469  
FXUS02 KWBC 030611  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
111 AM EST THU JAN 03 2019  
 
VALID 12Z SUN JAN 06 2019 - 12Z THU JAN 10 2019  
   
..OVERVIEW, GUIDANCE EVALUATION, AND PREFERENCES
 
 
THE MODELS INDICATE THE UPPER TROUGH MOVING ONSHORE ALONG THE WEST  
COAST BY 12Z SUN 06 JAN STEADILY PROGRESSES ACROSS THE COUNTRY,  
REACHING THE PLAINS ON MON, GREAT LAKES ON TUE, AND THEN THE  
NORTHEAST ON WED 09 JAN. THE MODELS AND ENSEMBLES ARE IN LARGE  
SCALE AGREEMENT ON THE PATTERN WITH TYPICAL TIMING AND PHASING  
DIFFERENCES, PARTICULARLY OVER THE LOWER LAKES AND NORTHEAST ON  
DAY 7. THE MANUAL FORECASTS BLENDED THE 12Z ECMWF/12Z GFS/12Z  
CANADIAN GLOBAL WITH THE RESPECTIVE 12Z ECMWF AND 18Z GEFS  
ENSEMBLE MEANS FOR DAYS 3-6 BEFORE GIVING MORE WEIGHT TO THE MEANS  
ON DAY 7 THU 10 JAN.  
 
IN THE WAKE OF THE DEVELOPING EASTERN TROUGH, HEIGHTS RISE IN THE  
CENTER OF THE COUNTRY, LEADING TO A DRY PERIOD WITH WARM  
TEMPERATURES IN THE MIDDLE OF NEXT WEEK.  
 
IN THE MIDDLE OF NEXT WEEK, ANOTHER EASTERN PACIFIC SYSTEM SHOULD  
APPROACH THE WESTERN COAST AND MOVE ONSHORE TUE-WED, AND POSSIBLY  
INLAND ON THU 10 JAN. THERE IS CONSIDERABLE SPREAD IN BOTH THE  
TIMING AND PHASING OF THE TROUGH FROM MODEL TO MODEL, RUN TO RUN,  
AND EVEN AMONG THE MEANS. THIS LEADS TO LOW CONFIDENCE AS TO THE  
LOCATION AND STRENGTH OF THE TROUGH AND LOWS EMBEDDED WITHIN THE  
TROUGH. THE DIFFERENCES RESULT IN A PREFERENCE FOR THE ENSEMBLE  
MEANS PLUS AN ALERT TO WATCH FOR CHANGES IN THE FORECAST AS THERE  
IS A LARGE SPREAD IN POSSIBLE SOLUTIONS IN THE EASTERN PACIFIC,  
WEST COAST TUE AND WED, AND INLAND TO THE NORTHERN ROCKIES AND  
GREAT BASIN THU 10 JAN.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
THE MODELS STILL INDICATE PERIODS OF PRECIPITATION ACROSS THE  
COASTAL STATES FROM CALIFORNIA TO WA, WITH HIGHEST TOTALS THIS  
PERIOD CENTERED ON NORTHWEST CALIFORNIA, WITH  
VALLEY RAINS AND MOUNTAIN SNOWS. THERE CONTINUES TO BE POTENTIAL  
FOR LOCATIONS RECEIVING 5-10 INCHES LIQUID IN NORTHWEST CA FOR THE  
MULTI-DAY TOTALS. LIGHTER AMOUNTS EXTEND INLAND INTO THE  
SOUTHWEST AND NORTHERN ROCKIES.  
 
WITH LOW PRESSURE CROSSING FROM THE MS VALLEY TOWARDS THE GREAT  
LAKES MON-TUE 08 JAN,  
A STRIPE OF SNOW IS EXPECTED IN PORTIONS OF THE GREAT LAKES, WITH  
A TRANSITION TO RAIN IN THE OHIO VALLEY. AS THE TRIPLE POINT LOW  
DEVELOPS NEAR SOUTHERN NEW ENGLAND, THERE IS POTENTIAL FOR THE  
SNOW TO EXTEND EAST FROM THE GREAT LAKES ACROSS INTERIOR NEW YORK  
AND CENTRAL TO NORTHERN NEW ENGLAND, WITH AREAS OF HEAVY SNOW  
POSSIBLE. SNOW EXTEND FROM THE LAKES INTO UPSLOPE AREAS OF THE  
CENTRAL APPALACHIANS.  
 
EXPECT TEMPERATURES TO BE ABOVE NORMAL OVER A MAJORITY OF THE  
LOWER 48, THOUGH THE NORTHEAST MAY TREND DOWN AT LEAST TO NORMAL  
BY NEXT WED AS UPPER TROUGHING AMPLIFIES OVER THE REGION. WARM  
ANOMALIES TO THE EAST OF THE ROCKIES WILL BE MOST PRONOUNCED ON  
MULTIPLE DAYS FROM THE CENTRAL PLAINS THROUGH THE UPPER  
MISSISSIPPI VALLEY AND FROM THE SOUTHERN PLAINS INTO OHIO VALLEY  
ON SUN-MON. THE COOL ANOMALIES WILL BE FOCUSED IN THE PERIODS OF  
WET WEATHER NEAR THE WEST COAST AND SUNDAY IN THE SOUTHWEST.  
 
PETERSEN  
 
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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