[LeArc] Forecast Discussion : MLI@ 4/29/2003 1:43:14 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 290640
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
135 AM CDT TUE APR 29 2003

.OVERVIEW...MOST SIGNIFICANT RAIN EVENT NOW EVIDENT TO OCCUR NEXT 48
HOURS SINCE LAST WARM SEASON OVER ALL OF FORECAST AREA!  WELCOME
RAINS SHOULD ALLEVIATE SOMEWHAT OUR DRY CONDITIONS THAT HAVE BUILT UP
PAST 8 MONTHS.  HIGH CONFIDENCE IN RAIN AND AT LEAST MODERATE RAIN
AMOUNTS...WITH LOCALLY HEAVY POTENTIAL.  FIRST...REGION UNDER
VIGOROUS LARGE SCALE SPRING SOUTHWEST FLOW WHICH WE HAVEN'T SEEN IN
QUITE A WHILE.  SECOND...MODERATE TO STRONG BOUNDARY NOW SETTING UP
SOUTH OF AREA ALONG I-70 IN MISSOURI.  THIRD...WITH SOUTHWEST FLOW...
THE GULF IS OPEN WITH SURFACE DEWPOINTS NOW INTO LOWER 60S WELL INTO
MISSOURI.  SO...ALL MAJOR FACTORS NEEDED FOR SIGNIFICANT RAINS IN
PLACE...MODERATE TO HIGH SURFACE MOISTURE...NICE BOUNDARY WITH DECENT
TRIGGER IN FORM OF FRONT AND SOUTHWEST OVERRUNNING FLOW.  CURRENT
SATELLITE AND SURFACE FEATURES AT 06Z SHOWING PRECIPITATION BREAKING
OUT IN CENTRAL HIGH PLAINS WHERE IT SHOULD BE DEVELOPING AS THE
BEGINNINGS OF SURFACE LOW NOW WINDING UP IN COLORADO.  LEADING EDGE
OF HIGH CLOUDS NOW INTO WESTERN IOWA WITH WEAK SURFACE RIDGE DRAPED
ALONG I-35 MOVING EAST AT 15 MPH.

...TIMING CLOUDS AND ARRIVAL OF PRECIPITATION...NATURE OF RAINFALL
AND AMOUNTS NEXT TWO DAYS MAJOR FORECAST ISSUE...SECONDARY IS RISK
OF SEVERE WEATHER SOUTH SECTIONS LATE WEDNESDAY INTO THURSDAY...

.DIAGNOSIS AND DAYS 1-3...ALL MODELS SHOW STRONG LOW PRESSURE AND
WARM FRONTAL OVERRUNNING LATE TODAY AND ESPECIALLY TONIGHT INTO
WEDNESDAY.  PLAN TO USE UKMET WITH SOME INPUTS FROM ETA BASED ON
MODEL QPF PERFORMANCE AND MAINLY FORCING FIELDS WHICH SUPPORT IT AS
MOST REASONABLE.  THUS...HIGH AND MID CLOUDS TO INCREASE TODAY WITH
PARTLY SUNNY SKIES TO GIVE WAY TO CLOUDS AND SOME RAIN WEST SECTIONS
BY SUNSET.  STRONG EAST LAKE EFFECT WINDS SUPPORT VERY STABLE
CONDITIONS WITH STRONG OVERRUNNING TONIGHT FOR CATEGORICAL POPS MOST
AREAS WITH RAIN AND POSSIBLY EMBEDDED THUNDER SOUTH SECTIONS TONIGHT
CLOSER TO WARM FRONT...GOOD RAINS A GIVEN OF ~.5" OR GREATER AMOUNTS
MOST AREAS WITH VERY STABLE LI'S OF +8 TO +14.  WEDNESDAY...KEEP
CATEGORICAL MOST AREAS WITH LOCALLY HEAVY RAINS WITH GOOD TEMPERATURE
GRADIENT WITH WARM FRONT STALLING CLOSE TO WHERE IT NORMALLY ENDS UP
THIS TIME OF YEAR FOR THIS TYPE EVENT...NEAR I-80. THIS SUPPORTS HIGH
50S ALONG HIGHWAY 20 TO LOWER 80S ALONG MISSOURI BORDER.  DEFINITELY
CHANCE OF SOME SEVERE ALONG WARM FRONT IN FORM OF MAINLY LARGE HAIL BUT
WILL HOLD OFF FOR NOW PUTTING IN ZONES TIL TONIGHT AS COVERAGE OF SEVERE
DEPENDENT ON WHAT HAPPENS NEXT 24-30 HOURS.  WILL CHANGE RAIN TO SHOWERS
AND THUNDERSTORMS SOUTHERN 2/3 AREA WEDNESDAY AS WARM FRONT APPROACHES.
TEMPERATURES...WILL GO NEAR GUIDANCE BLEND TODAY AND WITH HEAVY RAINS
ALSO NEAR GUIDANCE BLEND TONIGHT DESPITE CLOUDS. THEN BELOW GUIDANCE
NORTH AND JUST ABOVE SOUTH WEDNESDAY.  GO WITH CHANCE POPS WEDNESDAY
NIGHT INTO THURSDAY WITH SOME POSSIBILITY OF WAVE FORMING THURSDAY. WILL
TREND CLOSER TO UKMET TEMPS WITH SOME INPUTS FROM LOW LEVEL ETA THERMAL
FIELDS INTO THURSDAY.

EXTENDED (FRI-MON)...SLIGHTLY BELOW NORMAL TEMPERATURES AND QUIET
CONDITIONS INDICATED INTO LATE SUNDAY WITH SURFACE HIGH FROM CANADA.
THEN...ALL LONG RANGE SOLUTIONS SUPPORT ANOTHER DECENT STORM SYSTEM
OUT OF SOUTHWEST EARLY NEXT WEEK.  PHASING ISSUES SUPPORT NORMAL TOO
QUICK LIFTING OF SYSTEM INTO AREA AND WILL ADD LATE VERBIAGE WEST
AREAS AND DELAY POPS EAST TIL MONDAY.  TIMING ISSUES SUPPORT KEEPING
CHANCE POPS FOR NOW BUT THIS SYSTEM ALSO LOOKS PROMISING FOR DECENT
RAINS.  WILL KEEP AS SHOWERS AND STORMS BUT APPEARS RAIN MOST AREAS
MAY BE MORE PLAUSIBLE WITH SURFACE LOW LOCATION AND JET AXIS TO
SOUTH.

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

$$

NICHOLS