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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1559Z Apr 18, 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
1159 AM EDT FRI APR 18 2014

VALID 12Z MON APR 21 2014 - 12Z FRI APR 25 2014

...OVERVIEW...MODEL PREFERENCES...UNCERTAINTY ASSESSMENTS...

THE OVERALL FLOW PATTERN TRANSITION HAS GENERALLY BEEN RESOLVED
OVER THE EASTERN PACIFIC...WITH THE GEFS/ECENS IN DECENT AGREEMENT
WITH THE LARGE-SCALE FEATURES FROM WEST COAST TO EAST COAST.

THE THEME DURING THE LATTER HALF OF THE PERIOD FOR THE WEST
COAST...IS THE EMERGENCE OF A NEGATIVE-TILT TROUGH... ALIGNED
ALONG 50 NORTH LATITUDE FROM APPROXIMATELY 160W LONGITUDE TO THE
THE OLYMPIC PENINSULA.

IN THE PLAINS TO THE CONTINENTAL DIVIDE...THE EJECTION OF THE
MAJORITY OF THE 500MB CUTOFF AND ITS ASSOCIATED UPPER-LEVEL
TROUGH/COLD POOL IS REASONABLY DEPICTED BY THE TWO MEANS...WITH
GOOD CLUSTERING FROM THE 18/00Z GFS/ECMWF DETERMINISTIC RUNS
THROUGH DAY 5. AFTER DAY 5...THE DOWNSTREAM MIGRATION OF THE
SYSTEM ENCOUNTERS STRONG NORTHWESTERLY SHEAR FROM A DEEP CYCLONE
IN THE CANADIAN MARITIMES. ALTHOUGH THE DETERMINISTIC DETAILS OF
THE LOW TRACK THROUGH THE MIDWEST IS LESS THAN CLEAR FOR DAY
6...THE ECENS WOULD BE THE PREFERENCE...FOR A WEAKER SURFACE
FEATURE TIED TO THE OCCLUSION AND A SLIGHTLY DEEPER SURFACE WAVE
ALONG THE SOUTHERN END OF THE 'FRONT'...WHERE THE BETTER PROSPECTS
FOR ISOLATED CONVECTION...MID-LEVEL WARM ADVECTION AND THERMAL
CONTRASTS WOULD BE ON THE INCREASE THROUGH TIME. OVERALL...THE
GENERAL PATTERN AND FORECAST PHILOSOPHY REMAINS UNCHANGED FOR THE
MID-LEVEL RIDGE TO GRADUALLY SWEEP NORTHEASTWARD AND EJECT THE
CANADIAN MARITIME/EAST COAST TROUGH.

...SENSIBLE WEATHER HIGHLIGHTS...
AMPLE MID-UPPER LEVEL TROUGH ENERGIES OVER THE CENTRAL US DAY 3
INTERACT OVER THE EASTERN AND NORTHEAST THROUGH DAY 5. MODEST
PCPN/SOME STRONGER CONVECTION IN ADVANCE AND DECENT POST-FRONTAL
COOLING HIGH PRESSURE ARE ANTICIPATED ACROSS NEW ENGLAND INTO
EARLY DAY 6.

UPSTREAM...AN AMPLIFIED MID-UPPER LEVEL TROUGH AND BIG HEIGHT
FALLS WORKS INLAND ACROSS THE GREAT BASIN...LOWER COLORADO RIVER
BASIN...AND THROUGH THE SOUTHERN PLAINS. ISOLATED WINTRY
PRECIPITATION IN THE NORTHWEST AND HIGHEST ELEVATIONS OF THE
DIVIDE...THEN WELL-ORGANIZED LOW/FRONT TO DEVELOP AND INCREASINGLY
FOCUS MOISTURE/PCPN ALONG WITH POST-FRONTAL COOLING ACROSS THE
REGION.  HEAVIEST PCPN POTENTIAL SHOULD BE CLOSER TO THE MAIN LOW
TRACK ACROSS NWRN US/NRN ROCKIES TERRAIN AND OUT ACROSS THE
N-CENTRAL US...BUT DYNAMIC SUPPORT AND INSTABILITY SHOULD ALSO
OFFER A CONVECTIVE SPARK FARTHER SOUTHWARD ACROSS THE WELL WARMED
S-CENTRAL AND E-CENTRAL US AS MOISTURE RETURNS FROM THE GULF OF
MEXICO.  YET ANOTHER DYNAMIC TROUGH AND SURFACE SYSTEM WITH
ENHANCED PCPN REACHES THE NWRN US IN ABOUT A WEEK.

VOJTESAK/SCHICHTEL