EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1200 PM EDT FRI MAY 06 2016 VALID 12Z MON MAY 09 2016 - 12Z FRI MAY 13 2016 ...PATTERN OVERVIEW... THE OMEGA BLOCK IN THE U.S. IS EXPECTED TO GRADUALLY DEAMPLIFY AS THE LARGE-SCALE LOWS ON BOTH THE WEST AND THE EAST COASTS SLOWLY RETREAT. THE WESTERN U.S. RETREATING LOW WILL APPEAR TO MOVE ACROSS THE PLAINS THROUGH DAY 4/TUESDAY BEFORE SHEARING OFF TO THE EAST ALONG A QUASI-STATIONARY FRONT ACROSS THE MID-ATLANTIC THROUGH DAY 7/NEXT FRIDAY. MEANWHILE...SHORTWAVE ENERGY WILL DIG DOWN FROM WESTERN CANADA INTO THE NORTHERN ROCKIES AND NORTHERN PLAINS THROUGH DAY 5/WEDNESDAY BEFORE INTERACTING WITH OR TRYING TO MERGE WITH THE SHEARED-OFF ENERGY ACROSS THE EASTERN U.S. ...MODEL PREFERENCES/UNCERTAINTY ASSESSMENT... MODEL GUIDANCE IS IN GENERAL AGREEMENT WITH THE AFOREMENTIONED PATTERN EVOLUTION. THE UNCERTAINTY IS REGARDING THE DEGREE OF INTERACTION BETWEEN THE SHORTWAVE DIGGING DOWN FROM WESTERN CANADA WITH THE REMAINING ENERGY COMING FROM THE WESTERN U.S. RETREATING LOW. BOTH OF THE ECMWF AND THE GFS ARE STILL COMING TO A STEADY SOLUTION ON THE DETAILS OF THE PATTERN FROM DAY 5/WED AND BEYOND. THUS...AN ENSEMBLE MEAN APPROACH WILL BE INCORPORATED FOR THIS TIME FRAME. BETWEEN THE GEFS AND THE EC MEANS...IT APPEARS THAT THE EC MEANS CONTINUE TO PROVIDE STEADIER SOLUTIONS THAN THOSE FROM THE GEFS. THE WPC BLEND USES A BLEND OF THE 00Z ECMWF AND 06Z GFS STARTING ON DAY 3...AND TRENDS MORE TOWARDS THE EC MEANS BY DAY 7. THE TWO PIECES OF ENERGY COULD MERGE INTO A SINGLE SYSTEM BY DAY 7 IN THE NORTHEASTERN U.S. ...WEATHER HIGHLIGHTS... THE DAY 3-4 SYSTEM EXITING THE SOUTH CENTRAL PLAINS IS EXPECTED TO GENERATE DEEP CONVECTION...WITH STEEP MID-LEVEL LAPSE RATES...PRODUCING SCATTERED TO NUMEROUS SHOWERS AND BELOW NORMAL TEMPERATURES BENEATH THE COLD CORE MID-LEVEL CYCLONE. A WEST-TO-EAST ORIENTATION OF THE PRECIPITATION AXIS (DOWNSTREAM) IS ANTICIPATED FOR DAY 4...BETWEEN THE CENTRAL PLAINS AND THE OHIO VALLEY...BEFORE THE CYCLONE EXITS THE EAST COAST ALONG A QUASI-STATIONARY FRONTAL BOUNDARY ACROSS THE MID-ATLANTIC. ACROSS THE WEST...SPLIT-FLOW GENERATES A PERIOD OF OFFSHORE FLOW AND MILD...TRANQUIL CONDITIONS ALONG THE COASTLINE...AND ABOVE NORMAL TEMPERATURES AND GENERALLY DRY WEATHER...FOR THE INTERIOR (WEST OF THE DIVIDE). KONG/VOJTESAK