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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0638Z Jan 26, 2015)
 
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Abbreviations and acronyms used in this product
 
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
138 AM EST MON JAN 26 2015

VALID 12Z THU JAN 29 2015 - 12Z MON FEB 02 2015

...ACTIVE SPLIT-FLOW FOR THE LOWER 48...
 

...GUIDANCE AND UNCERTAINTY ASSESSMENT...

THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A
COMPOSITE BLEND OF THE REASONABLY COMPATABLE 18 UTC GFS AND 12 UTC
ECMWF AND ECMWF/NAEFS ENSEMBLE MEANS THROUGH DAY4/FRI. SWITCHED TO
AN INCREASINGLY ECMWF ENSEMBLE MEAN CENTRIC SOLUTION DAYS 5-7 IN A
PATTERN WITH GROWING FORECAST SPREAD AND UNCERTAINTY. THE 12 UTC
ECMWF AND NAEFS MEAN ALSO FALL IN A SIMILAR GUIDANCE CLUSTER AS
THE ECMWF ENSEMBLE MEAN AND REMAIN VIABLE TO A LESSER DEGREE.

WPC PREFERRED GUIDANCE LEANS THROUGH THE FORECAST PERIOD WITH FLOW
EVOLUTION GENERALLY ON THE MORE AMPLIFIED SIDE OF A COMPOSITE OF
THE FULL ENVELOPE OF SOLUTIONS. THIS MAINTAINS GOOD WPC CONTINUITY
AND STRONGLY DOWNPLAYS QUITE DRASTICALLY DIFFERENT GUIDANCE BASED
FROM 12/18 UTC GFS IN THE SAT-NEXT MON TIME FRAME. THIS IS
ESPECIALLY EVIDENT WITH THE DEPTH/BREATH OF A CANADIAN AIRMASS
INTRUSION AND LEAD LOW DEVELOPMENTS AND WEATHER FOCUS DOWN INTO
THE LOWER 48. 


...PATTERN OVERVIEW AND SENSIBLE WEATHER HIGHLIGHTS...

THE MEDIUM RANGE PERIOD STARTS LATE WEEK WITH AN AMPLIFYING NRN
STREAM MID-UPPER LATITUDE PATTERN AT MID-UPPER LEVELS. THIS IS
HIGHLIGHTED BY A WARMING WRN NOAM MEAN RIDGE WHOSE DEVELOPMENT
SHOULD ALLOW DEEP DOWNSTREAM CARVING OF AN INCREASINGLY COLD AIR
FED EAST-CENTRAL NOAM MEAN TROUGH. A SERIES OF ENERGETIC EMBEDDED
IMPULSES ALOFT LEND SURFACE BASED LOW/SYSTEM GENESIS. WPC PROGS
OFFER A TRAILING COLD FRONTAL SURGE DOWN ACROSS THE US SRN TIER IN
THE WAKE OF THE TRACK OF AN ORGANIZED WINTER PCPN FOCUSING LOW
FROM THE GREAT LAKES/MIDWEST DAY 3/WED TO THE NORTHEAST DAY 4/FRI
ON THE HEELS OF A MAJOR LEAD SHORT RANGE STORM...BUT WITH LESS
AVAILABLE MOISTURE. WPC PROGS THEN SHOW A MORE FRIGID ARCTIC BLAST
INTO THE CENTRAL US BY DAY 5/SAT THAT SUBSEQUENTLY SPREADS RAPIDLY
SOUTHWARD AND OUT ACROSS THE ERN US DAY 6/SUN WITH WAVY FRONTAL
PASSAGE. THIS LEADS TO ANOTHER POTENTIAL COLD LOW/WINTER PCPN
THREAT POSSIBLY FROM THE N-CENTRAL STATES AND MIDWEST/GREAT LAKES
BY SAT TO THE MID-ATLANTIC AND ESPECIALLY THE NERN US THEN
OFFSHORE SUPERBOWL SUNDAY.

MEANWHILE AT LOWER LATITUDES...AN ERN PACIFIC MID-UPPER LEVEL
TROUGH NEARS CA/SWRN US/NW MEXICO LATE WEEK PAST NEXT WEEKEND. THE
WOULD ALLOW FOR POTENTIAL FOR INCREASED SRN STREAM IMPULSE AND
LEAD MOISTURE FEED/PCPN INTO SRN CA/SWRN US AND DOWNSTREAM TO
INTERACT WITH COLDER AIRMASS DELIVERY THROUGH THE SRN ROCKIES/NRN
MEXICO TO OVERRUN THE S-CENTRAL US. PLAN TO PLAY-DOWN HEAVIER
MODEL/ENSEMBLE QPFS AND TO A LESSER EXTENT POPS FROM THE HIGH
FREQUENCY FROM ECMWF ENSEMBLES GIVEN UNCERTAINTY WITH THE
NATURE/TIMING OF THESE TYPE OF SYSTEMS.

SCHICHTEL