981  
FXUS02 KWBC 081600  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1059 AM EST FRI FEB 08 2019  
 
VALID 12Z MON FEB 11 2019 - 12Z FRI FEB 15 2019  
   
..OVERVIEW
 
 
A STRONG MEAN RIDGE EXTENDING FROM THE NORTH PACIFIC INTO ALASKA  
WILL LIKELY BE THE DOMINANT INFLUENCE ON THE PATTERN FROM THE  
EASTERN PACIFIC ACROSS THE LOWER 48. IN ASSOCIATION WITH THIS  
MEAN RIDGE, FOR MOST OF THIS WEEK MULTI-DAY MEANS VALID AT THE  
EXTENDED TIME FRAME HAVE BEEN ADVERTISING A STRONG POSITIVE HEIGHT  
ANOMALY CENTER JUST SOUTH OF THE ALASKA PENINSULA.  
TELECONNECTIONS RELATIVE TO THIS ANOMALY CENTER SUPPORT A DEEP  
MEAN TROUGH ALOFT NEAR THE WEST COAST AND WEST-SOUTHWESTERLY FLOW  
DOWNSTREAM WITH SOMEWHAT ABOVE NORMAL HEIGHTS OVER THE EAST.  
CORRESPONDING TO THIS PATTERN EXPECT A STRONG TEMPERATURE GRADIENT  
BETWEEN BELOW/MUCH BELOW NORMAL TEMPERATURES OVER THE WEST COAST  
STATES/NORTHERN ROCKIES-PLAINS AND ABOVE NORMAL TEMPERATURES OVER  
THE SOUTH WITH A PREVAILING STORM TRACK FROM THE CENTRAL PLAINS  
THROUGH THE GREAT LAKES. SPECIFICS OF THE WEST COAST TROUGH WILL  
AFFECT LOCATION/INTENSITY OF HEAVIEST PRECIPITATION OVER THE WEST  
WHILE THERE IS BETTER AGREEMENT ON ANOTHER RELATIVE MAXIMUM OF  
PRECIPITATION OVER THE EAST-CENTRAL U.S.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT AND PREFERENCES
 
 
OVER RECENT DAYS THE MODEL AND ENSEMBLE GUIDANCE HAS SHOWN  
SIGNIFICANT DIFFERENCES ULTIMATELY STEMMING FROM UNCERTAINTY OVER  
THE EXACT SHAPE OF THE PACIFIC RIDGE AND ENERGY FLOWING AROUND THE  
EASTERN SIDE OF IT. IN ADDITION THERE WAS A MEANINGFUL CLUSTERING  
OF GUIDANCE THAT WAS SHOWING A FAIR DEGREE OF WESTWARD TROUGH  
ELONGATION OVER THE EASTERN PACIFIC BY THE TUE-WED TIME FRAME--AN  
EVOLUTION NOT PARTICULARLY FAVORED BY TELECONNECTIONS THAT  
SUGGESTED TROUGHING SHOULD BE AT LEAST AS FAR EAST AS THE WEST  
COAST AND NOT AS ELONGATED. 24 HOURS AGO THE GEFS MEAN WAS  
ACTUALLY CLOSEST TO THE TELECONNECTION-FAVORED PATTERN BY WED-THU  
WHILE PROBABLY HALF ECMWF MEMBERS ACTUALLY HAD RIDGING JUST INLAND  
FROM THE WEST COAST. TODAY'S 00Z CYCLE HAS BROUGHT A PRONOUNCED  
ADJUSTMENT IN THE 00Z ECMWF/ECMWF MEAN TOWARD TROUGHING  
ALONG/INLAND FROM THE WEST COAST AROUND MIDWEEK AND THE CMC/CMC  
MEAN CONCUR IN PRINCIPLE. NOW THE GFS RUNS ARE PULLING OFF ENERGY  
OVER THE EASTERN PACIFIC, LEADING TO LOWER CONFIDENCE SOLUTIONS  
DOWNSTREAM. THE 00Z GEFS MEAN STRAYED TOWARD SOME ASPECTS OF  
EARLIER ECMWF/ECMWF ENSEMBLE RUNS BUT THE 06Z VERSION IS SHOWING  
SOME TRENDING TOWARD THE NEW MAJORITY CLUSTER. AS A RESULT THE  
EXTENDED FORECAST BLEND IS BASED ON THE 00Z ECMWF/CMC AND 00Z  
ECMWF MEAN/06Z GEFS MEANS WITH A LITTLE 00Z UKMET INCLUDED EARLY  
IN THE WEEK. THIS REPRESENTS A SIGNIFICANT CHANGE FROM  
CONTINUITY, AND WHILE CONFIDENCE IS NO BETTER THAN AVERAGE DUE TO  
THE SPREAD/VARIABILITY SEEN IN GUIDANCE THUS FAR, THE FACT THAT  
THIS CLUSTER BETTER MATCHES TELECONNECTION-FAVORED FLOW DOES  
PROVIDE GREATER CONFIDENCE THAN WAS PREVIOUSLY THE CASE.  
 
