EXTENDED FORECAST DISCUSSION...CORRECTED NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1159 AM EDT WED MAR 12 2014 VALID 12Z SAT MAR 15 2014 - 12Z WED MAR 19 2014 ...OVERVIEW... COLD UPPER-LEVEL TROUGH REMAINS A FIXTURE OVER EASTERN CANADA AND THE NORTHEAST THIS FORECAST PACKAGE...WITH A CONTINUED INFLUX OF CANADIAN AIR MIGRATING THROUGH THE PLAINS...GREAT LAKES AND INTO THE SOUTHEAST NEXT WEEKEND. IN THE WEST...A PROGRESSIVE FLOW PATTERN ALONG 50 NORTH LATITUDE WITH A STRONG SHORTWAVE RIDGE SANDWICHED BETWEEN TWO PACIFIC-GULF OF ALASKA BASED SYSTEMS TRACKS THROUGH THE PACIFIC NORTHWEST THIS PERIOD. DOWNSTREAM...THE SPLIT-FLOW PATTERN WILL PREVAIL DURING THE FIRST HALF OF THE WEEKEND...WITH SOUTHERN STREAM ENERGY MIGRATING THROUGH THE SOUTHERN PLAINS AND ACROSS THE GULF COAST. THIS ENERGY ENTRAINS INTO THE BASE OF THE UPPER-LEVEL TROUGH AND EXITS THE EASTERN SEABOARD NEXT MONDAY. DURING THE LATTER HALF OF THIS FORECAST PERIOD (MONDAY THROUGH WEDNESDAY)...A NORTHERN STREAM SYSTEM WILL MIGRATE ACROSS THE NORTHERN ROCKIES AND DROP INTO THE PLAINS STATES AND MIDWEST. ...GUIDANCE EVALUATION AND MODEL PREFERENCES... CONTINUED TO FOLLOW THE FORECASTS OF THE 11/00Z & 12/00Z CYCLES OF THE GEFS/ECENS MEANS...FOR THE MIGRATION OF SHORTWAVE ENERGY ACROSS THE NORTHERN ROCKIES. THIS ENERGY DIGS SOUTHWARD THROUGH THE PLAINS STATES...AND ALLOWS THE MID-LEVEL RIDGE TO AMPLIFY---ALBEIT FOR ONLY A BRIEF SPELL---THROUGH DAY 5...BEFORE THE NEXT PACIFIC SYSTEM DRIVES EAST-SOUTHEASTWARD THROUGH THE ALASKA PANHANDLE...PACIFIC NORTHWEST AND NORTHERN ROCKIES. DOWNSTREAM...THE MEANS ARE NOT PARTICULARLY STABLE AFTER DAY 5...SO MAINTAINING CONTINUITY THROUGH DAY 6...WILL BE A CHALLENGE AS THE SYSTEM DEPARTS THE EASTERN SEABOARD AND THE AIRMASS BEHIND IT QUICKLY 'MODIFIES' INTO A SLIGHTLY WARMER/DRIER AIRMASS. A KEY FEATURE OF THE PATTERN...A SURFACE WAVE MIGRATION FROM THE LOWER MS VALLEY---ACROSS THE SOUTHEAST--TO THE OUTER BANKS (DAYS 4-5). A FOUR-CYCLE TREND OF THE ECENS MEANS INDICATE A DEEPER AND MORE 'WELL-DEFINED' SURFACE WAVE...BUT ITS NOT NECESSARILY A MORE STABLE SOLUTION...VS THE 'WEAKER-INVERTED TROUGH' SOLUTIONS OF THE GEFS ENSEMBLE MEAN. BUT THE PRIMARY SENSIBLE WEATHER FEATURE TO TRACK...REGARDLESS OF THE SOLUTION OF CHOICE...WILL BE THE COLD FRONT (M6C AT 850 MBS)...ALLOWING FOR THE TRANSITION FROM LIQUID TO