[LeArc] Forecast Discussion : MLI@ 8/9/02 2:00:15 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 091901
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
200 PM CDT FRI AUG 9 2002

.OVERVIEW...WHOAAA...VERY DYNAMIC AND CHALLENGING FORECAST!  SMALL BUT
VIGOROUS UPPER LOW IN MONTANA SLIDING DUE EAST AT 15 MPH.  FRONTAL
BOUNDARY AT 18Z FROM WESTERN MN SW INTO CLOSED LOW SE COLORADO. SPORADIC
CONVECTION CONTINUES ALONG/AHEAD OF BOUNDARY.  UPPER MIDWEST SURFACE
HIGH SLIDING EAST AS WESTERN SYSTEM APPROACHES. UPPER AIR ANALYSIS SHOWS
SIGNIFICANT ENERGY MOVING INTO NW NORTH AMERICA WITH ABOVE NORMAL
BAROCLINICITY IN PLACE FOR A VIGOROUS PATTERN NEXT SEVERAL DAYS.

...POPS WITH FROPA LATE SATURDAY AND IMPACT ON TEMPS NEAR TERM ISSUE AND
THEN AND STRONG SYSTEM WITH HEAVY RAIN POTENTIAL EARLY NEXT WEEK MEDIUM
RANGE CHALLENGES...

.DIAGNOSIS AND DAYS 1-3...MODELS CONTINUE TO SLIGHTLY UNDERPLAY STRENGTH
OF NW US UPPER SYSTEM AS IN PAST FEW DAYS BUT HANDLE LARGER SCALE
DYNAMICS OK. ETA-2M TEMPS REMAIN VERY INCONSISTENT AS IN PAST SO ONLY
USED FOR TRENDS. 18Z VERIFICATION SUPPORTS USING BLEND OF ETA DYNAMICS
AND AVN/NGM TEMPS. THUS...KEEP LOW CHANCE POPS TOMORROW PM AS BOUNDARY
APPROACHES INTO EVENING WITH TEMPS SLIGHTLY ABOVE MAV/FWC BLEND WITH
SUNSHINE AND SW SFC WINDS AHEAD OF BOUNDARY FOR DECENT WAA.  SUNDAY...
LIGHT WEST WINDS AND LOTS OF SUNSHINE AS WEAK HIGH SLIDES EAST AHEAD OF
A DEVELOPING MAJOR TROUGH DIVING SE INTO NORTH PLAINS BY MONDAY.  ALL
MODELS THEN SUPPORT A FAVORABLE PATTERN FOR SIGNIFICANT AND WIDESPREAD
PRECIPITATION TO OCCUR WITH LOCALLY HEAVY AMOUNTS.  E-W BOUNDARY STALLS
FAR SOUTH SECTIONS SUNDAY NIGHT TO ALLOW NOCTURNAL CONVECTION AS LL JET
KICKS IN AHEAD OF APPROACHING UPSTREAM STRONG SYSTEM. TRIPLE POINT MOVES
OVER AREA MONDAY WITH LOTS OF DYNAMICS AND VORT MAXES AHEAD OF COLD
FRONT. THEN...EXCEPTIONALLY STRONG COLD FRONT PASSES LATE MONDAY WITH
GOOD UPPER SUPPORT FOR ANOTHER ROUND OF CONVECTION. WITH LOTS OF
MOISTURE IN PLACE AND GOOD DYNAMICS...THIS PATTERN SUGGEST WIDESPREAD 1+
INCH AMOUNTS AND AREAS OF 2 TO 5 INCHES REASONABLE IN A 24 TO 30 HOUR
PERIOD SO WILL INTRODUCE HEAVY RAIN WORDING.  KEEP LIKELY WORDING FOR
NOW BUT CATEGORICAL MORE REALISTIC WITH ONLY QUESTION OF TIMING WHICH
NEXT FEW SHIFTS SHOULD BE ABLE TO CLARIFY. PLAN ON ESF ISSUANCE FOR
SIGNIFICANT AND LOCALLY HEAVY RAINS. WILL BE INTERESTING TO SEE SHORTER
RANGE MODELS QPF FIELDS IN ANOTHER 24-36 HOURS.

EXTENDED (TUE-FRI)...ALL MEDIUM MODELS CONTINUE TO SUGGEST A VIGOROUS
JET DISPLACED WELL SOUTH IN LONG WAVE TROUGH OVER CENTRAL US FOR VERY
CHANGEABLE PATTERN.  LATEST AVNXT NOW MUCH STRONGER AND COLDER WITH THE
SEASONABLY STRONG MONDAY NIGHT COLD FRONT...AND POSSIBLY TOO COOL ON
TEMPS TUE AS REST OF MEDIUM MODELS NOT QUITE AS COLD/STRONG.  ALL MODELS
THO NOW SUPPORT MUCH COOLER TEMPS THROUGH MIDWEEK WHICH YESTERDAYS
EXTENDED FORECAST ALREADY PLANNED FOR...MAY MAKE SOME MINOR ADJUSTMENTS
DOWN ON TUESDAY AND THEN SLIGHTLY UP WEDNESDAY WITH NEXT FAST SHORT WAVE
AND GOOD CHANCE OF POPS AND THEN ONCE AGAIN COOLER THURSDAY WITH EVEN
STRONGER AND COOLER SHOT OF CANADIAN AIR PER UKMET WITH SOME INPUTS FROM
ECMWF/AVNXT BLEND.

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

NICHOLS