430
FXUS02 KWBC 301845
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
244 PM EDT MON JUN 30 2008
VALID 12Z THU JUL 03 2008 - 12Z MON JUL 07 2008
THE 00Z GFS/ECMWF/NCEP ENSEMBLE MEAN/ECMWF ENSEMBLE MEAN DISPLAY
GOOD AGREEMENT WITH THE GENERAL FLOW PATTERN DURING MUCH OF THE
MEDIUM FCST PERIOD. THIS PROVIDES HIGHER THAN AVERAGE CONFIDENCE
WITH THE FRONTAL POSITIONS INTO DAY 6. THE BIGGEST ISSUE REGARDED
THE EXACT POSITION OF THE DEEP CYCLONE IN THE GULF OF
ALASKA...WITH THE 00Z/06Z/12Z GFS SOLUTIONS ON THE EASTERN FRINGE
OF THE MULTI-MODEL AND MULTI-ENSEMBLE ENVELOPE. THE 00Z ECMWF
SHOWED BETTER AGREEMENT WITH THE OTHER GUIDANCE...SO IT WAS
PREFERRED NEAR AND DOWNSTREAM OF THE NORTHEAST PACIFIC. THE MODEL
CHOICE TODAY WAS THE 00Z ECMWF INTO SATURDAY BEFORE BLENDING IN AN
EQUAL PART OF THE 00Z NCEP ENSEMBLE MEAN THEREAFTER TO TAKE INTO
ACCOUNT UNCERTAINTY AT THAT TIME RANGE.
THE 00Z GUIDANCE CONTINUES TO SHOW SHRTWV ENERGY UNDERCUTTING THE
WESTERN CANADIAN RIDGE BY DAY 5...WHICH FITS IN WITH THE POSITION
OF THE APEX OF THE WESTERN CANADIAN RIDGE. THE POLAR FRONT IS
EXPECTED TO CROSS THE GREAT LAKES AND NORTHEAST BY DAY 4 WITH A
TRAILING STNRY BNDRY REACHING BACK INTO THE CNTRL PLAINS. THIS
FRONT SHOULD BECOME QUASI-STATIONARY ACROSS THE EAST CENTRAL
UNITED STATES BEFORE WEAKENING LATE NEXT WEEKEND. THE 06Z GFS
SHOWS A FEW GRIDSCALE FEEDBACK VORTICITY MAXIMA MOVING THROUGH THE
MID-SOUTH THIS PERIOD...SOUTH OF THE ECMWF SOLUTIONS. CONSIDERING
THE POSITION OF THE FRONTAL BOUNDARY...THE GFS PLACEMENT MAY NOT
BE THAT BAD BUT THE VORTICITY MAXIMA APPEAR MUCH TOO STRONG/SPUN
UP. CONSIDERING THE 06Z GFS FLOW PATTERN ALONE /OUT OF SYNC WITH
THE REST OF THE GUIDANCE/...ITS SOLUTION WAS GENERALLY DISCOUNTED.
EITHER WAY...A MODERATE TO HEAVY RAIN POTENTIAL EXISTS FROM THE
CENTRAL PLAINS/MID MISSISSIPPI VALLEY EASTWARD INTO THE
MID-ATLANTIC STATES FROM LATE THIS WEEK INTO THIS WEEKEND.
AN UPPER TROUGH IS EXPECTED TO LIE DOWN INLAND OF THE GULF COAST
THIS PERIOD...WITH VARIOUS RUNS OF THE GFS/ECMWF SHOWING A
POSSIBLE CLOSED UPPER CYCLONE NEAR THE WESTERN GULF COAST NEXT
SUNDAY AND MONDAY. ON THE 06Z GFS/00Z CANADIAN...THIS GENERATED A
CYCLONE IN THE WESTERN GULF OF MEXICO. EITHER WAY...MODERATE TO
HEAVY RAINS ARE POSSIBLE ACROSS THE CENTRAL AND WESTERN UNITED
STATES GULF COAST THIS PERIOD. AFTER COORDINATION WITH NHC...KEPT
THE SURFACE TROUGH OFFSHORE THE LOUISIANA AND TEXAS COAST.
ROTH/HEDGE
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