AS FOR INDIVIDUAL SYSTEMS, CLUSTERING HAS IMPROVED WITH THE  
LEADING SYSTEM TRACKING FROM THE WEST THROUGH THE MIDWEST/GREAT  
LAKES AND SOUTHEASTERN CANADA/NEW ENGLAND MON-WED. GFS ISSUES  
BEGIN WITH THE SYSTEM DROPPING SOUTHEAST OFF THE ALASKA  
PANHANDLE/BC AT THE SHORT/EXTENDED RANGE INTERFACE, WITH THE  
DOMINANT MODEL CLUSTER SHOWING A MUCH STRONGER SYSTEM REACHING THE  
NORTHERN PACIFIC NORTHWEST BY TUE. THEN THIS SYSTEM EJECTS INLAND  
AND PRODUCES ANOTHER CENTRAL PLAINS THROUGH GREAT LAKES STORM BY  
THU-FRI. AT THE SAME TIME THE NEXT BUNDLE OF SHORTWAVE ENERGY  
SHOULD BRING ANOTHER SYSTEM SOUTHEASTWARD TOWARD THE PACIFIC  
NORTHWEST LATE IN THE WEEK, WITH INTERMEDIATE TIMING PROVIDING THE  
BEST STARTING POINT GIVEN DECENT CLUSTERING FOR A DAY 7 FORECAST.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
THE OVERALL MEAN PATTERN FEATURING STORM SYSTEMS DROPPING  
SOUTHEASTWARD INTO THE WESTERN U.S. AND THEN TRACKING NORTHEAST  
THROUGH THE CENTRAL PLAINS AND BEYOND WILL PRODUCE ACTIVE WEATHER  
OVER PORTIONS OF THE WEST AS WELL AS THE NORTHERN PLAINS AND MANY  
AREAS FROM THE MISSISSIPPI VALLEY TO EAST COAST. ONE STRONG  
SIGNAL FOR HIGHEST 5-DAY TOTALS OF PRECIPITATION EXTENDS FROM  
WESTERN OREGON INTO NORTHERN-CENTRAL CALIFORNIA. DAY-TO-DAY  
VARIATIONS IN UPPER TROUGH SPECIFICS COULD PRODUCE SIGNIFICANT  
ACTIVITY TO THE NORTH OR SOUTH OF THIS AREA AS WELL. SOME OF THIS  
MOISTURE WILL EXTEND INTO THE ROCKIES. ESPECIALLY OVER THE  
NORTHWEST EXPECT A CONTINUED THREAT FOR LOW ELEVATION SNOW AT  
TIMES GIVEN PERSISTENCE OF BELOW NORMAL TEMPERATURES. THE OTHER  
HIGHLIGHTED AREA FOR HIGHEST 5-DAY PRECIP TOTALS EXTENDS ACROSS  
THE OHIO/TENNESSEE VALLEY REGION AND TO SOME DEGREE ACROSS THE  
MID-ATLANTIC/SOUTHERN NEW ENGLAND. HEAVIEST ACTIVITY WILL LIKELY  
ACCOMPANY TWO SEPARATE STORM SYSTEMS SPACED ABOUT THREE DAYS  
APART. THE NORTHERN PLAINS INTO NORTHERN NEW ENGLAND SHOULD SEE  
MOSTLY SNOW FROM THESE SYSTEMS WITH RAIN OVER THE SOUTHERN  
LATITUDES AND A VARIETY OF PRECIPITATION TYPES IN-BETWEEN.  
DEPENDING ON THE DEGREE OF DEVELOPMENT, ANY INDIVIDUAL STORM MAY  
PRODUCE STRONG WINDS OVER SOME AREAS.  
 
WITHIN THE AREA OF BELOW NORMAL TEMPERATURES OVER MUCH OF THE WEST  
AND INTO THE NORTHERN PLAINS, EXPECT GREATEST ANOMALIES TO BE OVER  
THE NORTHERN PLAINS WITH READINGS CONSISTENTLY 15-25F BELOW  
NORMAL. PACIFIC NORTHWEST COLD ANOMALIES MAY NOT BE QUITE AS  
EXTREME IN ABSOLUTE TERMS BUT COULD HAVE A BETTER CHANCE TO  
APPROACH OR EXCEED DAILY RECORD VALUES AT SOME LOCATIONS. FARTHER  
EASTWARD, WARM SURGES AHEAD OF EACH PROGRESSIVE STORM SYSTEM MAY  
BRING MORNING LOWS 20F OR GREATER ABOVE NORMAL AND AFTERNOON HIGHS  
GENERALLY 10-20F ABOVE NORMAL.  
 
RAUSCH  
 
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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