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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1600Z Sep 26, 2014)
 
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Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1200 PM EDT FRI SEP 26 2014

VALID 12Z MON SEP 29 2014 - 12Z FRI OCT 03 2014

WPC MEDIUM RANGE SURFACE FRONTS/PRESSURES AND 500 MB PROGS HAVE
BEEN PRIMARILY DERIVED FROM A 50-50 BLEND OF OVERALL COMPATABLE
GUIDANCE FROM THE 00 UTC GFS/ECMWF DAYS 3-5 MON-WED AND THEN THEIR
00 UTC GFS/ECMWF ENSEMBLE MEANS DAYS 6/7 IN A PERIOD OF INCREASING
FORECAST SPREAD. WPC CONTINUITY WAS ALSO INCORPORATED.

LEAD MID-UPPER LEVEL TROUGHING IN A SEPARATE SRN STREAM FAVORS
FRONTAL WAVE FOCUS FROM THE CENTRAL GULF COAST TO COASTAL
CAROLINAS MON/TUE WITH WPC PROGS POSITIONING WELL SUPPORTED BY A
LARGE CLUSTER OF GFS/ECMWF/CANADIAN ENSEMBLE MEMBERS. THIS WILL
FOCUS POTENTIAL FOR HEAVY SERN US/MID-ATLANTIC RAINFALL.

OVERTOP...NRN STREAM MID-UPPER LEVEL TROUGHING AND ASSOCIATED
SURFACE SYSTEM REFLECTION AND POST-PASSAGE COOLING SEEMS WELL
DEFINED NOW IN THE GFS/ECMWF BY MON/TUE OUT FROM THE GREAT LAKES
TO THE NRN MID-ATLANTIC. THIS TRACK MAY WELL SUPPORT SOME
SUBSEQUENT PHASING INTO MIDWEEK WITH BY THEN A NEWD LIFTING SRN
STREAM COASTAL LOW ALLOWING FOR A HEAVIER PCPN POTENTIAL UP INTO
NEW ENGLAND MIDWEEK BEFORE BEING A OFFSHORE MARINE INTEREST DAYS
6/7...ALBEIT WITH A GOOD CHANCE OF POST-FRONTAL COOLING HIGH
PRESSURE IN ITS WAKE DOWN THROUGH THE ERN/SERN US...ALL DOWNSTREAM
OF AN AMPLIFIED MID-UPPER LEVEL RIDGE IN A SLOWLY EVOLVING OVERALL
FLOW PATTERN.

UPSTREAM...THIS SOLUTION HIGHLIGHTS SIGNIFICANT SHORT RANGE
MID-UPPER LEVEL TROUGHING OVER THE GREAT BASIN AND ASSOCIATED
LOWER ATMOSPHERIC CYCLOGENESIS/FRONTOGENESIS BEING EJECTED NEWD
THROUGH THE ROCKIES INTO THE PLAINS BY EARLY NEXT WEEK...ALL
BUMPING INTO THE AMBIENT AND WARMING/AMPLIFIED CENTRAL US
MID-UPPER LEVEL RIDGE POSITION. THIS UNSETTLING/COOLING FEATURE
OVER THE WEST WILL REMAIN A MAJOR FOCUS FOR WIDEPSREAD PCPN
INCLUDING A THREAT FOR SOME NRN ROCKIES ELEVATION SNOW AND LEAD
ROCKIES TO PLAINS CONVECTIVE DEVELOPMENT. THIS SCENARIO HAS GOOD
GUIDANCE SUPPORT AND OCCURS IN RESPONSE TO POTENT KICKER NERN
PACIFIC TROUGH ENERGY AND DIGGING SEWD OVER THE NORTHWEST TO THE
INTERMOUNTAIN WEST AND ROCKIES BY MIDWEEK. SUSPECT EXPLICIT MODEL
CONVECTION MAY BE UNDERDONE OVER THE SRN PLAINS THEN CONSIDERING
INCREASING DYNAMIC SUPPORT IN A PATTERN WITH IMPROVING MOISTURE.
THE THREAT COULD BE MORE PRIMED OVER THE PLAINS NEWD THROUGH THE
E-CENTRAL US DAYS 6/7 AS AMPLE TROUGH ENERGY WORKS OUT FROM THE
WRN US AND THE GULF OF MEXICO INCREASINGLY OPENS UP...ALBEIT WITH
GUIDANCE MORE VARIED WITH THE EXTENT OF STREAM SEPARATION WITH THE
MOST SEPARATED 00 UTC ECMWF PRODUCING THE GREATEST QPF. THIS IS
BEING FOLLOWED BY SPC IN THEIR CONVECTIVE OUTLOOK.

SCHICHTEL