[LeArc] Forecast Discussion : MLI@ 8/8/02 1:21:26 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 081823
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
120 PM CDT THU AUG 8 2002

.OVERVIEW...ANALYSIS INDICATES SURFACE AND UPPER AIR RIDGE STILL IN
PLACE OVER MIDWEST WITH SURFACE RIDGE AXIS AT 17Z FROM GREAT LAKES
SOUTHWEST INTO MISSOURI.  SLOW MODIFICATION CONTINUES WITH SFC TEMPS
ABOUT 2 DEGREES WARMER THAN YESTERDAY UNDER A MOSTLY SUNNY SKY.  UPPER
AIR ANALYSIS SHOWS SEASONABLY STRONG CLOSED UPPER LOW OVER IDAHO MOVING
EAST AT 15 MPH WITH MODELS AGAIN TOO WEAK ON REINITIALIZING THIS SYSTEM.
REASONABLE TO EXPECT THIS MODEL BIAS OF A BIT TOO MUCH SPIN DOWN OR
WEAKENING TO CONTINUE NEXT FEW DAYS AS IT MOVES EAST.

...ASSESSING POPS WITH FROPA THIS WEEKEND AND IMPACT ON TEMPS NEAR TERM
AND STRONG SYSTEM MIDWEEK MEDIUM CHALLENGES...

.DIAGNOSIS AND DAYS 1-3...AS MENTIONED ABOVE...MODELS NOT SURPRISINGLY
20 TO 30 METERS TOO WEAK ON NW US UPPER SYSTEM AND REMAIN CONSISTENT
WITH THIS TYPICAL MODEL BIAS OF ABOUT THIS MUCH PAST TWO DAYS...SEE NO
REASON FOR THIS NOT TO CONTINUE INTO WEEKEND.  THUS...MODELS NEXT FEW
RUNS SHOULD CAPTURE/HAVE MORE COHERENT FORCING WITH TREND OF SLIGHTLY
BETTER CHANCE OF POPS WITH FROPA BY LATE SATURDAY.  ALSO TIMING OF FROPA
IS FAVORABLE FOR DIURNAL CONVECTION MAX FOR SLIGHTLY HIGHER POPS.
THUS...WILL BUMP POPS A TAD HIGHER OR JUST ABOVE GUIDANCE BLEND. TEMPS
NEXT THREE PERIODS WILL USE BLEND OF PERSISTENCE AND MODEL BLEND OR
LOWER MINS TONIGHT WITH LIGHT WINDS AND CLEAR SKIES FOR ONE MORE NIGHT
OF GOD RADIATIONAL COOLING AND ALSO A TAD LOWER FOR FRIDAY HIGHS WITH
LIGHT SE WINDS LIMITING WAA. SATURDAY...LIMITED FORCING AND MOISTURE
EARLY SUPPORTS AT LEAST PARTLY SUNNY SKIES AND WITH SW WINDS AHEAD OF
SYSTEM AND COMPRESSIONAL HEATING...WILL TREND TEMPS UP AS MODEL GUIDANCE
TOO COOL AND INCONSISTENT WITH TRAJECTORIES AND TEMPS FROM THESE SOURCE
REGIONS.  LATER SHIFTS NEED TO EVALUATE CLOUD COVER AND IF MORE CLOUDS
EXPECTED...MAY NEED TO TEMPER MAX TEMPS BUT FOR NOW SEE THIS AS NOT
LIKELY. SUNDAY...WITH WEST WINDS AND LOWER DEWPOINTS AND LOTS OF
SUNSHINE WILL TREND ON HIGH SIDE OF GUIDANCE FOR MAX TEMPS.

EXTENDED (MON-THU)...ALL MODELS INDICATE STRONG UPPER TROUGH AND SFC
CANADIAN DIVING INTO CENTRAL PLAINS BY TUESDAY AM.  STRONG WAA AHEAD
OF THIS SYSTEM WITH GOOD UPPER DIFFLUENCE AND DECENT SFC AND UPPER AIR
FORCING SUPPORT HIGHER POPS LATE MONDAY AND MONDAY NIGHT WITH FROPA.
PLAN TO BUMP TEMPS UP AGAIN ON MONDAY AHEAD OF FRONT AS MEX/FMR GUIDANCE
OF 70S TO NEAR 80 WITH SW WINDS INCONSISTENT EVEN WITH SOME CLOUDS.
LATEST MODEL BLEND WITH STRONG FRONT TUESDAY INTO THURSDAY SUPPORT
MEX/FMR ARE AT LEAST 2 CATEGORIES TOO WARM WHICH IS NOT UNUSUAL WITH
STRONGER SYSTEMS AND WILL ADJUST TEMPS DOWNWARD ACCORDINGLY.  MORE
LIKELY IF LATEST FORECAST TRENDS DO OCCUR...MAY NEED TO LOWER TEMPS
ANOTHER CATEGORY OR SO MORE NEXT COUPLE DAYS.  WIDESPREAD RAINS VERY
FAVORABLE FOR LATE MONDAY AND MONDAY NIGHT WITH LOCALLY HEAVY RAINS AND
OF COURSE RISK OF SEVERE BUT SINCE DAY 4 WILL GO MOSTLY WITH LIKELY
WORDING FOR NOW DEPENDING ON TIMING OF FROPA.  PLAN TO LOOK AT UKMET
DAYS 4-6 THIS PM TO SEE IF ANY FURTHER ADJUSTMENTS WARRANTED.

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

NICHOLS