FREEZING/FROZEN PRECIPITATION ALONG THE NORTHWEST PERIPHERY OF THE SURFACE FEATURE. AS DRAWN NOW (DAY 5)...THIS BOUNDARY IS COMPLETELY OVERSPREADING THE NORTHEAST AND SPREADING OUT ACROSS THE PIEDMONT. ITS MODIFIED COUNTERPART---PLUNGING INTO THE WESTERN GULF OF MEXICO AND THROUGH SOUTH TEXAS. A SECOND KEY FEATURE AND CHALLENGE IN THE MEDIUM RANGE...WILL BE IN THE NORTHERN PLAINS BEGINNING DAY 5 AND TRANSLATING DOWNSTREAM INTO THE GREAT LAKES...CENTRAL PLAINS...TO THE MID-MS/WRN OH VALLEYS...DAYS 6-7. THE MEANS GENERALLY SUPPORT A NORTHERN STREAM SYSTEM AT THE SURFACE...AND THE DEVELOPMENT OF A BROAD...PACIFIC WARM FRONT SPREADING ACROSS THE CANADIAN ROCKIES AND NORTHERN HIGH PLAINS FROM DAY 5 INTO DAY 6. THE DETERMINISTIC RUNS AND THEIR MEANS--ARE UNFORTUNATELY AT ODDS---WITH THE LOCATION OF SECONDARY CYCLOGENESIS FORMING ALONG 100 W LONGITUDE. ALOFT...THE MEANS LOOKED BETTER BUT DO NOT NECESSARILY SUPPORT THE NOTION THAT A SECONDARY SURFACE SYSTEM WILL TRACK SOUTHEASTWARD...IN 'ALBERTA CLIPPER' TYPE FASHION THROUGH THE MISSOURI VALLEY. WITH WARM ADVECTION BROADENING FROM THE OZARKS INTO THE OHIO VALLEY BY NEXT TUESDAY (DAY 6)...THE DAY 6-7 GRAPHICS DEPICT A CLOSED SURFACE WAVE MIGRATING JUST NORTH OF DUE EAST TOWARDS THE CENTRAL GREAT LAKES. ...SENSIBLE WEATHER HIGHLIGHTS... IN THE EAST...THERE WILL BE A MUCH COOLER WEATHER PATTERN WITH EMPHASIS ON THE CANADIAN FRONTAL PASSAGES AND WAVINESS ALONG THE FRONT MAKING FOR A TRICKY P-TYPE FORECAST ACROSS THE EAST CENTRAL COASTAL PLAINS DAY 4-5. STAY TUNED THE TWO SYSTEMS MIGRATING THROUGH THE WEST SHOULD IMPACT WASHINGTON...OREGON...THEIR CASCADE RANGES--DOWNWIND TO THE NORTHERN DIVIDE. PERIODS OF MID-LEVEL WARM ADVECTION MOISTURE-PRECIPITATION COULD GENERATE 1/10TH TO 1/2 INCH LIQUID TOTALS THIS MEDIUM RANGE PERIOD. THE MID-LEVEL SHORTWAVE RIDGE SETTLES OVER CENTRAL AND SOUTHERN CALIFORNIA AND THE LOWER HALF OF THE COLORADO RIVER BASIN...SO THE PACIFIC 'COLD' FRONT WILL GENERALLY BE DRY FOR SOUTHERN CALIFORNIA...BUT CARRY SOME COOLER...BREEZY/WINDY CONDITIONS AND A FEW SHOWERS WITH THEM FOR NORTHERN CALIFORNIA...THE NORTHERN SIERRA AND ALONG 42W TO THE NV/ID STATE LINE. THE MID-LEVEL WARM ADVECTION PATTERN SUGGESTS WINDY...DOWNSLOPING FLOW FOR THE DIVIDE REGION OF THE MT/WY AND HIGH-ELEVATION PRECIPITATION/WINDS FOR UPSLOPE REGIONS OF IDAHO IN THIS PATTERN. VOJTESAK