482
FXUS02 KWBC 021846
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
246 PM EDT SUN AUG 02 2009
VALID 12Z WED AUG 05 2009 - 12Z SUN AUG 09 2009
MEDIUM RANGE MODEL AND ENSEMBLE MEMBER SPREAD AND UNCERTAINTY IN
THIS PATTERN REMAINS BELOW NORMAL WITH OVERALL FLOW HIGHLIGHTS
THAT INCLUDE AN AMPLIFIED WRN CANADIAN RIDGE AND ERN NOAM TROUGH
ALOFT INTO MIDWEEK. THIS COUPLET PROGRESSES SLOWLY EASTWARD AND
DEAMPLIFIES OVER THE REST OF THE WEEK...BUT LOCALLY HEAVIER
CONVECTIVE RAINS SHOULD CONTINUE TO FOCUS IN DEEPER MOISTURE
UNDERNEATH ALONG/AHEAD OF A LEAD AND WAVY CENTRAL AND ERN US
FRONTAL ZONE.
MEANWHILE...AN UNSETTLING AND COOLING CLOSED ERN PAC LOW/TROUGH
SHIFTS INLAND ACROSS THE WRN US...AND SHOULD FOCUS SUMMER PCPN
OVER THE NWRN STATES. THE WRN US TROUGH AMPLITUDE IS QUITE
UNSEASONAL AND EJECTING IMPULSE ENERGIES INTO THE CENTRAL THEN ERN
US WILL ALSO IN THIS PATTERN ACT UPON A SLOWLY RISING CENTRAL THEN
ERN US HEIGHT FIELD THAT BUILDS IN CONJUCTURE WITH NRN STREAM
DEAMPLICATION.
WE SEE NO COMPELLING REASON AFTER CONSIDERATION OF 12 UTC GUIDANCE
TO ADJUST CONTINUITY MUCH IN THIS PATTERN SO THE FINAL HPC PRELIM
MEDIUM RANGE SURFACE FRONTS/PRESSURES AND 500 MB PROGS HAVE BEEN
PRIMARILY RERIVED FROM A 70-30% BLEND OF THE 00 UTC ECMWF AND
QUITE SUPPORTIVE 00 UTC ECMWF ENSEMBLES DAYS 3-6...INCREASING TO A
NEAR 50-50 BLEND BY DAY 7. THIS IS IN CONSIDERATION OF
UNCERTAINTIES IN SYNOPTIC DETAIL INHERENT TO THESE TIME RANGES.
PREFERENCE FOR LEANING MORE ON THE FORECAST DETAILS OF THE 00 UTC
ECMWF VERSUS OTHER QUALITY MODELS WAS BASED UPON RECENT CONTINUITY
AND VERIFICATION...BUT THE DIFFERENCES BETWEEN THE VARIOUS
DETERMINISTIC SOLUTIONS FOR THIS PARTICULAR CYCLE ARE SMALLER THAN
NORMAL.
CISCO/SCHICHTEL
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