[LeArc] Forecast Discussion : MLI@ 7/23/2003 4:45:43 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 230943
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
430 AM CDT WED JUL 23 2003

REGION ENTRENCHED IN NORTHWEST FLOW WITH SEASONALLY STRONG UPPER TROUGH
DOMINATING EASTERN HALF OF CONUS PROVIDING BELOW NORMAL TEMPS.
BROAD AND PERSISTANT HEAT DOME OVER SOUTHWEST STATES SHOWING SIGNS 
OF HEADING EAST WITH H5 HEIGHT RISES OVER THE UPPER MIDWEST AND 
PLAINS...BUT THIS WILL TAKE ABOUT ANOTHER 24 HRS OR SO 
AS THERE IS STILL JET ENERGY DIVING DOWN BACKSIDE OF EASTERN TROUGH.
CLOSER TO HOME...VORT MAX SHOWS UP NICELY ON SATELLITE
SOUTH/EAST OF THE QUAD CITIES. SCATTERED LIGHT SHOWERS ASSOCIATED
WITH THIS FEATURE HAVE MOVED INTO CENTRAL IL...WITH 
SUBSIDENCE ON BACKSIDE SCOURING OUT LINGERING CLOUDS FROM NORTH TO 
SOUTH.

LITTLE FORECAST CONCERNS IN SHORT TERM...WITH MAIN CHALLENGE TEMPS AND
POTENTIAL FOR RECORD/NEAR RECORD LOWS TONIGHT. BEYOND THE FOCUS
SHIFTS TO INCREASING HEAT/HUMIDITY BY THE WEEKEND AND TIMING OF NEXT
FRONT AND PCPN CHCS. 

TODAY...
VORT MAX WILL DIVE SOUTHEAST THROUGH CENTRAL IL THIS MORNING WITH
SUBSIDENCE RESULTING IN CLEAR/MAINLY CLEAR SKIES TO START AT MOST 
LOCATIONS. FORECAST SOUNDINGS SHOW FAIRLY STEEP LLVL LAPSE RATES 
WITH LINGERING CYCLONIC FLOW AND MOISTURE. THEREFORE...EXPECT CU TO 
ONCE AGAIN DEVELOP LATE MORNING WITH ETA CU RULE SUGGESTING 
SCT-BKN CU FIELD. REVIEW OF SATELLITE FROM TUE LENDS CREDENCE TO 
ETA WITH PLENTY OF CU NOTED AT MIDDAY THROUGH THE PLAINS 
AND AS FAR NORTH AS SOUTHERN CANADA. SO...HAVE OPTED TO GO WITH 
SUNNY-->PARTLY CLOUDY TREND ON SKY COVER. LITTLE WARMING NOTED FROM
TUE IN LLVLS WHICH TRANSLATES INTO TEMPS SIMILAR TO TUE...POSSIBLY 
A DEG OR TWO 
 
TONIGHT...
COOL NIGHT ON TAP WITH IDEAL RADIATIONAL COOLING SETUP WITH SURFACE 
HIGH PASSING OVERHEAD RESULTING IN CLEAR SKIES...LIGHT WINDS AND
LOTS OF DRY AIR. TEMPS AT 09Z BENEATH RIDGE AXIS GENERALLY IN THE 
L/M 50S WITH SOME U40S IN VALLEYS AND LOW LYING AREAS.
EXPECT SIMILAR CONDITIONS TONIGHT AND AS A RESULT...WENT 1-2 CATS 
BELOW GUIDANCE. WOULD NOT BE SURPRISED TO SEE SOME 40S IN
FAVORED VALLEYS LIKE THE WAPSI. ALSO...SOME FOG POSSIBLE MAINLY IN
LOW LYING AREAS OR VALLEYS...BUT NOT WIDESPREAD ENOUGH TO 
WARRANT MENTION IN ZONES. 

