EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1154 AM EDT THU MAY 22 2014 VALID 12Z SUN MAY 25 2014 - 12Z THU MAY 29 2014 ...OVERVIEW... GRADUAL AMPLIFICATION OF THE PATTERN EAST OF THE MISSISSIPPI IS EXPECTED. A BRIEF TRANSITION AWAY FROM THE COOLER/LESS HUMID AIRMASS AND NORTHWEST FLOW PATTERN ACROSS THE NORTHEAST WITH A BUILDING RIDGE SLOWLY PROPAGATING EAST-NORTHEASTWARD IN ADVANCE OF A SLOW-MOVING TROUGH ORIGINATING IN THE ROCKIES AND CENTRAL PLAINS. OUT WEST...A POSITIVE-TILT TROUGH WITH ORIGINS IN THE GULF OF ALASKA IS POISED TO MAKE LANDFALL EARLY MONDAY ACROSS PUGET SOUND AND THE OLYMPIC PENINSULA...THEN DROP A PACIFIC COLD FRONT SOUTHWARD INTO NORTHERN CALIFORNIA AND EASTWARD INTO WESTERN MONTANA/NORTHERN IDAHO BY WEDNESDAY. THIS FRONT PUSHES INTO THE NORTHERN PLAINS ON THURSDAY. ...MODEL PREFERENCES/UNCERTAINTY ASSESSMENT... AT 500MB...THE 22/00Z CYCLE LOOKED TO BE IN VERY GOOD AGREEMENT AND MAINTAIN EXCELLENT CONTINUITY FROM 24 HOURS AGO...WITH RESPECT TO THE BULK OF THE 'LEAD' 500MB TROUGH ENERGY EJECTING OUT OF THE SOUTH CENTRAL ROCKIES ON MONDAY MORNING 27/12Z. THE DETERMINISTIC 22/00Z GFS/ECMWF WERE VIABLE SOLUTIONS THROUGH 28/12Z AND WERE USED IN THE BLEND THROUGH 28/00Z. THE SURFACE FEATURES ARE POORLY-DEFINED FEATURES AND EACH FORECAST CYCLE 'RE-DEFINING' THE STRONGER MID-LEVEL ENERGY AND TRANSPOSING THEIR DYNAMICS DOWN TO THE SURFACE. THE DEPARTING 'LEAD' WAVE OR ITS 'CUTOFF' LOOKS MUCH LIKE A MCV THAT ROLLS EASTWARD ACROSS THE SOUTH CENTRAL PLAINS (KS/OK) DURING THE DAY ON TUESDAY. GIVEN THAT THE OPERATIONAL RUNS SHOW LITTLE IF ANY SURFACE REFLECTION WITH THIS ENERGY...LATITUDE/LONGITUDE ARE POINTS OF CONTENTION AMONGST THE DETERMINISTIC 22/00Z RUNS...EVEN INTO WEDNESDAY WITH ANY DISTINCT SURFACE FEATURE. THE 22/00Z ECENS/GEFS AND NAEFS HAVE A CENTRAL LOCATION OF THE SYSTEM (ALOFT) INVOF OF SOUTHEASTERN KANSAS...AND FOR NOW...WILL UTILIZE THE GFS/ECMWF AND THEIR MEANS FOR DAY 6-7 TO HANDLE THE LARGE SPREAD. FOR DAYS 6-7...THIS BLEND LACKS SOME DEFINITION INVOF THE CANADIAN MARITIMES AND OFF THE EASTERN SEABOARD...WITH THE NAEFS MORE OF A MIDDLE GROUND SOLUTION WITH THE DEPTH AND POSITION OF THE UPPER-LEVEL TROUGH. THE ECENS IS DEEPER...THE GEFS...SHARPER AND SLOWER. THE SURFACE GRAPHICS DO INDICATE SOME CANADIAN AIRMASS FRONT MIGRATING THROUGH THE NORTHEAST...BUT