Prognostic Meteorological Discussion
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000 FXUS02 KWBC 081600 PMDEPD EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1100 AM EST MON FEB 08 2016 VALID 12Z THU FEB 11 2016 - 12Z MON FEB 15 2016 ...OVERVIEW... AN AMPLIFIED WRN RIDGE/ERN TROUGH MEAN PATTERN WILL SUPPORT CONTRASTING TEMPERATURE EXTREMES WITH WELL ABOVE NORMAL READINGS OVER THE WEST AND MUCH BELOW NORMAL OVER THE EAST. IN BOTH CASES AT LEAST A FEW DAILY RECORD VALUES MAY BE APPROACHED OR EXCEEDED. WITHIN THIS REGIME THE PRIMARY FCST ISSUES INVOLVE SPECIFICS OF ERN U.S. UPR TROUGHING/SFC LOW PRES NEAR THE NERN COAST LATE WEEK INTO THE WEEKEND AND DETAILS OF SHRTWV ENERGY REACHING THE WEST COAST AROUND SAT. ...GUIDANCE EVALUATION/PREFERENCES... BASED ON THE LATEST ARRAY OF GUIDANCE AND CONTINUITY... THE UPDATED FCST BLEND INCORPORATES SOME ASPECTS OF THE 06Z GFS/GEFS MEAN AND 00Z ECMWF/ECMWF MEAN FROM DAY 3 THU INTO DAY 5 SAT AND MOSTLY THE ENSEMBLE MEANS BY DAY 6 SUN. AN EXCLUSIVELY ENSEMBLE MEAN BLEND FOR DAY 7 MON USES THE 00Z ECMWF MEAN/00Z NAEFS MEAN/06Z GEFS MEAN IN ORDER FROM HIGHEST TO LOWEST WEIGHTING. FOR THE AMPLIFYING ERN TROUGH LATE WEEK INTO THE WEEKEND THE LAST FEW 12-HRLY RUNS OF THE ENSEMBLE MEANS HAVE BEEN TRENDING STEADILY DEEPER/MORE AMPLIFIED. COMPARING THE GFS/ECMWF RUNS... THE ECMWF HAS GENERALLY BEEN MORE AMPLIFIED WITH GFS RUNS TRENDING THAT WAY BUT ECMWF DETAILS HAVE BEEN ERRATIC. RESOLVING SOME OF THESE DETAILS WILL BE CRUCIAL IN THE FCST FOR LOW PRES EXPECTED TO EVOLVE OFF THE NERN COAST BY EARLY SAT. THIS SYSTEM APPEARS TO HAVE A FAIR DEGREE OF COMPLEXITY WITH POTENTIAL FOR COMBINED INPUT FROM WAVINESS CROSSING THE SRN TIER/SRN MID ATLC AND GRTLKS/NEW ENGLAND LOW PRES ASSOC WITH THE UPR LOW DESCENDING FROM HUDSON BAY. AS OF 12Z SAT... ONLY RECENTLY HAS ENSEMBLE GUIDANCE BEEN STARTING TO SHOW SOME TIGHTENING OF THE ENVELOPE FOR SFC LOW TRACK. THE STRONG/WWD 00Z ECMWF SOLN DOES NOT HAVE CONTINUITY FROM ITS PRIOR RUNS AND WHILE IT FALLS WITHIN THE WRN PART OF THE ENSEMBLE SPREAD IT IS NOT QUITE TO THE POINT OF BEING EXTREME. WWD TREND OF THE 06Z GFS TOWARD THE GEFS MEAN ALONG WITH ESTABLISHED CONTINUITY WOULD FAVOR A TRACK CLOSEST TO THE 00Z ECMWF MEAN WHICH IS ALSO ACHIEVED BY THE AFOREMENTIONED MODEL/ENSEMBLE MEAN COMPROMISE. DETAIL DIFFS WITH THE UPR TROUGH HEADING INTO THE WEST BEGIN TO SHOW UP DURING THE WEEKEND. THE COMPACT UPR LOW THAT FORMS OFF CA IN THE 00Z GFS DOES NOT APPEAR IN OTHER LATEST/RECENT RUNS FROM VARIOUS OPERATIONAL MODELS BUT IS STILL WITHIN THE BROAD ENSEMBLE SPREAD. AS THE UPR TROUGH CONTINUES INTO ERN NOAM THERE IS ALSO UNCERTAINTY OVER STRENGTH/TIMING OF THE NRN PORTION OVER CANADA/NRN TIER CONUS. COMPARED TO THE MAJORITY SOLN CLUSTERING THE GFS/GEFS-BASED SOLNS ARE FASTEST WITH THE NRN PART OF THE UPR TROUGH AND ASSOC SFC REFLECTION WHILE SHOWING MORE SEPARATION ALOFT OVER THE WEST COAST/SOUTHWEST. AS A RESULT BY THE END OF THE PERIOD CONSENSUS SHOWS MORE CYCLONIC FLOW OVER THE FOUR CORNERS/SRN PLAINS THAN FCST BY THE GFS/GEFS MEAN. ACCOUNTING FOR THESE CONSIDERATIONS LEADS TO THE GREATER EMPHASIS ON THE 00Z ECMWF AND COMPROMISE NAEFS MEAN VERSUS THE GEFS MEAN. ...SENSIBLE WEATHER HIGHLIGHTS... OVER THE WEST EXPECT ANOMALIES FOR TEMPS TO AVERAGE IN THE PLUS 5-15F RANGE WITH SOME HIGHS 10-20F ABOVE NORMAL REACHING THE NRN PLAINS ON SOME DAYS AS WELL. UPR TROUGH PASSING THROUGH THE WEST DURING THE WEEKEND SHOULD BRING A MODEST COOLING TREND TO SOME AREAS. MOST PCPN SHOULD BE CONFINED TO THE PAC NW/EXTREME NRN ROCKIES. WHILE THE ERN STATES SHOULD BE QUITE COLD FOR THE PERIOD AS A WHOLE THE GREATEST ANOMALIES SHOULD OCCUR DURING THE WEEKEND WITH SOME HIGHS POTENTIALLY 20-30F BELOW NORMAL. AT THE SAME TIME THE STG SFC GRADIENT BTWN LOW PRES OFF THE NERN COAST AND A HIGH DROPPING INTO THE NRN TIER/MS VLY WILL PRODUCE BREEZY TO WINDY CONDS AND DANGEROUSLY COLD WIND CHILL VALUES. SOME LOCATIONS SHOULD SEE SIGNIFICANT LAKE EFFECT SNOWFALL GIVEN VERY LOW ICE COVER THUS FAR. FROM LATE WEEK INTO THE WEEKEND CONFIDENCE IS LOWER THAN DESIRED IN DETERMINING PRECISE SNOWFALL COVERAGE/INTENSITY FROM THE NRN PLAINS SEWD THROUGH THE OH VLY/MID ATLC INTO THE NORTHEAST... CORRESPONDING TO SPREAD IN IMPORTANT MEDIUM TO SMALLER SCALE DETAILS ALOFT AND TRACK OF THE SFC LOW OFF THE NERN COAST BY SAT. A BAND OF MOSTLY SNOW SHOULD BEGIN WORKING EWD FROM THE PLAINS BY SUN-MON AHEAD OF WARMER AIR MOVING INTO THE CNTRL U.S. LATE IN THE PERIOD. RAUSCH $$

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