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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1554Z Apr 20, 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
1154 AM EDT SUN APR 20 2014

VALID 12Z WED APR 23 2014 - 12Z SUN APR 27 2014

...OVERVIEW...
FOLLOWING THE LEAD OF THE PREVIOUS WPC SHIFT...GRAPHICS AND
FORECAST REASONING...SEE THE MERIT OF INCORPORATING SOME OF THE
NAEFS BEYOND DAY 5...AND STEERING/BACKING AWAY FROM A
DETERMINISTIC APPROACH. PARTICULARLY...THE DETERMINISTIC ECMWF
APPROACH... WHICH IS A FASTER SOLUTION THAN ITS ENSEMBLE PACKAGE
OVER THE GREAT LAKES AND WEAKER ALOFT ALONG THE PACIFIC WEST COAST
BEYOND DAY 5.

...MODEL PREFERENCE/UNCERTAINTY ASSESSMENT...
THE 20/00Z ENSEMBLE GUIDANCE REMAINS CONSISTENT WITH THE PRIMARY
SYNOPTIC-SCALE FEATURES AND OVERALL FLOW PATTERN SETUP ACROSS THE
LOWER 48. THEY CONTINUE TO FORM A SOLID CONSENSUS CLUSTER OF
SOLUTIONS INVOF THE UPPER GREAT LAKES REGION FOR DAY 4-5. AND
PROVIDE A NEGATIVE-TILT TROUGH SCENARIO ACROSS THE EXTREME
SOUTHEAST GULF OF ALASKA AND INVOF THE PACIFIC NORTHWEST AFTER DAY
5. THE 20/00Z ECENS...NAEFS AND GEFS LOOKED LIKE GOOD CHOICES
THROUGH DAY 7.

OF THE DETERMINISTIC GUIDANCE...
THE 20/00Z ECMWF SPLITS THE ENERGY ENTERING THE PACIFIC NORTHWEST
(FRIDAY) AND IS NOT NEARLY AS AMPLIFIED WITH THE NEXT UPPER-LEVEL
VERSUS THE 20/00Z DETERMINISTIC CANADIAN-GFS-UKMET. THIS SOLUTION
GENERATES A FAST-MOVING SURFACE WAVE OVER THE SOUTH CENTRAL PLAINS
BY DAY 6-7 THAT DOES NOT SEEM TO ACCURATELY DEPICT THE PROJECTED
FLOW PATTERN IN THE WESTERN THIRD OF THE NATION. OR FOR THAT
MATTER...THE FLOW IN THE EASTERN CONUS. SOMETHING CANADIAN-LIKE OR
GFS-LIKE SEEMS TO FIT THE PROJECTED FLOW PATTERN ALOFT AND AT THE
SURFACE IN BETTER FASHION.

OVER WESTERN ONTARIO AND LAKE SUPERIOR... THE ECMWF IS THE DEEPEST
ALOFT--60 METERS DEEPER--THAN OTHER SOLUTIONS...INCLUDING ITS
ENSEMBLE MEAN. PRIOR TO DAY 5...CAN INFUSE ASPECTS OF THE
DETERMINISTIC GUIDANCE...INCLUDING THE ECMWF-GFS-UKMET ALONG WITH
THE NAEFS/ECENS/GEFS FOR THE ENTIRE FORECAST AREA.

AFTER DAY 5...WILL WHITTLE OUT THE DETERMINISTIC ECMWF ALTOGETHER
AND WHITTLE DOWN THE CANADIAN/GFS DETERMINISTIC FOR DETAILS. BUT
DO LIKE THE GFS/CANADIAN IN THE IN THE CONTEXT OF AN
AMPLIFIED/ENERGETIC SOUTHWEST/SOUTHERN PLAINS MID-LEVEL SYSTEM
CARVING OUT OF THE BASE OF A NEGATIVE-TILT UPPER-LEVEL TROUGH
AXIS. AND DOWNSTREAM...A SLIGHTLY MORE AMPLIFIED RIDGE EAST OF
100W...WHICH IS ACCOUNTED FOR MANUALLY IN THE SURFACE GRAPHICS DAY
6-7...AS A SLOWER AND AMPLIFYING HIGH PLAINS CYCLONIC
FLOW...WITHOUT GULF MOISTURE SUPPORT.

...SENSIBLE WEATHER HIGHLIGHTS...
MID-TO UPPER-LEVEL TROUGH AND SURFACE SYSTEM OFF THE NORTHEAST
COAST MIGRATING INTO THE CANADIAN MARITIMES WILL BE GENERATING
SHOWERS ACROSS MAINE AND THE HIGHER ELEVATIONS OF NORTHERN NEW
ENGLAND. A COOL...POST-FRONTAL NORTHWEST FLOW CONTINUES INTO DAY
4.

ACTIVE BUT ISOLATED DRYLINE CONVECTION TO PREVAIL ACROSS THE
SOUTHERN AND WEST CENTRAL HIGH PLAINS TUESDAY AND WEDNESDAY
EVENINGS. BREEZY TO WINDY CONDITIONS AND RISING TEMPERATURES
PRECEDE THE EJECTION OF A PACIFIC SYSTEM MIGRATING ACROSS THE
PACIFIC NORTHWEST AND NORTHERN ROCKIES. RAIN...SHOWERS AND
HIGH-ELEVATION SNOWS ARE ANTICIPATED FROM THE SIERRA AND CASCADES
INTO THE NORTHERN PLAINS...DAKOTAS AND EASTWARD INTO THE UPPER
GREAT LAKES THROUGH THURSDAY. PERHAPS A REPEAT PERFORMANCE IN THE
DAY 6-7 TIME FRAME WHEN THE NEXT PACIFIC SYSTEM BEGINS ITS EXIT
FROM THE CONTINENTAL DIVIDE. IE...MORE HOT WINDS AND ANOTHER
DRYLINE EVENT(S) FOR SOUTHWEST KANSAS...SOUTHEAST COLORADO AND THE
TX/OK PANHANDLES.

PACIFIC NORTHWEST...SIERRA...CASCADES AND GREAT BASIN REMAIN
ACTIVE REGIONS OF SENSIBLE WEATHER NEXT FRIDAY AND INTO NEXT
WEEKEND. SOUTHERN END OF THE PACIFIC FRONT IS NOT EXPECTED TO BE
MOISTURE-LADEN...BUT SHOULD BE BREEZY AND COOLER BEHIND THE FRONT.
   

VOJTESAK