[LeArc] Forecast Discussion : MLI@ 8/17/02 1:40:10 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 171843
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
140 PM CDT SAT AUG 17 2002

12Z UPPER AIR ANALYSIS AND WATER VAPOR IMAGERY SHOW VIGOROUS 
UPPER LOW NORTH OF THE ARROWHEAD OF MN. FAST UPPER FLOW WITH NEXT DISTURBANCE
DIVING SOUTH THROUGH PACIFIC NORTHWEST. AT SURFACE...18Z ANALYSIS
SHOWS DEEPENING LOW PRESSURE OVER SOUTHWEST ONTARIO WITH 
COLD FRONT TRAILING SOUTH THROUGH WI INTO VICINITY OF THE MISSISSIPPI RIVER. 
GUSTY NORTHWEST WINDS BEHIND FRONTAL PASSAGE...WITH GUSTS TO NEAR 25 MPH.
ISALLOBARIC COUPLET CONTRIBUTING TO STRONGER WINDS IN THE UPPER MIDWEST AND
GREAT LAKES. MUCH COOLER DRIER POST FRONTAL AIRMASS WITH TEMPS BEING
HELD IN THE 60S IN NE EVEN UNDER FULL SUNSHINE! DEWPOINTS LOWERING INTO THE
U30S/L40S IN THE NORTHERN PLAINS. 
 
CONCERNS REVOLVE AROUND TEMPS TONIGHT AND SUNDAY...THEN PRECIPITATION
CHANCES SUNDAY NIGHT AND MONDAY WITH STRONG ISENTROPIC LIFT AND 
IMPACTS OF CLOUDS/PRECIPITATION ON TEMPS. 

NEAR TERM...FRONT STILL HAS PUSH WITH MSAS INDICATING 3 HR/2 MB RISES AND
WILL BE THROUGH EASTERN SECTION BY 00Z. HOWEVER...WITH MAIN ENERGY 
AND ASSOCIATED SURFACE WAVE LIFTING NORTHEAST AND UPPER FLOW ZONAL EXPECT 
FRONTAL PROGRESSION TO SLOW WITH FRONT STALLING NEAR I-70 CORRIDOR IN MO. 
CONVECTION TO PERSIST ALONG FRONTAL ZONE WITH DEBRIS CLOUDINESS IN SOUTHERN 
SECTIONS. WILL MONITOR LATEST RADAR/SATELLITE TRENDS FOR POSSIBLE
INCLUSION OF POPS IN FAR SOUTH AND EASTERN ZONES. OTHERWISE...CLEAR OR 
MOCLEAR AND MUCH COOLER. WINDS TO SUBSIDE INTO THE 5 TO 10 MPH RANGE 
AFTER DARK. NGM SFC PARCEL TRAJECTORIES INDICATE SOURCE REGION EASTERN SD 
WHERE MORNING READINGS RANGED FROM NR 50 TO U50S. ETA 2M TEMPS WERE 
ABOUT 2-5 DEGS TOO COOL THIS MORNING ON MINS IN PLAINS AND MAKE 
NECESSARY ADJUSTMENTS STAYING ON COOL SIDE OF GUIDANCE ESPECIALLY NORTHERN 
1/2 WITH CLEAR/MOCLEAR SKIES...DECREASING WINDS AND DRY AIR. 
ETA ONLY MODEL WITH LIGHT QPF IN SOUTH IN 06Z-12Z TIMEFRAME AND DISREGARDED 
GIVEN DEPTH OF COLD AIR AND FURTHER SOUTH FRONTAL POSITIONING. 

SUNDAY...LOOKS LIKE ABSOLUTELY BEAUTIMOUS WITH COPIOUS AMOUNTS OF DRY AIR
AND ABUNDANT SUNSHINE. TEMPS WILL BE THE CHALLENGE AS ETA 2M TEMPS
VERIFYING ABOUT 3-4 DEGS TOO WARM IN MANY AREAS IN NE AT 18Z. 
EVEN WITH MODIFICATION AND SOLAR INSOLATION...GUIDANCE LOOKS A LITTLE WARM 
GIVEN CURRENT OBS IN PLAINS AND WILL SIDE TOWARD COOLER END OF GUIDANCE
SHAVING A COUPLE 2-3 DEGS. 

