141  
FXUS02 KWBC 111552  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1051 AM EST MON FEB 11 2019  
 
VALID 12Z THU FEB 14 2019 - 12Z MON FEB 18 2019  
   
..OVERVIEW
 
 
MODELS/ENSEMBLES SHOW STRONG CONSENSUS THAT A REX BLOCK PATTERN  
ACROSS THE CENTRAL/NORTH PACIFIC, EXTENDING FROM NEAR HAWAII TO  
ALASKA, SHOULD PERSIST THROUGH THE NEXT WEEK, LEAVING THE FLOW  
REGIME ACROSS THE CONUS LARGELY QUASI-ZONAL. TELECONNECTIONS  
RELATIVE TO THE STRONGEST 500 HPA POSITIVE HEIGHT ANOMALY CENTER  
CONTINUE TO FAVOR A POSITIVELY-TILTED MEAN TROUGH NEAR THE PACIFIC  
NORTHWEST WITH WEAK POSITIVE HEIGHT ANOMALIES FROM THE SOUTHERN  
PLAINS LUMBERING EASTWARD INTO THE SOUTHEAST AND A BROAD REGION OF  
MODESTLY CYCLONIC UPPER-LEVEL FLOW ACROSS MUCH OF THE CONUS.  
SHORTWAVE ENERGY EJECTING FROM THE NORTHEASTERN PACIFIC EVERY  
COUPLE DAYS WILL MOVE INTO THEN CROSS THE CONUS, UNDERGOING  
GRADUAL AMPLIFICATION IN THE BROAD CYCLONIC FLOW. ADDITIONALLY, A  
PERSISTENT AND RELATIVELY STRONG THERMAL GRADIENT FROM THE CENTRAL  
U.S. TO THE OHIO VALLEY/GREAT LAKES WILL SERVE TO INTENSIFY  
ANOTHER LOW PRESSURE SYSTEM BY LATER THIS WEEK AS IT TRACKS INTO  
THE INTERIOR NORTHEAST.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT AND PREFERENCES
 
 
FROM THE END OF THE SHORT RANGE (WEDNESDAY) INTO THE MEDIUM RANGE  
(THURSDAY) THE 00Z/06Z MODELS/ENSEMBLES SHOWED A LARGE AMOUNT OF  
SPREAD IN THE NORTHEASTERN PACIFIC REGARDING THE EVOLUTION OF A  
VERY SHARP/SHEARED TROUGH THAT WILL EITHER COME INTO WA/OR IN ONE  
STRONGER PIECE VIA THE NORTHERN PORTION (ECMWF/CANADIAN) OR TWO  
WEAKER PIECES (GFS/UKMET). CONTINUITY AND MAJORITY OF ENSEMBLES  
FAVORED THE ECMWF-LED CONSENSUS AND OPTED TO USE THAT CLUSTER AS  
THE BASIS FOR THE FORECAST. THIS PREFERENCE CARRIED THROUGH THE  
ENTIRE MEDIUM RANGE PERIOD DUE TO THE TIMING DIFFERENCES  
DOWNSTREAM (GFS QUICKER, ECMWF SLOWER). BY FRI/SAT THIS RESULTED  
IN A STORM TRACK OUT OF THE MID-MS VALLEY AND INTO THE NORTHEAST  
BUT AT A PACE ABOUT 18-24 HRS SLOWER THAN THE 00-06Z GFS RUNS.  
 