THIS AIRMASS SEEMS TO MODIFY RATHER QUICKLY WITH UPSTREAM MOISTURE AND ENERGY SWIFTLY BUILDING IN FROM THE WEST. ALONG THE WEST COAST...ALL THREE ENSEMBLE MEANS DEPICT A POSITIVE-TILT 'LONGER' WAVE TROUGH DAYS 6-7...WITH A CLUSTER OF GEFS/ECENS MEMBERS ATTEMPTING TO PINCH OFF AN EMBEDDED SYSTEM/IMPULSE ALONG THE SOUTHERN END OF THIS LONGWAVE INVOF NORTH CENTRAL CALIFORNIA AROUND DAY 7. THE 22/00Z DETERMINISTIC GFS/ECMWF WERE A VERY GOOD COMPROMISE FOR A DAY 6-7 PROJECTION OF HEIGHT FALLS. ...SENSIBLE WEATHER HIGHLIGHTS... A PERSISTENCE FORECAST FOR SHOWERS AND THUNDERSTORMS OVER THE SOUTHERN HIGH PLAINS AND NOCTURNAL RAINFALL DOWNSTREAM INTO THE OZARKS/LOWER HALF OF THE MISSOURI VALLEY. UNTIL THE BULK OF THE UPPER-LEVEL LOW EJECTS OUT OF THE ROCKIES...ANTICIPATE MID-LEVEL ENERGY TO CONTINUALLY ROTATE NORTHEASTWARD INTO THE CENTRAL PLAINS...AND ENVIRONMENTAL CONDITIONS--AT SMALLER SCALES--TO DICTATE AND DRIVE THE CONVECTIVE CLUSTERS FORMING LEE OF THE ROCKIES. AS HAS BEEN HIGHLIGHTED PREVIOUSLY...A PROLONGED PERIOD OF MUCH-NEEDED RAINFALL ACROSS A LARGE PORTION OF THE PLAINS STATES INTO THE MIDWEST WILL BE THE RESULT OF A PERSISTENT CYCLE OF MCS DEVELOPMENT. HOT AND HUMID CONDITIONS ANCHOR ACROSS THE SOUTHEAST AND FLORIDA WITH A BUILDING MID-LEVEL AND UPPER-LEVEL RIDGE. AND TEMPS OVER THE GREAT LAKES SHOULD TREND WARMER DURING THE WEEKEND INTO NEXT WEEK...WITH AN AXIS OF ABOVE NORMAL TEMPS SPREADING NORTHEASTWARD FROM THE PLAINS TO THE GREAT LAKES & OHIO/TENN VALLEYS AROUND DAY 5. THEN ACROSS THE APPALACHIANS...THE NORTHEAST AND MID-ATLANTIC STATES FOR DAY 6 AND 7. NEW ENGLAND WILL BE THE LAST HOLD OUT FOR WARMING...BUT GRADUALLY AN UPTICK IN TEMPERATURES ARE EXPECTED. IN THE NORTHWEST...THE 120+ METER HEIGHTS FALLS ARE IMPRESSIVE FOR LATE MAY FROM NORTHWEST MONTANA SOUTHWESTWARD INTO NORTHWEST CALIFORNIA. THIS IMPLIES A NARROW BAND OF MODERATE RAINFALL TUCKED BACK ALONG THE LOW-LEVEL BAROCLINIC ZONE...AND EMBEDDED WITHIN THE LEADING EDGE OF THE UPPER-LEVEL FRONT...A BAND OF LIGHTER PRECIPITATION. THE 22/00Z DETERMINISTIC ECMWF IS A SLIGHTLY DEEPER SOLUTION VERSUS THE 00Z GFS ALONG THE OREGON/CALIFORNIA BORDER TUESDAY NIGHT AND WEDNESDAY MORNING...BUT BOTH INDICATE SIGNIFICANT RAINFALL FOR THE CASCADES OF NORTHERN OREGON AND SOUTHERN WASHINGTON INVOF THE LOW-LEVEL BAROCLINIC ZONE. VOJTESAK