...WHICH IS PRETTY CLOSE TO A WEAK TROUGH/WARM FRONT LIKE 
FEATURE.  THIS CONVECTION SEEMS TO BE ABOVE AND ON THE NORTH SIDE OF 
THE WARM TOUNGE ALOFT...AND SHOULD HAVE A HARD TIME DROPPING SOUTH 
INTO CWA.  WILL HAVE TO WAIT UNTIL FRONT MOVES IN...AND VORT MAX 
MOVES ACROSS IT AFTER ABOUT 9-10 PM FOR ANY CONVECTION TO DEVELOP.  
EVEN THIS CONVECTION SHOULD BE MOSTLY ELEVATED...DEVELOPING ABOVE 
THE WARM LAYER BETWEEN 850-900MB.  WITH FRONT MOVING THROUGH ON 
SUNDAY...CONVECTION LOOKS PRETTY GOOD...ESPECIALLY SOUTH WHERE 
DIURNAL HEATING WILL BE GREATEST...AND THE UPPER LEVEL TROUGH AND 
VORT MAX THE CLOSEST.  WILL NOT BE CHANGING GOING WEATHER AND POP 
FORECAST MUCH.  SUNDAY NIGHT PRECIP SHOULD BEGIN SHIFTING SOUTH OF 
THE AREA...AND HAVE GONE DRY NORTH TO JUST CHANCE SOUTH.

MONDAY VORT MAX MOVES THROUGH THE UPR LVL CYCLONIC FLOW...AND THOUGH 
NOT OVERLY APPARENT ON STRAIGHT MODEL DATA...BUFKIT SOUNDINGS FOR 
MONDAY SHOW HIGH ENOUGH LAPSE RATES BEHIND THE FRONT FOR MONDAY 
AFTERNOON FOR SOME SHALLOW CONVECTION WITH SHOWERS AND A FEW 
THUNDERSTORMS ACROSS THE CWA.  LOW POPS WILL FIT...WITH COVERAGE 
LIKELY TO BE FAIRLY LOW.

TUESDAY'S DRY FORECAST STILL LOOKS GOOD...THOUGH THERE SHOULD BE A 
PRETTY GOOD CUMULUS FIELD OVER THE AREA...AND PERHAPS SOME SHOWERS 
POSSIBLE DURING THE AFTERNOON AND EVENING.  HAVE DECIDED TO LEAVE 
DRY FOR NOW...THOUGH LATER MODEL RUNS MAY CHANGE THIS DECISION.

EXTENDED...WEDNESDAY THROUGH SATURDAY.
NEXT FRONT MOVES THROUGH ON WEDNESDAY AND WEDNESDAY NIGHT...STALLING 
AND WASHING OUT A FRONT ACROSS IOWA FOR THURSDAY.  WITH UPPER LEVEL 
RIDGING MOVING IN...DECIDED TO LEAVE IN PLACE THE PRECIP FOR 
WEDNESDAY AND WEDNESDAY NIGHT...BUT LEAVE THURSDAY DRY...THOUGH 
TIMING WILL HAVE TO BE WATCHED TO SEE IF PRECIP IS NEEDED FOR 
THURSDAY MORNING.  FRIDAY AND SATURDAY THE NEXT SYSTEM BREWS OVER 
THE NORTHERN HIGH PLAINS...BUT LIKE THE CURRENT SYSTEM ONLY BRING 
FRONT TO MN/IA BORDER AREA BY SATURDAY...ESPECIALLY WITH WARM 700MB 
TEMPS ONCE AGAIN NOSING INTO THE MIDWEST.  FRIDAY AND SATURDAY DRY 
FOR NOW.  HAVE GONE ABOVE GUIDANCE FOR BOTH DAYS...WITH STRONG 
SOUTHERLY FLOW LIKELY TO PUSH TEMPS WELL ABOVE NORMALS FOR LATE JULY.

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

$$

LE