EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1152 AM EDT MON JUN 01 2015 VALID 12Z THU JUN 04 2015 - 12Z MON JUN 08 2015 ...OVERVIEW... UPPER-FLOW PATTERN 'RESHUFFLE' AT HIGH LATITUDE 'COMMENCES' THIS MEDIUM RANGE PERIOD. ACROSS THE NORTH AMERICAN CONTINENT --- TROUGH EMERGES OVER EASTERN CANADA AND AN UPPER-LEVEL RIDGE EMERGES OVER WESTERN CANADA. FOR THE LOWER 48 --- THE WEATHER PATTERN FOCUS WILL BE IN THE SOUTHWEST --- WITH ENERGY 'UNDERCUTTING' THE WESTERN CANADA UPPER RIDGE --- PRODUCING AN ACTIVE CUTOFF LOW --- THAT MIGRATES SLOWLY FROM CALIFORNIA TO THE GREAT BASIN. A PROMINENT SHORTWAVE RIDGE WILL PREVAIL ALONG 100W FORCING CONFINING CONVECTIVE INITIATION IN A MORE SEASONAL "HIGH PLAINS/LEE OF THE ROCKIES" CONFIGURATION. ...UNCERTAINTY ASSESSMENT... CRUCIAL TIME FRAME AND MEDIUM RANGE FORECAST CHALLENGE WILL OCCUR BETWEEN DAYS 4-5 --- OVER THE MISSOURI VALLEY --- WHEN THE NORTHWEST FLOW ASSOCIATED WITH THE EMERGING EASTERN CANADA TROUGH MIGRATES INTO THE US. AS MENTIONED IN THE PREVIOUS PMDEPD --- THE DAY 8+ ANOMALY IS SHOWING THE AMPLIFIED PATTERN "WE HAVE BECOME FAMILIAR WITH" --- RETURNING TO NORTH AMERICA BY PERIOD'S END. IN THE EAST---THE CHALLENGE WILL BE EARLY IN THE PERIOD --- WITH A SLOW-MOVING MID-LEVEL SHORTWAVE THAT MEANDERS OVER CENTRAL AND SOUTHERN APPALACHIA. IN THE WEST---THE FORECAST SHOULD BE STRAIGHT-FORWARD EARLY IN THE PERIOD UNTIL DAY 5 --- THEN QUESTIONS ARISE WITH THE PROJECTED PATH AND 'CHARACTER' OF THE CUTOFF ONCE IT REACHES THE CENTRAL GREAT BASIN (INVOF CENTRAL UTAH/EAST CENTRAL NEVADA). ...MODEL PREFERENCES... THE 1 JUNE/00Z MODEL CYCLE WAS A REASONABLE FORECAST SOLUTION AND SOME ASPECTS OF THE DETERMINISTIC GUIDANCE COULD BE RELIED UPON HEADING INTO EARLY DAY 6 --- THOUGH THE ECENS/NAEFS MEANS WILL BE THE PREFERRED FORECAST APPROACH FOR THE ENTIRE PERIOD. THE DETERMINISTIC APPROACH HAS ITS WEAKEST MOMENTS OVER THE NORTHERN DIVIDE ON DAY 3 --- AND IN SHORT --- WITH THE SHEARING OUT OF ENERGY DOWNSTREAM ACROSS THE DAKOTAS FOR DAY 4 INTO THE EASTERN CANADA TROUGH. WHAT WOULD BE 'PREFERRED' IS FOR THIS 'EASTWARD-MIGRATING' ENERGY TO FORM AN 'MCS-TYPE' SYSTEM OVER NORTHEAST WYOMING/EASTERN MONTANA---THEN HAVE IT SWEEP OVER THE UPPER-LEVEL RIDGE AND HEAD EAST-SOUTHEASTWARD INTO THE MIDWEST. THAT WOULD BE A 'TYPICAL' EARLY JUNE NOCTURNAL PRECIPITATION PATTERN FOR THE PLAINS. BUT AM NOT QUITE SURE AT A DAY 4-5 TIME SCALE--- I COULD PIN-POINT THE EXACT PLACE WHERE CONVECTIVE INITIATION TAKES PLACE AND THE 'NEXT' MCS ROLLS OUT. WOULD SUGGEST (FROM PERSONAL EXPERIENCE/OBSERVATION)--- THE 1/00Z GFS IS THE FASTER SOLUTION OVER CENTRAL CANADA ON DAY 3-4 AND THAT WOULD POSSIBLY GENERATE FORECAST 'FLIP-FLOP' DOWN THE ROAD---THAT FOR NOW --- IS NOT WORTH THE TROUBLE. FOR ITS THAT FASTER APPROACH --- THAT REALLY QUESTIONS WHAT THE EASTERN CONUS TROUGH LOOKS LIKE AT DAY 7---AND THE GFS LOOKS VERY DIFFERENT VERSUS THE ECMWF. ALL THE RESULT OF A SHORTWAVE THAT UNDERCUTS THE RIDGE IN THE ALASKA PANHANDLE ...SENSIBLE WEATHER HIGHLIGHTS... VERY MUCH A SUMMER 'LOOK' TO THE PRECIPITATION DISTRIBUTIONS NATION WIDE --- WITH CONVECTIVE FOCUS ACROSS THE NORTHERN PLAINS AND INTERMOUNTAIN WEST DURING THE AFTERNOON AND EVENING HOURS. AS IS THE CASE IN EARLY JUNE--- EXPECT THE OCCASIONAL ORGANIZED CLUSTER OF SHOWERS AND THUNDERSTORMS TO MIGRATE DOWNSTREAM OF THE ROCKIES AND WEAKEN AS THEY MOVE INTO THE MISSOURI AND UPPER MISSISSIPPI VALLEYS. THE EXCEPTIONS --- ALONG THE WEST COAST WITH THE PACIFIC 'FRONT' AND UPPER-LEVEL CUTOFF MOVING INLAND. AND ALONG THE SOUTHEAST COAST --- WITH RESIDUAL FRONTAL BOUNDARY MOISTURE AND WEAK SURFACE TO MID-LEVEL WAVE ENERGY GENERATING SOME ORGANIZED RAINFALL INVOF THE CAROLINAS AND DELMARVA. VOJTESAK