[LeArc] Forecast Discussion : MLI@ 7/24/2003 2:21:49 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 241918
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
215 PM CDT THU JUL 24 2003

.OVERVIEW...ANALYSIS SHOWS SURFACE HIGH NOW SLIDING TO THE EAST WITH
WINDS COMING AROUND TO SOUTH.  WEAK VORT MAX OVER SD PRODUCING SOME
HIGH CLOUDS ALONG RETURNING WARM FRONT.  LIMITED MOISTURE AND FORCING
SUGGEST IF ANY POPS DEVELOP THIS PM TO BE WEST OF I-35.  UPPER
ANALYSIS SHOWS STRONG JET ENTERING PACIFIC NORTHWEST SLIDING EAST
NEXT 36 HOURS TO ALLOW FOR FRONTOGENESIS AND FAVORABLE CONVECTIVE
CONDITIONS LATE FRIDAY INTO WEEKEND AS ENERGY AND NEXT FRONT INTERACT
WITH RETURNING WARM FRONT. PERSISTENCE STILL DOING WELL WITH TEMPS
RUNNING 2-4 DEGREES WARMER THAN YESTERDAY.

...WARMING TREND WITH CHANCE POPS WITH STORMS LATE FRIDAY INTO
WEEKEND AND AGAIN INTO EARLY NEXT WEEK MAIN ISSUES...

.DIAGNOSIS (DAYS 1-3)...MODELS SHOWING SIGNIFICANT VARIANCE ON NEXT
FRONT AND ASSOCIATED CONVECTION THROUGH MONDAY.  TREND TOWARD BLEND
OF NGM QPF...ETA FRONTAL AND THEN EXTENDED GFS/ECMWF/UKMET UPPER LOW.
THUS...LOWS TONIGHT NEAR TO SLIGHTLY BELOW BLEND WITH LIGHT SOUTH
WINDS AND MOSTLY CLEAR SKIES.  THEN SOUTH WINDS TO INCREASE TO 15 TO
25 MPH BY PM WITH HIGHS PUSHING INTO 85 TO 90 DEGREE RANGE.  THEN
CONDITIONS STILL REMAIN FAVORABLE FOR LATE PM EARLY EVENING
CONVECTION TO INITIATE NEAR SIOUX FALLS TO SLIDE EAST SOUTHEAST AFTER
MIDNIGHT SATURDAY MORNING.  CURRENT TIERED POPS REMAIN REASONABLE
WITH BEST CHANCE ALONG AND NORTH OF HIGHWAY 30.  THEN SATURDAY FRONT
TO SLOWLY SAG ACROSS AREA WITH HOT AND HUMID CONDITIONS.  NO
SIGNIFICANT FORCING OR SHEAR...THUS STORMS MORE OF PULSE VARIETY BUT
SOME SEVERE POSSIBLE AS CAPES OF 2500-3500 AND LI'S -4 TO -8.
DEWPOINTS SHOULD RISE WELL INTO 70S PUSHING HEAT INDICES TO AROUND
100 AS MAX TEMPS REACH NEAR 90.  CHANCE POPS REASONABLE FOR NOW.
LATEST BLEP CALCULATIONS STILL SUPPORT LITTLE CHANCE OF STRONG WINDS
(LESS THAN 40 KNOTS) FRIDAY NIGHT DUE TO MARGINAL INSTABILITY AND
WEAKER LOWER LEVEL WINDS. SATURDAY HOWEVER...TEMPS REACHING INTO
UPPER 80S WITH LOWER 70 DEWPOINTS SHOULD PASS CONVECTIVE TEMPERATURE
FOR RE-IGNITION.   WEAKER WIND SHEAR MID LEVELS SUGGEST PULSE
CONVECTIVE MODE BUT WITH BOUNDARY AROUND...BLEP CALCULATIONS SUPPORT
STRAIGHT LINE WINDS AROUND 53 KNOTS WITH ISOLATED TORNADIC POTENTIAL
WITH BOUNDARY AND ALSO DECENT 0-1 KM ESTIMATED SHEAR OF 15 KNOTS FOR
LOW END F1 STRENGTH...OR ~80 KNOTS. APPEARS BEST "CROSSOVER" TEMPS IN
EVENING TO "NON-SEVERE" WINDS ARE ~83/72 (FALLING BELOW) WHICH WOULD
OCCUR MID EVENING.  IF CONDITIONS OCCUR FOR TORNADIC POTENTIAL...THE
"CROSSOVER TEMPS" RUN AS LOW AS 78-79F OVER 72F DEWPOINT...OR MORE
LATE EVENING. THUS...APPEARS UNLESS MODEL THERMAL FIELDS ARE OFF THAT
THESE VALUES ARE A GOOD FIRST GUESS AT THIS STAGE...BETTER ESTIMATES
NEXT 24 HOURS. IMPORTANT POINT IS WITH LIMITED ORGANIZATION...ANY
SEVERE WINDS WOULD TEND TOWARD LIMITED IN AREAL COVERAGE AND
STRENGTH. SUNDAY...KEEP CHANCE POPS...ESPECIALLY SOUTH OF FRONT AS IT
SLIDES SOUTH WITH SIMILAR SEVERE HIGH WIND STRENGTH POTENTIALS SOUTH
OF HIGHWAY 34 MID PM SUNDAY INTO MID EVENING AHEAD OF FRONT.

.EXTENDED (MON-THU)...ALL MODELS SUGGEST LONG WAVE NEAR AREA WITH
NORTHWEST FLOW.  POOR CONFIDENCE IN PHASING REMAINS...ALL SOLUTIONS
SUGGEST WAVE MAY FORM ON FRONT ON MONDAY...AND WITH FRONT JUST TO
SOUTH...KEEP POPS.  TUESDAY WILL KEEP POPS OUT WITH COOLER HIGH
MOVING IN THROUGH WEDNESDAY WITH WARMING BY THURSDAY. PLAN TO POPS
OUT FOR NOW WITH LIMITED FORCING EVIDENT YET.  TREND FOR TEMPS...GO
LOW SIDE OF MEX FOR TUE/WED AS LATEST GFS/UKMET ARE STRONGER THAN
LAST NIGHT/S GFS RUN.

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

$$

NICHOLS