[LeArc] Forecast Discussion : MLI@ 6/27/2003 4:40:21 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 272123
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
420 PM CDT FRI JUN 27 2003

SCATTERED SHOWERS AND ISOLD THUNDERSTORMS DEVELOPING RECENTLY ALONG
WEAK SURFACE TROUGH/FRONT ACROSS SOUTHERN MN/WI ATTIM.
THIS POSES INITIAL SHORT TERM CONCERN...AS TO WHETHER SOME OF THIS
ACTIVITY WILL PROPAGATE OR DEVELOP INTO NORTHERN SECTIONS
EARLY THIS EVE. 12Z UPPER AIR ANALYSIS SHOWS NORTHWEST FLOW WITH
SEVERAL EMBEDDED DISTURBANCES. OF MOST IMPORTANCE IS SHORTWAVE
DIVING INTO NORTHERN PLAINS ATTIM GENERATING SCATTERED CONVECTION 
ACROSS THE DAKOTAS. THIS SYSTEM IS THE SECOND CONCERN IN THE
SHORT TERM PERIOD.  

MODELS IN GENERAL AGREEMENT IN STALLING/WEAKENING SURFACE TROUGH
IN SOUTHERN MN/WI. BEST CONVERGENCE LOOKS TO STAY JUST
NORTH OF CWA...SO WILL NOT MENTION ANY SHOWERS IN THE NORTH EARLY THIS
EVENING. ATTENTION THEN TURNS TO DECENT SHORTWAVE WHICH
MODELS SHIFT ACROSS UPPER MIDWEST ON SAT. ACCOMPANYING THE 
SHORTWAVE WILL BE A FRONTAL SYSTEM. MOISTURE TRANSPORT AND 
DIVERGENCE FROM LEFT EXIT REGION OF UPPER JET POINT TO 
BULK OF PCPN ACROSS SOUTHERN MN/NORTHERN IA/SOUTHERN WISCONSIN...WHERE
SOME POTENTIAL EXISTS FOR SMALL MCS. HOWEVER...SECONDARY PCPN
AREA MAY DEVELOP LATER THIS EVE IN WESTERN IA WITH FRONTAL ZONE
INTERACTING WITH NOSE OF 35 KT LLJ. MEAN FLOW WOULD STEER THIS 
ACTIVITY IN OUR DIRECTION. WITH ALL BEING SAID...GUIDANCE 
LIKELY POPS IN THE WEST AND NORTH FOR LATER TONIGHT LOOK REASONABLE.
TAPERED TO JUST CHC POPS IN THE EAST. CLOUDS AND 
SOUTHERLY WINDS TO RESULT IN WARMER MINS AND GUIDANCE LOOKS 
REASONABLE...THOUGH IF CLOUDS/PCPN SLOW AND WINDS REMAIN LIGHT ENOUGH
THEN POTENTIAL TO BE FEW DEGS COOLER.  
 
ON SAT...EXPECT PCPN TO SHIFT ACROSS CWA DURING THE MORNING.
MAIN QUESTION IS WHETHER ANY CLEARING CAN OCCUR TO 
ALLOW FOR SUFFICIENT DESTABILIZATION FOR REDEVELOPMENT OF CONVECTION 
ALONG THE FRONT DURING THE AFTERNOON...WITH POTENTIAL FOR FEW
SEVERE STORMS GIVEN FAVORABLE SHEAR. MAIN POTENTIAL WILL BE WITH HAIL
WITH FAVORABLE WBZ/S IN 9000-11000 FT. HOWEVER...WITH DECENT SHEAR IN
LOWEST 3 KM AND ANY ROTATION GIVEN INVERTED V TYPE SOUNDINGS
SUPPORT POTENTIAL FOR DAMAGING WINDS. SPC CURRENTLY HAS MUCH 
OF CWA OUTLOOKED IN SLIGHT RISK FOR SAT. BELIEVE WE/LL SEE SOME 
THINNING IN CLOUDS AND ENOUGH DESTABILIZATION FOR SCATTERED
SHOWERS/TSTMS TO REDEVELOP DURING THE AFTERNOON...WITH EAST OF A CID
TO FFL LINE. BUMPED UP MAXES JUST A TAD WITH ANTICIPATION
OF SOME SOLAR INSOLATION AND LITTLE CHANGE IN THERMAL PARAMETERS.
DOESN/T TAKE MUCH SUN AND TEMPS JUMP. 

FRONT SLOWS UP SAT EVE...AND KEPT CHC POPS IN SOUTH AND EAST.
HARD TO ARGUE AGAINST SLIGHT CHC POPS IN FAR SOUTH ON SUN.
THIS AREA WILL BE IN CLOSE PROXIMITY TO FRONTAL ZONE. 
BOUNDARY THEN BEGINS TO WASH OUT ON MON...THUS CONTINUED WITH DRY
FORECAST. NUDGED TEMPS UP WITH LITTLE POST FRONTAL COOLING
BOTH SUN AND MON.  

EXTENDED (TUE-FRI)
HEAT AND HUMIDITY BUILD OVER THE PLAINS EARLY ON WITH UPPER RIDGE.
FRONTAL ZONE WASHES OUT TO OUR SOUTH ON TUE. LACK OF FORCING AND 
STRENGTHENING CAP SUPPORT GOING WITH DRY FORECAST TUE...WHICH BLENDS 
WELL WITH SURROUNDING WFO/S. HEAT AND HUMIDITY REALLY TAKE HOLD
OF THE AREA ON WED WITH UPPER RIDGE OVERHEAD...SQUELCHING PCPN CHCS 
AS WELL. THU-FRI SHORTWAVE ENERGY SHIFTS ACROSS NORTHERN STATES 
ON PERIPHERY OF MAIN WESTERLIES...SLOWLY SUPPRESSING UPPER RIDGE TO 
THE SOUTH. MEANWHILE...FRONTAL ZONE SAGS SOUTH TOWARD REGION. IF 
MODELS ARE CORRECT IN DEPICTING FRONT THROUGH SOUTHWEST NE 12Z 
THU...THEN OLD RULE SAYS IT WILL BE IN CWA WITHIN 24 HRS. 
THEREFORE...HAVE INTRODUCED PCPN CHCS.

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

$$