250
FXUS02 KWBC 081917
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
315 PM EDT TUE JUL 08 2008
VALID 12Z FRI JUL 11 2008 - 12Z TUE JUL 15 2008
..FINAL MEDIUM RANGE FORECAST DISCUSSION
FINAL GRAPHICS MADE NO SIGNIFICANT CHANGES TO THOSE ISSUED EARLIER
THIS MORNING.
WE KEPT THE 50-50 DETERMINISTIC ECMWF/GFS BLEND USED IN THE
MORNING PRELIM PROGS.
THE GLOBAL NUMERICAL MODELS ARE IN AGREEMENT WITH THE FLOW ACROSS
MOST OF THE CONTINENTAL UNITED STATES THRU DAY 4...HOWEVER
ENSEMBLES/MODELS SHOW HIGHER UNCERTAINTY SPREADING INTO THE CONUS
FROM THE ERN PACIFIC AND GULF OF ALASKA BEGINNING SUN DAY 5.
THOUGH THERE IS STILL SOME CONSENSUS OF 12Z/08 MODELS ON SOME KIND
OF 500MB TROF/CLOSED LOW OVER BRITISH COLUMBIA FOR MON DAY 6...THE
PATTERN UPSTREAM OVER SWRN ALASKA IS ANYBODYS GUESS. THE 12Z/08
GFS SHOWS RATHER POOR CONTINUITY FROM ITS 00Z AND 06Z RUNS OVER
SRN ALASKA/ SWRN CANADA BEYOND DAY 5 IN ITS PLACEMENT OF VARIOUS
VORTICES. THE NEW 12Z/08 ECMWF CONTINUITY LOOKS OK THRU DAY 5 THEN
IT TOO BECOMES RATHER DIFFERENT ACROSS SRN ALASKA INTO SWRN
CANADA. SO WE HAVE DECIDED TO STAY WITH OUR PRELIM CONTINUITY OF A
50/50 BLEND OF 00Z/08 GFS AND ECMWF FOR OUR FINAL MEDIUM RANGE
GRAPHICS THIS AFTERNOON.
HPC SEES NO REASON TO JUMP ON ANY PARTICULAR SHORTWAVE AND ALLOW
IT TO BECOME DOMINANT. THIS IS ESPECIALLY TRUE IN THE PACIFIC
WHERE WE DEFINITELY PREFER THE FLATTER SIDE OF THE ENVELOPE OF
MODEL AND ENSEMBLE SOLUTIONS. OVER THE REST OF THE CONUS WE FAVOR
SLIGHTLY LESS AMPLITUDE ALOFT THAN THE EARLY PRELIM PROGS. THE
12Z/08 ECMWF LOOKS SUSPECT AS IT BEGINS TO AMPLIFY AND SLOW DOWN
A 500MB TROF OVER THE NERN CORNER OF THE CONUS DAY 5 AND BEYOND.
..REGIONAL HIGHLIGHTS
..SOUTHEAST
MOISTURE POOLED ALONG A DYING FRONT WILL SUPPORT GENERAL DIURNAL
CONVECTION FRI-SAT. BY SUN...WITH THE BOUNDARY
DISSIPATED...CONVECTION OVER INLAND AREAS OF THE SOUTHEAST WILL
BECOME MORE SCTD...AND CONCENTRATE ON THE USUAL
SEABREEZE/OROGRAPHIC BOUNDARIES. A SECOND FRONT MAY BRING ANTHER
BATCH OF ORGANIZED SHOWERS LATE SUN-TUE TO PORTIONS OF THE UPPER
SOUTH.
...FRONT PUSHING INTO THE ERN CONUS ON SRN EDGE OF THE
WESTERLIES...
CONVECTION COULD BE STRONG ALONG A FRONT EDGING INTO THE UPPER MS
VLY/NWRN GRT LAKES FRI EVE...WITH A SOMEWHAT LESSER CHANCE OF
STRONG STORMS AND LOCALLY HEAVY RAINS AS IT PUSHES SWD AND EWD
INTO THE OH VLY/NEW ENG BY SUN. FOR NEXT MON/TUE...MOST OF THE SWD
PUSH OF THIS FRONT SHOULD BE GONE BELOW LATITUDE 35N...THOUGH THE
FRONT WILL STILL BE A FOCUS FOR SHOWERS/TSTMS.
..SOUTHWEST MONSOON AREA.
MONSOONAL MOISTURE NOW IN PLACE SHOULD REMAIN DIURNALLY ACTIVE
INTO EARLY SUN DAY 5 BEFORE MORE WESTERLY FLOW ALOFT NEAR THE 4
CORNERS REGION BECOMES LESS FAVORABLE FOR WIDESPREAD ACTIVITY. THE
MORE WESTERLY FLOW ALOFT IS COMING IN CONJUNCTION WITH THE
DEVELOPMENT OF A 500MB TROF ALONG THE W COAST EARLY NEXT WEEK.
..TROPICAL ATLANTIC.
HURCN BERTHA IS EXPECTED TO STAY WELL OFFSHORE WITH NO EFFECT ON
THE ATLANTIC OR GULF COASTS. PLEASE REFER TO BULLETINS FROM TPC
CONCERNING THIS SYS.
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