341
FXUS02 KWBC 011800
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
159 PM EDT TUE JUL 01 2008
VALID 12Z FRI JUL 04 2008 - 12Z TUE JUL 08 2008
THE FLOW PATTERN ACROSS THE UNITED STATES IS EXPECTED TO BECOME
LESS AMPLIFIED DURING THE MEDIUM RANGE PERIOD. PERSISTENT
VORTICES CONTINUE TO HAUNT THE NORTHEAST PACIFIC AND NORTHEAST
CANADA. ENERGY ROUNDING THE SOUTHERN PERIPHERY OF THE PACIFIC
VORTEX WILL UNDERCUT RIDGING ACROSS NORTHWEST CANADA...BREAKING
DOWN THE AMPLIFIED RIDGE ACROSS THE INTERMOUNTAIN WEST. THE
RESULT WILL BE A MORE WESTERLY FLOW ALONG THE NORTHERN TIER OF THE
CONTIGUOUS UNITED STATES...AND RELATIVELY HIGH HEIGHTS OVER MOST
THE REST OF THE COUNTRY...IMPLYING TYPICAL SUMMERTIME CONDITIONS.
A FRONTAL ZONE EXTENDING FROM THE MID ATLANTIC TO THE PLAINS
SHOULD DISSIPATE BY NEXT MONDAY AS HEIGHTS STEADY RISE. UNTIL IT
DOES SO...IT SHOULD BE THE FOCUS FOR MODERATE TO HEAVY RAINFALL
FROM MISSOURI EASTWARD THROUGH THE NORTHERN MID-ATLANTIC STATES.
THE 00Z ECMWF WAS AN OUTLIER SOLN WITH THE CLOSED CYCLONE OVER
OHIO NEXT SUNDAY...UNTIL THE 12Z GFS AND 12Z CANADIAN JOINED ITS
BANDWAGON. THIS DEVELOP SEEMS UNLIKELY CONSIDERING THE BREAKING
DOWN OF THE SHORTWAVE RIDGE TO ITS WEST. THE 06Z GFS WAS A SLOW
OUTLIER WITH ENERGY MOVING ALONG THE US/CANADIAN BORDER...AND NOT
USED. DOWN SOUTH...THE ECMWF HAS TRENDED AWAY FROM AN EAST-WEST
ORIENTED UPPER TROUGH INLAND OF THE GULF COAST...WHILE THE GFS
SHOWS BETTER CONTINUITY AND INDICATES AN UPPER CYCLONE CLOSES OFF
IN TEXAS BEFORE RETROGRADING...A FAIRLY TYPICAL DEVELOPMENT FOR
JULY BUT SOMEWHAT TO THE NORTH OF NORMAL. WILL CONTINUE TO
INDICATE TROUGHING NEAR THE NORTHWEST GULF COAST AS MODERATE TO
HEAVY PRECIPITATION WOULD BE POSSIBLE THERE IF THE GFS SOLUTION IS
CORRECT. FOR THE PRESSURES...USED THE 00Z ECMWF THROUGH SATURDAY
MORNING...BEFORE BLENDING ITS SOLUTION WITH THE 00Z NCEP ENSEMBLE
MEAN THEREAFTER TO RESOLVE DETAIL DIFFERENCES...WHICH KEPT GOOD
CONTINUITY.
ROTH/HEDGE
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