EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1200 PM EDT WED APR 26 2017 VALID 12Z SAT APR 29 2017 - 12Z WED MAY 03 2017 ...LATE SEASON WINTER STORM EXPECTED TO BRING SNOW TO THE SOUTHERN/CENTRAL ROCKIES AND PORTIONS OF THE ADJACENT HIGH PLAINS THIS WEEKEND...WITH SNOW ALSO POSSIBLE ACROSS THE UPPER MISSISSIPPI VALLEY EARLY NEXT WEEK... ...THREAT FOR HEAVY AND EXCESSIVE RAINFALL OVER SOUTHERN PORTIONS OF THE PLAINS AND MISSISSIPPI VALLEY THIS WEEKEND...ESPECIALLY FROM OKLAHOMA INTO ARKANSAS AND MISSOURI... ...PATTERN OVERVIEW AND GUIDANCE EVALUATION... MODEL GUIDANCE REMAINED IN GOOD AGREEMENT WITH THE LARGE SCALE FLOW PATTERN OVER THE LOWER 48 THIS WEEKEND AND INTO THE EARLY HALF OF NEXT WEEK WHICH WILL FEATURE A MEAN CENTRAL U.S. TROUGH SANDWICHED BETWEEN UPPER RIDGING OVER THE EASTERN PACIFIC AND WESTERN ATLANTIC. WITHIN THE MEAN FLOW...A CLOSED UPPER LOW OVER THE FOUR CORNERS REGION ON SATURDAY WILL SLOWLY EDGE EAST/NORTHEASTWARD TOWARDS THE CENTRAL PLAINS THIS WEEKEND. ON MONDAY...THE DYNAMIC SYSTEM...INCLUDING A DEEPENING SURFACE LOW...WILL LIFT THROUGH THE UPPER MISSISSIPPI VALLEY WHILE UPSTREAM ENERGY STREAKS SOUTHEASTWARD INTO THE PACIFIC NORTHWEST AND POTENTIALLY AMPLIFIES OVER THE INTERMOUNTAIN WEST AND ROCKIES. GERHARDT ...WEATHER HIGHLIGHTS... MODERATE TO HEAVY ON SNOWFALL IS EXPECTED OVER THE FRONT RANGE OF THE COLORADO AND WYOMING ROCKIES AS AN UPPER TROUGH AMPLIFIES OVER THE CENTRAL/SOUTHERN ROCKIES FRIDAY INTO SATURDAY...WITH SNOW POSSIBLY EXPANDING INTO THE ADJACENT HIGH PLAINS ON SATURDAY. INCREASING MOISTURE ADVECTING NORTHWARD OUT OF THE GULF OF MEXICO WILL HEIGHTEN THE RISK FOR HEAVY RAINFALL ACROSS THE MIDDLE TO LOWER MISSISSIPPI VALLEY. MULTIPLE FORECASTS SEEM TO BE TARGETING HEAVIER AMOUNTS IN ARKANSAS AND ADJACENT PORTIONS OF SURROUNDING STATES MO/OK/TX/LA/MS. PLEASE REFER TO THE STORM PREDICTION CENTER (WWW.SPC.NCEP.NOAA.GOV) FOR INFORMATION ON THE SEVERE WEATHER THREAT WITH THIS SYSTEM. ALSO...ACCUMULATING SNOW WILL BE POSSIBLE FOR PORTIONS OF THE UPPER MISSISSIPPI VALLEY AS THE UPPER TROUGH/CLOSED LOW AND ASSOCIATED DEEP SURFACE CYCLONE LIFT THROUGH THE UPPER MIDWEST SUN/MON...BUT THERE REMAINS SOME UNCERTAINTY WITH THE DETAILS OF THE TRACK AND STRENGTH OF THE LOW AND RESULTANT TEMPERATURE PROFILES AND DURATION OF EACH PRECIPITATION TYPE. A HIGH AMPLITUDE UPPER RIDGE OVER THE SOUTHEASTERN U.S. COULD BRING WIDESPREAD RECORD HIGH OR NEAR RECORD HIGH TEMPERATURES TO THE SOUTHEAST AND MID-ATLANTIC STATES THIS WEEKEND...BUT THEN TEMPERATURES SHOULD DECLINE TO NEAR NORMAL AFTER A COLD FRONT CROSSES THE REGION EARLY NEXT WEEK. WELL ABOVE NORMAL TEMPERATURES ARE FORECAST ACROSS SOUTHERN CA INTO THE DESERT SOUTHWEST EARLY TO MIDDLE PORTIONS OF NEXT WEEK AS WARM AIR ALOFT PROGRESSES DOWNSTREAM FROM THE ANTICYCLONE IN THE EASTERN PACIFIC. PETERSEN