EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 251 AM EDT FRI APR 01 2016 VALID 12Z MON APR 04 2016 - 12Z FRI APR 08 2016 ...WINTER CONDITIONS ACROSS THE GREAT LAKES REGION AND NORTHEAST NEXT WEEK... ...OVERVIEW... THREE ALBERTA CLIPPERS AND THEIR ASSOCIATED SURFACE LOWS DOMINATE THE SENSIBLE WEATHER PATTERN --- ACROSS THE LOWER 48 THIS FORECAST PERIOD. FROM THE NORTHERN ROCKIES AND UPPER MISSOURI VALLEY TO THE GREAT LAKES...MIDWEST AND OHIO VALLEY... THIS SERIES OF MID-LEVEL DISTURBANCES WILL GENERATE PERIODS OF COLD ADVECTION BEHIND THEIR COLD FRONTS---WINTER PRECIPITATION ALONG AND NORTH OF THE SURFACE LOW TRACK---AND APPRECIABLE RAIN AND RAIN SHOWER ACTIVITY WITHIN THEIR WARM SECTORS. ...MODEL PREFERENCES... DAYS 3-5 (NEXT MONDAY-WEDNESDAY) --- THE 31/12Z GEFS/ECENS MEANS AND THEIR DETERMINISTIC RUNS WERE MORE THAN ACCEPTABLE PIECES OF FORECAST GUIDANCE WITH RESPECT TO --- MAINTAINING CONTINUITY WITH THE PREVIOUS WPC NATIONAL TEMPERATURE...PRECIPITATION PROBABILITIES AND SURFACE GRAPHICS. LIKEWISE...THE SPACING...DEPTH AND STORM TRACKS FOR THE FIRST AND SECOND CLIPPERS MIGRATING THROUGH THE NORTHEASTERN QUARTER OF THE COUNTRY WERE VERY REASONABLE. FOR DAY 6-7...THE DETERMINISTIC GFS GETS A TAD FASTER AND MAY BE SLIGHTLY OVERDONE WITH ITS SURFACE LOW DEPTH VERSUS THE ECMWF...BUT THE REASONS WHY ARE PRETTY CLEAR. ALONG WITH THE 31/12Z DETERMINISTIC CANADIAN --- BOTH SOLUTIONS PHASE THE THIRD CLIPPER WITH A JET WESTERLY STREAK EXITING THE CENTRAL ROCKIES. WHEREAS THE ECMWF... MAINTAINS SEPARATION...SENDING THE JET STREAK DOWNSTREAM ACROSS THE SOUTHEAST AND MAINTAINING THE SFC-TO-700MB LOW-LEVEL CHARACTERISTICS AND ESSENCE OF WHAT A CLIPPER SYSTEM REPRESENTS. IN THAT...THE SURFACE COLD FRONT DOES NOT GENERATE MUCH PRECIPITATION ALONG ITS SOUTHERN FLANKS...MORE WIND THAN COLD ADVECTION ALONG ITS WESTERN QUADRANT --- AND GENERALLY NARROW-BANDED PRECIPITATION WITHIN THE DEFORMATION SHIELD (ITS STRONGLY-SHEARED MID-LEVEL NORTHERN PERIPHERY). THE UPSHOT OF THE DIFFERENCES ARE: THE GFS HAS A 987MB LOW ON/AFTER 7/18Z NORTHWEST OVER NORTHWEST QUEBEC AND DEEP COLD ADVECTION RACING DOWNWIND OF THE CENTRAL APPALACHIANS INTO THE DELMARVA BY 8/00Z. AND THE ECMWF ? --- A 1002MB (CLIPPER) JUST NORTH OF DETROIT ON/AFTER 7/18Z --- AND VERY LITTLE IF ANY COLD ADVECTION EAST OF THE APPALACHIAN TRAIL. THIS ECMWF SOLUTION IS PREFERRED. ...UNCERTAINTY ASSESSMENT... TO ME ANYWAY--- THE RATHER INNOCUOUS CUTOFF CIRCULATION OFF THE CALIFORNIA --- IS MORE OF A CURIOSITY THAN A SENSIBLE WEATHER MAKER ... UNLESS YOU WANT NEAR-RECORD