THURSDAY AND THURSDAY NIGHT...
ONE LAST DAY OF COMFORTABLE HUMIDITY AND BELOW NORMAL TEMPS WITH
REGION STILL UNDER INFLUENCE OF SURFACE RIDGE AXIS...WHICH
GRADUALLY SHIFTS EAST DURING THE DAY. LIMITED MIXING BUT MORE SUNSHINE
WITH LESS COVERAGE TO CU FIELD. RESULT...TEMPS JUST A FEW
DEGS WARMER THAN THOSE ON WEDNESDAY. WENT WITH AN EAST/WEST GRADIENT 
ON TEMPS THURSDAY NIGHT WITH COOLER READINGS AND NEAR OR JUST BELOW 
COOL END OF GUIDANCE USED IN THE EAST WITH LIGHT WINDS...AND 
SLIGHTLY WARMER READINGS WITH BLEND OF GUIDANCE USED IN THE WEST WHERE
WINDS WILL STAY UP.   ..05..
  
.LONGER RANGE(FRI-TUE)...MEDIUM RANGE MODELS GENERALLY AGREE ON 
SHIFTING LARGE SFC HIGH TO THE EAST...WITH BRISK RETURN FLOW SETTING 
UP ACRS THE AREA FRIDAY IN AN INCREASING SOUTHWEST GRADIENT. PROGGED 
XGFS AND ECMWF LLVL THERMAL VALUES BUILDING INTO THE AREA SUGGEST 
WIDESPREAD MID TO UPPER 80S BY LATE FRIDAY AFTERNOON ACRS THE 
CWA...WITH SFC DPTS RECOVERING BACK INTO THE MID TO UPPER 60S. THUS 
IN A PREFRONTAL WARMING DAY WILL GO ABOVE NEW MEX HIGHS. TROUGH 
DIGGING ACRS THE GRT LKS IN STORM TRACK ACRS THE NORTHERN CONUS... 
WILL USHER IN COLD FRONT AT THE SFC INTO INCREASING THTA-E AND 
UNSTABLE AIRMASS FOR THUNDERSTORM/MCS CHANCE LATER FRI NIGHT AND 
INTO SAT MORNING. MEDIUM RANGE MODEL ENSEMBLE SUGGESTS FRONT JUST 
NORTHWEST OF THE CWA BY 12Z SAT...WITH NOCTURNAL CONVECTION 
POTENTIALLY BLEEDING INTO AT LEAST THE NORTH HALF OF THE CWA. THERE 
MAY BE SOME CAP ISSUES ACRS THE SOUTH INHIBITING LATE NIGHT 
POTENTIAL...BUT STILL PLAN ON INTRODUCING CHANCE FOR ALL BUT 
SOUTHEAST CWA. CONTINUING TO FOLLOW A EURO AND XGFS BLEND...SFC HIGH 
WILL CONTINUE TO LAY OUT LLVL BAROCLINICITY IN A EAST-TO-WEST 
FASHION ACRS EAST IA AND NORTHWEST IL ON SAT FOR CONTINUED STORM 
THREAT. DIFFERENCES POP UP ON SUNDAY IN HOW FAR SOUTH THE BOUNDARY 
GETS PUSHED ACRS MO. XGFS PUSHES BOUNDARY SOUTH ENOUGH FOR A DRY DAY 
OVER THE ENTIRE CWA...WHILE EURO AND ITS STRONGER CENTRAL PLAINS SFC 
WAVE SOLUTION KEEPS BOUNDARY FURTHER NORTH AND STORM CHANCE OVER AT 
LEAST THE SOUTHERN THIRD. WILL TREND WITH THE FURTHER NORTH SOLUTION 
FOR NOW. CURRENT SIGNALS SUGGEST ANOTHER ROUND OF BACKDOOR HIGH ACRS 
THE GRT LKS AND COOLING NORTH TO NORTHEAST SFC FETCH FOR MON AND 
TUE. WOULD SEEM TO BE A DRY PERIOD...BUT NORTHWEST FLOW ALOFT MAY 
BRING A DISTURBANCE ACRS THE AREA IN TIME FOR A PRECIP CHANCE BY 
TUE. WILL STILL GO DRY FOR NOW WITH UNCERTAINTIES.  ..12..

RECORD LOWS 7/24

BRL 53 (1905)
CID 50 (1927)
DBQ 51 (1992)
MLI 54 (1947 AND PREVIOUS)

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

$$