849
FXUS02 KWBC 021809
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
208 PM EDT WED JUL 02 2008
VALID 12Z SAT JUL 05 2008 - 12Z WED JUL 09 2008
THE WESTERLIES ARE FORECAST TO ALIGN ALONG THE NRN TIER OF STATES
AND SRN CANADA DURING MOST OF THE MEDIUM RANGE PERIOD AS THE
CYCLONE OVER THE NORTHEAST PACIFIC SLOWLY FADES. LATE IN THE
PERIOD...WEAK RIDGING RETURNS TO THE NORTHWEST AND WEAK TROUGHING
TO THE NORTHEAST. SEASONABLY HIGH HEIGHTS ARE EXPECTED ACROSS
MUCH OF THE CONTIGUOUS UNITED STATES. OVERALL...THE 00Z GUIDANCE
WAS QUITE SIMILAR DURING THE MEDIUM RANGE PERIOD. THE 12Z
GUIDANCE INTRODUCED NO NEW WRINKLES INTO THE FORECAST. A BLEND OF
THE 00Z GFS/ECMWF WAS USED FOR PRESSURES THROUGH THE PERIOD TO
TAKE CARE OF DETAIL DIFFERENCES AMONGST THE GUIDANCE...WHICH
MAINTAINED GOOD CONTINUITY.
..NORTHERN ROCKIES
THE 00Z/12Z CANADIAN INSIST UPON TROUGHING WHERE NONE OF THE OTHER
GUIDANCE...INCLUDING ENSEMBLE MEANS...FAVOR TROUGHING /ACROSS
MONTANA EARLY MONDAY/. CONSIDERING THE EXISTENCE OF CLOSED
CYCLONES IN THE NORTHEAST PACIFIC AND NORTHEAST CANADA...RIDGING
IN THIS AREA WOULD BE PREFERRED...SO DID NOT USE THE 00Z/12Z
CANADIAN FOR ANY FORECAST PARAMETERS.
..NORTHERN PLAINS
A SECONDARY BOUNDARY DROPS IN THE NORTHERN PLAINS BY MONDAY
MORNING. DESPITE SUBSTANTIAL DIFFERENCES BETWEEN THE ECMWF AND
NON-ECMWF GUIDANCE WITH THE POST-FRONTAL SURFACE HIGH...FRONTAL
BOUNDARIES WERE SHOWN SIMILARLY IN THE 1000-850 HPA THICKNESS
PATTERNS SO A COMPROMISE PRESSURE PATTERN WAS USED.
..MIDWEST TO MID-ATLANTIC STATES AND GREAT LAKES
A NEARLY STATIONARY FRONT FROM THE PLAINS TO THE MID-ATLANTIC
STATES SUBSTANTIALLY WEAKENS BY MONDAY MORNING. UNTIL THEN...IT
SHOULD ACT AS THE FOCUS FOR MODERATE TO HEAVY RAINS FROM THE
MID-MISSISSIPPI VALLEY THROUGH THE NORTHERN MID-ATLANTIC STATES
THIS WEEKEND. ACROSS THE GREAT LAKES/UPPER OHIO VALLEY...THE
00Z/12Z GFS ARE SLOWER TO MOVE A SMALL CLOSED CYCLONE THROUGH THE
REGION THAN THE OTHER GUIDANCE THIS WEEKEND/MONDAY. THE 06Z NCEP
ENSEMBLE MEMBERS SHOWED EVEN SPREAD BETWEEN THE GFS AND NON-GFS
CAMPS...A COMPROMISE APPROACH WAS WARRANTED IN THIS CASE.
..GULF COAST
THE MODELS ARE COMING INTO BETTER AGREEMENT CONCERNING THE
ORGANIZATION OF A RETROGRADING UPPER LOW MOVING FROM THE
NORTH-CENTRAL THROUGH THE NORTHWEST GULF COASTS INTO TEXAS DURING
THIS PERIOD. IN TANDEM WITH ITS ASSOCIATED SURFACE
TROUGH...MODERATE TO HEAVY RAINS ARE EXPECTED FROM THE MISSISSIPPI
DELTA WESTWARD EARLY NEXT WEEK.
ROTH/HEDGE
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page