591  
FXUS02 KWBC 051600  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1059 AM EST TUE FEB 05 2019  
 
VALID 12Z FRI FEB 08 2019 - 12Z TUE FEB 12 2019  
   
..OVERVIEW
 
 
UPPER RIDGING WILL DOMINATE THE AREA JUST WEST OF THE GULF OF  
ALASKA AS WELL AS ACROSS THE FLORIDA STRAITS. THIS WILL FAVOR  
RENEWED TROUGHING ALONG THE WEST COAST AND BROAD WSW FLOW ALOFT  
THROUGH THE EAST.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT AND PREFERENCES
 
 
FOR DAYS 3-4 (FRI-SAT), THE LOW ACROSS THE NORTHEASTERN  
U.S./CANADA AND THE LOW OFFSHORE OF THE U.S. WEST COAST BOTH  
SEEMED WELL HANDLED BY THE OPERATIONAL AND ENSEMBLE MODELS, SO THE  
WPC FORECAST WAS BASED ON A BLEND OF THE 00Z OPERATIONAL ECMWF AND  
ITS ENSEMBLE AS WELL AS THE 00Z GFS AND GEFS AND 06Z GFS. BY DAYS  
5-6, THE OPERATIONAL 00Z ECMWF BEGAN TO SPLIT THE UPPER-LEVEL  
ENERGY NEAR AND IN THE WESTERN U.S., SENDING A SHORTWAVE EASTWARD  
INTO THE INTERMOUNTAIN WEST AND LEADING TO A MORE PROGRESSIVE  
PATTERN AT DAYS 6-7 ACROSS THE CENTRAL U.S. OTHER MODELS DO NOT  
HAVE THIS TENDENCY, AND IT IS NOT WELL SUPPORTED BY THE MEANS, NOR  
BY TELECONNECTIONS RELATED TO THE UPPER RIDGING NEAR ALASKA. THUS  
OPTED NOT TO USE THE OPERATIONAL 00Z EC FOR THE LATTER HALF OF THE  
MEDIUM RANGE PERIOD. THE EC/GEFS MEANS WERE USED, WITH SOME  
CONTINUITY AS WELL.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
MUCH BELOW AVERAGE TEMPERATURES WILL BE FOCUSED OVER THE NORTHERN  
HIGH PLAINS THROUGHOUT THE MEDIUM RANGE PERIOD, NORTH OF AN ARCTIC  
FRONT THAT WILL LINGER NEAR THE DIVIDE. BELOW AVERAGE TEMPERATURES  
WILL APPROACH THE MIDWEST AS WELL, WITH THE ENCROACHMENT OF ARCTIC  
AIR. THE REST OF THE WEST WILL MOSTLY SEE BELOW AVERAGE  
TEMPERATURES DUE TO THE PERSISTENT TROUGHING. A COLD FRONT IN THE  
EAST WILL PUSH THE WELL ABOVE AVERAGE TEMPERATURES ALONG THE  
EASTERN SEABOARD ON FRIDAY OUT TO SEA, WHICH WILL BE REPLACED BY  
NEAR AVERAGE TO COLDER THAN AVERAGE READINGS FOR THE WEEKEND.  
MEANWHILE, THE BEGINNING OF NEXT WEEK IS FORECAST TO BE WARM FOR  
THE SOUTHEAST.  
 
LAKE-EFFECT SNOWS WILL RESUME FRIDAY INTO SATURDAY AS COLDER AIR  
WRAPS AROUND THE DEPARTING SURFACE LOW. LATE THIS WEEKEND AND INTO  
EARLY NEXT WEEK, ANOTHER ROUND OF POTENTIALLY HEAVY PRECIPITATION  
WILL SPREAD INTO THE MID-MISSISSIPPI AND TENNESSEE VALLEYS VIA THE  
COMBINATION OF ANOTHER WEAK IMPULSE OUT OF THE ROCKIES AND A SLOW  
SURGE OF MOISTURE ATOP A WARM FRONT ALONG THE GULF COAST. THROUGH  
THE WEST, LOW PRESSURE SYSTEMS WILL BRING SEVERAL ROUNDS OF LIGHT  
TO MODERATE VALLEY RAIN/MOUNTAIN SNOW TO THE REGION, ESPECIALLY  
FROM CENTRAL CA/SIERRA NORTHWARD TO OREGON.  
 
TATE/FRACASSO  
 
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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