APRIL WARMTH AND LOCALLY BREEZY EAST TO NORTHEAST WINDS. A BY-PRODUCT OF A DECENT PACIFIC SURFACE HIGH TO ITS NORTH AND A DRY NORTHEASTERLY INFLOW INTO ITS NORTHERN QUADRANT --- THE MOMENTUM OF THE OFFSHORE SLOWLY CAUSES THE CIRCULATION TO DRIFT FURTHER AND FURTHER AWAY FROM SHORE. IT REALLY SHOULD NOT BE A PRECIPITATION THREAT THROUGH DAY 7 --- AND MORE A CHALLENGE WITH HIGH TEMPERATURES FROM BROOKINGS OREGON TO MONTEREY CALIFORNIA --- WITH THE CHANNELED EAST AND NORTHEAST WINDS. THE DETERMINISTIC GFS PROBABLY IS NOT THE CHOICE HERE --- WITH ITS VERY SMALL WINDOW FOR A NELY-TO-ELY 70OMB FLOW BETWEEN TUESDAY NIGHT AND WEDNESDAY. ITS SOLUTION SEEM TOO PROGRESSIVE WITH THE MID-LEVEL RIDGE EROSION ALONG THE WEST COAST. COMPARE THIS TO THE ECMWF SOLUTION --- THAT CREATES A CLOSED 700MB HIGH INVOF 35N 135W ON TUESDAY NIGHT AND MIGRATES IT TO 42N 127W BY THURSDAY MORNING. AND MORE IMPORTANTLY --- FITS THE SYNOPTIC-SCALE MEDIUM RANGE PATTERN FOR THE RIDGE TO WEAKEN OVER THE ALASKA PANHANDLE. I PREFER THIS --- WHICH ALLOWS FOR THE RELEASE OF ANOTHER 'SHEET' OF MODIFIED-ARCTIC AIR INTO THE DAKOTAS AND CENTRAL GREAT LAKES FOR THE 7/12Z TO 8/12Z FORECAST PERIOD. ...SENSIBLE WEATHER HIGHLIGHTS... COLD CANADIAN AIR LOCKS IN ACROSS NORTHERN NEW ENGLAND FOR MONDAY THROUGH WEDNESDAY AND A SECOND 'SHEET' MIGRATES FROM THE SOUTHERN CANADIAN PRAIRIES TO THE CENTRAL GREAT LAKES FOR WEDNESDAY...THURSDAY AND FRIDAY. AT ITS PEAK ON WEDNESDAY --- THE COLD WILL CREATE SINGLE-DIGIT READINGS FOR LOWS IN THE USUAL PLACES... NORTHERN MINNESOTA...NORTHERN WISCONSIN...THE ADIRONDACKS...WHITES AND NORTHERN MAINE --- AND WIDESPREAD TEENS/LOW 20S ALONG MUCH OF THE ENTIRE 1-90/94 CORRIDOR FROM LOWER MICHIGAN TO BOSTON. THE ARCTIC-MODIFIED AIRMASS AND ITS REPLENISHMENT --- IS THE PERFECT 'DRAPE' AND SETUP FOR THE SERIES OF CLIPPERS TO GENERATE PERIODS OF WINTER-LIKE CONDITIONS. THESE SYSTEMS AND THEIR MIGRATORY STORM TRACKS SHOULD GENERATE SEVERAL ROUNDS OF SNOW AND SNOW SHOWERS ALONG THEIR NORTHERN PERIPHERY --- FROM THE GREAT LAKES TO NEW ENGLAND AND THE UPSLOPE-FAVORED REGIONS OF NORTHERN APPALACHIA. PLEASE CONSULT THE DAY4-7 WINTER WEATHER PROBABILITIES FOR THE GENERAL PROSPECTS AND LIKELIHOOD FOR WINTER-LIKE CONDITIONS DURING THIS MEDIUM RANGE PERIOD. WARM AND DRY IN THE SOUTHWEST AND RIO GRANDE. OCCASIONALLY BREEZY WITH LARGE TEMPERATURE FLUCTUATIONS FROM THE CONTINENTAL DIVIDE TO THE MISSISSIPPI RIVER. THE SOUTHEAST AND SOUTHERN MID-ATLANTIC REGION SHOULD RECEIVE THE BULK OF THE DAY3-7 NATIONAL RAINFALL THIS PARTICULAR FORECAST PERIOD. VOJTESAK