THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


EXTENDED FORECAST DISCUSSION




EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1146 AM EDT MON SEP 01 2014

VALID 12Z THU SEP 04 2014 - 12Z MON SEP 08 2014

...OVERVIEW AND GUIDANCE EVALUATION/PREFERENCES...

RIDGING OVER THE SRN TIER CONUS AND E-CNTRL/NERN PAC... WITH SOME
DEGREE OF TROUGHING NEAR THE WEST COAST... SHOULD BE THE MOST
PERSISTENT FEATURES AS VIEWED FROM THE MULTI-DAY MEAN PERSPECTIVE.


AFTER SOME SIGNIFICANT SPREAD AND RUN TO RUN DIFFS THERE APPEARS
TO BE IMPROVED CLUSTERING WITH THE DETAILS OF SHRTWVS CROSSING THE
NRN CONUS/SRN CANADA AND THUS BETTER AGREEMENT WITH TIMING OF THE
FRONT PROGRESSING EWD/SEWD FROM THE UPR MS VLY/PLAINS.  BY LATE
FRI-SAT THE 06Z GFS BECOMES MORE AMPLIFIED THAN MOST OTHER SOLNS
WITH THE LEADING SHRTWV CROSSING THE NERN QUADRANT OF THE CONUS
WHILE THE 00Z ECMWF BECOMES DEEPER/SLOWER THAN CONSENSUS WITH AN
UPSTREAM SYSTEM OVER CNTRL CANADA.

FARTHER WWD SOLNS AGREE FAIRLY WELL THAT REBUILDING OF THE RIDGE
OVER THE PAC SHOULD ENCOURAGE SOME DEGREE OF TROUGH AMPLIFICATION
OVER THE NORTHWEST LATE IN THE PERIOD.  DOWNSTREAM ISSUES AS WELL
AS 00Z GFS AMPLITUDE OF THE CA TROUGH PRECLUDE USE OF THE
OPERATIONAL MODELS BEYOND DAY 4 FRI BUT AN AVG OF THE 00Z-06Z
GFS/00Z ECMWF SEEMS REASONABLE AS A BETTER DEFINED VERSION OF THE
ENSEMBLE MEANS OVER THE NWRN CONUS/NRN PLAINS INTO SRN CANADA BY
DAY 7 MON.

OVER LOWER LATITUDES... IT REMAINS TO BE SEEN IF SERN RIDGING
ALOFT WILL BE AS STG AS SHOWN IN LATEST GFS RUNS BY NEXT MON.  THE
06Z GEFS MEAN SHOWS SOME SUPPORT FOR THE 00Z/06Z GFS RUNS BUT THE
00Z CMC MEAN CONFINES ITS RIDGE TO NEAR 30N LATITUDE IN CONTRAST
TO THE EXPANSIVE ERN RIDGE OF THE OPERATIONAL 00Z CMC.  AS FOR
TROPICAL FEATURES EXPECT A CURRENT AREA OF DISTURBED WEATHER OVER
THE BAY OF CAMPECHE TO BE WELL INLAND OVER MEXICO BY THE START OF
THE MEDR PERIOD... WHILE AN ERN PAC SYSTEM MAY TRACK TO THE S/W OF
BAJA CALIF.  AFTERNOON ISSUANCE WILL REFLECT TODAYS NHC/WPC
COORDINATED TRACK FOR THIS POTENTIAL SYSTEM.

THE MOST AGREEABLE ASPECTS OF GUIDANCE ARE REFLECTED WELL BY A
GENERAL MODEL/ENSEMBLE MEAN BLEND DAYS 3-4 THU-FRI.  A 60/40 BLEND
OF THE 00Z ECMWF MEAN/06Z GEFS MEAN... WHICH ARE SIMILAR IN
PRINCIPLE BUT DIFFER A LITTLE IN DEFINITION... SERVES AS THE
STARTING POINT FOR SAT-MON.  THE RESULTING FCST YIELDS BETTER THAN
AVG CONTINUITY OVER THE LOWER 48.


...SENSIBLE WEATHER HIGHLIGHTS...

THE PRIMARY FEATURE OF NOTE WILL BE THE FRONT PUSHING EWD/SEWD
FROM THE UPR MIDWEST/CNTRL PLAINS INTO THE SRN TIER.  THE FRONT
WILL BE ACCOMPANIED BY AREAS OF CONVECTION WHICH MAY PROVIDE SOME
LOCALLY INTENSE RNFL.  PROGRESSION SHOULD BE SUFFICIENT TO LOWER
THE POTENTIAL FOR WIDESPREAD HVY TOTALS THOUGH ENOUGH DECELERATION
MAY OCCUR TO ENHANCE RNFL OVER THE SRN MID ATLC.  HIGHEST WARM
SECTOR MAX TEMP ANOMALIES OF PLUS 10-15F SHOULD EXTEND FROM THE
MIDWEST INTO NORTHEAST THU-FRI.  EXPECT SIMILAR ANOMALIES ON THE
COOL SIDE OF THE FRONT FROM THE NRN INTO CNTRL PLAINS. 
COMBINATION OF A PSBL PERIOD OF LOW LVL UPSLOPE FLOW OVER THE SRN
HALF OF THE HIGH PLAINS BEHIND THE AFOREMENTIONED FRONT AND THEN
MONSOONAL MSTR RETURNING FROM MEXICO SHOULD LEAD TO INCREASED
COVERAGE/INTENSITY OF RNFL FROM THE SRN HIGH PLAINS INTO THE
SOUTHWEST.

RAUSCH





Last Updated: 1146 AM EDT MON SEP 01 2014