[LeArc] Forecast Discussion : MLI@ 5/19/2003 3:35:58 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 192032
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
330 PM CDT MON MAY 19 2003

STRONG SURFACE COLD FRONT AT 18Z REACHED FROM 1012 LOW NEAR 
KMSP...SOUTH-SOUTHWEST ACROSS WESTERN IA TO NEAR KTOP. 88D MOSAIC 
SHOWED MOST FRONTAL CONVECTION FOCUSED IN KMCI REGION WITH WEAK 
ELEVATED POST FRONTAL RETURNS INTO EASTERN IA. BAND OF SHOWERS THAT 
DEVELOPED THIS MORNING ALONG WEAK PREFRONTAL TROF AND SURFACE 
THETA E RIDGE ALONG MISS RIVER HAVE SINCE MOVED EAST OUT OF FORECAST 
AREA. WARM TEMPERATURES AT MID LEVELS LIKELY RESPONSIBLE FOR KEEPING 
LID ON FURTHER CONVECTION IN AREA SO FAR THIS AFTERNOON. SHORT TERM 
FORECAST CHALLENGE CENTERS ON THIS COLD FRONT AND ASSOCIATED POPS... 
TEMPERATURES AND WIND IMPACTS TONIGHT INTO EARLY TUESDAY.

NO SIGNIFICANT DIFFERENCES IN MODELS NOTED...WITH EXCEPTION OF 
TIMING OF SURFACE COLD FRONT...WHICH SLOWER ETA HAD BETTER HANDLE ON 
WITH RESPECT TO PRESSURE FIELDS AT 18Z AND THUS FOLLOWED THROUGH 
THIS EVENING. THE FRONT...WHICH SURFACE ANALYSIS SHOWS LAGGING 
BEHIND THE PRESSURE TROUGH BY AT LEAST 50 MILES...WILL PUSH ACROSS 
MISS RIVER BETWEEN 00Z AND 03Z...THEN EAST OUT OF NORTHWEST IL ZONES 
AROUND 06Z. BEST CHANCES FOR PRECIP WILL BE DURING THIS TIME PERIOD. 
AT UPPER LEVELS...H5 TROUGH ANALYZED NEAR MT AT 12Z WEAKENS AND 
PASSES TO NORTH AROUND 12Z TUESDAY. EMBEDDED VORT MAX ROUNDING BASE 
OF TROUGH SEEN ON WATER VAPOR IMAGERY AND HANDLED BY 18Z META 
CURRENTLY ASSISTING STRONGER CONVECTION OVER NORTHEAST KS THIS WILL 
TRACK INTO NORTHWEST IL AROUND 03Z TO ENHANCE CONVECTION ALONG 
FRONT. AT SAME TIME...JET LEVEL DIVERGENCE COUPLET ASSOCIATED WITH 
ENTRANCE REGION OF 100KT JET MAX NEAR LAKE WINNEPEG AND 90KT JET 
MOVING OUT OF NEW MEXICO THIS MORNING WILL ENHANCE LIFT OVER EAST 
CENTRAL IA INTO NORTHWEST ILLINOIS 00Z TO 06Z. THUS...EVERYTHING 
STILL APPEARS TO BE COMING TOGETHER FOR WIDESPREAD FRONTAL AND POST 
FRONTAL CONVECTION FOR THE FIRST HALF OF TONIGHT. SPC SEVERE RISK 
WELL TO SOUTH LOOKS REASONABLE GIVEN LACK OF SHEAR AND CONSIDERABLE 
CLOUD COVER TODAY THAT HAS LIMITED LOW LEVEL INSTABILITY WITH LAPS 
CAPES GENERALLY BELOW 800 J/KG AND LI/S LIMITED TO -2 OR HIGHER. 
RAISED POPS TO 80 PERCENT FOR EASTERN HALF AND KEPT 70 PERCENT 
ACROSS THE WEST THIS EVENING. STRONG PRESSURE GRADIENT AND 35KT H85 
WINDS ON PROFILERS BEHIND FRONT WILL MAKE FOR WINDY CONDITIONS 
BEHIND FRONT LATE TONIGHT WITH PLUNGING TEMPERATURES. WENT BELOW 
GUIDANCE...ESPECIALLY IN NORTHWEST WHERE IT WILL BE DEEPEST IN COLD 
AIR BEFORE SUNRISE. GUIDANCE ALSO LOOKS TOO WARM FOR TUESDAY. 
AIRMASS BEHIND FRONT OVER NORTHERN PLAINS ONLY REACHING 50S THIS 
AFTERNOON. WENT BELOW GUIDANCE...BUT STAYED WITHIN ACCEPTABLE RANGE 
TO COORDINATE WITH SURROUNDING GRIDS...THAT IS UPPER 50S TO AROUND 
60. HIGH SETTLES OVER AREA TUESDAY MORNING SETTING STAGE FOR COLD 
NIGHT AND WENT CLOSE TO COMPROMISE BETWEEN COOLER MET AND FWC 
GUIDANCE.

GFS CONTINUES TO POINT TOWARD MORE AMPLIFIED SOLUTION FOR 
WEEKEND...WITH UPPER LOW CUTTING OFF TO EAST AND RIDGE BUILDING TO 
WEST. UK AND CANADIAN NOT AS BULLISH...WITH WEAKER UPPER LOW OVER 
EASTERN GREAT LAKES INSTREAD OF GFS OHIO VALLEY SOLUTION. GFS 
SOLUTION WOULD BE MORE FAVORABLE FOR COOLER AND MORE SHOWERY 
CONDITIONS FROM FRIDAY THROUGH MONDAY TIMEFRAME...BUT NOT ENOUGH 
CONFIDENCE YET INTRODUCE SHOWERS FOR FRIDAY AND SATURDAY...BUT DID 
KEEP CHANCES IN SUNDAY INTO MONDAY. DID NOT CHANGE TEMPERATURES MUCH 
AND LATER UPDATES MAY HAVE TO ADJUST DOWNWARD TO WELL BELOW NORMAL 
IF MEDUIM RANGE GUIDANCE TRENDS TOWARD CURRENT GFS SOLUTION. 

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

$$

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