IN THE WAKE OF THE LATE WEEK EASTERN LOW PRESSURE SYSTEM, MODELS  
HAVE AT LEAST COME INTO BETTER AGREEMENT ON THE NATURE OF THE FLOW  
ACROSS THE WESTERN/CENTRAL U.S. BY THE WEEKEND. THERE, THE GFS WAS  
MORE AGREEABLE WITH THE ECMWF AS NUMEROUS AREAS OF PACIFIC  
SHORTWAVE ENERGY PUSH INLAND. A MORE SIGNIFICANT TROUGH SHOULD  
PUSH INTO THE WESTERN U.S. BY SUN-MON AS SHOWN BY THE MAJORITY OF  
DETERMINISTIC SOLUTIONS AND ENSEMBLE MEANS. BOTH THE GEFS MEAN AND  
ECMWF ENSEMBLE MEAN WERE SIMILAR ON TIMING/AMPLITUDE THOUGH THE  
DETERMINISTIC RUNS HIGHLIGHTED THE REMAINING DIFFERENCES IN  
DETAILS. THIS WILL CARRY A SOUTHERN STREAM SYSTEM THROUGH THE  
SOUTHWEST WITH HIGH PRESSURE NOSING SOUTHEASTWARD OUT OF SOUTHERN  
CANADA THROUGH THE HIGH PLAINS INTO THE MIDWEST.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
THE PERSISTENT UPPER TROUGH ALONG THE WEST COAST WILL PRODUCE  
MULTIPLE ROUNDS OF LOW-ELEVATION RAIN AND MOUNTAIN SNOW (WITH  
VARYING SNOW LEVELS) FROM CALIFORNIA TO THE PACIFIC NORTHWEST.  
SYSTEMS WILL ALSO SPREAD RAIN/SNOW EAST INTO THE INTERIOR WESTERN  
U.S., WITH HEAVY SNOW POSSIBLE AT THE HIGHER ELEVATIONS. THE LOW  
PRESSURE SYSTEM MOVING FROM THE CENTRAL U.S. TOWARD THE GREAT  
LAKES THU-FRI WILL LIKELY PRODUCE AN AREA OF WINTRY WEATHER  
ALONG/NORTH OF THE SURFACE LOW TRACK. THE EXTENT OF WINTER WEATHER  
AND THE DEGREE TO WHICH HEAVY SNOW MAY BE POSSIBLE REMAINS  
SOMEWHAT UNCERTAIN GIVEN THE MODEL DIFFERENCES DESCRIBED ABOVE.  
THE SAME HOLDS TRUE FOR WINTER WEATHER POTENTIAL IN THE NORTHEAST  
FRI-SAT. WHILE AT LEAST SOME WINTRY WEATHER IS LIKELY IN WARM  
ADVECTION AHEAD OF THE WARM FRONT, ANY POTENTIAL COASTAL LOW  
DEVELOPMENT WOULD ENHANCE THE POTENTIAL FOR HEAVIER PRECIPITATION  
ACROSS NEW ENGLAND, WITH THE BEST CHANCES FOR SIGNIFICANT SNOWS  
ACROSS THE INTERIOR. FARTHER SOUTH, THE COLD FRONT WILL LIKELY  
PRODUCE WIDESPREAD RAINS FROM THE LOWER MISSISSIPPI VALLEY TO THE  
EASTERN SEABOARD.  
 
WELL BELOW AVERAGE TEMPERATURES ARE EXPECTED TO PERSIST FROM THE  
INTERIOR PACIFIC NORTHWEST TO THE NORTHERN PLAINS THROUGH THE  
FORECAST PERIOD. MAX/MIN TEMPERATURES RANGING FROM 10 TO 30 DEG F  
BELOW AVERAGE WILL BE POSSIBLE THROUGH THE WEEK AND INTO THE  
WEEKEND ACROSS THESE AREAS. TEMPERATURES WILL INITIALLY BE ABOVE  
AVERAGE OVER THE SOUTHERN/CENTRAL PLAINS (THU) TO THE EASTERN  
SEABOARD (THU/FRI), BUT THEN COLDER TEMPERATURES SHOULD SPREAD  
FARTHER SOUTH/EAST IN THE WAKE OF THE LOW PRESSURE SYSTEM, WITH  
TEMPERATURES 5 TO 15 DEG F BELOW AVERAGE ACROSS MUCH OF THE  
CENTRAL/EASTERN STATES. THE EXCEPTION WILL BE AREAS FROM THE  
SOUTHERN PLAINS TO THE SOUTHEAST WHERE TEMPERATURES WILL REMAIN  
NEAR SEASONAL NORMS EVEN INTO THE WEEKEND.  
 
FRACASSO/RYAN  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION AND WINTER WEATHER OUTLOOK  
PROBABILITIES ARE FOUND AT:  
 
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
 

 
 
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