347  
FXUS02 KWBC 050630  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
129 AM EST SAT JAN 05 2019  
 
VALID 12Z TUE JAN 08 2019 - 12Z SAT JAN 12 2019  
   
..OVERVIEW AND GUIDANCE EVALUATION/PREFERENCES
 
 
A MODERATELY PROGRESSIVE FLOW PATTERN WILL BE IN PLACE ACROSS THE  
CONUS DURING THE EXTENDED FORECAST PERIOD, WITH FAIRLY AMPLIFIED  
UPPER WAVES TRAVERSING THE COUNTRY EVERY FEW DAYS. NO SIGNALS FOR  
ANY SIGNIFICANT INCURSIONS OF ARCTIC AIR ARE SEEN IN THE GUIDANCE.  
A LOOK AT HEMISPHERIC D+8 500 HPA ANOMALIES REVEALS STRONGLY  
POSITIVE ANOMALIES CENTERED BETWEEN GREENLAND AND WESTERN EUROPE,  
HELPING TO DISPLACE THE COLDEST AIR FROM THE ARCTIC REGIONS INTO  
EURASIA AND AWAY FROM NORTH AMERICA. TELECONNECTIONS ASSOCIATED  
WITH THIS AND OTHER HEMISPHERIC ANOMALY CENTERS SUGGEST A  
CONTINUED TENDENCY FOR UPPER RIDGING TO REBUILD ACROSS WESTERN  
NORTH AMERICA - BUT WITH CONTINUED PROGRESSIVE FLOW ACROSS THE  
NORTH PACIFIC THE RIDGE WILL LIKELY BE A SOMEWHAT TRANSIENT  
FEATURE.  
 
MODELS/ENSEMBLES SHOWED RELATIVELY GOOD CONSENSUS EARLY IN THE  
EXTENDED PERIOD WITH RESPECT TO ONE LOW PRESSURE SYSTEM CROSSING  
THE GREAT LAKES/EASTERN STATES AND ANOTHER APPROACHING THE WEST  
COAST. A BLEND OF THE ECMWF/GFS/CMC WAS USED AS A BASIS FOR THE  
FORECAST DURING DAYS 3-5 (TUE-THU). MODELS BEGIN TO SHOW GROWING  
DIFFERENCES FROM THU ONWARD, BOTH WITH RESPECT HOW DEEP TROUGHING  
WILL BE ALONG THE EASTERN SEABOARD AND HOW QUICKLY IT WILL LIFT  
OUT, AS WELL AS THE TIMING AND AMPLITUDE OF DEAMPLIFYING SHORTWAVE  
ENERGY MOVING INTO THE WESTERN U.S. AND AMPLIFYING ONCE AGAIN AS  
IT REACHES THE CENTRAL U.S. FROM FRI ONWARD. FINALLY, MODELS SHOW  
SOME CONSENSUS THAT ANOTHER AMPLIFIED UPPER TROUGH SHOULD APPROACH  
THE WEST COAST BY LATE FRI-SAT, WITH MODELS SHOWING THE EXPECTED  
DIFFERENCES FOR THE DAY 6-7 TIME PERIOD AS TO THE AMPLITUDE AND  
EVOLUTION OF THIS FEATURE AS IT NEARS THE COAST. USE OF  
DETERMINISTIC ECMWF AND GFS SOLUTIONS CONTINUED THROUGH DAYS 6-7,  
ALBEIT WITH WEIGHTING REDUCED SUBSTANTIALLY IN FAVOR OF SLIGHT  
MAJORITY WEIGHTING OF ENSEMBLE MEANS (ECENS AND GEFS).  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
THE SYSTEM CROSSING THE EASTERN U.S. TUE-WED MAY PRODUCE AREAS OF  
HEAVY SNOW ACROSS NORTHERN NEW ENGLAND, WITH THE POTENTIAL FOR  
LAKE EFFECT SNOW TO LINGER EVEN AFTER THE LOW PRESSURE SYSTEM  
DEPARTS. HEAVY PRECIPITATION, LOW ELEVATION RAIN AND MOUNTAIN  
SNOW, ARE ALSO LIKELY FROM CALIFORNIA TO THE PACIFIC NORTHWEST  
TUE-WED AS A STRONG LOW PRESSURE SYSTEM APPROACHES, PUSHING A COLD  
FRONT INLAND. THIS SYSTEM MAY ALSO PRODUCE AREAS OF HIGH WINDS  
NEAR THE COAST. BY THU-FRI AS SHORTWAVE ENERGY CROSSES THE ROCKIES  
AND ENTERS THE CENTRAL U.S., INFLOW OF MOISTURE FROM THE GULF OF  
MEXICO WILL INCREASE IN THE VICINITY OF A WARM FRONT, WITH  
PRECIPITATION EXPECTED TO INCREASE IN COVERAGE FOR AREAS FROM THE  
SOUTHERN PLAINS TO THE LOWER MISSISSIPPI VALLEY. TEMPERATURES WILL  
INITIALLY BE WELL ABOVE AVERAGE FOR MOST OF THE CENTRAL/EASTERN  
U.S. TO BEGIN THE FORECAST PERIOD ON TUE, WITH HIGH TEMPERATURE  
ANOMALIES OF +10 TO +20 DEG F FOR MANY AREAS. COOLER TEMPERATURES  
WILL PREVAIL IN THE WAKE OF A COLD FRONT BY MID TO LATE WEEK, BUT  
TEMPERATURES WILL ONLY DECREASE TO NEAR AVERAGE LEVELS. MEANWHILE,  
TEMPERATURES ACROSS AREAS FROM THE NORTHERN ROCKIES TO THE  
NORTHERN/CENTRAL PLAINS WILL REMAIN ABOVE AVERAGE THROUGH THE  
MIDDLE OF NEXT WEEK BEFORE THE ARRIVAL OF THE NEXT COLD FRONT LATE  
IN THE WEEK.  
 
RYAN  
 
WPC MEDIUM RANGE 500 MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDEXES 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  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 
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