THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


EXTENDED FORECAST DISCUSSION




EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1200 PM EDT TUE SEP 23 2014

VALID 12Z FRI SEP 26 2014 - 12Z TUE SEP 30 2014

WPC MEDIUM RANGE SURFACE FRONTS/PRESSURES AND 500 MB PROGS ALONG
WITH ASSOCIATED 2.5 KM RESOLUTION SENSIBLE WEATHER GRIDS HAVE BEEN
PRIMARILY DERIVED FROM A BLEND OF THE 00 UTC ECMWF/ECMWF ENSEMBLE
MEAN AND THE 06 UTC GFS/GFS ENSEMBLE MEAN DAYS 3-5 FRI THROUGH THE
UPCOMING WEEKEND. LEANED JUST ON THESE ENSEMBLE MEANS BY MON/TUE
IN A PERIOD OF INCREASING DAYS 6/7 FORECAST SPREAD.

OVERALL...THE 06 UTC GFS/GEFS MEAN OVERALL TRENDED MORE IN LINE
WITH 00 UTC ECMWF/ECMWF ENSEMBLE MEAN VERSUS THE 00 UTC GFS/GEFS
MEAN. IN ALL THESE 3-7 DAY GUIDANCE BLENDS...WEIGHTED THE OVERALL
MORE AMPLIFIED AND LESS PROGRESSIVE ECMWF/ECMWF ENSEMBLE MEAN MORE
THAN THE GFS/GFS ENSEMBLE MEAN AS THAT SEEMS THE NATURE OF THE
FLOW AND CONSIDERING LEAD-IN WATER VAPOR LOOPS.  HOWEVER...THIS IS
A VERY COMPLEX AND STREAM DEPENDENT FLOW PATTERN RIPE WITH
UNCERTAINTY ESPECIALLY AT SMALL/MID SPATIAL SCALES AND WITH
SENSIBLE WEATHER FOCUS.

THIS PATTERN IS HIGHLIGHTED BY LEADING AND MEANDERING/LINGERING
WEAKNESSES ALOFT CENTERED OFF/NEAR THE EAST COAST...AND ALL
THROUGH THE CENTRAL US WHERE DEEP GULF MOISTURE COULD FAVOR HEAVY
RAINS CENTERED OVER THE LOWER MS VALLEY/GULF COAST STATES.
UPSTREAM...A DEEP MID-UPPER LEVEL TROUGH/LOWS MOVING OVER THE WRN
US THIS WEEK THEN EJECTS INTO THE N-CENTRAL US BY EARLY NEXT WEEK.
THIS LATTER SYSTEM HAS LESS FORECAST SPREAD AND BETTER
PREDICTABILITY THAN THE LESS DEFINED LEAD SYSTEMS AND SHOULD
SPEARHEAD LEAD SURFACE LOW/FRONTAL DEVELOPMENT AND WIDESPREAD
PCPN/CONVECTION FOCUS FOLLOWED BY COOLING TEMPS IN ITS WAKE.

SCHICHTEL





Last Updated: 1200 PM EDT TUE SEP 23 2014