[LeArc] Forecast Discussion : MLI@ 7/3/2003 5:30:02 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 032212
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
500 PM CDT THU JUL 3 2003

RUNNING LATE...APOLOGIES. SETUP FAVORABLE FOR SEVERE WX (DAMAGING 
STRAIGHT LINE WINDS 60-80 MPH WITH BOW ECHO/DERECHO) AND 
HEAVY RAIN/LOCALIZED FLASH FLOODING DUE TO INTENSE RAINFALL RATES
NEXT 24 TO 36 HRS. 12Z UPPER AIR ANALYSIS SHOWS TROUGH OFF WEST 
COAST WITH H25 JET MAX OF 100 KTS IN NORTHERN ROCKIES. UPPER LOW WAS 
LOCATED OVER NORTH CENTRAL CANADA WITH PRESSURE FALLS SUPPORTIVE 
OF SOUTH/SOUTHEAST JOG SUPPRESSING MAIN WESTERLIES FURTHER SOUTH 
ACROSS THE NORTHERN TIER OF STATES...WITH CWA ON EDGE...AND THUS AT 
GREAT RISK FOR SEVERE MCS. INTENSE HEAT IN CENTRAL PLAINS WITH
TEMPS WELL INTO THE 100S RESULTING IN INCREDIBLE INSTABILITY...PRIMING
THE PUMP FOR WHAT LOOKS TO BE VERY ACTIVE NIGHT TO OUR WEST. 
CLOSER TO HOME...BOUNDARY FROM EARLY MORNING CONVECTION SHOWS UP 
NICELY ON SATELLITE OVER EASTERN AND SOUTHERN WISCONSIN. FEW STORMS
HAVE DEVELOPED ON THIS FEATURE LAST FEW HOURS. SECOND BOUNDARY 
SHOWS UP ESPECIALLY IN PRESSURE FIELDS FROM NEAR CEDAR RAPIDS TO THE
QUAD CITIES TO SOUTH OF CHICAGO...WITH FEW STORMS INTO 
NORTHWEST INDIANA AS BOUNDARY INTERACTS WITH MID LEVEL SHORTWAVE
DIVING INTO THE GREAT LAKES. 

TONIGHT...MAIN CONCERN IS MCS DEVELOPMENT AND PROPAGATION. SHORTWAVE
SHOWWS UP IN ANALYSIS OVER CENTRAL ROCKIES. THIS IN CONJUNCTION
WITH RIGHT ENTRANCE REGION OF UPPER JET MAX RESULTING IN
RAPID INCREASE IN UPWARD VERTICAL MOTION IN PLAINS...WITH CONVECTION 
TO CONTINUE DEVELOPING IN WESTERN PLAINS. CONVECTION DOESN/T
HAVE LONG BEFORE IT ENCOUNTERS INTENSE HEAT AND STRONG MOISTURE FEED
AT WHICH TIME...SHOULD SEE RAPID INTENSIFICATION. 
SUPERCELLS WILL GEL INTO MCS AND SHIFT EASTWARD PER FORWARD PROPAGATING
CORFIDI VECTORS. ADDITIONAL CONVECTION POSSIBLE LATER THIS EVENING
IN SOUTHEAST SD/SOUTHWEST MN/NORTHEAST NE/NORTHWEST IA WITH
LLJ INTERACTION. WITH LATER START AND FOCUS A BIT FURTHER WEST...CONCERNED
THAT THE AREA MAY NOT SEE MUCH IN WAY OF PCPN TONIGHT.
WITH COLD POOL THOUGH COULD SEE ACCELERATION IN FORWARD SPEED. 
MODELS SHOW BOUNDARY ACROSS NORTHERN 1/2 DEPICTED IN THETA-E GRADIENT
AND MSLP. THUS IF CONVECTION CAN MAKE IT INTO CWA IT WILL
TRANSLATE SOUTHEAST ALONG THIS FRONTAL ZONE PUTTING NORTHERN SECTIONS
AGAIN AT RISK. NOT AS CONFIDENT THAT PCPN WILL MAKE IT INTO THE
CWA...SO BACKED OFF TO CHANCE POPS NORTHWEST WITH TOKEN 20 POP IN THE
QUAD CITIES. 

AM VERY CONCERNED THAT WE MAY BE LOOKING AT MCS JUST ENTERING 
WESTERN IOWA AROUND 12Z TOMORROW MORNING...WITH LITTLE IN THE WAY OF 
DEBRIS OVERHEAD. THIS WOULD SPELL TROUBLE AND BE WORST CASE 
SCENARIO...AS AMPLE OPPORTUNITY TO BECOMING EXTREMELY UNSTABLE 
BEFORE IT WOULD ARRIVE PRIMARILY DURING THE AFTERNOON. COMPLEX WOULD 
REINTENSIFY WITH POTENTIAL FOR DERECHO AFFECTING THE NORTHERN 1/2 TO 
2/3RDS GIVEN THE EXTREME NATURE OF THE ENVIRONMENT WITH DAMAGING 
STRAIGHT LINE WINDS OF 60 TO 80 MPH OR POSSIBLY GREATER...AND 
INTENSE RAINFALL/FLASH FLOODING. ENTIRE CWA IN MODERATE RISK PER 
SWODY2. OF CONCERN IS WITH IT BEING THE FOURTH OF JULY AND LOTS OF 
FOLKS OUTDOORS. ANYONE OUTDOORS TOMORROW WILL WANT TO MAKE SURE THEY 
WILL HAVE ACCESS TO WEATHER INFORMATION. TEMPS WILL BE A REAL 
CHALLENGE...AND DEPENDANT ON TIMING OF CONVECTION.
 
SATURDAY NIGHT...POTENTIAL FOR SOUTHERN SECTIONS TO BE GENESIS REGION
WITH NOCTURNAL CONVECTION PER LLJ AND POSITION OF BOUNDARY. 
COULD SEE MORE SEVERE INITIALLY BEFORE TRANSITIONING TO HEAVY RAIN AND
FLASH FLOOD THREAT WITH VEERING LLJ AND EAST-WEST FRONT 
FAVORABLE FOR REPEATITIVE CONVECTION. HAVE MENTIONED DAMAGING WINDS 
AND HEAVY RAIN IN THE SOUTHERN ZONES. 

MESOSCALE SETUP WILL INFLUENCE SUNDAY...ATTIM MOST OF THE AREA COULD BE
DRY WITH MAIN FOCUS TO OUR SOUTH AND WEST ALONG TAIL END OF 
FRONTAL ZONE. THIS BOUNDARY LIFTS BACK NORTH LATE SUNDAY NIGHT/MONDAY
WITH PERHAPS MORE SEVERE WX AND POTENTIAL FOR MCS.

EXTENDED (MON-THU)
UPPER TROUGH DIGS OFF WEST COAST RESULTING IN DOWNSTREAM AMPLIFICATION
OF UPPER RIDGE OVER ROCKIES...WITH NORTHWEST FLOW DOMINATING
BY MIDWEEK. SURFACE HIGH WILL SHIFT ACROSS THE GREAT LAKES WITH LLVL 
FLOW USHERING IN DRIER AIR BRINGING A BREAK FROM THE HUMID 
CONDITIONS. FRONTAL ZONE TO THE SOUTH BEGINS TO RETURN LATE WEEK WITH
INCREASING HUMIDITY AND CHANCE OF SHOWERS AND THUNDERSTORMS.

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

$$

05