SUNDAY NIGHT/MONDAY...CHANGES IN STORE. AFFORMENTIONED SHORTWAVE DIVING SOUTH
THROUGH PACIFIC NORTHWEST WILL MOVE QUICKLY EASTWARD ACROSS THE
PLAINS AND MIDWEST. STRONG ASCENT WILL OCCUR OVER THE FRONTAL ZONE SUN NIGHT
AND MON AHEAD OF SHORTWAVE WITH 40+ KT LLJ AIDING STRONG THERMAL/MOISTURE
ADVECTION TOWARD REGION. MODELS IN FAIRLY DECENT AGREEMENT WITH 
THIS SCENARIO THOUGH DIFFER ON PLACEMENT OF HEAVIEST QPF...WITH TENDANCIES
TO SHIFT IT FURTHER NORTH FROM 24 HRS AGO. WILL BUMP UP POPS INTO
LIKELY/CATEGORICAL SOUTHERN HALF AND TAPER POPS OFF HEADING NORTHWARD.
GIVEN DEPTH OF COLD AIR...MAINLY RAIN WITH STRATIFICATION NORTH OF HIGHWAY 34
WITH FEW TSTMS POSSIBLE. SOUTH OF HIGHWAY 34 MORE SHOWERY WITH 
THUNDER AND SOME POTENTIAL FOR HAIL CLOSER TO PROXIMITY OF FRONTAL ZONE AND
BEST LIFT. SPC HAS JUST ABOUT ENTIRE AREA IN SLIGHT RISK 12Z SUN-12Z MON
AND WOULD TRIM THIS BACK TO ALONG AND SOUTH OF HIGHWAY 34. 
DECENT RAINS LOOK LIKE GOOD POSSIBILITY WITH STRONG THERMAL/MOISTURE ADVECTION.
SHORTWAVE TO EXIT EAST DURING AFTERNOON BRINGING END TO RAIN...BUT
CLOUDS TO LINGER WITH SOME SUNSHINE. TEMPS WILL BE TRICKY BUT WITH EVEN WITH
SUNSHINE WET GROUND TO LIMIT POTENTIAL WITH SUN NOT AS STRONG AND PLAN
TO SLASH GUIDANCE. NOT ENTIRELY OUT OF REALM OF POSSIBILITIES THAT SOME AREAS 
COULD STAY IN THE 60S ON MON.

GREAT LAKES HIGH DOMINATES MON NIGHT INTO TUE WITH EAST TO SOUTHEAST WIND
PROVIDING LITTLE WARMING...AND WILL CONTINUE ON LOW END OF GUIDANCE
MAKING ADJUSTMENTS AS NECESSARY. 
  
EXTENDED (WED-SAT)...
MRF AND UKMET ABOUT 12-18 HRS OR SO SLOWER WITH WARM FRONTAL PASSAGE AND NOW
SUGGEST TUE NIGHT/EARLY WED. WILL INCLUDE CHC PCPN NORTH 1/2. 
THEN...MUCH WARMER AND HUMID CONDITIONS TO SETTLE IN ON WED AND THU WITH 
MID LEVEL CAP AND WILL TAKE HIGH SIDE OF FMR/MEX GUIDANCE TACKING 
ON A DEG OR TWO. LATE WEEK MODELS INDICATE AMPLIFICATION TO UPPER PATTERN WITH 
HEAT DOME BUILDING ONCE AGAIN IN THE WESTERN US...WHILE ENERGY DIVING SOUTH 
FROM CANADA CARVES TROUGH OVER THE EASTERN US. THIS WOULD SUGGEST 
DECENT COOL DOWN BY WEEKEND.

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