265  
FXUS02 KWBC 071601  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1100 AM EST MON JAN 07 2019  
 
VALID 12Z THU JAN 10 2019 - 12Z MON JAN 14 2019  
   
..OVERVIEW
 
 
THE ACTIVE PATTERN ACROSS THE NORTHEAST PACIFIC WILL SUPPORT THREE  
SIGNIFICANT UPPER-LEVEL TROUGHS FORECAST TO REACH THE WEST COAST  
DURING THE MEDIUM-RANGE PERIOD. MEANWHILE, GREATER UNCERTAINTIES  
ARE INDICATED FOR THIS WEEKEND ALONG THE EAST COAST AS GLOBAL  
MODELS SHOW GREATER DISCREPANCIES ON THE DEGREE OF DEVELOPMENT ON  
A POTENTIAL COASTAL STORM OR NOR'EASTER.  
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
GLOBAL MODELS THIS MORNING SHOWED VERY GOOD AGREEMENT ON THE  
EVOLUTION OF THE SYNOPTIC PATTERN ACROSS THE CONUS THROUGH DAY 5  
SATURDAY. THE TIMING AND THE AMPLITUDE OF THE SECOND UPPER-LEVEL  
TROUGH REACHING THE WEST COAST REMAINED AGREEABLE THIS WEEKEND,  
WHILE A LOW PRESSURE SYSTEM IS FORECAST TO FORM OVER EASTERN  
TEXAS. THIS WAS WHEN THE MODELS BEGAN TO DIVERGE ON THE EVENTUAL  
EVOLUTION OF THE LOW AS IT PROGRESSES EASTWARD INTO THE EAST COAST  
THIS WEEKEND. THE LAST TWO RUNS OF THE GFS TOOK A MORE DECISIVE  
TURN TOWARD MORE AGGRESSIVE CYCLOGENESIS NEAR THE MID-ATLANTIC  
COAST SUNDAY INTO MONDAY. ON THE OTHER HAND, THE 00Z ECMWF  
REMAINED FASTER/PROGRESSIVE AND MUCH LESS AGGRESSIVE ON DEVELOPING  
THIS SYSTEM NEAR THE EAST COAST. THE 06Z GEFS SHOWED ONLY MODEST  
DEVELOPMENTS, WHICH WAS QUITE AGREEABLE WITH THE 00Z EC MEAN.  
THEREFORE, THE WPC SEA-LEVEL PRESSURE FIELD WAS DERIVED FROM A  
CONSENSUS OF THE 00Z ECMWF/EC MEAN WITH THE 06Z GFS/GEFS FOR DAYS  
6 AND 7, WHICH YIELDED GOOD CONTINUITY FROM THE PREVIOUS WPC  
FORECASTS. MORE OF THE DETERMINISTIC COMPONENTS WERE USED FOR  
DAYS 3-5.  
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
EXPECT THE POTENTIAL FOR MULTIPLE ROUNDS OF HEAVY PRECIPITATION  
(LOW ELEVATION RAIN AND MOUNTAIN SNOWS) ACROSS THE WEST COAST  
DURING THE FORECAST PERIOD AS A RAPID SUCCESSION OF PACIFIC  
SYSTEMS IMPACTS THE REGION. AS SHORTWAVE ENERGY REACHES THE  
SOUTHERN PLAINS/LOWER MISSISSIPPI VALLEY BY FRI-SAT, AREAS OF  
HEAVY RAIN WILL BE POSSIBLE, WITH PRECIPITATION SPREADING EAST  
INTO THE SOUTHEAST/SOUTHERN MID-ATLANTIC BY SAT NIGHT/SUN. COLD  
AIR TO THE NORTH OF THE SYSTEM COULD RESULT IN AREAS IF WINTRY  
PRECIPITATION. THE DEGREE OF WINTER WEATHER POTENTIAL FROM THE  
SOUTHERN APPALACHIANS TO THE MID-ATLANTIC SAT-SUN IS HIGHLY  
UNCERTAIN FOR THE REASONS DESCRIBED ABOVE.  
 
ABOVE AVERAGE TEMPERATURES WILL PERSIST THROUGH THE FORECAST  
PERIOD ACROSS THE NORTH CENTRAL U.S., WITH MAX TEMP ANOMALIES IN  
THE +10 TO +15 DEG F RANGE (EVEN WARMER FOR SOME AREAS) THROUGH  
MUCH OF THE PERIOD. THE COLDEST TEMPERATURES WILL BE ACROSS THE  
NORTHEAST, WHERE TEMPERATURES AS COLD AS 10 TO 20 DEG BELOW  
AVERAGE WILL BE POSSIBLE FROM FRI THROUGH THE WEEKEND INTO EARLY  
NEXT WEEK.  
 
KONG/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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